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Theeffecto
Prot
specif
A p
offootballsp
tect he
fic fati
project f
pecificfatigu
er kne
igue o
yo
funded b
READER
UN
ueondynam
ees - Ex
n dyn
outh fo
by the U
DR MA
R IN PAEDIA
NIVERSITY
mickneestab
xplori
amic k
ootball
EFA Re
ARK DE STE
ATRIC SPO
OF GLOUC
bilityinfem
ing the
knee s
l playe
esearch
E CROIX
ORT AND E
CESTERSH
maleyouthpl
Dr Mark D
e role o
stabilit
ers
Grant P
EXERCISE
HIRE
layers
De Ste Cro
of foot
ty in fe
Program
ix 1
tball
emale
me
Theeffecto
1. Exe
1.1 Ack
2. Re
2.1 Inci
2.2 Inci
2.2 Risk
2.3 Inju
2.4 The
2.5 Mus
2.6 The
2.7 Isok
2.7.1 ‘C
2.7.2 ‘F
2.7.3 Ag
2.7.4 Se
2.8 Neu
2.9 Effe
2.10 Co
3. Re
4. Me
4.1 Par
4.1.1 Et
4.2 Stud
4.3 Pro
4.3.1 A
4.3.2 Le
4.3.3 D
4.3.4 Fu
offootballsp
ecutive S
knowledgme
view of L
dence of inj
dence of AC
k factors for
ry mechani
e anatomy o
scle, tendon
e role of the
kinetic dyna
Conventiona
Functional’ H
ge and mat
ex differenc
uromuscula
ect of fatigue
onclusions..
esearch Q
ethods.....
rticipants.....
thical consi
dy Design..
cedures.....
nthropomet
eg stiffness
etermining
unctional H
pecificfatigu
CSummary
ents............
Literature
jury in footb
CL injury....
r ACL injury
sms...........
of the knee.
n and leg st
hamstring
amometry: m
al’ Hamstrin
Hamstring/Q
turation effe
ces in H/Q r
r control an
e on dynam
..................
Questions
...............
..................
derations...
..................
.................
try..............
..................
the ‘Q’ ang
amstring/Q
ueondynam
CON..............
..................
..............
ball.............
..................
y.................
..................
..................
tiffness.......
and quadric
measureme
g/Quadrice
Quadriceps
ects on the H
ratio – why
nd knee stab
mic knee sta
..................
s and Ob
..............
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le...............
uadriceps r
mickneestab
NTE..............
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ceps muscl
ent of conce
eps ratio (CH
ratio (FH/Q
H/Q ratio....
girls are at
bility...........
ability..........
..................
bjectives..
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ratio............
bilityinfem
ENTS..............
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es (muscula
entric and ec
H/Q)...........
Q)................
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risk............
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maleyouthpl
Dr Mark D
S ...............
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ar stability..
ccentric torq
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De Ste Cro
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ix 2
......... 4
........... 6
......... 7
............ 7
.......... 9 .......... 11.......... 14.......... 14........... 15.......... 21.......... 22.......... 22......... 23.......... 23......... 28......... 31.......... 34........... 36
........ 37
........ 38
......... 38
........ 38.......... 39........ 39........ 39.......... 40........ 41........ 42
Theeffecto
4.3.5 E
4.3.6 SA
4.4 Stat
5. Re
5.1 Par
5.2 FH/
5.3 Rela
5.4: EM
5.5 Sum
6. Dis
6.1 Ove
6.2 Influ
6.3 Influ
6.4 Influ
7. Ap7.1 Cur
8. Fut
9. Re
10. Ap
offootballsp
lectromyog
AFT90 fatig
tistical anal
sults.......
rticipant Cha
/Q ratio.......
ative Leg st
MD..............
mmary of re
scussion.
er-view of th
uence of foo
uence of foo
uence of foo
plied Imprrent eviden
ture Rese
ferences
ppendice
pecificfatigu
raphy.........
gue protoco
ysis............
..............
aracteristics
..................
tiffness.......
..................
esults..........
..............
he main find
otball specif
otball specif
otball specif
plications nce of effect
earch Dir
..............
s............
ueondynam
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ol.................
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s.................
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dings..........
fic fatigue o
fic fatigue o
fic fatigue o
and Rectiveness of
rections..
..............
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mickneestab
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on FH/Q rat
on leg stiffne
on EMD......
commendneuromusc
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bilityinfem
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io...............
ess.............
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dations....cular training
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maleyouthpl
Dr Mark D
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De Ste Cro
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ix 3
........ 43
........ 46........ 47
...... 48
....... 48
....... 48....... 52...... 53...... 58
..... 59
....... 59
....... 60...... 67....... 71
....... 77
......... 78
........ 81
........ 82
...... 101
8
Theeffecto
Context:
It is well re
compared
modifiable
factors hav
that this rel
of growth a
injury towa
knowledge
functioning
aimed to e
associated
Methods:
36 elite you
FA Women
set from p
group. Rela
Delay (EMD
SAFT90 pro
Key Findin
Football sp
FH/Q, altho
detrimental
all age gro
Fatigue infl
fatigue. Ne
feedback re
U17 age g
offootballsp
Ex
ecognised t
to males w
(anatomica
ve been pro
lative risk m
and maturat
ards the en
of the eff
of female
examine the
with dynam
uth academ
n’s Super Le
eak height
ative leg stif
D) were de
otocol.
ngs:
pecific fatigu
ough the r
l effect on n
oups. Howe
luenced the
euromuscula
esponses (
group incre
pecificfatigu
xecu
hat females
when hours
l and hormo
oposed for
may peak in
tion are mo
nd of matc
fect that fo
youth footb
e effect of f
mic knee sta
my female fo
eague club
velocity a
ffness, Fun
termined pr
ue had little
atio was re
neuromuscu
ever, these
e U15 group
ar functioni
(EMD) as w
eased mus
ueondynam
utiv
s appear to
s of athlete
onal) and m
this sex di
n the pubert
ost prevalen
ches, when
ootball spec
ballers, thro
football spe
ability in elit
ootballers (
. Anthropom
nd ‘Quadric
nctional Ham
re and post
e influence o
educed pos
ular stability
negative e
p the greate
ng was dim
well as redu
scular stab
mickneestab
ve S
o have a gr
e exposure
modifiable (m
ifference. L
tal / immedi
nt. Injury inc
n fatigue is
cific fatigue
ugh the pu
ecific fatigue
e youth fem
U13, U15 a
metric varia
ceps Angle
mstring/Qua
t an age ap
on muscula
st fatigue c
y with signif
ffects were
est with a r
minished th
uced feed-f
ility (FH/Q
bilityinfem
Sum
reater relati
are taken
muscular an
Limited epid
iately post p
cidence data
s most like
e has on th
bertal years
e on muscu
male footbal
and U17 ag
ables includ
e’ (Q angle
adriceps (FH
ppropriate s
ar stability o
close to ful
ficantly long
e significant
reduction in
e most in t
forward res
ratio) and
maleyouthpl
Dr Mark D
mma
ve risk of n
into accou
nd neuromu
demiologica
pubertal ye
a also show
ely to be p
he muscula
s, is limited
ular and ne
lers.
ge groups) w
ing maturat
) were det
H/Q) ratio, a
simulated fo
of the knee
l knee exte
ger EMD re
tly greater i
n FH/Q and
the U13 ag
sponses (low
d feed-forw
layers
De Ste Cro
ary
non-contact
unt. A num
uscular func
al informatio
ars when th
ws an incre
present. Cu
ar and neu
d. Therefore
euromuscula
were recrui
tion determ
termined fo
and Electro
ootball matc
, as determ
ension. Fat
corded pos
in the U13
increase in
ge group w
wer leg stif
ward mecha
ix 4
t ACL injury
ber of non
ctioning) risk
on suggests
he influence
ased risk o
urrently ou
uromuscula
e, this study
ar variables
ted from an
mined as off
or each age
omechanica
ch using the
mined by the
tigue had a
st fatigue fo
age group
n EMD pos
with reduced
ffness). The
anisms (leg
y
-
k
s
e
of
r
r
y
s
n
f-
e
al
e
e
a
r
p.
st
d
e
g
Theeffecto
stiffness) p
neuromusc
Implication
Our finding
neuromusc
1. Tha
resi
duri
2. Tha
towa
train
3. Tha
mov
4. Tha
as a
5. Tha
train
6. Tha
neu
inclu
7. Tha
neu
(Dr Mar
offootballsp
post fatigu
cular feedba
ns for prac
gs suggest
cular conditi
at a neurom
stance and
ing the warm
at muscular
ards full kn
ning aimed
at training in
vements
at training p
a primary go
at training i
ning should
at training i
uromuscular
ude fundam
at training d
uromuscular
rk De Ste C
pecificfatigu
ue and thi
ack mechan
ctice: Key r
that the f
oning progr
muscular c
d is underta
m-up when
r conditionin
nee extensio
at improvin
ncludes fas
programmes
oal as well a
s both age
be recomm
in younger
r feed-forwa
mental move
during pube
r qualities
Croix – Princ
ueondynam
s may be
nisms (EMD
recommend
following n
rammes for
conditioning
aken in the
fatigue is n
ng includes
on (in partic
ng landing p
st velocity m
s are espec
as improvin
e group an
mended, imp
age group
ard mechan
ement skill d
rty is enha
cipal Resea
mickneestab
e a compe
D) when fatig
dations
eed to be
r elite femal
g programm
e middle or
not present
s and focus
cular the fir
performance
movements
cially effect
ng torque pr
d maturatio
plemented
ps focuses
nisms in re
developmen
nced and in
archer)
bilityinfem
ensatory m
gue is prese
considered
e youth foo
me is focus
end of tra
ses on the
rst 15° of k
e
s as well as
tive in enha
roduction as
onal stage
and develo
on the de
esponse to
nt
ndividualise
maleyouthpl
Dr Mark D
mechanism
ent.
d in the fu
otballers:
sed on be
aining sessi
portion of
knee flexion
s more con
ancing neur
s a seconda
specific. S
ped as earl
evelopment
fatigue. Th
ed to focus
layers
De Ste Cro
for the re
urther deve
ing related
ons rather
the movem
) – this sho
ntrolled slow
romuscular
ary goal
Specific neu
y as possib
and enha
is training
on both m
ix 5
eduction in
elopment o
d to fatigue
than solely
ment that is
ould include
wer velocity
functioning
uromuscula
ble
ncement o
should also
uscular and
n
of
e
y
s
e
y
g
r
of
o
d
Theeffecto
1.1 Ack
Firstly I
work on
comple
assistan
paediat
thank M
assistan
Glouces
I would
coache
to all o
willingn
young f
Finally
knowled
offootballsp
knowledge
would like
n this projec
te this proj
nce in stud
tric muscle
Miss Jasmi
nce in data
stershire fo
like to tha
s of each a
of the girls
ess to enga
female play
I would lik
dge of the e
pecificfatigu
ments
to thank Mi
ct as withou
ject. I woul
dy design a
physiology
ine Campb
a collection
r their supp
nk Bristol L
age group fo
who volun
age in the
ers would n
e to thank
effect footba
ueondynam
iss Abigail P
ut her hard
d also like
and reviewi
y has been
bell, Miss F
n. I would
port during t
Ladies Acad
or encourag
nteered to t
research pr
not have be
UEFA for
all specific f
mickneestab
Priestley (M
work and d
to thank D
ing the fina
invaluable
Felicity Doy
also like to
he project.
demy for al
ging the gir
take part in
rocess our
en enhance
funding thi
fatigue has
bilityinfem
MSc by Rese
dedication it
Dr Rhodri L
al report. T
throughou
yle and Mis
o thank all
lowing us a
ls during te
n the study
understand
ed.
is project a
on dynamic
maleyouthpl
Dr Mark D
earch stude
t would not
Lloyd and D
Their knowle
t the projec
ss Elizabet
of the sta
access to th
esting. Impo
y. Without
ding of the r
and contribu
c knee stab
layers
De Ste Cro
ent) who wa
have been
Dr Jon Oliv
edge and e
ct. I would
h Williamso
aff at the U
heir players
ortantly a big
their comm
relative risk
uting to ou
ility in youn
ix 6
as funded to
n possible to
ver for thei
expertise in
also like to
on for thei
University o
s and to the
g thank you
mitment and
k of injury in
ur increased
ng girls.
o
o
r
n
o
r
of
e
u
d
n
d
Theeffecto
2.1 Inciden
There is a
injury. Thes
al., 2009).
players and
factors inclu
female soc
but importa
et al., 2002
youth fema
range of iss
all of these
incidence in
Definition a
injury rates
In possibly
et al. (200
selected by
this popula
compared
time in both
when playe
prevalent t
performanc
sex differen
reported hi
during both
However, t
to severe
injuries/100
(Sweden) (
offootballsp
Re
nce of injur
growing e
se data are
Neverthele
d in particul
uding growt
ccer players
antly the ma
2; Walden e
ale professio
sues surrou
e in detail. I
n female yo
and severity
.
the most co
9) reported
y UEFA. Ba
ation is 8 inj
with trainin
h the first a
ers are mor
towards the
ce is lowere
nce in injur
gher injury
h training (
here was n
injury. Earl
00h compar
(Engstrom e
pecificfatigu
evie
ry in footba
pidemiolog
e still predo
ess there is
lar female y
th and matu
s from a wid
ajority of da
et al., 2010
onal players
unding injury
t should be
outh footbal
y of injury;
omprehens
d data for 7
ased on ho
juries per 1
ng. Importan
nd second
re fatigued t
e end of a
ed (Bangsbo
ry incidence
incidence
(4.7 Vs 3.8
o sex differ
ier data su
red with 5 i
et al., 1991
ueondynam
ew o
all ical eviden
ominantly ba
s growing r
youth playe
uration. The
de range of
ata is from
0). There is
s (Schiff et
y incidence
e noted how
lers may be
b) method
sive injury in
7 consecuti
ours of athle
000h of ex
ntly, the fin
halves of m
towards the
a game an
o et al., 200
e rate in fo
rates for S
8 injuries/1
rence when
uggested th
injuries per
). The 7 ye
mickneestab
of li
ce base m
ased on ma
recognition
er who may
ere are a nu
f age group
adult profes
limited info
al., 2010; R
data and it
wever that l
e attributed
of assessm
ncidence stu
ive season
ete exposur
xposure and
ndings dem
matches. Th
e end of ma
nd the am
07). A num
ootball with
Swedish pro
000h) and
n incidence
hat females
r 1000h) in
ear study by
bilityinfem
iter
apping out
ales and fro
for the nee
be at grea
umber of inj
s, using a r
ssional play
ormation re
Rumpf and
t is beyond
limitations i
to one or m
ment and re
udy in male
s from the
re the data
d was signif
monstrate an
his would su
atch play. S
mount of hi
ber of stud
conflicting
ofessional m
match pla
data were
s have a h
professiona
y de Loes e
maleyouthpl
Dr Mark D
atu
the incide
om adult po
ed to map
ater risk of i
ury inciden
range of sa
yers (Haggl
egarding the
Cronin, 201
the extent o
n our curre
more of the
eporting of
e profession
first team
suggests t
ficantly gre
n increasing
uggest that
Studies have
gh intensit
ies have at
findings. H
male compa
ay (28.1 Vs
expressed
higher injury
al players f
et al (2000)
layers
De Ste Cro
re
nce of foot
opulations (
injury rate
njury due to
ce studies a
ample sizes
lund et al.,
e incidence
12). There
of this repor
ent knowled
following lim
injuries; c)
nal footballe
squads of
that injury i
ater during
g injury ten
injury rates
e shown th
ty work an
tempted to
Hagglund e
ared to fem
s 16.1 inju
in relation t
y rate than
from the sa
also report
ix 7
tball related
(Ekstrand e
s in female
o numerous
available on
(n = 45 - )
2009; Lilley
e of injury in
are a whole
rt to explore
dge of injury
mitations: a
reporting o
ers Ekstrand
23 squads
ncidence in
match play
ndency with
s are highe
at fatigue is
nd technica
explore the
et al. (2009
male players
ries/1000h)
to moderate
n males (12
ame country
ted a highe
d
et
e
s
n
),
y
n
e
e
y
)
of
d
s
n
y
h
r
s
al
e
)
s
).
e
2
y
r
Theeffecto
incidence r
(2002) con
mean incid
incidence fe
that expos
Despite the
of major inj
There are f
youth playe
undertook
reported th
during train
compared w
appropriate
rate than st
of injury is
than boys.
injuries/100
olds. These
related inju
surprising t
and injury
would coinc
that occur d
to maturatio
suggestions
initial findin
literature, e
(Walden et
injury risk c
play. Impor
males (19 V
There appe
female you
different inj
offootballsp
rate in fema
ducted a 5
dence rate
ell when ex
ure to mor
e recorded
uries.
far fewer st
ers, and ev
a review of
at injury in
ning; b) ‘lo
with ‘high s
e warm up a
trikers and g
greater in la
. They sug
00h in 9-12
e data wou
ry during ch
that the aut
risk. Even
cide with p
during this t
onal status
s are base
ngs. Some
exploring th
t al., 2011)
compared w
rtantly they
V 27y).
ears to be o
uth footballe
jury surveil
pecificfatigu
ales compar
year retros
of 12 inju
xposure alm
re training
reduction in
tudies on w
en less foc
f literature e
the youth p
ow skill’ and
skill’/experie
are related
goalkeeper
ate compar
ggest that
2y-olds, 65.
uld suggest
hildhood an
hors have n
given that
rogression
time period
as well as
ed on limite
of these su
he epidemio
. Walden e
with their ma
reported th
only 2 studi
ers (Schiff e
lance meth
ueondynam
red with ma
spective inj
uries per 1
most doubled
and match
n injury inci
which to jud
cusing on yo
examining
players was
d less exp
enced playe
to fewer inj
s; e) that m
red with ear
total injur
8 injuries/1
t that there
nd that child
not conclud
elite youth
through pu
. More stud
chronologi
ed empirica
uggestions
ology of AC
et al. (2011
ale counterp
hat females
ies that hav
et al., 2010
hods to exa
mickneestab
ales (9.5 Vs
ury survey
000h. Inter
d (to as low
h play help
dence there
dge the inju
outh female
injury incide
s: a) more
erienced p
ers; c) a gre
uries; d) De
maturity statu
rly maturers
ry incidenc
000h in 13
is a signif
dren aged 1
ded that the
h performer
berty and a
dies are nee
cal age giv
l data and
are further
CL injury in
) conclude
parts and th
s tend to su
ve focused
0; Lislevand
amine injury
bilityinfem
7.5 injuries
of Australia
restingly th
w as 5 injuri
s to develo
e was a co
ury incidenc
e players. R
ence data i
likely to occ
players are
eater trainin
efenders an
us is not rel
s; f) that girl
e in relati
3-15y-olds a
ficant age e
3-15y are m
re may be a
rs tend to b
all of the as
eded that fo
ven these d
more stud
r supported
n football fr
that femal
hat injury is
stain their A
exclusively
d et al., 20
y rates in 1
maleyouthpl
Dr Mark D
s/1000h) Mo
an female p
hey also re
es/1000h) a
op strategie
ncomitant i
ce of expos
Rumpf and
in 6-18 yea
cur during m
more likel
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ore recently
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at a young
cidence rate
et al. (201
girls. They
ix 8
y Lilley et al
d reported a
t the injury
vely sugges
ent injuries
the numbe
ete hours in
12) recently
allers. They
rather than
in an injury
training and
higher injury
the severity
er injury risk
age is 8.0
h in 16-18y
e of footbal
s finding it is
ational stage
s age range
tal changes
e in relation
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pport these
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2007). In th
showed tha
adolescents
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colleagues
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company. D
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ge group, fr
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ratio (93.3
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btained ins
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ely to occur
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ix 9
h play rathe
a during a 2
vand et al.
players to
age group
ancial costs
n adulthood
as well as
rshall et al.
008), results
low among
significantly
of suffering
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itation, then
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ncidence of
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uency of AC
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to withstan
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e taken into
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particularly
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confounded
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outlined the
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relative risk
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eral popula
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ly greater a
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ation is alm
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c and intrins
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terns of inju
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ation has g
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athletes (Kn
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ar that injur
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ury within a
t risk facto
male and
erstand the
tions where
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factors that
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utukian, 199
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nly due to t
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n and Hewe
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ong-term d
th the incre
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tudies have
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es for ident
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ernal risk f
phy et al.,
ry patterns
ly, no sport
n increasing
ors associa
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mechanis
e issue rela
or Sandra S
at remains
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their greate
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suffering p
comparison
uries place
ett, 2009). T
osts, and t
disability, si
eased risk o
substantial
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tifying athle
risk factors
s outside th
factors may
2010b). Fo
can be spo
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ted with A
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poorly und
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unt for mor
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The cost of
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of re-injury (
discussion
gly examin
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s for sport
e body or f
y be assoc
or both sex
ort-specific,
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ange of spo
ACL injury
s well as s
ed in ACL
owth and m
8) suggests
derstood. Nu
ative risk of
of growth a
layers
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re injuries th
e to athletic
rt” (p.11).
osteoarthrit
etes who do
on at a gre
this injury i
s can be c
and the p
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and invest
ned sex diff
e risk facto
and develo
injury are
factors insid
ciated with
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and based
rchers are
orts (Knowle
are multifa
port specifi
injury risk
maturation a
s that ACL
umerous re
injury in fe
and matura
ix 11
han females
c tasks tha
tis (OA) is
o not suffe
eater risk o
is estimated
considerably
ossibility o
al., 2009).
tigation into
ferences o
ors for ACL
oping injury
traditionally
de the body
ACL injury
is the mos
d on varying
increasingly
es, 2010). I
actorial and
c (Hewitt e
k is furthe
are relevan
injury in the
eviews have
emale youth
ation on this
s
at
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r
of
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susceptible
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fat content
explanation
associated
knee are o
the female
kinematics
abductors a
the angle d
patella and
an importa
patellofemo
angle but
dimensiona
in standing
participant
techniques
analysis is
plane used
and matur
adolescenc
offootballsp
the intrins
in female a
2000). Beca
e to injury th
om the wide
t (Bartlett,
n for sex d
with an exc
often couple
population
and EMG a
and greater
described b
a line draw
ant measu
oral joint. H
available m
al kinematic
and supine
positioning
and positio
the most r
. To date th
ation, whic
ce.
pecificfatigu
sic or inter
and male k
ause of a
han men. T
er female pe
1999). The
ifference in
cessive valg
ed with dec
(Brophy e
analysis tha
r hip adduct
y a line dra
wn from the
urement as
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methods ra
cs. A recent
e positions
. Therefore
oning shoul
reliable tec
here are no
ch may be
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rnal risk fa
knee injury
anatomical
he reasons
elvis and gr
e Quadrice
n ACL injur
gus loading
reased kne
et al., 2010a
at during ki
tion of supp
awn from th
tibial tuberc
s it intend
here are cu
ange from
t study by S
has demon
compariso
d be avoide
hnique but
studies tha
e a contrib
mickneestab
actors, ther
rates: anato
differences
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reater genu
eps angle (
ry rates, wi
g of the kne
ee and hip f
a). Brophy
cking action
porting limb
he anterior s
cle through
s to pred
urrently no
using simp
Stensdotter
nstrated sig
on of Q ang
ed. Stensdo
that Q ang
at have exa
uting facto
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re are gen
omical, neu
s, women
his include
valgum, le
(Q-angle) h
th the ratio
ee (Hewett e
flexion, and
et al. (2010
ns females
bs than male
superior ilia
the centre
ict the qu
standardise
ple goniome
r et al. (200
gnificant diff
les betwee
otter et al (2
gle can var
amined chan
or to the in
maleyouthpl
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erally 3 th
uromuscular
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ss muscle m
has been s
onale that h
et al., 2009
d pronation
0c) have a
exhibit low
es. The Q a
ac spine thr
of the pate
uadriceps f
ed methods
eters, to ra
09) using fo
ferences be
n studies th
2009) conc
ry dependin
nges in the
ncreased in
layers
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heories to
r and horm
thought to
d hip- and k
mass and g
studied as
high Q-ang
). Valgus a
at the subt
lso reported
wer activatio
angle is det
rough the c
lla (see figu
forces acti
s for asses
adiography
our different
etween tech
hat have us
clude that 3
ng upon the
Q angle du
ncidence ra
ix 12
explain the
onal factors
o be more
nee-loading
greater body
a possible
les may be
ngles at the
talar joint in
d, using 3D
on of the hip
termined as
centre of the
ure 2.2). It is
ng on the
ssing the Q
and three
t techniques
hniques and
sed differen
D kinematic
e projection
uring growth
ates during
e
s
e
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y
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e
e
n
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p
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e
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e
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s
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t
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n
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g
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Figure 2.2:
Evidence a
neuromusc
neuromusc
component
hence not
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changes in
understand
chronologic
According
injury, or
neuromusc
incidence o
could have
2005). Pre-
relative inju
renders the
because it
offootballsp
Sex differe
also sugges
cular system
cular system
ts are usef
offering an
inking chan
n the relat
ding may h
cal age or m
to Bartlett
poor musc
cular theory
of knee inju
e a significa
-participatio
ury incidenc
e female ath
can be im
pecificfatigu
ences and d
sts that fem
m. Oestrog
m (Hewett,
ful in terms
ny opportun
ges in horm
tive risk in
help us to
maturation s
(1999), spo
cle strength
, training an
ury in femal
ant effect o
on training o
ce in female
hletes more
proved by
ueondynam
determinatio
male sex h
gen is kno
2000). Unf
s of unders
nity for inter
monal status
n female y
identify b
stage.
orts particip
h are parti
nd strength
e athletes,
on the num
of the muscu
es (Hewett,
e susceptibl
preventativ
mickneestab
on of the Q a
hormones m
own to bot
fortunately,
standing the
rvention in
s during gro
outh footba
best practic
pants with e
icularly vul
differences
but lowerin
mber of kne
ulature whic
, 2000). Th
e to ACL in
e training (
bilityinfem
angle (The
may have
h directly
even thou
e phenome
this area (
owth and m
allers durin
ce in term
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nerable to
s may accou
ng these fig
ee injuries i
ch stabilises
erefore, the
njuries is a
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maleyouthpl
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significant
and indirec
gh the ana
enon; they
(Hewett, 20
aturation m
ng growth
s of pre-h
igament lax
ligament
unt for only
gures by ev
n female a
s the knee j
e neuromus
more attrac
2010). Un
layers
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itect, 2011)
effects on
ctly affect
atomical an
cannot be
000, Yoo et
may help us
and matur
habilitation
xity, previo
injury. Reg
a portion o
ven a small
athletes (He
joint may d
scular back
ctive topic fo
derstanding
ix 13
the female
the female
d hormona
modulated
t al., 2010)
to elucidate
ration. This
at a given
us ligamen
garding the
of the highe
percentage
ewett et al.
ecrease the
kground tha
or research
g these risk
e
e
al
,
).
e
s
n
t
e
r
e
,
e
at
,
k
Theeffecto
factors is im
injury who m
2.3: Injury
Mechanica
Garrett, 20
contact. On
environmen
remaining
2007). A n
moments a
mechanism
step/stop d
inadequate
from a unan
The injury a
on one leg
cutting ma
mechanism
basketball
ACL injurie
while the fo
Given the in
to be an u
(Knowles,
multifactoria
neutralise t
2.4: The a
It is beyon
understand
and matura
and the pro
position, to
offootballsp
mportant to
may especi
mechanism
lly, ACL inj
007). There
nly 30% of c
nt this could
70% of all
non-contact
at the knee
m of a sports
deceleration
e knee and
nticipated c
appears to
g and rapid
noeuvre (H
ms of ACL in
and cutting
es usually o
oot is in a cl
ndividualise
rgent need
2010). Eve
al (i.e. hor
the effects o
anatomy of
nd the scop
ding its artic
ation. The k
oximal tibia
o flexion wh
pecificfatigu
develop in
ially benefit
ms
ury occurs
are two ty
cases are c
d be an op
reported A
t ACL injur
e that app
s related no
n, cutting m
hip flexion
change of di
predominan
change of
Hughes and
njury, thoug
g injuries ma
occur during
osed-chain
ed timing of
to identify
en though
rmones, an
of a number
f the knee
pe of this r
culation is i
knee joint is
(Perrin, 19
ich brings t
ueondynam
tervention s
from target
when an e
ypes of mec
caused by s
posing play
ACL injuries
ry occurs w
ly excessiv
on-contact A
movements,
(at or nea
irection of p
ntly occur in
f direction i
d Watkins,
gh they vary
ay occur m
g a deceler
position.
f growth and
modifiable
the mecha
natomy, len
r of these fa
report to de
important, g
a modified
993). The k
the foot clo
mickneestab
strategies a
ted interven
excessive te
chanisms th
some kind o
yer, a goalp
s are non-
when a per
ve loading
ACL injury in
sudden ch
ar full exten
play) (Silver
n two partic
nitiated on
2006). Bo
y by sport (
ore often in
ration mano
d maturation
e risk factor
anisms ass
ngth of spo
actors (Hew
escribe full
given the g
hinge joint
nee travels
ser to the t
bilityinfem
and to ident
ntions (Brop
ension forc
hat lead to
of contact fr
post or anot
contact in
rson thems
on the AC
n football co
hange of dir
nsion), or a
rs and Mand
cular types o
one leg, s
oth landing
i.e., landing
n football) (
oeuvre com
n of female
rs and bette
sociated wit
orts particip
wett, 2000).
y the anato
growth in lo
formed by
principally
thigh (Kings
maleyouthpl
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tify those at
phy et al., 2
ce is applied
an ACL in
rom an outs
ther object
origin (Silv
selves gene
CL (Yu and
ontexts com
rection, lan
lapse of c
delbaum, 20
of movemen
such as a s
and pivot
g injuries m
(Hewett et a
mbined with
youth footb
er understa
th female
pation), tra
omy of the
ong bone du
the articula
from exten
ston, 1996)
layers
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t increased
2010b).
d on the AC
njury: contac
side force; i
on the field
vers and M
erates larg
d Garrett,
mmonly invo
ding from a
concentratio
007).
nt: landing f
side-cutting
ing are ve
ay occur m
al., 2008). N
a change
ballers, ther
and injury m
knee injuri
ining may
e knee joint
uring biolog
ation of the
nsion in the
. It is a mo
ix 14
risk of ACL
CL (Yu and
ct and non
n a sporting
d/court. The
andelbaum
e forces o
2007). The
olves a one
a jump with
on (resulting
from a jump
and cross
ry common
more often in
Non-contac
of direction
re continues
mechanisms
es may be
be able to
t. However
gical growth
distal femu
anatomica
dified hinge
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d
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e
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r
e
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n
n
ct
n
s
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r,
h
r
al
e
j
j
Theeffecto
joint in the
together wi
joint in the
contributing
contraction
intermedius
kicking (Le
consist of
contributes
The ACL is
knee in a
(forward) w
stability to t
the ACL is
and Garbut
injury to the
ACL injury
mechanism
contractile
and four ex
ligament (
neuromusc
evidence s
the dynami
2006).
2.5: Muscle
Functional
forward an
muscle act
Lephart 20
neuromusc
and protec
muscular st
offootballsp
sense that
th inward ro
human bod
g to both
of the qua
s and latera
ehance et a
biceps fem
hugely to s
s one of the
movement
with respect
the joint (G
stressed in
tt, 2002). Th
ese ligamen
occurs as
ms of the k
structures o
xtracapsula
PCL) (Hug
cular quadr
uggests tha
ic stabilising
e, Tendon
stability is
d feedback
tions occurr
002). Conv
cular system
ction agains
tiffness dur
pecificfatigu
extension
otation of th
dy (Grimsha
its stability
adriceps fem
alis muscles
al., 2009).
moris, semi
stride powe
main supp
t known as
t to the fem
rimshaw et
n the first 45
he ligament
nts of the kn
a result of
nee (Hughe
of the knee
r ligaments
ghes and W
riceps and
at the great
g structures
and Leg st
provided by
k systems (
ring before
versely, fe
m after sens
st injury rel
ring function
ueondynam
is accompa
he tibia (Pe
aw et al., 20
y and func
moris musc
s (Perrin, 19
Knee flexio
itendinosus
r (Lehance
orting ligam
s anterior
mur. In add
t al., 2006,
5º of knee f
ts, together
nee can ser
f a lack of
es and Wa
. These stru
s: lateral liga
Watkins, 2
hamstring
ter incidenc
s rather tha
tiffness
y static and
Wikstrom e
the sensor
eedback is
sory detectio
ied on ade
nal tasks. Th
mickneestab
anied by ou
rrin, 1993).
006) and no
ction. Knee
cles, which
993); and ha
on is produ
s and semi
et al., 2009
ments of the
tibial trans
ition, the lig
Hughes and
flexion then
with the mu
riously affec
stability pro
atkins, 2006
uctures are
ament, med
2006). Dyn
actions at
ce of ACL i
an the passi
d dynamic r
et al. 2006)
ry detection
the stim
on. Rieman
equate feed
herefore, it
bilityinfem
tward rotati
The knee
o fewer than
e extensio
consist of t
as a major
ced by the
imembrano
9).
e knee and
lation, whe
gament als
d Watkins,
n relaxes as
uscles, prov
ct a player’s
ovided by t
6). Passive
the joint ca
dial ligamen
amic stabi
t the knee
njury in fem
ive stability
restraints w
). Feed-forw
n of a disru
ulation of
n and Leph
dback and f
is useful fo
maleyouthpl
Dr Mark D
ion of the ti
is also the
n 12 muscle
n is accom
the rectus f
role in sprin
e hamstring
sus muscle
it is respons
ere the tibi
o provides
2006). Dur
s the knee f
vide joint su
s career (Gr
the dynamic
stability is
apsule, late
nt, ACL and
lity is rela
e (Ahmad e
males is du
structures
within the jo
ward system
uption (Bon
a correct
hart (2002) f
feed-forwar
r club phys
layers
De Ste Cro
bia, and fle
most comp
es cross the
mplished p
femoris, vas
nting, jumpi
g muscle gr
es (Perrin,
sible for sup
a is moved
a degree o
ing everyda
flexes furthe
upport and s
rimshaw et a
c and pass
provided b
eral and med
d the poster
ated to mu
et al., 200
e to sex dif
(Hughes a
oint and reli
ms include
ci 1999; Ri
tive respon
found that j
rd systems
iotherapists
ix 15
exion occurs
lex synovia
e knee joint
primarily by
sti medialis
ng and ball
roup, which
1993) and
pporting the
d anteriorly
of rotationa
ay activities
er (Coombs
stability and
al., 2006).
sive stability
by the non
dial menisc
rior cruciate
uscular and
06). Curren
fferences in
nd Watkins
es on feed
anticipatory
iemann and
nse of the
oint stability
to improve
s and sports
s
al
t,
y
s,
-
h
d
e
y
al
s,
s
d
y
-
ci
e
d
t
n
s,
-
y
d
e
y
e
s
Theeffecto
therapists i
of joint stif
modelling t
the importa
During grou
system is c
However it
landing ca
crucial in m
of antagoni
it can doub
2007). Data
ACL and s
comparativ
similar patt
kinematic
ligament lo
biomechan
tasks. It is
on ACL loa
possible thr
and Hawkin
The ability
angle) refe
tendon stiff
actions. Ac
1. Increase
because th
stretched b
increase te
the ability o
passive str
2006). If th
both the h
(Holcomb e
(Hughes a
offootballsp
nvolved in i
ffness induc
to understan
ance and ef
und contact
critical. The
t is well re
n stress th
maintaining j
istic muscle
ble or even
a from adult
subsequent
ve data on c
tern of liga
motor cont
ads compa
ical modell
beyond the
ading but a
rough chan
ns 2010).
of the musc
ers to musc
fness as we
ctivation of a
es in musc
here are mo
because the
ndon stiffne
of the musc
ructures of
he strength
hamstrings
et al., 2007
and Watkins
pecificfatigu
injury preve
ced by the
nd knee liga
ffectiveness
t, when pot
e ACL can
cognized th
he passive
joint stabilit
es. In vivo e
n triple joint
ts indicate t
tly increase
children. Ho
ament loadi
trol during
ared to adul
ing to explo
e scope of t
dult studies
ges in knee
cles to resis
cle stiffness
ell as the ela
agonist mus
cle activatio
ore cross br
e tendon-e
ess simply b
cles of the
the knee, s
of the qua
and anteri
). Therefore
s, 2006) a
ueondynam
ention or reh
surroundin
ament load
s of the mu
tential to inj
provide up
hat the inte
ligament s
y predomin
exploration o
t stiffness a
that sideste
e the relat
owever, it is
ing to that
childhood
ts. Howeve
ore ligamen
this Chapte
s seem to d
e flexion ang
st movemen
s. The stiffn
astic prope
scles play a
on increase
ridges stron
longation re
because ten
knee to pr
such as the
driceps sig
ior cruciate
e, muscle s
as co-activa
mickneestab
habilitation
ng muscles
ing and sub
uscles in pr
jure the AC
to 86 % o
ernal and e
structures b
antly by inc
of hamstrin
and decreas
epping and c
tive risk of
s likely that
of adults.
the growin
er, this sugg
nt loading d
er to explore
demonstrat
gle, shank a
nt within the
ness of the
rties of joint
a substantia
e muscle s
ngly bound;
elationship
ndons are s
revent tibiof
e ACL, will
nificantly e
e ligament
stiffness is
ation increa
bilityinfem
to be able t
s. The use
bsequent kn
roviding this
CL exists, th
of the resist
external for
beyond the
creasing join
g or quadri
ses joint la
cutting mov
f injury (Llo
t such move
It may be
ng child ma
gestion requ
during childh
e the effect
e that redu
angle and f
e tibiofemor
whole limb
t structures
al role in se
specific stif
2. Tendons
is non-line
stretched (B
femoral she
l be put un
xceeds the
(ACL) bec
an importa
ases as lim
maleyouthpl
Dr Mark D
to accuratel
of neurom
nee joint sta
s stabilizatio
he response
tance to an
rces incurre
eir capacity
nt stiffness
ceps co-co
axity by up
vements are
oyd et al.
ements in c
that due t
ay be pred
uires furthe
hood and d
t of altering
uction in pe
foot location
ral joint (ma
b is affecte
and stiffne
etting limb s
ffness (its
s increase
ear, so incre
Blazevich et
ear movem
nder strain
e strength o
come more
nt factor in
mb stiffnes
layers
De Ste Cro
ly measure
uscular bio
ability has e
on (Lloyd e
e of the neu
nterior tibial
ed at the k
. Muscular
through co
ntraction su
to 50% (Ru
e most likely
2005). Th
children dem
to the deve
disposed to
r investigat
during vario
movement
ak tibial sh
n during lan
aintain a pa
d by both
ess arising f
stiffness for
resistance
in stiffness
eases in m
t al. 2011).
ent, the les
(Hughes an
of the hams
e susceptib
preventing
s increase
ix 16
the amoun
omechanica
emphasized
et al. 2005)
uromuscula
translation
knee during
forces are
-contraction
uggests tha
ussell et al
y to load the
ere are no
monstrate a
elopment o
o additiona
ion, utilizing
ous dynamic
t mechanics
ear force is
ding (Myers
articular join
muscle and
from muscle
r 2 reasons
to stretch
as they are
muscle force
The greate
ss likely the
nd Watkins
strings, then
le to injury
g ACL injury
s. This co
t
al
d
).
r
.
g
e
n
at
l.
e
o
a
of
al
g
c
s
s
s
t
d
e
s:
)
e
e
r
e
s,
n
y
y
-
Theeffecto
activation h
(Horita et
accepted a
correlations
and stride c
al., 1998; r
stiffness ar
as research
and its rela
been assoc
1998), but
explosive a
Interestingl
predominan
somewhat
forces, as w
Greater leg
times at fa
cohort of sp
highlighting
also been
related to
important p
relationship
velocities)
several bio
reflex cont
contact and
these intera
perform SS
In terms o
commonly,
highlight th
stiffness is
component
offootballsp
has been s
al. 2002).
as a recogn
s have been
cadence (F
r > 0.8), all
re becoming
hers attemp
ationship to
ciated with
it has also
activities (Sh
y, whilst t
ntly on the
surprising
well as to st
g stiffness w
aster runnin
printers (5.8
g the requir
highlighted
both 30 m
performanc
p between
and increa
omechanica
tribution, a
d stiffness
acting com
SC functions
of human p
the entire
e stiffness
typically v
ts: muscle,
pecificfatigu
hown to be
Within the
ised measu
n reported b
Farley and G
l of which a
g more com
pt to gain a
performanc
increased
o been con
horten, 198
there is a
role of leg
given that
tore and reu
will enable a
g velocities
86 N·m-1) w
rement of e
in the pae
metre and
e paramete
shorter gr
ased vertica
l paramete
ntagonist m
properties
ponents tha
s.
performanc
body acting
of a joint or
viewed as t
joint, tend
ueondynam
e important
e fields of
ure of lower
between hig
Gonzalez, 1
are importa
mmonplace
a better und
ce and inju
metabolic
nsidered as
87; Walshe
growing
stiffness in
high leg st
utilise, elast
a faster rebo
s. Harrison
when compa
effective reb
ediatric liter
100 metre
ers in footb
round cont
al ground r
rs that cont
muscle co-
of the mus
at enables
e, stiffness
g as a mas
r tendon (K
the combin
on, ligame
mickneestab
for limb st
sports phy
r limb SSC
gher levels
1996; r > 0.
ant for footb
within the f
derstanding
ry preventio
economy w
s a critical
et al., 1996
interest in
performan
tiffness is r
tic energy (K
ound when
et al. (200
ared to a gr
bounding p
rature, whe
sprint time
ball. Additio
act times
reaction for
trol leg stiff
-activation,
scle and jo
researcher
s can be v
ss and spri
Kubo et al.,
nation of in
nt, cartilage
bilityinfem
tiffness prio
ysiology an
function (K
of leg stiffn
.8), and eco
ball perform
fields of spo
of the com
on. Not only
whilst runnin
component
6) and sprin
determinin
ce rather th
required in
Kuitunen et
sprinting, re
04) reported
roup of end
roperties fo
ere drop jum
es (Hennes
onal resear
(which are
rces. Padua
fness includ
lower extr
oint complex
rs to determ
viewed with
ng. Whilst
2007; Kubo
dependent
e and bone
maleyouthpl
Dr Mark D
or to jump l
d biomech
Kuitunen et
ess and gre
onomy of ru
mance. Stud
orts biomec
mplexities of
y have high
ng sub-max
t of maxim
nt performa
ng leg stif
han injury p
order to a
t al., 2002).
eflected by
d higher leg
urance run
or high velo
mp perform
ssy and K
rch by Kra
e associate
a et al. (20
ding; muscl
remity kine
x. It is the
mine the ab
hin an isol
recent stud
o et al., 200
values of
e (Latash a
layers
De Ste Cro
landings fro
anics, leg
al., 2002).
eater runnin
unning gait
dies of lowe
chanics and
f lower limb
h levels of l
ximally (Da
al performa
nce (Bret e
ffness the
prevention.
bsorb grou
shorter gro
g stiffness
ners (3.38
ocity runnin
mance was
Kilty, 2001),
m (2000) d
ed with fas
006, 2005)
e activation
ematics dur
total meas
bility of an i
lated musc
dies have a
06; Hortia e
a number
and Zatsior
ix 17
om a heigh
stiffness is
Established
ng velocities
(Dalleau e
er extremity
d physiology
b mechanics
leg stiffness
alleau et al.
ance during
et al., 2002)
focus has
This seems
und reaction
ound contac
values in a
N·m-1), thus
g. This has
significantly
which are
detailed the
ster running
highlighted
n and force
ring ground
surement o
ndividual to
cle or more
attempted to
et al., 2002)
of differen
rsky, 1993)
t
s
d
s
et
y
y
s
s
,
g
).
s
s
n
ct
a
s
s
y
e
e
g
d
e,
d
of
o
e
o
),
t
).
j
Theeffecto
Lower limb
stiffness [kv
calculate th
exert both
considered
Blackburn
properties,
have less h
length imp
difference i
During rep
rebounding
spring-mas
the mecha
linear sprin
of gravity
locomotion
The signific
highlighted
stiffness an
and an incr
joint prior to
and to our
Additionally
is present a
by fatigue t
ground con
There are a
range of fa
2006; Girar
fatigue, som
show no ch
difficult to a
the nature o
offootballsp
stiffness h
vert]), runni
he torsional
a vertical a
in unison.
et al. (20
as a contri
hamstring s
osed via jo
n hamstring
peated SSC
g against th
ss model (C
nics of hum
ng, and the
(Farley an
is the relat
cance of leg
(Kubo et a
nd electrom
reased pre-
o ground co
knowledge
y it is essen
as this may
then this m
ntact (from e
a few studie
atigue proto
rd et al. 201
me show a
hange in st
attribute the
of the fatigu
pecificfatigu
as previous
ing and jum
l correlate a
and horizon
Most studie
09a,b) has
ibuting facto
stiffness co
oint perturb
g stiffness is
C activity,
he ground.
Cavagna, 19
man locom
total mass
nd Gonzale
ive stiffness
g stiffness p
l., 2007). F
yographic a
-activation l
ontact. This
e there are
ntial to know
increase th
may mean th
either a jum
es that hav
ocols, and t
11; Morin et
decrease i
tiffness (Gir
ese differing
ue protocol,
ueondynam
sly been me
mping protoc
at an isolat
tal force co
es have foc
s explored
or in wome
mpared to
bation from
s evident du
the human
Consequen
975). The m
motion, whe
of the perf
ez, 1996).
s of the seri
parameters
ollowing res
activity on ju
evel of mus
s feed-forwa
no studies
w if these fe
he relative r
hat neurom
mp, during a
ve explored
the results
t al. 2006).
n stiffness
rard et al. 2
g findings to
, and the m
mickneestab
easured via
cols (leg sti
ted joint (jo
omponent a
cused on wh
sex differe
en’s greater
males and
a structur
uring childh
n body is
ntly researc
model is de
reby the m
former deno
Crucial to
ies elastic c
s in augmen
search ana
ump perform
scle were b
ard mechan
s exploring
eed-forward
risk of injury
uscular fee
pivoting mo
the effects
are conflic
Some stud
(Dutto and
2011; Hunte
o mechanist
ethods use
bilityinfem
a vertical ju
iffness [kleg
int stiffness
and therefor
hole limb st
ence in ha
r ACL injury
a reduced
ral perspec
hood remain
essentially
chers deve
eemed the
musculoskel
otes a singl
effective
component
nting dynam
lysing the in
mance it wa
both influent
ism is poor
this mecha
mechanism
y. If feed-fo
ed-forward a
ovement etc
s of fatigue
cting (Dutto
ies have sh
Smith 2002
er and Smi
tic structure
d to calcula
maleyouthpl
Dr Mark D
mping and
g]), or isolat
s [kjoint]). W
re both fact
tiffness but
amstring st
y risk. They
capacity fo
ctive. Wheth
ns to be inve
acting as
eloped what
simplest m
letal system
e point, act
leg stiffnes
(SEC) (Hor
mic moveme
nfluences o
as purporte
tial mechan
rly understo
anism in yo
ms are com
rward mech
ability to sta
c) is reduce
on leg stiffn
o and Smith
hown an inc
2; Comyns
ith, 2007; M
es but they
ate leg stiffn
layers
De Ste Cro
hopping te
ted joint mo
When runnin
tors are req
a recent stu
tructural an
y reported t
or resisting
her this str
estigated.
a spring,
t is referre
eans of un
m symboliz
ting through
ss function
rita et al., 20
ents has re
of tendon sti
ed that tendo
nisms for sta
ood in the gr
uth female
promised w
hanisms are
abilise the j
ed.
ness in adu
h 2002; Co
crease in st
et al. 2006
Morin et al.
could be in
ness. Hunte
ix 18
ests (vertica
ovements to
ng, humans
quired to be
udy by Troy
nd materia
hat females
changes in
ructural sex
continually
d to as the
derstanding
es a single
h the centre
n in human
002).
cently been
iffness, join
on elasticity
abilising the
rowing child
footballers
when fatigue
e influenced
oint prior to
ults, using a
omyns et al
tiffness afte
6) and some
2006). It is
fluenced by
er and Smith
al
o
s
e
y
al
s
n
x
y
e
g
e
e
n
n
t
y
e
d
s.
e
d
o
a
.
r
e
s
y
h
Theeffecto
(2007) also
study som
stiffness. D
to the spee
consideratio
that have e
contact AC
an at risk g
of feed-forw
It is impor
normalisatio
issues of g
to determin
the influenc
children, o
revealed th
lower levels
how these v
The stiffnes
a muscle a
elastic com
mechanism
afferent fee
This feedba
rate of cha
stiffness ba
co-ordinatio
injury.
It is expect
leg stiffness
et al., 2002
against the
for paediatr
Previous lit
offootballsp
o state that
e participa
Data has als
ed of the m
on when co
explored the
CL injury is m
roup, it is s
ward mecha
rtant to no
on procedu
rowth and m
ne data rela
ce of leg le
wing to th
hat children
s of leg stif
variables di
ss of the mu
and rise in
mponent (SE
m that influ
edback (fee
ack include
nge, which
ased on age
on and sub
ted that inc
s in order to
2). Addition
e ground (M
ric leg stiffn
terature rev
pecificfatigu
the respons
ants increas
so shown th
movement (O
omparing d
e effects of
most likely t
omewhat s
anisms in th
ote that wh
ures are us
maturation a
ative to both
ength is oft
e non-linea
n use a sig
ffness than
iffer betwee
uscles and
force (Elec
EC) increas
ences mov
edback from
es afferent
are essent
e, maturatio
bsequent jo
reases in b
o maintain
ally, alterat
cMahon an
ness measu
vealing gro
ueondynam
se of fatigu
sed stiffnes
hat differenc
Oliver and
ata from di
fatigue on
to occur wh
urprising th
he neuromu
hen explori
sed. This is
are paramo
h body mass
en ignored
ar variation
gnificantly s
adults (Oli
en different
tendons ar
ctromechan
es EMD an
vement co-
m muscle an
information
tial for the d
on or influen
oint position
body mass
true spring-
tions in limb
nd Cheng, 1
ures, whethe
owth-related
mickneestab
e to leg stif
ss, some
ces in stiffn
Smith, 201
ifferent stud
leg stiffnes
hen fatigue
at there is n
scular cont
ing differen
s particularl
ount. Thus w
s and leg le
. This is a
n in leg len
slower hopp
iver and Sm
age groups
re also influe
nical delay
nd reduces r
-ordination
nd tendon b
n from musc
detection of
nced by fati
ning to eith
as a result
-mass mod
b length wi
1990). Howe
er the same
d increases
bilityinfem
ffness may
remained t
ness betwee
0) and ther
dies. To ou
ss in childre
is present,
no empirica
rol of knee
nces in leg
y importan
when norma
ength (McM
pertinent is
ngth develo
ping freque
mith, 2010)
s throughou
enced the d
[EMD]). A
rate of force
and injury
based recep
cle spindles
f limb posit
gue could a
er increase
of puberty
el behaviou
ll also chan
ever, owing
e trend exis
s in tendon
maleyouthpl
Dr Mark D
be very ind
the same
en children
refore this n
r knowledg
n. Given da
and that yo
al evidence
stability wh
g stiffness
t in paedia
alizing leg s
ahon and C
ssue when
opment. Pa
ency, and p
, however i
t childhood
delay betwe
greater com
e developm
risk is the
ptors) on m
s about mu
ion. Therefo
all influence
e or decrea
will lead to
ur during gr
nge the kin
g to the limit
sts for relati
n elastic pro
layers
De Ste Cro
dividualised
and some
and adults
needs to be
e there are
ata indicatin
oung girls a
base explor
en fatigue i
between g
tric populat
stiffness it is
Cheng, 199
examining
aediatric lite
produce cor
it is current
and adoles
een neural e
mpliance o
ment. Anothe
e influence
muscle tendo
uscle length
ore differen
e individuals
ase the rela
o increases
round conta
ematics of
ted publishe
ive stiffness
operties of
ix 19
and in thei
decreased
are related
e taken into
e no studies
ng that non
appear to be
ring the role
s present.
groups tha
tions where
s necessary
0), howeve
stiffness in
erature has
rresponding
tly unknown
scence.
excitation o
f the series
er importan
of altering
on stiffness
hs and thei
nces in SEC
s movemen
ative risk o
in absolute
act (Granata
rebounding
ed literature
s is unclear
the vastus
r
d
d
o
s
-
e
e
at
e
y
r
n
s
g
n
of
s
t
g
s.
r
C
t
of
e
a
g
e
r.
s
Theeffecto
lateralis (Ku
2003) sugg
Owing to th
that growth
control of S
within the m
research h
reducing ag
phase of th
Grossett et
spindles, th
result in inc
are variab
developme
suggested
al., 1997),
(Grosset et
responsible
by children
One factor
exhibited b
strength (a
consistent,
differences
perform at
that lower
2006). How
stiffness an
changes in
active stiffn
developme
an urgent
control of
influenced
offootballsp
ubo et al., 2
gest that SS
he neural re
h and matu
SSC functi
musculotend
has sugges
gonist inhib
he SSC, a
t al. (2007)
hus increas
creases in
les deeme
nt in intrins
as becomin
muscle fibr
t al., 2005).
e for the lon
compared
that may in
by females c
absolute an
although s
become in
the same l
levels of s
wever, very
nd there a
stiffness d
ness increa
nt in muscle
need for m
knee stab
by fatigue i
pecificfatigu
2001) and
SC function
egulation of
urity may ha
on, mecha
don unit are
sted that G
ition and en
nd a reduc
also sugge
sing muscu
both the m
ed to influe
sic neuromu
ng more ef
re twitch tim
. Recent re
nger ground
to adults (L
nfluence mu
compared w
nd relative)
small, throu
ncreasingly
evel as the
strength ma
y few studie
ppear to b
uring childh
ases with
e force prod
more studies
ility for inju
in female yo
ueondynam
age-related
is likely to b
SSC functi
ave on neu
noreceptors
e implicit in
Golgi tendon
nabling an i
ction in intr
est the pote
ular contrac
agnitude an
ence SSC
uscular prop
fficient as e
me enhance
esearch has
d contact tim
Lazaridis et
uscle stiffne
with males
(Hughes
ugh childhoo
larger so
e average b
ay increase
es have ex
be no studi
hood. Thos
age and c
duction (Gr
s exploring
ury preven
outh footba
mickneestab
d increases
be affected
ion, it is nec
uromuscula
s (Golgi te
the recoil n
n organs u
increased p
amuscular
ential for ag
ction recoil
nd velocity
function (
perties durin
evidenced b
ement (Lin e
s identified
mes and gre
al., 2010).
ess is musc
may be du
and Watkin
od and the
that at the
boy (Wood a
the relativ
xamined the
es that hav
e data that
can in par
osset et al,
g the role o
tion in chi
allers of diffe
bilityinfem
in musculo
by biologica
cessary to c
r adaptatio
ndon organ
nature of the
undergo a
pre-stretch o
Golgi tend
ge-related d
velocity. D
of the pre-
(Cronin et
ng childhoo
by increased
et al., 1997
a number o
eater angula
cle strength
ue, at least
ns, 2006).
transition
age of 16
and De Ste
ve risk of A
e age and
ve explored
are availab
rt be attrib
2005, 2007
of feed-forw
ldren. Add
ering ages
maleyouthpl
Dr Mark D
otendon stif
al maturity.
consider the
ns. When c
ns and mu
e specific m
process of
of the musc
on organ d
developmen
Developme
stretch com
al., 2002)
od, the neur
d musculot
7) and rate
of neuromu
ar displacem
. Lower lev
in part, to
Sex differe
into adoles
years and
e Croix, 201
ACL injury (
sex assoc
d the role
ble indicate
buted to th
7, Lambertz
ward mecha
itionally ho
and matura
layers
De Ste Cro
ffness (Lam
e potential
considering
scle spindl
muscle actio
f desensitiz
cle during th
density (Ov
nts in intrafu
nt of these
mponent, bo
). As a re
ral regulatio
endon stiffn
of torque d
uscular prop
ments at th
vels of musc
lower levels
ences in s
scence. The
d later only
11). It could
(Hughes an
ciated chan
of fatigue
e that both p
he to the a
z et al., 200
anisms in th
ow this me
ational statu
ix 20
mbertz et al.
implications
g the neura
es) presen
on. Previous
zation, thus
he eccentric
valle, 1987)
usal muscle
e properties
oth of which
esult of the
on of SSC is
ness (Lin e
evelopmen
perties were
e knee join
cle stiffness
s of muscle
strength are
ereafter, the
a few girls
d be argued
nd Watkins
ges in limb
in inducing
passive and
age related
03). There is
he dynamic
echanism is
us may help
,
s
al
t
s
s
c
).
e
s
h
e
s
et
t
e
t
s
e
e
e
s
d
s,
b
g
d
d
s
c
s
p
Theeffecto
us to desc
appropriate
2.6: The ro Quadriceps
running an
performing
form of mu
Muscular c
prevention
At the knee
(flexors) an
(Grimshaw
increase th
Watkins, 20
load on the
However, i
hamstrings
tibia, which
Agonist/ant
the joints th
as the mu
antagonist)
agonist mu
balance its
This muscle
action happ
2006). In o
the body s
Eccentric a
2006); or a
tension and
(pp.97). On
Peterson, 1
offootballsp
cribe the a
e design and
ole of the h
s and hams
nd jumping
dynamic m
uscle activity
contribution
of injuries.
e joint, mus
nd the cont
et al., 200
e joint cont
006). The a
e proximal t
if the shea
, a resultan
h will increas
tagonist mu
hat they cro
uscle that c
). The anta
scle (Grims
antagonist
e force prod
pens when
other words
egment, the
action is wh
as Pitman
d is overco
ne purpose
1989), for e
pecificfatigu
associated
d implemen
hamstring a
string musc
in sports
movements s
y is essenti
is very im
scular stabi
tribution of
06). As the
tact forces a
activity of th
tibia, and, t
ar load exe
nt anteriorly
se ACL stra
uscle groups
oss (Osterni
contracts w
agonist mus
shaw et al.,
is consider
duction can
the muscle
, when the
e muscles
hen muscle
and Peters
ome by the
e of the ecc
example the
ueondynam
relative ris
ntation of pr
and quadri
le groups a
such as v
such as lan
ial to provid
mportant to
ility is provi
both musc
quadriceps
and limit sh
e knee flex
therefore, m
erted by the
y directed s
ain (Hughes
s, such as t
ig, 2000), in
while anoth
scle is the
2006). The
red essentia
n take the fo
e tension is
muscles d
shorten an
tension is
son (1989)
e external l
centric acti
e quadricep
mickneestab
sk of injury
re-habilitatio
ceps musc
are involved
volleyball an
nding and cu
de adequate
o maintain
ided by the
cles groups
s and hams
hear movem
xors and ext
minimal stra
e quadricep
shear force
s and Watki
the quadric
n this case t
er muscle
one that o
e capacity o
al for joint st
orm of both
s developed
evelop suff
d cause jo
developed
explained
load, it pro
on is to de
ps works e
bilityinfem
y in this p
on strategie
cles (Musc
d in several
nd basketb
utting (side-
e joint stab
joint stabil
e quadricep
s is crucial
string musc
ment within t
tensors sho
ain should b
ps is great
may be ex
ns, 2006).
eps and ha
the knee jo
resists or
offers a res
of each mus
tability (Ost
concentric
d and the m
ficient tensi
int moveme
and the mu
“when a m
ogressively
ecelerate th
eccentrically
maleyouthpl
Dr Mark D
population
es.
ular stabili
important
ball (Bamac
-stepping),
ility (Hughe
lity and it
s (extensor
for the sta
les contrac
the tibiofem
ould, ideally
be caused o
ter than th
xerted on th
amstrings, w
int. The ago
counteract
sistance du
scle to prod
ternig, 2000
and eccent
muscle shor
on to overc
ent (Pitman
uscle length
muscle can
lengthens
he motion o
y when des
layers
De Ste Cro
and contrib
ity)
motor abilit
c et al., 20
dynamic sta
es and Wat
is also he
rs) and the
ability of the
ct, they act
moral joint (H
y, result in a
on the knee
e one exe
he proxima
work togethe
onist muscl
ts its motio
uring the ac
duce adequ
0).
tric actions.
rtens (Grims
come the re
n and Peter
hens (Grim
nnot develo
instead of
of a joint (
scending th
ix 21
bute to the
ties such as
008). When
ability in the
kins, 2006)
elpful in the
hamstrings
e knee join
in a way to
Hughes and
a zero shea
e ligaments
rted by the
l end of the
er to contro
e is defined
on (i.e. the
ction of the
uate force to
. Concentric
shaw et al.
esistance o
rson, 1989)
shaw et al.
op sufficien
shortening
Pitman and
e stairs. As
e
s
n
e
).
e
s
t
o
d
r
s.
e
e
ol
d
e
e
o
c
,
of
).
,
t
”
d
s
Theeffecto
Holcomb st
controlled m
The eccent
during forc
concluded
stability dur
progressive
velocity. Re
the knee e
thereby pos
2.7 Isokine
Isokinetic
measuring
training to
settings fo
isokinetic te
determinati
describe m
2006). Isok
scope of th
note that a
appropriate
valid and r
more reliab
actions. Fo
reader is di
2.7.1 Conv
The most
hamstring-q
value for th
2002). The
by the max
velocity (Aa
offootballsp
tated “an ec
movement i
trically co-a
ceful knee
that the ha
ring fast an
ely augmen
educed fun
extensors m
ssibly predi
etic dynam
dynamome
concentric
develop s
llowing inju
esting can
ion of the to
muscle actio
kinetic testin
his report to
as long as
e protocol a
reliable. Th
ble than flex
or further d
irected towa
ventional Ha
frequently
quadriceps
his CH/Q r
CH/Q ratio
ximal conce
agaard et a
pecificfatigu
ccentric mu
n the direct
acting hams
extension
amstring m
d forceful k
nted at grad
ction of the
may result i
sposing ath
ometry: Me
eters are u
and eccent
specific mus
ury or mus
be used to
orque gene
n when the
ng has beco
o explore th
s sound ha
and equipm
e current a
xion movem
detail regar
ards the rev
amstring/Qu
reported s
ratio (CH/Q
ratio, 0.6 a
o is calculat
entric knee
al., 1998). H
ueondynam
scle action
tion of the fo
strings have
(Coombs
muscles pos
knee extens
dually more
e antagonis
n muscular
hletes to inju
easuremen
used exten
tric torque,
scles or m
cle wasting
o evaluate q
erated (Bam
e rate of the
ome more p
he role of is
abituation/fa
ment adapta
available lit
ments and t
rding issues
views of De
uadriceps ra
strength rat
Q). Even tho
ppears to h
ted by divid
extensor (
However, a
mickneestab
occurs whe
orce of grav
e a dynamic
and Garbu
ssess the c
sion. This ca
e extended
st hamstring
r imbalance
ury (Rosene
nt of conce
nsively with
for exampl
muscle grou
g (Grimsha
quadriceps
mac et al., 2
e movement
popular with
sokinetic te
amiliarisatio
ation the iso
terature bas
that concen
s of isokin
Ste Croix (
atio (CH/Q)
tio of musc
ough, there
have gaine
ing maxima
(quadriceps
as Coombs
bilityinfem
en a muscle
vity” (2000,
c role in ma
utt, 2002).
capacity to
apacity for m
knee joint
gs due to a
es between
e et al., 200
entric and e
hin many f
e within spo
ups, and w
aw et al., 2
and hamst
2008). The
t (velocity)
h paediatric
esting in ch
on techniqu
okinetic tes
se suggest
ntric actions
etic testing
(2007) and
cles of the
e seems to
ed some ac
al concentric
s) moment
and Garbu
maleyouthpl
Dr Mark D
e is required
pp.229).
aintaining th
In fact, A
provide sig
muscular kn
positions a
activities tha
n the hamst
01).
eccentric to
forms of h
ort and exe
within rehab
2006). Reg
tring muscle
term isokin
is held cons
c population
ildren. It is
ues are in
ting with pa
ts that exte
s are more
g with paed
De Ste Cro
e knee has
be little con
cceptance (
c knee flexo
obtained a
utt (2002) s
layers
De Ste Cro
d to lower a
he stability
Aagaard et
gnificant dy
nee joint sta
and increas
at emphasiz
trings and
orque
human mo
ercise settin
bilitation an
arding the
e strength,
netic is a w
stant (Grim
ns and it is
however, i
place, com
aediatric po
ension mov
reliable tha
diatric popu
oix et al. (20
s been the
nsensus of a
(Coombs a
or (hamstrin
t a given jo
stated the u
ix 22
a load with a
of the knee
t al. (1998
ynamic join
abilization is
sing angula
ze loads on
quadriceps
ovement fo
ngs to targe
nd medicine
knee joint
providing a
word used to
shaw et al.
beyond the
mportant to
mbined with
opulations i
vements are
an eccentric
ulations the
003).
e concentric
a normative
nd Garbutt
ng) momen
oint angula
use of peak
a
e
)
t
s
r
n
s,
r
et
e
t,
a
o
,
e
o
h
f
e
c
e
c
e
t,
t
r
k
j
Theeffecto
moment ra
but has two
the concen
Secondly,
effect of m
contraction
joint move
quadriceps
1998).
2.7.2: Func
During forc
co-activate
group prov
words, co-a
action mod
eccentricall
and the ha
should be
representin
FH/Q ratio
relative to m
Garbutt (20
balance, an
observed d
would be th
2.7.3: Age
There are f
be due to t
the adult p
fewer studi
possible th
the concern
children to
offootballsp
tios to desc
o major lim
ntric hamst
usually the
uscle lengt
would take
ment only
muscle co
ctional Ham
ceful muscle
, with one g
ides contro
activation o
des. During
ly (Qecc); w
amstrings ac
described e
ng knee flex
for knee e
maximal co
002) stated
nd of particu
during knee
he recomme
and matura
few studies
he small nu
population t
es are avai
at the limite
n that ECC
higher risk
pecificfatigu
cribe norma
itations. Fir
tring mome
y are cited
th. In conce
e place for t
allows ecc
ontraction (
mstring/Quad
e actions, a
group provid
l and joint s
of these mu
leg flexion
hereas whe
ct eccentric
either as a
xion (Coom
extension is
oncentric qu
that a high
ular interest
extension.
endation.
ation effects
s examining
umber of stu
here is an
ilable on ch
ed informat
C testing, wi
of muscle i
ueondynam
al knee fun
rstly, the co
ent. This si
d irrespectiv
eptual term
the knee ex
centric ham
(during exte
driceps ratio
antagonist
ding directio
support via
uscle group
, the hams
en extendin
cally (Hecc)
Hecc/Qcon r
mbs and Ga
s calculated
uadriceps m
her H/Q rat
t would be
According
s on the H/Q
g age and s
udies that h
abundance
hildren, espe
ion on ECC
th its poten
injury. How
mickneestab
ction accou
ncentric qu
ituation doe
ve of the jo
s, the CH/Q
xtensors and
mstring mus
ension) or
o (FH/Q)
muscles su
onal movem
simultaneo
s is known
trings contr
ng the leg,
(Coombs a
ratio repres
arbutt, 2002
d by expre
moment obta
tio (conven
Hecc/Qcon du
to Coombs
Q ratio
sex associa
have determ
e of literatu
ecially inclu
C strength c
ntial for high
wever, there
bilityinfem
unts for the
adriceps m
es not aris
oint angle a
Q ratio imp
d flexors sim
scle action
vice versa
uch as the
ment via con
us eccentri
to occur a
ract concen
the quadric
and Garbutt
senting kne
2). As Aag
ssing maxi
ained at giv
tional or fu
ue to the hig
s and Garb
ated change
mined eccen
ure on isoki
uding female
capabilities
h muscle fo
is no reaso
maleyouthpl
Dr Mark D
main musc
moment is n
se during f
at which th
plies that co
multaneous
to be com
(during fle
quadriceps
ncentric act
c action (O
and takes p
ntrically (Hco
ceps contra
t, 2002). Th
e extension
aard et al.
mal eccent
ven angular
nctional) w
gh quadrice
butt (2002),
es in FH/Q
ntric forces
inetic ECC
es (De Ste
of children
orce produc
on to expec
layers
De Ste Cro
cle groups
ormally com
functional m
ey occur, i
oncentric (o
sly. Howeve
mbined with
exion) (Aag
s and hams
tion while th
sternig, 200
place throug
on) and the
ct concentr
herefore, th
n, or an Hc
(1998) exp
tric hamstri
r velocity. C
would repres
eps moment
a Hecc/Qcon
ratio. This
in children.
torque pro
Croix et al.
may have
ction, might
ct greater m
ix 23
of the thigh
mpared with
movements
gnoring the
or eccentric
er, true knee
h concentric
gaard et al.
strings often
he opposing
00). In othe
gh opposing
quadriceps
rically (Qcon
he H/Q ratio
con/Qecc ratio
plained, the
ng momen
Coombs and
sent greate
t production
ratio of 1.0
may in par
At least fo
oduction bu
. 2003). It is
arisen from
predispose
muscle injury
h
h
s.
e
)
e
c
,
n
g
r
g
s
)
o
o
e
t
d
r
n
0
rt
r
t
s
m
e
y
Theeffecto
with ECC a
familiarizati
As dictated
velocity inc
2007; Kellis
to 0.52 rad
tibial transl
relation to
activation
counterbala
more releva
in children.
FH/Q ratio
in relation t
protocol. F
potentiate t
FH/Q ratio
reported th
relative ecc
that young
It cannot b
across age
as evidenc
1987). The
significantly
with ratios
et al. 2007;
very few stu
study that h
Gerodimos
old trained
teenagers
angular vel
teenagers
offootballsp
actions in c
ion (Blimkie
d by the forc
creases in
s and Katis
d/s (0.8). Th
ation or sh
the femur
of the ha
ance this tib
ant estimat
It is impor
that movem
to age and
For example
the followin
in a small
hat the FH/
centric torq
boys have
be assumed
s during ch
ced by the
e few stud
y higher ec
ranging bet
; Forbes et
udies have
has included
et al. (200
male bask
and adults
locity of 3.1
(1.23) and
pecificfatigu
children com
e and Maca
ce-velocity r
pubertal ch
2007). The
his increase
ear at high
(Gerodimo
amstrings
bial shear o
e of the cap
rtant therefo
ment velocit
sex has be
e, during e
g concentri
group of 1
Q ratio inc
ue capabili
reduced inj
d that the re
ildhood and
incomplete
ies that ha
centric com
tween 0.84
al. 2009; Ig
directly me
d girls (De S
03) reported
ketball playe
has report
14 rad/s wi
adults (1.1
ueondynam
mpared to a
uley 2001).
relationship
hildren, teen
e FH/Q ratio
e in the rat
quadriceps
os et al. 20
during hig
or rotation. T
pacity for m
ore that wh
ty is taken i
een problem
eccentric/co
ic action. O
13 year-old
creases nea
ty compare
ury risk dur
elationship
d puberty b
myelinatio
ave measu
mpared to c
at the slow
ga et al. 20
easured the
Ste Croix et
d a non-sig
ers. Conflic
ted a signif
th 9-10 yea
9) (De Ste
mickneestab
adults, prov
p the FH/Q
nagers and
o was signi
tio at highe
s forces, an
003). Irresp
gh velocity
These data
muscular kn
en making
into accoun
matic due to
oncentric cy
Only one stu
d boys (Kel
ar full knee
ed with the
ring fast vel
between c
ecause chil
n of nerve
red the FH
concentric s
west velocity
09; Kellis a
FH/Q ratio
t al. 2007).
nificant age
ctingly, a cr
ficant age e
ar-olds prod
Croix et a
bilityinfem
vided they
ratio has be
d adults for
ficantly high
er velocities
nd increase
pective of
y moveme
a reinforce t
ee joint sta
age and se
nt. Meaningf
o the order
ycles theore
udy appears
lis and Kat
extension
extensors’
ocity movem
oncentric a
ldren have
fibres duri
H/Q ratio in
strength, de
y to 1.47 at
and Katis 20
in children
e effect on
ross section
effect for th
ducing a si
al. 2007). In
maleyouthpl
Dr Mark D
are given s
een shown
both sexe
her at 3.14
s is due to
e in internal
age or sex
ents signifi
the notion t
abilization th
ex associat
ful interpret
r of action c
etically the
s to have ex
tis 2007). K
due to the
concentric
ments near
and eccentr
immature n
ng childhoo
n children
epending up
the highest
007). As ca
and there a
FH/Q ratios
nal study o
he FH/Q ra
gnificantly
nterestingly,
layers
De Ste Cro
sufficient w
to increase
es (De Ste
rad/s (1.12
the signific
l rotation of
x, the incre
cantly con
that the FH/
han conven
ted compar
tation of the
cycling in th
eccentric
xamined an
Kellis and K
e knee flex
torque. Th
r full knee ex
ric actions i
neuromuscu
od (Brooks
have gene
pon movem
t velocity (D
n be seen
appears to
s between
of prepubert
atio at a rel
lower ratio
, the FH/Q
ix 24
arm-up and
e as angula
Croix et al
2) compared
cant anterio
f the tibia in
ease in co
ntributes to
/Q ratio is a
tional ratios
isons of the
e FH/Q ratio
he isokinetic
action may
ngle specific
Katis (2007
ors’ greate
his suggests
xtension.
is the same
ular systems
and Fahey
erally found
ment velocity
De Ste Croix
in table 2.1
be only one
12-17 year
tal children
atively high
(0.97) than
ratio at the
d
r
l.
d
r
n
-
o
a
s
e
o
c
y
c
)
r
s
e
s
y
d
y
x
,
e
r-
,
h
n
e
Theeffecto
slower velo
below 1.0
recruit their
al. (1993)
hypothesize
adults. This
boys must
speculation
protect thei
Croix et al.
offootballsp
ocity (0.52 r
for prepube
r entire mot
demonstra
ed that boy
s seems pla
be due to fa
n that there
ir immature
(2007).
pecificfatigu
rad.s-1) did
ertal childre
tor unit poo
ted a flatte
ys might be
ausible as W
actors othe
e might be
e musculosk
ueondynam
not demons
en may be
ol during ec
ening of th
e too immat
Weltman et
r than hype
a more pro
keletal syste
mickneestab
strate a sign
attributed
centric actio
he force-ve
ture to recr
al. (1986) r
ertrophy, su
onounced f
ems is supp
bilityinfem
nificant age
to the inab
ons (De Ste
locity curve
ruit their en
reported tha
ch as reduc
force suppr
ported by th
maleyouthpl
Dr Mark D
e effect. The
bility of 9-1
e Croix et a
e in the ec
ntire motor
at gains from
ced neurom
ression in p
he findings
layers
De Ste Cro
e functional
10 year-old
al. 2007). K
ccentric co
unit pool c
m resistanc
muscular inh
prepubertal
of the stud
ix 25
l ratio found
children to
Kawakami e
ondition and
compared to
ce training in
hibition. The
children to
dy of De Ste
d
o
et
d
o
n
e
o
e
T
T
Theeffectoffoo
Table 2.1: Paed
Authors De Ste Cro
Forbes et a Gerodimos Iga et al. (2
Kellis and K
otballspecificfat
diatric Function
oix et al. (2007)
al. (2009)
s et al. (2003)
2009)
Katis (2007)
tigueondynami
al Hamstring/Q
n Sex
121 M (n F (n
157 M 180 M(30 per age 45 M
17 M
ickneestability
Quadriceps Ratio
Age
n=49) 9, 17n=72)
11-1 12-1
group) 15y
13y
yinfemaleyouth
Dr Mar
o Findings
e (y) Velo
7, 24y 30º/
18y 60º/
17y 60°/ 60º/
60º/
hplayers
rk De Ste Croix
ocity (°/s)
s, 180º/s
s
/s
s, 250º/s
s, 180º/s
x 26
Key Findin
ratio ↑ as veno significansignificant aadults) significant a
no significanratio ↑ as ve
↓ ratio in cocompared w
ratio ↑ as knratio ↑ as ve
ngs
elocity increasesnt sex differencage effect (child
age effect (↓ rati
nt age effect elocity increases
onventionally trawith resistance tr
nee extends elocity increases
s ce dren ↓ ratio than
io in 18 year ol
s
ained footballerrained and cont
s
n
ds)
rs rols
Theeffecto
Evidence to
also in slow
who found
especially
there was
velocity to o
females. T
during conc
difference i
Conflicting
years has d
year olds (0
with age is
the relative
Ste Croix e
hamstring
experience
balance tow
effect in 1
footballers
with a deg
concentric t
in FH/Q ra
exploration
knee show
Significant
(Q/Hfunc) ra
fast velocit
children an
capacity fo
accompany
create large
be that adu
children, bu
offootballsp
o support th
w velocity c
that EMG a
in prepube
a trend fo
occur in the
hese findin
centric actio
n H/Qfunc ra
data are av
demonstrate
0.84) compa
attributed t
e increase in
et al. (2007
training in
d during s
wards quad
5 year-old
compared
gree of cau
testing at 1
atio demon
of whether
different ag
age and se
atio during k
ty moveme
nd teenager
or dynamic
ying eccent
e forces dur
ults have dif
ut direct ev
pecificfatigu
he fact that
concentric
amplitude de
rtal boys. A
or the large
e boys (21%
ngs sugges
ons as wel
atios from pr
vailable, an
ed significa
ared with 12
to a relative
n eccentric
7) and Forb
n youth fo
occer asym
driceps dom
football pl
with resista
ution as th
.08 and 4.3
nstrate how
r training sta
ge and sex
ex effects h
knee flexion
ents with a
rs (De Ste C
c knee jo
tric muscle
ring eccentr
fferent neu
idence to s
ueondynam
neuromusc
actions in c
ecreased w
Although th
est decline
%) and the
t that at a
l as eccent
re-puberty t
d a large c
ant age affe
2 year olds
ely greater i
hamstring
bes et al. (
ootballers.
mmetrically
minance (Iga
ayers on F
ance traine
he ratio is
32 rad/s. Th
w training s
atus influen
associated
have also b
n (e.g. ecce
adults dem
Croix et al.
int stabiliza
actions. T
ric actions d
ral mechan
support this
mickneestab
cular inhibitio
children is
with decreas
ere was no
in electrom
smallest fo
velocity of
tric actions
to adulthood
ross-section
ects in the F
(1.01) (For
ncrease in
torque. Thi
(2009) may
Recent w
strengthen
a et al. 200
FH/Q ratio
d footballer
calculated
e current co
status may
nces the FH
patterns is
been observ
entric quad
monstrating
2007). The
ation durin
This may be
due to fully
isms that c
notion rem
bilityinfem
on is prese
provided b
sing velocity
o significan
myographic
or the men (
f 0.52 rads
which cou
d during slo
nal study of
FH/Q ratio w
rbes et al. 2
concentric
s age relat
y be reflect
work has c
n the musc
09). Iga et a
with lower
rs and cont
using ecc
onflicting fin
y influence
H/Q ratio or
required.
ved for the
driceps / co
significantl
ese data su
ng forceful
e attributed
mature mus
control ecce
mains to be
maleyouthpl
Dr Mark D
nt not only
y Seger an
y of the con
t age differ
c (EMG) ac
(7%). No su
s-1 there wo
uld account
ow velocity m
f elite male
with signific
2009). This
quadriceps
ed differenc
tive of limit
confirmed
cles about
al. (2009) d
r ratios in
trols These
centric testi
ndings on th
the finding
if ratios fro
functional
oncentric ha
ly lower ra
uggest that
knee flex
d to a grea
sculoskelet
entric muscl
established
layers
De Ste Cro
in eccentric
nd Thorsten
centric mus
rence in thi
ctivity with
uch trend w
ould also b
for the non
movements
footballers
antly lower
reduction in
s torque com
ce in the st
ted focus o
that loadin
the knee,
emonstrate
convention
e data must
ng at 2.16
he age relat
gs. Howeve
om joints oth
quadriceps
amstrings) a
atios than
adults have
xion move
ater ability o
al systems.
le actions c
d. Although
ix 27
c actions bu
nson (2000
scle actions
is measure
decreasing
was found in
be inhibition
n-significan
s.
from 12-18
ratios in 18
n FH/Q ratio
mpared with
tudies of De
on eccentric
ng patterns
altering the
ed a training
nally trained
t be viewed
6 rad/s and
ted changes
er, a wide
her than the
s/hamstrings
at slow and
prepuberta
e a reduced
ments with
of adults to
. It may also
compared to
h these data
ut
)
s,
e,
g
n
n
t
8
8
o
h
e
c
s
e
g
d
d
d
s
r
e
s
d
al
d
h
o
o
o
a
Theeffecto
are of intere
are working
According t
influence m
on knee lax
prevention
hamstring s
Figure 2.3:
al., 2006).
Even thoug
greater qua
girls. They
hamstring s
2.7.4: Sex d
It appears t
susceptible
the FH/Q r
been sugg
differences
offootballsp
est the knee
g eccentrica
to Ahmad e
muscle stren
xity and mu
programs.
strength and
Quadriceps
gh the less
adriceps-to-
concluded t
strength, wh
differences
that adult fe
e to injury. A
ratio and a
ested that
in neurom
pecificfatigu
e is rarely in
ally.
et al. (2006)
ngth and lax
uscle streng
They obse
d strength r
s and hamst
mature ma
- hamstring
that girls aft
hich may pu
in H/Q ratio
emales dem
A high leve
ratio of les
sex differe
muscular rec
ueondynam
njured durin
), maturity w
xity. In their
gth to dete
erved signifi
ratios (figure
tring strengt
ale and fem
g ratio comp
fter menarch
ut them at ri
o – why girl
monstrate a
el of quadric
ss than 55%
ences in a
cruitment d
mickneestab
ng fast flexio
with associa
r study they
rmine the m
cant effects
e 2.3).
th for immat
male athlete
pared with
he increase
isk for ACL
ls are at risk
quadriceps
ceps streng
% may repr
dults in the
uring maxim
bilityinfem
on moveme
ated physio
examined
most appro
s of gender
ture and ma
es had very
immature b
ed their qua
injury.
k
s dominance
gth compare
resent a qu
e FH/Q rat
mal volunta
maleyouthpl
Dr Mark D
ents when th
ologic and h
the effects
priate time
r and matu
ature boys a
similar rati
boys, matur
driceps stre
e, which in
ed to hams
uadriceps do
tio of the
ary actions,
layers
De Ste Cro
he quadrice
hormonal ch
of gender a
to initiate A
rity on quad
and girls. (A
ios, mature
re boys, an
ength greate
turn makes
string streng
ominant ath
knee joint
with wome
ix 28
eps muscles
hanges may
and maturity
ACL injury–
driceps and
hmad et
e girls had a
nd immature
er than thei
s them more
gth reduces
hlete. It has
are due to
en having a
s
y
y
–
d
a
e
r
e
s
s
o
a
Theeffecto
lower perce
and Seger
children.
In a pair-m
hamstrings
the hamstri
were prosp
ACL ruptur
injury had
strength, c
however, h
compared t
Figure 2.4:
group. FAC
female ACL
These find
potential co
female ath
relative qua
offootballsp
entage recr
1989). How
matched con
isokinetic s
ing and qua
pectively sc
res (16 durin
significantly
compared to
had significa
to matched
: Percent in
CL, female
L injured; FC
ing indicate
ontributing
hletes who
adriceps str
pecificfatigu
uitment tha
wever, there
ntrol study,
strength to
adriceps of
creened bet
ng soccer a
y decrease
o matched
antly decrea
male athlet
ncrease in
ACL injure
C, female c
es that dec
mechanism
demonstra
rength may
ueondynam
an men durin
e are limited
Myer et al
ACL injury
132 female
tween 2002
and 6 during
d hamstrin
control ma
ased quadr
tes. These
responses
ed; FC, fem
control; MC,
creased re
m to ACL in
ate the com
be at increa
mickneestab
ng concent
d data inve
l. (2009) de
risk in fem
and male c
2 and 2007
g basketba
gs strength
ales. Those
riceps stren
data can be
and 95%
male contro
male contr
lative hams
njury in hig
mbination o
ased risk fo
bilityinfem
ric actions b
estigating se
etermined th
male athletes
collegiate so
7. After that
ll play). Tho
h, but simila
e females w
ngth, but no
e seen in fig
CI compar
ol; MC, ma
rol (Myer et
strings stre
h-risk fema
of decrease
or ACL injury
maleyouthpl
Dr Mark D
but not ecce
ex differenc
he associat
s. They me
occer and b
t period of
ose females
ar, or not d
who did no
ot decrease
gure 2.4 bel
ring study g
ale control.
t al., 2009).
ength and
ale athletes
ed relative
y.
layers
De Ste Cro
entric action
ces in the F
tion of quad
easured the
basketball p
time, they
s who suffe
decreased,
ot have an
d hamstring
low:
group to re
*P , 0.05.
recruitment
s. They con
hamstring
ix 29
ns (Westing
FH/Q ratio in
driceps and
e strength o
players, who
reported 22
ered an ACL
quadriceps
ACL injury
gs strength
eference
. FACL,
t may be a
ncluded tha
s and high
g
n
d
of
o
2
L
s
y
,
a
at
h
Theeffecto
Another fac
energy in th
ability of fe
(Komi and
utilize signi
However, t
has examin
sex differen
may in par
deal of ela
stored elas
there are s
data conce
relative ris
muscular in
the sex diffe
Interestingl
movement
females (D
compared t
actions. It is
compared
movement
males. It is
in females
the knee jo
females co
One of the
that no stud
likely to occ
peak torque
eccentric h
the angle a
work of Fo
quadriceps
offootballsp
ctor that mi
he muscle-t
emales com
Bosco 197
ificantly mo
he cross-se
ned sex diff
nces in FH/
rt be attribu
astic energy
stic energy i
sex differen
erning sex d
k of non-c
n nature. Th
erence rela
y, the same
velocities,
De Ste Cro
to males an
s generally
to males (
velocity, ap
speculated
(Westing a
oint during
mpared to m
biggest iss
dies appear
cur (0-30º o
e value for
amstring ac
at which PT
orbes et al
ranged fro
pecificfatigu
ight explain
tendon unit
mpared to m
78). Komi a
ore of the e
ectional stu
ferences in
/Q ratio at e
ted to that
y storage a
is not evide
ces in the
differences
contact ACL
hese data w
ated to relati
e study rep
irrespective
oix et al. 2
nd the lower
accepted th
(Seger and
ppear to hav
d that this tr
and Seger 1
flexion mo
males durin
sues with t
r to have de
of full knee
concentric
ctions. This
T occurs for
l. (2009) h
om 72 - 78º
ueondynam
n these sex
t during ecc
males in ut
nd Bosco (
nergy produ
dy of De S
n the FH/Q
either test v
fact that is
and thus an
ent. More lo
FH/Q ratio
in the FH/
L injury ma
would sugge
ive risk of in
orted signif
e of age, w
2007). Fem
r ratio can b
hat females
d Thorstens
ve a lower c
rend is due
1989). In an
ovements, w
ng childhood
he current
etermined th
extension).
quadriceps
may not ac
r each of th
ighlights th
º in 12 to 1
mickneestab
differences
centric actio
tilizing store
(1978) disco
uced in the
Ste Croix et
ratio in chi
elocity in pr
sokinetic co
ny potential
ongitudinal d
throughout
/Q ratio we
ay be attrib
est that neu
njury during
ficant sex d
with males d
males had s
be attributed
s have a gre
sson 2000)
capacity for
to lower m
n applied se
with high ec
d and into a
literature e
he functiona
. All of the s
s torque an
ccurately re
hese actions
his issue w
18 year-olds
bilityinfem
s is the cap
ons. There
ed elastic e
overed that
e pre-stretch
al. (2007)
ldren. Thes
repubertal,
oncentric/ec
benefits th
data are re
t childhood
might spe
buted to fa
romuscular
g childhood.
ifferences f
demonstrati
similar qua
d to a lower
eater capac
). However
r generating
motor unit ac
ense, these
ccentric kn
adulthood.
xamining th
al ratio at th
studies repo
d divided b
epresent the
s and musc
where angle
s compared
maleyouthpl
Dr Mark D
pacity to sto
is evidence
energy in th
t female pa
hing phase
appears to
se authors
teenage or
centric test
hat females
quired to re
. However,
culate that
actors othe
r recruitmen
for the FQ/H
ng significa
adriceps ec
r capacity fo
city for gene
, females
g concentric
ctivation du
e data sugg
ee extensio
he FH/Q ra
he point wh
orted in this
by eccentric
e functional
cle groups
es of peak
d with ecce
layers
De Ste Cro
ore and rele
e suggesting
he muscle-
articipants w
compared
be the only
reported no
r adults. The
ts do not al
s may have
einforce wh
based on
sex differe
er than thos
nt plays a cr
H ratio at sl
antly higher
ccentric mu
or hamstring
erating ecce
irrespective
c hamstring
ring concen
est that sta
on actions,
atio during c
ere knee in
s Chapter h
c peak torqu
l ratio as it
is different.
torque for
entric hamst
ix 30
ease elastic
g a superio
-tendon uni
were able to
with males
y study tha
o significan
ese findings
llow a grea
e in utilizing
ether or no
very limited
ences in the
se that are
rucial role in
ow and fas
r ratios than
scle torque
g concentric
entric torque
e of age o
torque than
ntric actions
abilization o
is lower in
childhood is
njury is mos
have used a
ue value fo
is likely tha
The recen
r concentric
tring angles
c
r
it
o
s.
at
t
s
at
g
ot
d
e
e
n
st
n
e
c
e
r
n
s
of
n
s
st
a
r
at
nt
c
s
j
Theeffecto
which rang
determined
achieved a
these musc
contact AC
concentric
(around 30
knee is clos
calculate th
more data
in females.
dynamic k
established
In their rev
CH/Q ratio
measures.
observed.
that occur
female athl
quadriceps
Even thoug
suffered AC
males. Low
result of inc
training sho
(Aagaard e
2.8: Neuro
The effectiv
joint helps
partnership
ACL in co
becomes o
offootballsp
ged from 3
d at differe
at the same
cle play in s
CL injury is m
and eccent
-80º of kne
ser to full ex
he FH/Q ra
are required
Whether t
nee stabilit
d.
view of liter
s between
They found
However, w
during spo
letes. They
torque ratio
gh Myer et
CL injury ha
w or lowered
creased con
ould be per
et al., 1998).
muscular c
veness of t
to create
p may incre
ntrolling an
of interest
pecificfatigu
1-38º. Ther
nt joint an
e joint angle
stabilizing th
mostly likely
tric torque p
ee flexion), w
xtension (0
atio using a
d on the FH
his will cha
ty and the
rature Hewe
sexes and
d that at sl
with increas
orts activitie
concluded
o at high ve
al. (2009)
ad a lower r
d values for
ncentric qua
rformed for
.
control and
he active m
e dynamics
ease the ris
nterior tibia
(Huston an
ueondynam
refore, with
gles are u
e. This clea
he knee du
y to occur is
production i
whereas it
-30º). Base
ngle specif
H/Q ratio du
ange our un
e susceptib
ett et al. (2
d to evaluat
ower testin
sed knee f
es, significa
that female
elocities dur
and Ahma
ratio values
r FH/Q ratio
adriceps st
the knee fle
d knee stab
muscular co
s knee sta
sk for an AC
al translatio
nd Wojtys,
mickneestab
hin current
used to rep
arly does no
ring childho
s not at the
is likely to o
is well reco
ed on this kn
fic torque v
uring childho
nderstanding
bility to kne
2008) wante
te the effec
g velocities
flexion/exten
antly greate
es, contrary
ring seated
d et al. (20
s compared
os represen
rength) may
exors, prefe
bility
ontrol system
ability. Any
CL injury (M
n is consid
1996). At
bilityinfem
literature,
present the
ot help in e
ood. Furthe
point wher
occur in the
ognized that
nowledge, i
values close
ood, espec
g of the ag
ee injury d
ed to deter
cts of incre
s, no gende
nsion angu
er CH/Q rat
y to males,
open-chain
006) measu
to non-inju
tative of kn
y indicate t
erably inclu
m in workin
neuromus
Myer et al.,
dered, the
low knee-f
maleyouthpl
Dr Mark D
concentric
e FH/Q rat
elucidating t
ermore, the
re peak torq
e mid-late r
t injury is li
t would see
e to full ext
ially using a
e and sex
during child
rmine if the
eased isokin
er differenc
ular velocitie
tios were o
do not incr
n isokinetic a
ured the CH
ured female
ee extensio
hat more h
ding eccen
ng synergist
scular imba
2004). Wh
hamstring
flexion ang
layers
De Ste Cro
and eccen
io, rather t
the function
joint angle
que is gene
ange of the
kely to occu
em more ap
tension. It i
angle speci
associated
dhood rem
ere were dif
netic veloci
ces in CH/Q
es, approac
observed in
rease the h
activity.
H/Q ratio, fe
es and matc
on (for exam
igh-resistan
tric muscle
tically with
alances tha
hen the fun
muscle, in
les (0 to 3
ix 31
tric torques
than torque
nal role tha
where non
erated. Peak
e movemen
ur when the
ppropriate to
is clear tha
fic data and
changes in
mains to be
fferences in
ty on these
Q ratio were
ching those
n male than
hamstring to
emales tha
ched contro
mple, as the
nce strength
contraction
the passive
at limit this
nction of the
n particular
30° of knee
s
e
at
-
k
nt
e
o
at
d
n
e
n
e
e
e
n
o
at
ol
e
h
n
e
s
e
r,
e
Theeffecto
flexion), qu
without bal
the ligamen
flexors may
in the con
developing
rupture the
There is sti
quickly eno
childhood a
associated
determined
prepuberta
relation to
landing to a
mature in a
activation
supported b
in adult ma
insight into
smaller in p
forces of la
in the hip a
to be no co
EMD has b
Figure 10.2
as a ±15
assumed a
as a few hu
and Perrin
Considering
provide dyn
an imposed
EMD is infl
offootballsp
uadriceps co
anced knee
nt (Myer et
y help balan
ntrol of hig
an approp
ACL during
ill some deb
ough to pro
are particu
changes in
d co-contrac
l children c
pre-landing
a greater e
adults comp
levels durin
by work of L
ales compa
landing me
prepubertal
anding. This
and torso) a
omparable d
been implic
2 demonstra
µV deviatio
s 9.6 Nm. D
undred mill
1999).
g this time
namic knee
d perturbati
luenced by
pecificfatigu
ontractions
e-flexor (ha
al., 2004).
nce active c
h knee ab
priate neuro
g manoeuvr
bate as to w
otect the joi
larly sparse
n knee mus
ction ratios
compared w
g CCR, ind
extent than
pared with c
ng the refl
Lazaridis et
ared with pr
echanisms d
children tha
s may includ
s opposed
data to supp
cated as a
ates one me
on from ba
Data from a
iseconds de
lapse and
e stability, E
ion or injuri
a number
ueondynam
pull the tib
amstring an
Myer et al.
contraction o
bduction to
omuscular
res that plac
whether refl
int once a
e. There a
cle activatio
(CCR) of t
with those
dicating that
children. T
children. Ho
lective or v
t al. (2010)
repubertal
during the p
an in adults
de relying o
to a knee a
port this view
risk factor
ethod of cal
aseline me
adults sugge
epending o
the need t
EMD should
ious stress.
of factors
mickneestab
bia forward
d gastrocn
(2009) sta
of the quad
rques or v
control ma
ce the athle
lective mus
large force
are few stu
on during la
the hamstrin
of adults. T
t adults pre
his suggest
owever, the
voluntary m
who also de
boys for th
prepubertal
s, they prob
on a proxim
and ankle st
w it remains
for knee in
lculation of
asurement
est that EM
on the musc
to develop
be conside
. It is impor
including th
bilityinfem
and increa
nemius) co-
ted that ade
driceps that
valgus colla
ay prevent
ete at risk fo
scular activa
is applied
dies that h
anding or pi
ngs and qu
They report
e-activated
ts that this
re were no
muscle act
emonstrate
e calf mus
years. As t
bably rely on
mal strategy
trategy (Rus
s an interes
njury in adu
EMD assum
to the ons
MDs vary be
cle examine
sufficient m
ered when
rtant to note
he transmis
maleyouthpl
Dr Mark D
ase stress o
-contraction
equate co-c
can compre
apse. They
the critical
or an injury.
ation and jo
to the liga
have exami
ivoting task
uadriceps d
ted signific
their hams
feed-forwa
age- or sex
ivation pha
ed higher an
cles. They
the incidenc
n different s
(one that u
ssell et al. 2
sting but unp
ults (Troy B
ming the on
set of force
etween 30 to
ed and mov
muscle tens
evaluating
e that it ha
ssion of mu
layers
De Ste Cro
on the ACL
n to decreas
contraction
ess the join
y also sugg
loading ne
oint stiffenin
ment, and
ined the ag
ks. Russell e
uring a lan
ant age dif
string musc
rd mechan
x-related di
ases. Thes
nd longer pr
provide an
ce rate of A
strategies to
uses the lar
2007). As th
proven hyp
Blackburn e
nset of elect
e productio
o 50 ms up
vement velo
sion rapidly
muscular re
s been sug
uscle force
ix 32
L, especially
se strain on
of the knee
nt and assis
gested tha
ecessary to
g can occu
data during
ge and sex
et al. (2007
ding task in
fferences in
cles prior to
ism is more
fferences in
se data are
re-activation
n interesting
ACL injury is
o control the
rge muscles
here appea
othesis.
et al. 2009)
trical activity
on which is
to as much
ocity (Shultz
y enough to
esponses to
ggested tha
through the
y
n
e
st
at
o
r
g
x
)
n
n
o
e
n
e
n
g
s
e
s
r
).
y
s
h
z
o
o
at
e
Theeffecto
series of ela
properties
comparing
significant
other musc
during child
there appea
The work o
and diseas
disease (a
also found
57ms) for k
show any s
that level of
Falk et al. (
and Zhou
58ms for g
males; 46m
composition
not sufficie
such as exc
this longer
stiffness an
greater ele
prepuberta
independen
longitudina
A number
females an
al. 2009; Z
difference i
Ste Croix e
in EMD of
sex differen
offootballsp
astic compo
of the exc
sex differe
sex differen
cle groups
dhood (Coh
ars to be on
of Gosset et
ed children
hip disorde
significantl
knee and e
significant d
f training st
(2009) repo
et al. (1995
irls) compa
ms for fema
n. However
nt to accou
citation-con
EMD. The
nd increase
ctrically stim
l children
nt of matu
l studies thr
of adult stu
d have attr
Zhou et al.
in EMD of t
et al. unpubl
the knee ex
nces were
pecificfatigu
onent (SEC
citation con
ences in EM
nce (Troy B
(Bell and J
hen et al. 2
nly one long
t al. (2010)
. They repo
er) compare
y greater E
elbow exten
difference b
atus did not
rted a signi
5) found si
red with 13
les). This lo
r, current lim
unt for the c
ntraction cou
erefore this
e the poten
mulated EM
indicating
uration. How
roughout ch
udies have
ibuted this
1995). Con
the hamstri
lished obse
xtensors du
reported in
ueondynam
C), changes
ntraction co
MD of the h
Blackburn e
Jacobs 198
2010; Falk e
gitudinal stu
focused on
orted a grea
ed to health
EMD in you
nsion and f
between the
t have an e
ficantly long
gnificantly
3-16 year-ol
onger EMD
mited eviden
child-adult
upling and m
s lower rate
tial for injur
MD for the
a potentia
wever, this
hildhood an
suggested
to greater m
nflicting dat
ngs during
rvations). O
uring isome
n either the
mickneestab
in the abilit
oupling pro
hamstrings
et al. 2009)
86). Very fe
et al. 2009;
udy.
n ankle stiffn
ater EMD in
hy controls,
ung children
flexion durin
e enduranc
ffect on EM
ger EMD in
longer EMD
ds (44ms fo
in children
nce sugges
differences
muscle fibre
e of force d
ry in childre
triceps sur
al increase
s hypothes
d including
d that male
musculo-ten
a from our
eccentric m
Only one stu
tric actions
8-12 year-
bilityinfem
ty of the act
cess (How
during ecc
. However,
ew studies
; Grosset e
ness and E
n children s
albeit only
n (9-12 yea
ng isometri
ce trained a
MD in 9-12 y
prepuberta
D values in
or boys; 47
n may be as
sts that diffe
. Therefore
e conductio
developmen
en. Howeve
ae in 7 yea
e in musc
is requires
female part
s demonstr
ndinous stiff
laboratory
muscle actio
udy appears
(Zhou et a
-old or 13-1
maleyouthpl
Dr Mark D
tion potentia
watson 2010
entric musc
conflicting
appear to
et al. 2010;
EMD of the t
suffering wit
in 6 childre
ars) compar
ic actions.
and untraine
year olds.
al boys com
n 8-12 year
7ms for girls
s a result o
erences in m
e difference
n velocity h
nt may red
er, Grosset
ar-old comp
cle-tendinou
s further in
ticipants.
rate a shor
fness in ma
on adults
ons over a
s to have ex
al. 1995) du
16 year-old
layers
De Ste Cro
al to propog
0). Recent
cle actions
data are a
have exam
Zhou et al
triceps sura
th Legg-Ca
en. Cohen e
red to adult
However, t
ed children
mpared with
r-olds (61m
s) and adult
f difference
muscle com
s in muscle
have been im
duce muscl
et al. (200
pared with
us stiffness
nvestigation
rter EMD c
ales (Troy B
have indica
range of ve
xplored sex
uring childho
d age group
ix 33
gate and the
adult data
showed no
available fo
mined EMD
. 1995) and
ae in norma
lve_Perthes
et al. (2010
ts (65ms vs
they did no
suggesting
adult males
ms for boys
ts (40ms fo
es in muscle
position are
e activation
mplicated in
e-tendinous
07) reported
11 year-old
s with age
employing
ompared to
Blackburn e
ated no sex
elocities (De
x differences
ood, and no
ps. Whethe
e
a
o
r
D
d
al
s
)
s
ot
g
s
s;
r
e
e
,
n
s
d
d
e
g
o
et
x
e
s
o
r
Theeffecto
EMD accou
no studies t
is surprising
risk group
childhood,
the age and
2.9 Effect o
After a fatig
patterns, co
2006). Adu
translation
subsequen
use antago
of Padua e
fatigued sta
strategy to
the ACL ap
when musc
the FH/Q ra
soccer spe
during child
maintain jo
(1993) sug
decreases
would sugg
children. H
using fema
Available d
during eithe
al. 2006). T
exercise m
characteris
children co
therefore le
offootballsp
unts for the
that have e
g that there
for non-co
particularly
d sex relate
of fatigue o
guing exerc
o-activation
ult studies
but that th
tly decreas
onist inhibiti
et al. (2006)
ate and als
protect the
ppears to b
cle fatigue i
atio signific
cific fatiguin
dhood but i
int stability
ggested tha
at a similar
gest that th
owever, thi
le participa
ata are rea
er a single
The ability
ay be relate
tics compa
ompared wit
ead to a low
pecificfatigu
greater rel
xamined se
e is only on
ntact ACL
for the kne
ed changes
on dynamic
cise bout, bi
n, kinematic
have repo
is is accom
ing joint sta
on strategie
) demonstra
o suggest t
e knee on la
e more pre
is present (
cantly decre
ng task (Sm
f fatigue ha
should form
at at least f
r rate with a
he FH/Q rat
is suggestio
nts across t
asonably co
or repeated
of children
ed to lower
ared to adu
th adults in
wer accumu
ueondynam
lative risk o
ex differenc
e study on
injury. It re
ee flexors a
in EMD, lin
c knee stab
omechanic
cs and kine
orted that s
mpanied by
ability (Meln
es by reduc
ated greater
that adults
anding. It is
evalent in th
(Small et al
eases at the
mall et al. 2
as a similar
m a major p
for the elbo
advancing m
tio would re
on requires
the age ran
nsistent ind
d bout of hig
to maintai
levels of fa
ults. Propos
clude: a) ch
lation of by-
mickneestab
of non-conta
es in EMD
the EMD o
emains to b
nd eccentri
nked to the r
bility
al and neur
etics, and s
submaxima
y significant
nyk and Go
cing hamstr
r co-activat
move to an
s well recog
he latter sta
l. 2010). Fo
e end of ea
010). There
r effect on c
art of preve
ow flexors,
muscular fa
emain simil
s further inv
nge.
dicating that
gh intensity
in force ou
tigue, which
sed mecha
hildren use
-products, b
bilityinfem
act ACL inju
in children d
of young gir
be identifie
c actions. F
relative risk
romuscular
stiffness pro
al fatigue n
tly longer la
ollhofer 2007
ring activati
ion ratios in
n ankle dom
gnized in th
ages of spo
or example
ach half of a
e appear to
children the
ention progr
concentric
tigue in 13
lar in the fa
vestigation,
t children fa
y exercise (
tput during
h in turn ma
anisms for
oxidative p
b) children’s
maleyouthpl
Dr Mark D
ury in girls
during ecce
rls given tha
ed how EM
Further stud
k of injury.
factors suc
operties are
not only in
atency of th
7). In a fatig
on (Padua
n females c
minant strat
e available
rting perfor
a recent st
a soccer ma
be no com
en the abilit
rammes. W
and eccen
year-old bo
atigued and
especially
atigue at a s
De Ste Cro
repeated
ay be reflec
the greater
pathways q
s lower abili
layers
De Ste Cro
is unclear a
entric muscl
at they are
D may cha
dy is needed
ch as muscl
e altered (P
creases an
he hamstrin
gued state,
et al. 2006
compared to
egy compa
literature t
rmance and
tudy has in
atch using
mparable da
ty to resist
Work by Kaw
ntric torque
oys. These
d non-fatigu
on the kne
slower rate
oix et al. 20
bouts of hi
ctive of diffe
r fatigue re
uicker than
ity to activa
ix 34
as there are
le actions. I
the most a
ange during
d to explore
le activation
Padua et al
nterior tibia
ng muscles
adults also
6). The work
o males in a
ared to knee
hat injury to
d most likely
dicated tha
a simulated
ata available
fatigue and
wakami et al
e production
limited data
ued state in
ee joint and
than adults
09; Ratel e
gh intensity
erent muscle
esistance in
n adults and
te their type
e
t
at
g
e
n
l.
al
s,
o
k
a
e
o
y
at
d
e
d
l.
n
a
n
d
s
et
y
e
n
d
e
Theeffecto
II muscle fi
and faster
possible se
repeated h
difference i
al. 2009). H
period of m
studies ha
childhood o
Data on the
well recogn
generally, e
Therefore,
However, n
Interestingl
FH/Q ratio
muscle act
fatigue indu
players. Th
production
they did no
eccentric to
in quadrice
activity of th
Howatson
biceps brac
exercise bo
caution sho
needed foll
EMD follow
seem to sh
greater inju
the deterio
Unfortunate
associated
offootballsp
bres and c
removal o
ex differenc
high intensi
n young ch
However, m
maturation a
ve examin
or between
e effects of
nized in ad
eccentric a
in a fatigue
no studies
y a recent
but does
tions (Olive
uced by a s
hey found s
of the quad
ot determin
orque produ
eps EMG a
he hamstrin
(2010) exa
chii in male
out. This fin
ould be tak
owing this t
wing 4 bouts
ow a signifi
ury risk. The
ration in m
ely, there a
changes in
pecificfatigu
) possible f
of metaboli
ce in fatigue
ty tasks (H
ildren and a
most of thes
and have u
ed the eff
the sexes.
muscle acti
ults that fa
ctions are
ed state the
appear to
study on a
not affect t
ira et al. 2
simulated 9
ignificant re
driceps both
ne eccentri
uction of the
activity only
ngs.
amined the
e adults and
nding was
en if a task
type of exer
s of 30s all o
icant increa
e mechanis
uscle cond
are no cur
n EMD afte
ueondynam
faster phos
c by-produ
e resistance
Hicks et al.
adults found
se data are
used varyin
fect of ecc
ion specific
atigue affect
more fatigu
e FH/Q ratio
o have rep
adults sugg
the FH/Qcon
009). Robin
0min footba
eductions in
h at half tim
c torque o
e quadricep
y at the end
chronic ef
d reported
despite an
k requiring
rcise. Zhou
out cycling
ase in EMD
sms involve
uctive, con
rrent data a
er fatiguing
mickneestab
phocreatine
ucts. Simila
e with fema
. 2001). On
d no sex dif
e from limite
ng methods
centric fatig
fatigue on
ts eccentric
ue resistant
o should inc
orted angle
gests that h
n ratio whic
neau et al.
all match in
n both conc
me and at th
of the hams
ps (13.3%).
d of the ma
ffects of ec
significantly
apparent r
a fast react
et al. (1996
exercise in
after fatigu
ed in the inc
tractile or e
available th
g exercise i
bilityinfem
e resynthes
ar mechanis
ales showin
ne of the f
fferences in
ed sources
s to induce
gue on ecc
either the F
c and conc
t than conc
crease and
e specific
heavy inten
ch points to
(2012) rec
n a very sm
centric (12.2
he end of th
strings but
Interesting
atch by no
ccentric fatig
y greater E
return of m
tion time or
6) also dem
adult males
ing trails wh
crease in E
elastic prop
hat permit
in children.
maleyouthpl
Dr Mark D
sis, improve
sms have
ng less fatig
few studies
either age
that do not
fatigue. Im
centric torq
FH/Q ratio o
entric actio
centric actio
the knee s
FH/Q ratio
nsity aerobi
o greater fa
cently repor
all sample
2%) and ec
he simulated
did also s
ly they foun
significant
gue and m
EMD up to
muscle funct
r fast gene
monstrated a
s. All of the
hich would
EMD after fa
perties and
us to exp
This data
layers
De Ste Cro
ed acid base
been prop
gue than m
s to exami
group (De
t adequatel
mportantly n
que produc
or EMD are
ons differen
ons (Roig e
should be m
after fatig
c training r
atigue durin
rted on neu
(n=8) of am
ccentric (25
d match. U
show a dec
nd a signific
t changes i
muscle dam
96 hours fo
tion and su
ration of hig
a significant
available a
predispose
atigue could
requires fu
lore the ag
is urgently
ix 35
e regulation
posed for a
males during
ne this sex
Ste Croix e
ly cover the
no available
ction during
sparse. It is
tly and tha
et al. 2009)
more stable
guing tasks
reduces the
ng eccentric
uromuscula
mateur male
.4%) torque
nfortunately
cline in the
cant decline
in the EMG
mage on the
ollowing the
uggests tha
gh forces is
t increase in
adult studies
the knee to
d be due to
urther study
ge and sex
y needed to
n
a
g
x
et
e
e
g
s
at
).
e.
s.
e
c
r
e
e
y
e
e
G
e
e
at
s
n
s
o
o
y.
x
o
Theeffecto
elucidate th
state.
2.10 Concl
Despite ev
13-18 year
that are as
neuromusc
As ACL ris
relative risk
dominant t
quadriceps
functioning
that explori
designs, an
fatigue, we
relevant ris
enable us
training stra
offootballsp
he relative r
lusions
idence that
old girls th
ssociated w
cular mecha
k is multifac
k in female y
than males
dominance
in this age
ing these m
nd examinin
e can start
sk factors t
to identify
ategies to re
pecificfatigu
risk of non-c
t the incide
here is a su
with this in
anisms have
ctorial it is i
youth athlet
and that
e then they
e group. Th
mechanisms
ng a range
to build a
that negativ
potential ri
educe the r
ueondynam
contact kne
nce rate of
rprising lac
creased ris
e been show
important to
tes. Limited
traditional f
y is an obv
is aligned w
s when fatig
e of muscul
a more com
vely affect
sk factors
elative risk
mickneestab
ee injury du
f ACL injury
k of empiric
sk are poo
wn to be im
o critically e
d evidence s
football tra
vious need
with evidenc
gue is prese
ar and neu
mprehensive
weight be
and implem
of injury – P
bilityinfem
ring childho
y per hours
cal data on
rly underst
mportant in r
examine the
suggesting
ining may
to explore
ce surround
ent as para
uromuscular
e and accu
aring knee
ment appro
Protect Her
maleyouthpl
Dr Mark D
ood when th
of exposu
this age gr
tood, even
reducing th
e underlying
that female
predispose
e FH/Q ratio
ding inciden
mount. By
r outcome
urate unde
joint funct
priate age
Knees.
layers
De Ste Cro
he child is i
re is most
roup. The m
though mu
e relative ri
g causes re
es are more
e individual
os and neu
nce and fat
utilising com
variables in
rstanding o
tion. This s
and matura
ix 36
n a fatigued
prevalent in
mechanisms
uscular and
isk of injury
elated to the
e quadriceps
s further to
uromuscula
igue means
mplex study
n relation to
of the mos
should then
ation based
d
n
s
d
y.
e
s
o
r
s
y
o
st
n
d
Theeffecto
R
Research Q
1. To
qu
pl
2. To
ha
sp
3. To
sp
Research O
1. E
ne
of
2. In
ex
3. To
kn
4. To
w
offootballsp
Rese
Questions
o what ex
uadriceps
layers?
o what ex
amstring to
pecific fatig
o what exte
pecific fatig
Objectives
xplore the e
euromuscu
f knee/hams
nvestigate w
xist after foo
o explore w
nee stability
o propose a
when fatigue
pecificfatigu
earcO
xtent does
ratio, leg s
xtent do ag
o quadricep
ue in youth
ent are mus
ue in youth
s
effects of fo
lar (EMD) c
string injury
whether any
otball speci
whether ther
y in a fatigue
appropriate
e is present
ueondynam
ch QObje
football s
stiffness an
ge and ma
ps ratio, leg
female foo
scle specific
female foo
ootball spec
components
y in young g
y age and m
fic fatigue.
re are musc
ed state.
age/matura
in young fe
mickneestab
Queecti
pecific fatig
nd electrom
aturation re
g stiffness
tball players
c compens
tball players
ific fatiguing
s of dynamic
girls.
maturation re
cle specific
ational relat
emale footba
bilityinfem
estioives
gue influen
mechanical
elated diffe
and electr
s?
atory mech
s?
g task on th
c knee stab
elated differ
compensato
ted training
allers
maleyouthpl
Dr Mark D
onss
nce the fu
delay in
erences inf
romechanic
hanisms in p
he muscular
bility that rel
rences in ke
ory mechan
to improve
layers
De Ste Cro
s an
unctional ha
female yo
fluence the
cal delay a
place follow
r (H/QFUNC)
ate to the re
ey outcome
nisms that c
dynamic kn
ix 37
nd
amstring to
uth footbal
e functiona
fter footbal
wing footbal
and
elative risk
e measures
contribute to
nee stability
o
ll
al
ll
ll
o
y
Theeffecto
4.1 Particip 36 females
were recrui
obtained (s
players. Pa
receiving v
age groups
their regula
vigorous ph
questionna
Exercise La
the accepta
criteria in th
fractures, s
reported pr
were also i
visit; 2) Drin
test. None o
4.1.1: Ethic Ethical app
(RESC) (se
working wi
obtained a
Bureau app
Participants
their relatio
a computer
given (the
participants
only availab
offootballsp
pants
s aged 12-1
ited to parti
see append
articipants w
verbal instru
s U13’s (n =
ar training
hysical activ
ire (see a
aboratory p
ance criterio
his study: (
surgery or
resence of
instructed n
nk alcohol i
of the partic
cal Consider
proval was o
ee Append
th children
Criminal R
proval is req
s were mad
onship with
r using an I
players pr
s name will
ble to the pr
pecificfatigu
18 y from a
icipate in th
dix). Verba
were given a
uctions (see
= 14), U15’s
regimens t
vity 48 hour
ppendix) in
procedures.
on as descr
1) histories
pain in the
delayed o
not to: 1) D
n the final 2
cipants repo
rations
obtained fro
ix A). RES
were follo
Record Bure
quired in the
de aware th
the Univers
D code and
rovided add
not be use
rincipal inve
ueondynam
Me
an FA Wom
his study an
l consent w
an informat
e appendix)
s (n = 9) an
throughout
rs proceedi
n accordan
Acceptanc
ribed in the
s of orthope
e spine or
nset muscl
Drink or eat
24 h before
orted any fo
om the Univ
SC approve
owed at all
eau (CRB)
e UK before
at they cou
sity, researc
d only acce
ditional con
ed and any
estigator.
mickneestab
etho
men’s Super
nd both play
was also o
tion sheet to
). Players in
nd U17’s (n
the experi
ng each tes
nce with th
ce to the stu
health que
edic problem
hamstring
e soreness
anything o
each visit;
orm of musc
versity of G
ed laborator
times and
check befo
e undertakin
ld withdraw
ch team or t
ssible by th
nsent for th
hard copies
bilityinfem
ods
r League T
yer and par
obtained fro
o explain th
n each squ
n = 13). Par
mental per
sting day. A
e Universit
udy was ap
stionnaire f
ms, such as
muscles ov
s (DOMS) a
other than w
drink caffei
culoskeletal
Gloucestersh
ry procedu
d all resear
ore data co
ng any work
w from the s
the club. Al
he research
he club to
s of data w
maleyouthpl
Dr Mark D
eam profes
rent written
om the club
he procedur
uad were re
rticipants w
riod and no
All participan
ty of Glou
proved if th
flow chart. T
s episodes
ver the pas
at a testing
water in the
ine within th
l disorder at
hire’s Resea
res and Un
rchers invo
ollection beg
k with childr
study at any
l the data c
team or cl
have acce
ere stored
layers
De Ste Cro
ssional yout
informed c
b prior to a
res involved
ecruited fro
were instruct
ot to take
nts complet
cestershire
he participan
There were
of hamstrin
st six mont
g session.
e final 3 h b
he final 12 h
t the time o
arch Ethics
niversity gu
lved in the
gan (Crimin
ren).
y point witho
collected wa
ub if prior c
ss to their
in a lockab
ix 38
th academy
consent was
approaching
d as well as
m the three
ted to avoid
part in any
ted a health
Sport and
nts satisfied
2 exclusion
ngs injuries
ths; (2) sel
Participants
before each
h before the
f testing.
s Committee
uidelines fo
e study had
nal Records
out affecting
as stored on
consent was
data). The
le draw and
y
s
g
s
e
d
y
h
d
d
n
s,
lf
s
h
e
e
r
d
s
g
n
s
e
d
Theeffecto
4.2 Study D
Participants
additional t
portable co
The purpos
the isokinet
anthropome
from peak h
During ses
followed by
repeat leg s
Figure 4.1: 4.3 Proced 4.3.1 Anthr
Age was co
the first vis
Stadiomete
Birmingham
Sessio
Contact data
collect
Trainisessio
Leg stiffne
offootballsp
Design
s were req
testing sess
ontact mat to
se of the ha
tic dynamom
etric data w
height veloc
ssion 3 pa
y the footb
stiffness, iso
Research d
dures
ropometry
omputed fro
sit to the la
er (Holtain
m, UK). Sitt
on 1
Mat a ion
ng on
ess
pecificfatigu
uired to vis
sion took p
o calculate
bituation se
meter as we
was also col
city (Mirwald
rticipants p
ball-specific
okinetic, an
design sche
om date of b
aboratory ac
Harpenden
ting height
ueondynam
sit the labo
place during
leg stiffness
ession was
ell as an int
lected in or
d et al. 2002
performed
fatigue tas
d EMG test
ematic
birth and da
ccording to
n, Crymych
was measu
S
Has
AnthropomeFamiliarisatiand isokinetDeterminatio
mickneestab
oratory at t
g a training
s (figure 4.1
to familiaris
troduction to
der to deter
2), as well a
baseline is
sk. Immedi
ts were perf
ate of testing
o the proce
h, UK) and
ured with a
Session 2
abituation session
Lab
etric data on with protoics. on of static Q
bilityinfem
he Univers
g session a
1).
se the partic
o the SAFT
rmine matu
as static ‘Q’
sokinetic/EM
ately post
formed.
g. Stature a
dures of W
d calibrated
a Holtain St
ocols
Q angle.
maleyouthpl
Dr Mark D
sity on 2 se
and involve
cipant with t
90. During
rational stat
’ angle.
MG tests in
the footba
and body m
Weiner and
d balance
tadiometer
Pre faEMG SAFTPost and le
layers
De Ste Cro
eparate occ
d repeated
the testing p
this session
tus defined
n a pre-fat
ll specific f
ass were m
Lourie (19
beam scal
(Crymych,
Session
Pre / posfatiguetesting
Lab
atigue H/QFU
measures T90 Fatigue tFatigue H/Qeg stiffness m
ix 39
casions. An
hops on a
protocol on
n
as years
tigued state
fatigue task
measured on
88) using a
es (Weylux
Dyfed, UK
3
st e
UNC and
task FUNC, EMG measures.
n
a
e
k
n
a
x
K)
Theeffecto
with the p
determined
For female
(age x leg
(mass by st
4.3.2 Leg s Participant
frequency o
period of 2
maintained
frequency
preferred f
whilst hopp
the broades
been advoc
below 1.5 H
extremities
maintenanc
studies use
for paediat
were perfo
instantaneo
calculated f
Where Kn is
contact tim
be reliable
offootballsp
osterior su
d using the f
es: Maturity
length)) +
tature ratio)
stiffness
performed
of 2.0 Hz.
20 consecu
by an audi
using the
requency,
ping. The ch
st possible
cated in pre
Hz have led
(Farley et
ce of desire
ed adult pop
ric populati
ormed on
ously collec
from the su
s the leg sti
e and Tf th
in paediatr
pecificfatigu
urface of th
following eq
y offset = −
(0.005841
))
4 sets of s
Participants
utive hops
io signal fro
digital metr
enabled gr
hoice of 2.0
range of ho
evious stud
d to an inab
al., 1991),
ed hopping p
pulations, t
ons, who m
a mobile
cted via a h
b-maximal
(in N x m
iffness, as c
e flight time
ic populatio
ueondynam
he knee tig
quation of M
− 9.376 + (0
x (age x s
sub-maxima
s were ask
in each se
om a quartz
ronome, as
reater contr
0 Hz was w
opping freq
dies using p
bility of mai
whilst freq
pace (Hoba
he choice o
may arguab
contact m
hand-held P
hopping tes
m-1)
calculated u
e (Dalleau e
ons (Lloyd e
mickneestab
ght against
Mirwald et a
0.0001882
itting heigh
al two-legge
ked to hop
et, at each
z metronom
s opposed
rol of move
within the b
uencies (1.
paediatric p
ntaining tru
quencies ab
ara et al., 20
of 2.0 Hz w
bly utilize le
mat (Smartj
PDA (iPAQ
st using the
using a con
et al., 2003
et al., 2009)
bilityinfem
t the meas
l. (2002):
x (leg lengt
ht)) + (0.002
ed hopping
two-legged
h given fre
me (SQ-44, S
to allowing
ement coor
oundaries p
.5 Hz – 3.0
populations
ue spring-m
bove 3.0 H
008). Additio
was deemed
ess consiste
jump, Fus
, Hewlett P
following e
tact mat, M
).This meth
). Relative l
maleyouthpl
Dr Mark D
suring box.
th x sitting
2658 age x
with 3 min
d on top of
quency. Ho
Seiko, UK).
g participan
rdination in
previously h
Hz; Hobara
(Lloyd et a
ass model
Hz have pre
onally, owin
d more atta
ent moveme
ion Sport,
Packard, US
equation:
M is total bod
hod has bee
eg stiffness
layers
De Ste Cro
. Age from
height)) +
x weight) +
rest betwee
the contac
opping freq
. Monitoring
nts to self
the lower
highlighted
a et al., 200
al., 2009). F
behaviour
evented the
ng to the fac
inable and
ent patterns
Australia),
SA). Leg st
dy mass, Tc
en previous
s will be det
ix 40
m PHV was
(− 0.0022 x
(0.07693 x
en sets at a
ct mat for a
quency was
g of hopping
select thei
extremities
as allowing
08) and has
Frequencies
in the lowe
e successfu
ct that those
sustainable
s. All jumps
, and data
tiffness was
c the ground
sly shown to
termined by
s
x
x
a
a
s
g
r
s
g
s
s
r
ul
e
e
s
a
s
d
o
y
Theeffecto
normalising
differences
4.3.3 Deter The Q ang
position. S
19mm and
the particip
iliaca anter
knee joint l
lateral on fi
240Hz was
and 3D ana
the softwar
60mm abo
analysis of
each partic
iliac spine,
postural an
offootballsp
g absolute
and this is
rmining the
le was dete
ix high spe
30mm dia
pant. These
rior superio
ine, tibial tu
ifth metatar
s used. Mar
alysis perfo
re model d
ove the tibi
the segme
cipant using
the patella
alysis trial a
Plate 4.
pecificfatigu
stiffness b
a dimensio
‘Q’ Angle
ermined us
eed camera
meter sphe
e landmarks
or, trochante
ubercle, late
rsal head (s
rker identific
rmed in vis
oes not pro
al tubercle
ntal rotation
g the Qualys
a and the tib
and entered
.1: Placeme
ueondynam
by body m
onless value
ing whole b
as (Prorefle
erical reflec
s were: late
er major, im
eral malleol
see plate 4.
cation was
ual 3D. A v
ovide a po
. The local
ns for the fe
sis Track M
bial tuberos
d as compo
ent of reflec
mickneestab
mass and
e.
body kinem
x, Qualysis
ctive marker
eral boarde
mmediately
us, betwee
.1). Exposu
undertaken
irtual marke
sition for th
l co-ordinat
emur and tib
Manager sof
sity of the ip
nents of an
ctive marker
bilityinfem
leg length
atics with t
s, Gothenbu
rs were pla
er of the ac
y superior a
en second a
ure time was
n using the
er for the ce
his marker.
tes for eac
bia. The qu
ftware. The
psilateral si
n angle anal
rs F
maleyouthpl
Dr Mark D
to accoun
the participa
urg) using
aced on ana
cromion, st
and central
and third me
s 2s and a
Qualysis Tr
entre of the
The virtua
ch segment
uadriceps an
e markers fo
ide were id
lysis calcula
igure 4.2: C
layers
De Ste Cro
nt for grou
ant in a sta
infrared lig
atomical lan
ternum, sac
to patella,
etatarsal he
sampling f
rack Manag
patella will
al marker is
t were dete
ngle was ca
or the anter
entified fro
ation.
Calculation o
b
a
ix 41
up/individua
atic standing
ht to detec
ndmarks on
crum, spina
, mid-latera
eads and on
requency o
ger software
be used as
s positioned
ermined fo
alculated fo
rior superio
m the static
of Q Angle
al
g
ct
n
a
al
n
of
e
s
d
r
r
r
c
Theeffecto
Qualysis T
markers, ov
was then t
provide ang
figure 4.2).
4.3.4 Funct
Peak torqu
Tested rang
for each pa
active rang
sudden res
performed
(Biodex Pr
Therefore,
determinati
All assessm
4.2). Testin
both conce
the slowest
by 240˚/s)
determined
determine
previous wo
consistent
mode. This
average tor
lever arm u
measureme
Participants
between m
importance
throughout
maximal ef
recorded d
offootballsp
rack manag
ver the 10s
transferred
gle a. This
The proced
tional Hams
ue assessm
ge of motio
articipant in
ge of motio
sistance at
before eac
ro Manual,
at the sta
ion of the ef
ments are p
ng occurred
entric and e
t angular ve
to reduce
d during dua
eccentric t
ork with pa
torque res
s in turn ca
rque. In the
up, and pul
ent participa
s performe
movements
e of either
the entire
ffort and v
uring conce
pecificfatigu
ger then pr
s trial. The
onto an ex
was then
dure was th
string/quadr
ments were
n was from
ndividually b
n. The rang
the end o
ch isokinetic
, Applicatio
art of each
ffects of gra
performed in
d at a slow
eccentric ac
elocity (60˚/
the risk of
al concentr
orque durin
ediatric pop
istance thro
uses stallin
e concentric
ll it down a
ants were in
d three ma
at different
pushing, p
range of m
isual feedb
entric quad
ueondynam
rovided a g
data was t
xcel worksh
subtracted
en repeate
riceps ratio
made on
90° to 0° o
by placing m
ge stop con
of each ran
c assessme
ons/ Opera
h test ses
avity on the
n a prone p
(60˚/s), inte
ctions with
/s) and con
injury (Ga
ic-concentr
ng ECC/EC
pulations ha
oughout th
ng of the lev
c quadriceps
as hard and
nstructed to
aximal effo
t angular ve
pulling or re
otion. Stan
back of the
riceps and
mickneestab
raph, plotte
hen exporte
heet. The m
from 180º
d on the no
the domin
of knee flexi
mechanical
ntrol was s
ge of moti
ent in acco
ations, Biod
ssion the p
limb and le
position for
ermediate (
extension u
ntinued with
ul, 1996). C
ic actions a
CC cycles.
as indicated
e entire ra
ver arm an
s measurem
d fast as po
o resist the l
orts at each
elocity. In p
esist the le
dardised ve
e recorded
eccentric h
bilityinfem
ed to demo
ed to a tex
mean was t
to determin
on dominant
nant leg, de
on (0° = ful
stops at th
set as soft s
on. Gravity
ordance wit
dex Medic
participant
ever arm co
both conce
(120˚/s) and
undertaken
h increasing
Concentric
and the pas
The passiv
d that childr
nge of mo
nd subseque
ment partici
ossible. How
lever arm a
h angular
particular it
ever arm a
erbal encou
torque pro
hamstrings
maleyouthpl
Dr Mark D
nstrate the
xt file in a n
then calcul
ne the qua
t side.
etermined b
l voluntary e
he beginnin
so as to re
y correction
th the man
cal System
relax their
uld be acco
ntric and ec
d fast angu
first. Testin
g angular ve
quadriceps
ssive eccen
ve eccentri
ren have dif
ovement in
ently influen
ipants were
wever, in th
s hard and
velocity wit
was stress
as hard an
uragement w
ovided. Pea
action and
layers
De Ste Cro
trajectory o
numerical fo
ated from
driceps ang
by kicking
extension),
ng and end
educe the p
ns for limb
ufacturer’s
s, Inc., Sh
r leg so th
ounted for.
ccentric tes
lar velocity
ng always
elocity (120
s muscle st
tric mode w
ic mode wa
fficulties in
the reactiv
nces the ca
e instructed
he eccentric
as fast as p
th a 30 s
sed to part
d as fast
was given d
ak torque v
later used
ix 42
of the three
ormat which
this data to
gle (b) (see
preference
determined
of their ful
possibility o
mass were
instructions
hirley, NY)
hat passive
sting (Figure
(180˚/s) fo
started with
0˚/s followed
trength was
was used to
as used as
maintaining
ve eccentric
alculation o
to push the
c hamstring
possible.
rest period
ticipants the
as possible
during each
values were
to calculate
e
h
o
e
e.
d
ll
of
e
s
).
e
e
r
h
d
s
o
s
g
c
of
e
g
d
e
e
h
e
e
Theeffecto
the FH/Q ra
torque ove
120˚/s and
Plate 4.2: P
4.3.5 Electr
Electromyo
Myomonito
the eccent
bipolar surf
line of the
electromyo
The Biode
allowing the
via a trigge
stop of all d
to activate
accepts sig
offootballsp
atio by exp
r three kne
180˚/s).
Prone positi
romyograph
ography wa
r III, DelSy
ric hamstrin
face electro
belly of th
graphic sig
x square w
e triggering
er box. The
data acquis
the Biodex
gnals that a
pecificfatigu
ressing ave
ee angles (
on adopted
hy
as quantifie
ys Inc., Bos
ng moveme
ode (DE- 2.
he muscle
nal with the
wave sync
g of the EM
EMG work
ition system
square wav
are betwee
ueondynam
erage eccen
(0-10°, 10-2
d during isok
ed with an
ton, MA, U
ent to dete
.3 MA; DelS
perpendicu
e greatest a
hronization
G software
ks software
ms in a give
ve signal ou
en 0 to 5 v
mickneestab
ntric hamstr
20° and 20
kinetic testin
n 8-channe
SA) to inve
ermine the
Sys Inc., Bo
ular to the
mplitude is
pulse is
e. The EMG
offers full t
n experime
utput to trig
volts, and c
bilityinfem
ring torque
-30°) and a
ng
el DelSys
estigate the
EMD. For
oston, MA,
muscle fib
detected (G
configurabl
G system sig
triggering ca
ental setup.
ger the sta
could be co
maleyouthpl
Dr Mark D
to average
at three an
EMG telem
e activity of
maximum
USA) was
bres becaus
Gleeson, 20
e via the
gnal was in
apabilities t
The Biodex
rt signal. Th
onfigured fo
layers
De Ste Cro
concentric
ngular veloc
metry syste
the hamstr
signal dete
positioned
se in this l
001).
Biodex AS
nterfaced to
to control th
x ASA softw
he Trigger M
or either po
ix 43
quadriceps
cities (60˚/s
em (DelSys
rings during
ection each
in the mid
location the
SA software
o the Biodex
he start and
ware is used
Module only
ositive-edge
s
s,
s
g
h
-
e
e
x
d
d
y
e
Theeffecto
signals or n
5V. The tra
the duratio
returning ba
signal, so t
EMG PC (
pressed by
EMG and b
Three elect
represented
by the Ga
preparation
cleaned wit
impedance
legs during
although w
testing (figu
Plate 4.3: a Following th
recorded w
couch. Part
lasting 10s
offootballsp
negative-ed
ansition poin
on of the tr
ack to the l
that when t
(laptop) sof
y the resear
biodex are c
trodes were
d by semite
astrocnemiu
n is an elect
th an alcoh
to below 5
testing. A
where possib
ure 4.3).
an illustratio
he applicati
with the part
ticipants we
were taken
pecificfatigu
dge signals.
nts of these
igger pulse
ow state. T
he appropr
ftware to s
rcher the B
completely t
e placed on
endinosus (
us (G), as
trical resista
hol wipe to
5kΩ. Partici
permanent
ble the elec
on of the pos
ion of surfa
ticipant in a
ere instructe
n. If muscle
ueondynam
. Positive-e
e voltages w
e is kept in
The trigger b
riate voltage
tart recordi
Biodex signa
time aligned
n the domin
(ST), and b
recommen
ance betwe
improve ap
pants were
pen was us
ctrodes wer
sitioning of
ce electrod
a prone pos
ed to relax
activity wa
mickneestab
dge or “risi
were defined
the high s
box detects
e change h
ing the EM
al (trigger) i
d.
nant limb o
biceps femo
nded by S
een the thre
pplication o
e also asked
sed to mark
re kept on d
the electrod
es participa
sition with t
and lay as
s evident th
bilityinfem
ng” was de
d as the eve
state for a
s a change
ad taken pl
MG data. W
is switched
on the med
oris (BF) an
Seniam (20
ee electrode
of the electr
d not to us
k the positio
during the f
des on the h
ants a base
the leg fully
still as poss
his procedu
maleyouthpl
Dr Mark D
efined to sta
ent. Once th
minimum a
in the Biode
lace, the tri
When the h
on. Theref
ial and late
d on the ca
007). The s
es of less th
rodes and
e any type
on of electro
fatigue task
hamstrings
eline measu
y extended
sible whilst
re was repe
layers
De Ste Cro
art from 0V
he 5V level
amount of
ex output s
igger box tr
old button
fore, the da
eral hamstri
alf muscle r
standard fo
han 5kΩ. Th
reduce the
of moisturi
odes for rep
k ready for
re of EMG
and suppo
3 measure
eated or the
ix 44
V and rise to
is reached
time before
quare wave
riggered the
(Biodex) is
ata from the
ng muscles
represented
or the skin
he skin was
acceptable
ser on thei
peat testing
post fatigue
activity was
orted by the
ements each
e electrodes
o
d,
e
e
e
s
e
s
d
n
s
e
r
g,
e
s
e
h
s
Theeffecto
repositione
Participants
the physica
was initiate
leg as muc
measureme
remind the
maximal vo
move (usin
Plate 4.4: T
Raw EMG
Acquisition
includes a
was band p
each of the
EMG RMS
Gastrocnem
The EMD
developme
the onset o
deviation a
(see Figure
measureme
offootballsp
d until the
s were prov
al movemen
ed and at a
ch as poss
ent. If the
participant
oluntary act
g the same
Trigger port
data was c
software, s
common m
pass filtere
e three angu
S amplitude
mius SM an
was determ
nt accordin
of EMD wa
nd the offse
e 4.3). The
ents for eac
pecificfatigu
principal in
vided with 2
nt of the lev
a constant v
sible before
investigato
to relax bef
tions as qu
e isokinetic p
indicating t
collected at
set up on a
mode rejecti
d at 20 – 4
ular velocitie
e recorded
nd biceps fe
mined as t
ng to the pro
as determin
et of EMD w
e maximal E
ch angular v
ueondynam
vestigator w
2 external tr
ver arm; 2) a
velocity (see
e the move
r could obs
fore starting
uickly as po
procedures
the trigger li
a sampling
Toshiba La
on ratio of
450 Hz usin
es (60˚/s, 1
in the act
emoris BF).
the time in
ocedure de
ned as a c
was determ
EMD value
velocity.
Light triggelever arm m
mickneestab
was confide
riggers for th
a light appe
e plate 4.4)
ement to re
serve that
g the lever a
ossible whe
previously
ight
g frequency
aptop (L20,
>80 dB an
ng the DelS
20˚/s and 1
tivity of the
nterval betw
eveloped by
change from
mined as the
was deter
red at the onmovement
bilityinfem
ent that a t
he start of t
eared on th
). Participan
educe the i
pre-activati
arm. The pa
n seeing th
highlighted
y of 1024 H
Toshiba Co
d an amplif
Sys Acquis
180˚/s) was
e hamstring
ween the o
y Zhou et al
m the EMG
e time taken
rmined as t
nset of the
maleyouthpl
Dr Mark D
rue baselin
the moveme
e trigger bo
nts were en
nfluence of
ion was tak
articipants w
he light and
d).
Hz and sent
orp. Tokyo,
fier gain of
ition softwa
normalised
gs muscles
onset of EM
l (1995). Ba
G mean bas
n (ms) to g
the shortes
layers
De Ste Cro
e value wa
ent of the le
ox when the
ncouraged
f pre-activa
king place
were remind
d feeling th
t directly to
Japan). Th
1000. Raw
are. The EM
d against th
s (semitend
MG activity
ased on this
seline level
enerate 9.6
st EMD from
ix 45
as recorded
ever arm: 1
e movemen
to relax the
ation on the
they would
ded to exer
e lever arm
the DelSys
he EMG uni
w EMG data
MG data fo
e maximum
dinosus ST
y and force
s procedure
to +15 µV
6-Nm torque
m the three
d.
)
t
e
e
d
rt
m
s
it
a
r
m
T,
e
e
V
e
e
Theeffecto
Figure 4.3:
4.3.6 SAFT
The SAFT9
Champions
the fatigue
changes in
with passiv
playing bou
with the in
movements
Figure 4.4: A
offootballsp
an illustrati
T90 Protoco
90 is base
ship level m
response o
both direc
ve rest inter
uts for U13)
ncorporatio
s (see figure
A diagramma
pecificfatigu
ion of the pr
ol
d on conte
match play (
of football m
ction and sp
rvals equiva
). The desig
n of four
e 4.4).
atic represen
ueondynam
rocess used
emporary ti
Prozone) a
match-play (S
peed over t
alent to thos
gn of the co
positioned
ntation of the
mickneestab
d to determ
me-motion
nd has bee
Small, 2010
he age app
se experien
urse is base
poles for
SAFT90 cou
bilityinfem
ine the EMD
analysis u
en validated
0). The free
propriate tim
nced on a m
ed around a
r the partic
urse
maleyouthpl
Dr Mark D
D (Zhou et
using data
by Lovell e
e running pr
me period i
match day (
a shuttle ru
cipants to
layers
De Ste Cro
al. 1995).
obtained fr
et al (2008)
rotocol inclu
nherent to
(eg 2 min re
n over a 20
navigate u
ix 46
rom English
to replicate
udes various
match-play
est between
0m distance
using utility
h
e
s
y,
n
e,
y
Theeffecto
The course
around the
three field
movement
was mainta
protocol wh
the particip
provided st
staggered a
Table 4.1: A
Age Grou
Under 13’s
Unger 15’s
Under 17’s
Before any
performed
to players.
4.4 Statisti
Statistical a
19.0 for W
homogenei
means and
correlation
(group) x 2
the H/QFUNC
and main e
and main
Bonferroni-
offootballsp
e was perfor
e first field p
poles, alth
intensity an
ained using
hich was re
pant usually
trong verba
at 30min int
Academy g
up
s
s
s
y testing is c
at their club
All procedu
ical Analys
analyses w
Windows; SP
ity and ske
d standard
co-efficient
(time) x 3 (
C, and a gro
effects. A 3
effects for
-corrected p
pecificfatigu
rmed with t
pole, follow
hough no c
nd activity p
g verbal sig
peated ran
y competes
l encourage
tervals.
ame duratio
Format
4 x 15 min
2 x 40 min
2 x 45 min
completed,
b before m
ures can be
sis
were perform
PSS Inc, C
ewness usi
deviation
ts were run
(angle) x 3
oup (3) x tim
3 (muscle) x
EMD. Sign
post hoc t-te
ueondynam
he participa
wed by forw
contact actio
performed b
gnals on an
domly and
s in (Table
ement throu
on.
nutes (2min
nutes (10mi
nutes (15mi
players per
atches. Thi
viewed on
med using
hicago). Fir
ng the Kol
were calc
to explore
(velocity) re
me (2) RMA
x 3 (group)
nificant inte
ests. The lev
mickneestab
ant perform
ward running
ons such a
by the partic
n audio CD
intermittent
4.1). The c
ughout the
rest betwe
n rest betw
n rest betw
rformed a s
is will includ
the CD atta
the Statisti
rstly the dis
lmogorov-S
culated for
relationshi
epeated me
ANOVA for
x 2 (time)
eraction or
vel of signif
bilityinfem
ing either b
g through t
as kicking
cipants whil
D. The aud
tly in order
coach and
protocol. P
en quarters
ween halves
ween halves
standard 10
de running
ached to thi
cal Packag
stribution o
Smirnov tes
each mea
ps between
easures ana
leg stiffnes
RMANOVA
main effec
ficance was
maleyouthpl
Dr Mark D
backwards r
the course,
or tackling
lst completi
io CD cont
to last for t
a member
articipants
s)
)
)
0 minute wa
and familia
s report
ge for Socia
of raw data
st. Descript
asure. Pea
n the key o
alysis of var
ss was used
A was used
cts were fu
s set at P <
layers
De Ste Cro
running or s
navigating
were perfo
ng the SAF
tains a 15
the duration
r of the res
ran in grou
Total play
60 minutes
80 minutes
90 minutes
arm up whic
ar dynamic
al Sciences
sets was c
ive statistic
rson produ
utcome var
riance (RMA
d to explore
d to explore
urther exam
0.05 for all
ix 47
sidestepping
the middle
ormed. The
FT90 course
min activity
n of a game
search team
ps of 3 or 4
ying time
s
s
s
ch is usually
movements
s (SPSS, v
checked fo
cs including
uct momen
riables. A 3
ANOVA) fo
e interaction
e interaction
mined using
tests.
g
e
e
e
y
e
m
4
y
s
v.
r
g
t
3
r
n
n
g
Theeffecto
5.1 Particip
A total of 3
U17 player
determined
right footed
menstruatin
participants
the contrac
Follicular p
group differ
group differ
± 592 m (U
Table 5.1: P
Age (y)
Stature (m
Body mass
Leg length
Offset from
Q angle (°)
* significant
5.2: FH/Q r
Mean (SD)
in table 5.2
were found
decreased
remained s
offootballsp
pant Chara
36 participa
rs. Age wa
d the left leg
d. Only on
ng and wa
s in the U17
ceptive pill)
hase (n = 7
rences in s
rences in Q
15) and 10
Participant
m)
s (kg)
h (cm)
m PHV (y)
)
t difference
ratio
data for FH
. Significan
d for the FH
from pre to
similar at 10
pecificfatigu
acteristics
nts comple
as determin
g as their do
ne participa
s in the fo
7 age group
) and were
7). Participa
tature, body
Q angle. Dis
590 ± 662 m
characterist
U
1
1.
4
6
-0.
14
between g
H/Q ratio by
t interaction
H/Q ratio. Th
o post fatig
0-20° (1.76
ueondynam
Re
ted the stud
ned from d
ominant leg
ant in the
ollicular pha
p self repor
e in the fol
ant characte
y mass, leg
stance cove
m (U17) for
tics by age
Under 13
2.1 ± 0.5
46 ± 0.06*
0.8 ± 6.7*
8.6 ± 3.4*
.28 ± 0.55*
4.52 ± 0.46
roups
y angle, vel
n effects for
he time x a
ue at 0-10°
± 0.74 vs
mickneestab
esu
dy consistin
date of bir
(based on
U13 age
ase during
rted that the
llowing pha
eristics can
g length and
ered during
each age g
group
locity and a
r angle x ve
angle intera
° (1.56 ± 0.
1.82 ± 1.12
bilityinfem
lts
ng of 14 U1
rth and tes
kicking pre
group self
testing. 5
ey were me
ases during
be seen in
d offset from
the SAFT9
group respe
Under 1
13.9 ± 0.
1.59 ± 0.0
51.9 ± 8.
73.4 ± 3.
1.11 ± 0.5
16.96 ± 0.
age group, p
elocity (p = 0
ction (figure
.94 vs 1.29
2 [absolute
maleyouthpl
Dr Mark D
13 players,
st date. Fo
eference) an
reported
participant
enstruating
g testing: L
n table 5.1.
m PHV. The
90 was 6320
ectively.
5
.6
08
.8
.8
55
.30
pre and pos
0.00) and ti
e 5.1) demo
9 ± 1.07 [ab
change +0
layers
De Ste Cro
9 U15 play
our of the
nd 32 partic
that they h
ts in the U
(two U17s
Luteal phas
There were
ere were no
0 ± 69 m (U
Unde
15.8
1.66 ±
61.9
79.8
2.93 ±
15.22
st fatigue ca
me x angle
onstrated th
bsolute cha
0.06]) and in
ix 48
yers and 13
participants
cipants were
had started
U15 and 11
were taking
se (n = 10
e significan
o significan
U13), 10525
er 17
± 0.5
± 0.06
± 8.2
± 3.8
± 0.58
± 0.31
an be found
e (p = 0.033
hat the ratio
nge -0.27])
ncreased a
3
s
e
d
1
g
)
t
nt
5
d
)
o
),
at
Theeffecto
20-30° (1.4
in the FH/Q
interaction
of flexion co
of flexion. N
(p = 0.019
(figure 5.1)
1.60 ± 1.07
0.07) there
remained u
change =
absolute ch
Figure 5.1:
0.75
1
1.25
1.5
1.75
2
FH/Q
ratio
offootballsp
45 ± 0.42 vs
Q ratio from
(figure 5.2)
ompared w
No other sig
) was foun
. Important
7). Although
e were age
unchanged
-0.39) and
hange betw
FH/Q ratio
P
pecificfatigu
s 1.68 ± 1.0
pre to pos
) demonstra
with an incre
gnificant int
nd with the
ly there we
h the time x
e related d
in the U13
increased
een the U1
pre and po
Pre‐fatigue
ueondynam
02 [absolute
t fatigue be
ated a redu
ease in the
teraction eff
ratio signif
re no main
x group inte
differences
3s (absolut
in the U1
5 and U17
ost fatigue b
mickneestab
e change +0
etween 0-10
uction in the
FH/Q ratio w
ffects were
ficantly hig
effects for
eraction effe
in the resp
te change
7s (absolu
age groups
by joint angl
Post‐
bilityinfem
0.23]). The
0° and 20-3
e FH/Q ratio
with increas
observed. A
her betwee
time (pre fa
ect did not
ponse to t
= +0.02), d
te change
s was 0.77.
e
‐fatigue
maleyouthpl
Dr Mark D
difference
30° was 0.5
o with incre
sing velocit
A significan
en 10-20° t
atigue 1.59
reach stati
he fatigue
decreased
= +0.38).
layers
De Ste Cro
in the abso
0. The ang
easing veloc
y at 10-20°
nt main effe
than 0-10°
9 ± 0.70 vs
stical signif
task. The
in the U15
The differe
0‐10°
10‐20°
20‐30°
ix 49
lute change
le x velocity
city at 0-10
and 20-30
ect for angle
and 20-30
post fatigue
ficance (p =
FH/Q ratio
5s (absolute
ence in the
e
y
°
°
e
°
e
=
o
e
e
Theeffecto
Figure 5.2:
0.75
1
1.25
1.5
1.75
2
FH/Q
ratio
offootballsp
FH/Q ratio
60
pecificfatigu
by joint ang
0°/s
Ve
ueondynam
gle and mov
120
elocity
mickneestab
vement velo
0°/s
bilityinfem
ocity
180°
maleyouthpl
Dr Mark D
°/s
layers
De Ste Cro
0‐10°
10‐20
20‐30
ix 50
°
0°
0°
T
T
0 6
6
2 6
*†
Theeffectoffoo
Table 5.2 FH/Q
Velocity/Ang0-10°
60°/s
120°/s
180°/s
10-20°
60°/s
120°/s
180°/s
20-30°
60°/s
120°/s
180°/s
* Significant an† Significant tim
otballspecificfat
Q ratio pre and p
gle U13 1.40 ± 1 2.01 ± 1 1.62 ± 1
1.50 ± 0 1.63 ± 0 1.76 ± 0 1.27 ± 0 1.38 ± 0 1.54 ± 0
gle x velocity inme x angle inter
tigueondynami
post fatigue by a
FH/Q ra3 U15
1.13 1.79 ± 1
1.09 1.43 ± 0
1.15 0.75 ± 0
0.63 1.75 ± 0
0.59 1.93 ± 0
0.65 2.09 ± 1
0.40 1.35 ± 0
0.45 1.46 ± 0
0.40 1.52 ± 0
nteraction effectraction effect
ickneestability
age group, mov
atio Pre Fatigu5 U17
1.01 1.42 ±
0.92 1.49 ±
0.75 1.08 ±
0.86 1.30 ±
0.88 1.90 ±
1.23 1.70 ±
0.54 1.18 ±
0.48 1.46 ±
0.69 1.49 ±
t
yinfemaleyouth
Dr Mar
vement velocity
e 7
0.70*
0.79
0.57
± 0.57*
± 0.75
± 0.57
0.26*
0.34
0.30
hplayers
rk De Ste Croix
and joint angle
U13 1.59 ± 1.61 1.71 ± 1.38 1.45 ± 0.92
1.69 ± 1.45 1.71 ± 1.35 1.76 ± 0.88
1.78 ± 1.40 1.36 ± 1.05 1.50 ± 0.93
x 51
e
FH/Q ratio U15
0.95 ± 1.18
1.27 ± 1.32
0.89 ± 0.49
1.34 ± 1.24
1.43 ± 0.62
1.60 ± 0.42
1.03 ± 0.50
1.23 ± 0.37
3 1.33 ± 0.30
o Post Fatigue U17
1.31 ± 0.68
1.04 ± 1.02
9 1.10 ± 1.10
2.17 ± 1.08
1.58 ± 1.04
1.99 ± 1.39
0 2.30 ± 1.04
7 1.88 ± 0.93
0 2.07 ± 1.1
†
8†
4
9
4†
3
3
Theeffecto
5.3: Relativ
Mean (SD)
5.3. RMAN
stiffness bu
slight decre
group post
group with
in the U13
group incre
Table 5.3: R
Group
U13
U15
U17
* Significan
Figure 5.3:
30
35
40
45
50
Relative Stiffness
offootballsp
ve Leg Stif
) data for re
NOVA revea
ut no signific
ease in stiff
t fatigue (fig
4 girls incre
age group
eased stiffne
Relative leg
nt group by t
Relative leg
pecificfatigu
ffness
elative leg s
aled a sign
cant main e
fness in the
gure 5.3). T
easing stiffn
(n = 10) bu
ess post fat
g stiffness (d
Pre
44.
46
36
time interac
g stiffness p
Pre
ueondynam
stiffness by
nificant grou
effects of gro
e U13 age
There was
ness and 5
ut a few did
tigue.
dimensionle
Fatigue
.6 ± 5.5*
.4 ± 8.8
.5 ± 6.6
ction effect
pre and pos
mickneestab
y age group
up x time in
oup or time
group com
an individu
girls decrea
d increase t
ess) by grou
st fatigue by
Po
bilityinfem
p, pre and p
nteraction e
e. This intera
pared to an
ualised res
asing stiffne
heir stiffnes
up and time
y group
ost
maleyouthpl
Dr Mark D
post fatigue
effect (p =
action effec
n increase
ponse to fa
ess. Most gi
ss (n = 4). A
e
Post
42.4
47.
41.0
U13
U15
U17
layers
De Ste Cro
e can be fou
0.022) for
ct can be att
in stiffness
atigue in th
irls stiffness
All girls in t
Fatigue
4 ± 7.7
1 ± 6.2
0 ± 6.1
ix 52
und in table
relative leg
tributed to a
s in the U17
he U15 age
s decreased
he U17 age
e
g
a
7
e
d
e
Theeffecto
5.4 EMD
Mean (SD)
presented f
time by gro
analysis re
and U17 gr
post fatigue
figures 5.4,
also observ
post fatigue
irrespective
compared w
groups (se
U15 and U
muscle (13
[60°/s], 122
offootballsp
) data for E
for each mu
oup interact
vealed that
roups and t
e was 78ms
, 5.5 and 5
ved. Irrespe
e compared
e of time, m
with the U1
e figures 5
U17 age gro
32 ± 51ms
2 ± 46ms [12
pecificfatigu
EMD by ag
uscle group
ion effect (p
t EMD was
this differen
s [U13], 40m
.6. A signif
ective of gr
d with pre f
muscle or m
15 (158 ± 6
.4, 5.5 and
oups (113
[BF], 133 ±
20°/s], 131
ueondynam
e group, pr
p and split b
p = 0.046) b
significantl
ce was gre
ms [U15] an
ficant main
roup, musc
fatigue [160
movement v
66ms vs 11
d 5.6). Ther
± 39ms vs
± 52ms [ST
± 51ms [18
mickneestab
re and pos
by moveme
but no othe
ly longer in
eater post fa
nd 50ms [U
effect for ti
cle or move
0 ± 68 ms
velocity EM
3 ± 39ms)
re were no
120 ± 40m
T], 127 ± 63
80°/s]) were
bilityinfem
st fatigue ca
nt velocity.
r interaction
the U13 a
atigue (abso
17] respect
ime (p = 0.
ement veloc
Vs 101 ± 4
D was sign
and U17 (
significant
ms). No sig
3ms [G]) or
e found.
maleyouthpl
Dr Mark D
an be found
RMANOVA
n effects we
ge group c
olute increa
tively). Thes
000) and g
city EMD w
43 ms] (se
nificantly lo
158 ± 66m
differences
gnificant (p>
r movement
layers
De Ste Cro
d in table 5
A revealed a
ere observe
compared w
ase in EMD
se data can
group (p = 0
was significa
e table 5.4
nger in the
s vs 120 ±
s in EMD b
>0.05) main
t velocity (1
ix 53
5.4. Data is
a significan
ed. Post hoc
with the U15
from pre to
n be seen in
0.005) were
antly longe
4). Likewise
e U13 group
40ms) age
between the
n effects fo
139 ± 69ms
s
nt
c
5
o
n
e
r
e,
p
e
e
r
s
T
T
6
S 6
G 6
A*†‡
Theeffectoffoo
Table 5.4: EMD
Muscle/VelocBiceps Femor
60°/s
120°/s
180°/s
Semitendonos
60°/s
120°/s
180°/s
Gastrocnemis
60°/s
120°/s
180°/s
All Combined * Significant gro† Significant ma‡ Significant ma
otballspecificfat
D pre and post f
city is U13
136 ± 6 103 ± 3 117 ± 3
sis
144 ± 5 106 ± 3 124 ± 4
124 ± 6 97 ± 48 123 ± 6
119 ± 4oup x time interain effect for timain effect for gro
tigueondynami
fatigue by age g
EMD Pre F U15
2 99 ± 36
2 86 ± 28
8 93 ± 27
4 97 ± 34
1 96 ± 37
6 101 ± 41
1 79 ± 17
93 ± 24
8 92 ± 43
9 93 ± 32 raction effect me oup
ickneestability
group, muscle a
Fatigue (ms) U17 Co
96 ± 35 11
95 ± 36 96
85 ± 33 10
97 ± 40 11
95 ± 35 10
84 ± 28 10
102 ± 61 1
92 ± 35 9
81 ± 31 1
92 ± 37 ‡ 1
yinfemaleyouth
Dr Mar
and movement v
ombined
13 ± 51
6 ± 32
00 ± 36
U 22 17 19
16 ± 49
00 ± 33
04 ± 42
22 17 20
05 ± 55
94 ± 38
01 ± 53
21 18 17
01 ± 43 † 19
hplayers
rk De Ste Croix
velocity
EMU13 U15
0 ± 111 143 ±
78 ± 57 127 ±
97 ± 60 145 ±
3 ± 106 141 ±
79 ± 45 125 ±
00 ± 62 150 ±
2 ± 122 117
85 ± 102 111
77 ± 80 145
97 ± 83 133
x 54
MD post fatigu5 U17
± 44 157 ± 52
± 42 146 ± 40
± 46 148 ± 32
±46 153 ± 48
± 42 141 ± 36
± 56 141 ± 39
± 42 165 ± 45
± 42 137 ± 46
± 53 144 ± 42
± 46 148 ± 42
ue (ms) Combined
2* 179 ± 85
0* 154 ± 51
2* 167 ± 53
8 178 ± 84
6 152 ± 46
9 167 ± 59
5 171 ± 91
6 150 ± 78
2 157 ± 63
2 160 ± 67
% C
5
6
6
5
5
6
6
6
5
5
Change
58%
60%
67%
53%
52%
61%
63%
60%
55%
58%
T
Theeffectoffoo
Figure 5.4: EMD
60
80
100
120
140
160
180
200
220
240
EMD (ms)
otballspecificfat
D by group pre
Pre
60°/s
tigueondynami
and post fatigu
PostEM
D(m
s)
ickneestability
ue for the biceps
U13
U15
U17
60
80
100
120
140
160
180
200
220
240
EMD (ms)
1
yinfemaleyouth
Dr Mar
s femoris
60
80
100
120
140
160
180
200
220
240
EMD (ms)
Pre
80°/s
hplayers
rk De Ste Croix
Pre
Post
120°/s
x 55
Po
U13
U15
U17
st
U13
U15
U17
T
Theeffectoffoo
Figure 5.5: EMD
60
80
100
120
140
160
180
200
220
240
EMD (ms)
otballspecificfat
D by group pre
Pre
60°/s
tigueondynami
and post fatigu
Post
1
1
1
1
1
2
2
2
EMD (ms)
ickneestability
ue for the semite
U13
U15
U17
60
80
100
120
140
160
180
200
220
240
P
18
yinfemaleyouth
Dr Mar
endonosis
60
80
100
120
140
160
180
200
220
240
EMD (ms)
re
80°/s
hplayers
rk De Ste Croix
0
0
0
0
0
0
0
0
0
0
Pre
Post
120
x 56
e
U13
U15
U17
0°/s
Post
U13
U15
U17
T
Theeffectoffoo
Figure 5.6: EMD
60
80
100
120
140
160
180
200
220
240
EMD (ms)
otballspecificfat
D by group pre
Pre
60°/s
tigueondynami
and post fatigu
P
1
1
1
1
1
2
2
2
EMD (ms)
ickneestability
ue for the Gastro
ost
U1
U1
U1
60
80
100
120
140
160
180
200
220
240
Pr
180
yinfemaleyouth
Dr Mar
ocnemus
13
15
17
re
0°/s
hplayers
rk De Ste Croix
60
80
100
120
140
160
180
200
220
240
EMD (ms)
Post
x 57
Pre
U13
U15
U17
120°/s
Posst
U13
U15
U17
Theeffecto
5.5: Summ
1. A tim
fatig
mor
2. A si
mov
3. EMD
fatig
4. A si
in th
fatig
offootballsp
mary of Res
me x angle
gue, irrespe
re flexed an
ignificant an
vement incr
D was sign
gue was gre
ignificant tim
he U13 age
gue
pecificfatigu
sults
e interaction
ective of ag
ngles.
ngle x veloc
reases the F
ificantly lon
eatest in the
me x age in
e group, no
ueondynam
n effect dem
ge, between
city interacti
FH/Q ratio d
nger post fa
e U13 age g
nteraction ef
o change in
mickneestab
monstrated a
n 0-10° of
ion effect in
decreases o
atigue in all
group
ffect for rela
n the U15s
bilityinfem
a significan
knee flexio
ndicated tha
only at the m
age groups
ative leg sti
s and a sig
maleyouthpl
Dr Mark D
nt decrease
on, compare
at irrespectiv
most extend
s but the ch
ffness indic
nificant inc
layers
De Ste Cro
in the FH/Q
ed with an
ve of age a
ded knee po
hange from
cated a slig
rease in th
ix 58
Q ratio pos
increase a
s velocity o
osition
pre to pos
ht decrease
he U17 pos
st
at
of
st
e
st
Theeffecto
6.1: Over-v This study
the negativ
but this det
young girls
angular ve
stability in
(determined
faster move
with the kn
who land in
children (H
torque valu
and/or only
of caution a
velocity mo
determinati
injury. Our
football spe
stability as
attributed to
greater dec
age related
differences
groups sho
groups FH/
other mech
increased
assumption
the EMD p
players wh
in younger
there is an
offootballsp
view of the
has reinfor
ve effects of
trimental eff
s when the
locity. This
young fem
d as the FH
ement veloc
ee in more
n more exte
ass et al.,
ues to descr
y assessed
as they do
ovements. O
ion of the F
statistical
ecific fatigu
determine
o the relativ
crease in c
d data did
in the fatig
owed no cha
/Q ratio inc
hanisms, r
relative ris
n is support
post fatigue
en fatigue i
, less matu
age effect
pecificfatigu
D main findi
rced the im
f fatigue on
fect disappe
e knee is c
has impor
male footba
H/Q) is impa
cities. Thes
extended p
ended posi
2005). Also
ribe the FH/
the ratio at
not represe
Our finding
H/Q ratio is
findings su
ue on dyna
d by the F
ve fatigue r
concentric q
not reach
gue related
ange in FH/
creased. Ho
rather than
sk of knee
ed by the n
e demonstr
is induced,
ure girls an
in the resp
ueondynam
Discings
portance of
female you
eared as th
closer to fu
rtant implica
llers as the
aired when
se findings
positions (L
tions with m
o, our findin
/Q ratio (wh
slow to me
ent what is o
s question
s not in the
uggest that
amic knee
FH/Q ratio,
esistance o
quadriceps
statistical
response
/Q ratio, the
owever, the
muscular
injury in
euromuscu
rates that
irrespective
nd reduces
ponse of fe
mickneestab
cuss
f using ang
uth footballe
he knee flex
ll extension
ations for th
e ability of
fatigue is p
have speci
ephart et a
more medio
ngs sugges
hich genera
edium angu
occurring c
the functio
position tha
t when usin
stability the
irrespective
of eccentric
torque afte
significanc
to muscula
e U15 age
e non-signif
stability, m
female you
ular findings
neuromusc
e of age or
with age,
eed-forward
bilityinfem
sion
le specific
ers was ev
xed. Additio
n the FH/Q
he determin
the muscu
present only
fic implicati
l., 2002) an
olateral join
st that previ
ally occur in
lar velocitie
loser to full
onal relevan
at the knee
ng the curr
ere are no
e of age or
hamstring
er fatiguing
e (p = 0.0
ar stability.
groups FH/
icant finding
may contrib
uth players
s in the curre
cular feedba
maturation
maturation
, pre-activa
maleyouthpl
Dr Mark D
n
data to exp
ident closer
onally this st
Q ratio decr
nation of m
ular system
y near full k
ions for fem
nd especiall
nt forces co
ious studies
the mid ra
es should be
knee exten
nce of most
is in when
rent field b
detrimenta
r maturatio
torque com
exercise. H
07) there w
From pre to
/Q ratio dec
gs would le
bute to a
s when fat
ent study. A
ack is imp
n. Important
and trainin
ation mecha
layers
De Ste Cro
plore the FH
r to full kne
tudy has sh
reases with
muscular dy
m to stabilis
knee extens
males who t
y postpube
ompared to
s that have
nge of the
e viewed wi
nsion and d
t previous l
it is likely to
based test
al effects o
n. This can
mpared with
However, a
were clear
o post fatig
clined and t
ead us to s
greater ex
tigue is pr
A significant
aired in yo
tly this effec
ng status. I
anisms whe
ix 59
H/Q ratio as
ee extension
hown that in
h increasing
namic knee
se the knee
sion, and a
tend to land
rtal females
prepuberta
e used peak
movement)
ith a degree
during faste
literature as
o sustain an
to examine
on muscula
n be mainly
a relatively
although ou
age related
gue the U13
he U17 age
suggest tha
xtent to the
resent. This
t increase in
outh female
ct is greate
Interestingly
en fatigue is
s
n
n
g
e
e
at
d
s
al
k
),
e
r
s
n
e
r
y
y
r
d
3
e
at
e
s
n
e
r
y
s
Theeffecto
present. Th
fatigue in y
improved in
demonstrat
the older a
reduced ab
further inve
normal grow
of muscula
cope with fa
significant
would tenta
when fatigu
This resear
effect on ne
and therefo
reduced n
youngest a
musculoske
ratio) and n
group. This
changes in
appear to
significant
and neuro
reinforce th
is essential
2006, 2009
fatigue resi
6.2: Influen The manife
angle, angu
was to exa
angular vel
offootballsp
he leg stiff
younger ag
n older play
te the effec
age groups
bility to utilis
estigation u
wth and ma
ar stability m
atigue may
difference
atively sugg
ue is presen
rch is the f
euromuscul
ore may be
euromuscu
age group
eletal syste
neuromusc
s status ma
limb propo
show signs
impairment
muscular f
he suggestio
l in female y
9) however
stance, whi
nce of foot
estations of
ular velocity
mine the ef
locities. A s
pecificfatigu
ness result
ged players
yers (U17).
ctiveness of
post fatigu
se neuromu
using non-t
aturation. T
mechanism
be related
in EMD of
gest that yo
nt.
first of its k
lar functioni
a potential
lar functio
p (U13) m
ms. The U1
ular (EMD)
ay be due
ortions as we
s of compe
to feed-ba
feed-forward
on from pre
youth footb
this improve
ich has not
tball specif
functional c
y, and actio
ffects of foo
significant ti
ueondynam
ts suggest
s (U13), re
The relativ
f football sp
ue, and this
uscular fee
trained con
he age rela
s and neur
to either a g
the three m
outh female
ind to dem
ing of the m
factor in th
ning in bo
ay be a
15 age grou
) capability
to their pu
ell as shifts
ensatory m
ack mechan
d mechani
evious rese
ballers to red
ement shou
previously
fic fatigue o
changes oc
on type (Gre
otball specif
me by joint
mickneestab
that feed-f
emain simila
ve leg stiffn
pecific train
s may be a
dback mec
ntrol groups
ated variabi
romuscular
growth/mat
muscles ex
footballers
onstrate th
muscles that
he increased
oth feed-fo
protective
up were the
post fatigu
ubertal statu
in metabol
mechanisms
nisms. This
sms when
arch that tr
duce the re
uld be age/m
been presc
on FH/Q ra
ccurring with
een, 1997).
fic fatigue o
t angle inter
bilityinfem
forward me
ar in pube
ness data o
ning, with e
a potential c
chanisms. H
s, as this m
lity in our fi
feed-forwa
urational ef
xamined wa
s do not mo
at football s
t support th
d relative ris
rward and
mechanism
only group
e and may
us and the
ic specialis
that may
age group
fatigue w
raining to im
elative risk o
maturation
cribed.
tio
h fatigue are
One of the
on the FH/Q
raction effe
maleyouthpl
Dr Mark D
echanisms a
rtal aged p
obtained in
nhanced pr
compensato
However, th
may simply
ndings sug
ard and fee
ffect and/or
as found in
ove to an an
specific fati
e knee in y
sk of injury
feed-back
m for thei
to show re
y be consid
interacting
ation. The o
help to pr
increased
was present
mprove neu
of injury (He
specific and
e multiple a
e aims of th
Q ratio at dif
ct was foun
layers
De Ste Cro
are compro
players (U1
the current
re-activation
ory mechan
his hypothe
y reflect ch
gest that th
edback mec
a training e
the curren
nkle domina
igue has a
outh female
in this pop
k mechanis
ir relatively
educed mus
ered a high
g effects of
oldest age g
otect the jo
both muscu
t. Our find
romuscular
ewett 2000;
d important
and depend
e present in
fferent joint
nd in the cu
ix 60
omised with
15) and are
t study may
n evident in
nism for the
sis requires
hanges with
he response
chanisms to
effect. As no
nt study, we
ant strategy
detrimenta
e footballers
ulation. The
sms in the
y immature
scular (FH/Q
h injury risk
f hormones
group (U17
oint despite
ular stability
dings would
r functioning
; Myer et al
tly related to
on the join
nvestigation
angles and
urrent study
h
e
y
n
e
s
h
e
o
o
e
y
al
s
e
e
e
Q
k
s,
)
e
y
d
g
l.
o
nt
n
d
y,
Theeffecto
indicating t
lower post-
influence o
compared w
is reduced
(Griffin et a
muscular d
peak torque
in the later
same move
that muscu
10° of knee
changes in
FH/Q ratio
eccentric h
concentric a
the knee a
the quadric
that in fema
full knee e
implications
in extende
indicated th
therefore th
of a footbal
It is difficult
angle spec
with which
reduction in
after fatigui
of laborator
have deter
appear to b
however un
indicated th
full knee e
offootballsp
that irrespe
-fatigue com
of fatigue d
with pre fat
and functio
al., 2006).
ynamic kne
e to calcula
stages of f
ement (Haw
lar stability
e extension
n the joint a
following f
hamstring m
and eccent
pproaches
ceps conce
ale youth pl
extension
s for footba
ed positions
hat females
he findings o
ll match ma
t to compar
cific FH/Q ra
to compar
n the FH/Q
ing exercise
ry based fat
rmined torq
be no studi
npublished
hat the ang
extension in
pecificfatigu
ctive of ag
mpared to
disappears
tigue. These
onal stabilit
The data f
ee stability
ate the FH/Q
football mat
wkins et al.,
is reduced
n. These fin
angle in you
football spe
muscle actio
ric torque d
extension t
ntric torque
ayers the a
when fatig
llers as com
s (eg pivo
tend to lan
of the curre
ay be a caus
re our findin
atios in you
re our findi
ratio calcul
e (Small et a
tigue protoc
ue with the
es that hav
data from o
gle specific
n adults wh
ueondynam
e the FH/Q
pre-fatigue
and by 20
e findings a
ty relies ma
from the cu
is joint angl
Q ratio. Epi
tches when
2001, Olse
when fatig
ndings supp
uth female
ecific fatigue
on is less e
data in the c
that the ab
e production
ability of the
gue is pres
mmon move
oting, twistin
nd with the k
ent study wo
se for increa
ngs to previ
uth female f
ngs. A num
lated in the
al., 2010; R
cols includin
e hip in a fl
ve explored
our laborato
FH/Q ratio,
hen fatigue
mickneestab
Q ratio at th
e. As the k
0-30° of kn
are importa
ainly on dyn
urrent study
le specific a
idemiologic
fatigue is p
en et al., 200
gue is prese
port the vie
players. By
e, we have
effective in
current stud
ility of the h
n is diminis
e dynamic m
sent is co
ement patte
ng, kicking
knee in mor
ould propos
ased relativ
ous literatu
footballers
mber of ad
mid range
Rahnama et
ng repeated
lexed posit
d the influen
ory, in a larg
, determine
e is presen
bilityinfem
he most ex
nee moves
nee flexion
nt as near f
namic stabi
y highlights
and reinforc
cal data sug
present and
04). The da
ent, but only
ew that the
y observing
e shown tha
extended
y it is evide
hamstrings
shed and th
muscular sys
mpromised
erns within t
g, landing).
re extended
se that landi
ve risk of inj
re as this is
post fatigue
ult studies
of the mov
t al., 2003).
d isokinetic
ion which i
nce of fatig
ge sample o
ed with the
t (El Naga
maleyouthpl
Dr Mark D
xtended join
s into a mo
n the FH/Q
full knee ex
lity to prote
s that the i
ces the inap
ggests that
d after num
ata from the
y as the kne
stability sy
g the chang
at in youth
knee posit
ent that whe
to act ecce
he ratio dec
stem to sta
. These fi
the game s
Landing
d positions (
ing from a j
ury in youth
s the first st
e. There is
have dem
vement (usin
These stud
actions and
s not funct
ue on angl
of adult part
hip extende
r, 2012: un
layers
De Ste Cro
nt position
ore flexed p
Q ratio incr
xtension, st
ect the knee
nfluence of
ppropriate u
injury is mo
erous repet
present stu
ee approac
ystems are
ge in the an
female foo
tions. By ex
en in a fatigu
entrically to
creases. Th
bilise the kn
indings has
ituation pla
mechanics
(Hass et al.
ump in the
h female foo
tudy to hav
also limited
onstrated a
ng peak tor
dies have us
d downhill r
tionally rele
e specific F
ticipants (n
ed, increase
npublished
ix 61
(0-10°) was
position the
reased pos
tatic stability
e structures
f fatigue on
use of using
ore frequen
titons of the
udy sugges
ches the las
affected by
ngle-specific
otballers the
xploring the
ued state as
o counterac
his suggests
nee close to
s particula
ce the knee
data have
., 2005) and
later stages
otballers.
ve examined
d adult data
a significan
rque values
sed a range
running, and
evant. There
FH/Q ratios
= 110), has
es closer to
PhD). This
s
e
st
y
s
n
g
nt
e
st
st
y
c
e
e
s
ct
s
o
r
e
e
d
s
d
a
nt
)
e
d
e
s,
s
o
s
Theeffecto
compensat
reduced ne
response t
immature a
compromis
hamstrings
no significa
does not ch
the adult lit
(due to a la
as the knee
2012). For
athletes to
found incre
knee flexio
may be at
protective
angle spec
effects of e
training effe
first hypoth
there are p
lengthening
movement,
given the a
whether a q
can accoun
hypothesis.
be related
experience
about the k
(2009) dem
found in co
However, i
individuals
age groups
offootballsp
tory mecha
euromuscu
to protect t
and develo
ed neurom
to act ecce
ant main ef
hange with
terature tha
arger decre
e approach
example C
calculate jo
easing FH/Q
n. Our data
risk during
mechanism
cific differen
eccentric to
ects and/or
hesis is true
rotective m
g (and subs
remains to
angle relate
quadriceps
nt for the l
. It may be t
to tradition
d during foo
knee, alteri
monstrated a
nventionally
if traditiona
we would h
s would ha
pecificfatigu
nism of inc
lar function
the joint. T
oping musc
muscular eff
entrically cl
ffect for join
increasing
at suggests
ease in the
es full exte
oombs and
oint angle-s
Q ratio valu
a suggest th
g movemen
m of increa
nce are dif
orque prod
r d) a comb
e for the U
echamism a
sequently l
o be investig
ed effects
dominance
lack of pro
that our find
al football
otball trainin
ing the bala
a training e
y trained foo
al football t
have expec
ave had m
ueondynam
creasing th
ning (longe
The data fr
cular syste
fects of fati
ose to full
nt angle ind
knee exten
s that there
quadriceps
nsion (Aaga
d Garbutt (2
pecific FH/Q
ues as the
hat even w
nts when th
sing muscu
fficult to pre
uction; b)
bination of t
17 age gro
acting on th
imit eccent
gated. Its is
in adults is
e is evident
otective effe
dings of a n
training effe
ng in youth
ance towar
effect in 15 y
otballers co
training in
cted to see
ore exposu
mickneestab
he FH/Q w
er EMD po
rom the cu
m is not
gue (see E
knee exten
dicating tha
sion when
is a protec
s concentric
aard et al.,
2002) used
Q ratio valu
knee exten
when fatigue
he knee is
ular stabilit
escribe but
quadriceps
these factor
oup given th
he younger
ric torque p
s also unlike
s not differe
in the fema
ect at more
non-significa
ects. Recen
male footba
rds quadric
year-old foo
ompared wit
female you
significant
ure to trad
bilityinfem
hen fatigue
ost fatigue)
urrent study
developed
EMD sectio
sion when
at the FH/Q
fatigue is n
ctive mecha
c torque tha
1998, Coom
a small sam
ues through
nded, and t
e is not pres
almost full
y. The me
t could be
dominance
rs. In the c
heir post p
age groups
production)
ely that the
ent betwee
ale youth fo
e extended
ant effect of
nt work has
allers asym
ceps domina
otball playe
th resistanc
uth players
age effects
itional train
maleyouthpl
Dr Mark D
e is presen
) and prop
y may sug
enough to
n). In parti
fatigue is p
Q ratio in yo
ot present.
anism of an
an in eccen
mbs and Ga
mple (n = 1
out a 90° ra
he highest
sent that fe
y extended
echanisms
related to
e in female
urrent study
ubertal stat
s (U13 and
at the ext
second hyp
en males a
ootballers in
knee posi
f joint angle
s confirmed
mmetrically s
ance (Iga e
ers on FH/Q
ce trained fo
s produces
s in the curr
ning. The f
layers
De Ste Cro
nt was in r
posed as
ggest that y
o compens
cular the a
present. We
outh female
This is in c
n increased
tric hamstri
arbutt, 2002
5) of adult
ange of mov
values we
emale youth
d due to th
behind this
either a) m
es; c) footb
y it is unlik
tus. Howev
U15) to red
remes of th
pothesis ha
nd females
the curren
itions is an
on the FH/
d that loadi
strengthen t
et al. 2009
Q ratio with
ootballers a
quadricep
rent study a
fact that w
ix 62
response to
a muscula
young girl’s
sate for the
ability of the
e also found
e footballers
contrast with
d FH/Q ratio
ings torque
2; El Nagar
recreationa
vement and
re at 10° o
h footballers
he lack of a
s adult/child
maturationa
ball specific
ely that this
ver, whethe
duce muscle
he range o
as crediance
s. However
t study, and
n interesting
/Q ratio may
ing patterns
the muscles
). Iga et al
lower ratios
nd controls
ps dominan
as the olde
e found no
o
r
s
e
e
d
s
h
o
)
r,
al
d
of
s
a
d
al
c
s
r
e
of
e
r,
d
g
y
s
s
l.
s
.
t
r
o
Theeffecto
significant
large group
reported sig
18 year old
ratio with
compared
developme
one study u
teenagers
teenagers (
youth bask
a non-signi
previous st
position wit
greater for
prone posit
versus sup
relationship
the present
hamstring a
functionally
The data fr
ratio. One o
potentially
periods of
which may
procedure t
kicking mo
useful, if no
play. The la
degree of c
= 0.07) the
fatigue. We
a significan
This equate
pre to post
offootballsp
age differe
p of male y
gnificantly lo
ds (0.84) co
age was a
with the re
nt of quadr
using non-t
and adults
(1.23) and
ketball playe
ficant age e
tudies cited
th the hip fle
knee flexio
tion (Black
ine or pron
p is altered.
t study, is t
and quadric
y relevant (W
om the curr
of the reaso
be ascribe
rapid dece
y reduce th
that involve
tions may
ot more log
ack of any
caution, as
ere appears
e found no s
nt decrease
es to an ab
t fatigue of
pecificfatigu
nces in the
youth footba
ower FH/Q
ompared wit
attributed to
elative incre
riceps dom
rained child
with 9-10
adults (1.19
ers (12-17 y
effect on FH
d here use
exed. This i
n in a sittin
et al., 199
e positions
An advant
hat it provid
ceps muscl
Worrell et al
rent study s
ons why we
ed to the fo
leration, ho
he amount
es more ext
place great
gistically diff
statistically
although th
s to be age
significant a
in the ratio
solute diffe
f 0.77. This
ueondynam
e FH/Q rati
allers aged
ratios, dete
th 12 year o
o a relativ
ease in ecc
inance in tr
dren reporte
year-olds
9) (De Ste
year-old) wh
H/Q ratios (G
ed peak tor
s particular
g position w
93). Therefo
should be
tage of the
des a close
es during m
l., 1990).
shows no in
e have foun
ootball spec
owever the
of eccentr
treme chan
ter stress o
ficult, to exp
significant
he exploratio
e group ass
absolute ch
in the U15
rence in the
s difference
mickneestab
o is in con
12-18 year
ermined in a
olds (1.01)
ely greater
centric ham
raditional fo
ed age asso
producing
Croix et al.
ho have rep
Gerodimos
rque to det
rly importan
when comp
ore, direct
viewed with
assessmen
r approxima
many functi
teraction or
nd no statis
cific protoco
protocol ha
ric work do
ges in direc
on the ecce
plore chang
age effects
on of age e
sociated dif
ange in the
’s (-0.39) an
e FH/Q ratio
e in the fat
bilityinfem
trast to a r
rs (Forbes
a seated po
(Forbes et
r increase
mstring torqu
ootball train
ociated effe
a significan
., 2007). Th
ported simil
et al. 2003
termine the
t given that
pared to the
comparison
h a degree
nt of torque
ation of the
onal and s
r main effec
stically sign
ol. The mo
as limited c
one during
ction and a
entric propo
ges in the F
s in the cur
effects did n
fferences in
e FH/Q ratio
nd a signific
o between t
igue related
maleyouthpl
Dr Mark D
recent cros
et al., 2009
osition using
al. 2009). T
in concent
ue, reinforc
ning in male
ects betwee
ntly lower F
here is one
lar findings
). It should
e FH/Q rat
t torque app
e more ecolo
n of torque
of caution,
in the supi
e length ten
porting acti
cts of fatigue
ificant fatig
ovements in
cutting and
the protoc
lso includes
ortion of th
FH/Q ratio p
rrent study
not reach sta
n the FH/Q
o in the U13
cant increas
the U15 an
d response
layers
De Ste Cro
s-sectional
9). Forbes e
g peak toqu
This reduct
tric quadric
cing a pote
e players. C
en prepuber
FH/Q ratio
study on tr
to the curre
be noted th
tio and from
pears to be
ogically val
obtained f
as the leng
ne position
sion relatio
vities, and
e and age o
ue related
n the SAFT
sideways m
col. A footb
s jumping,
e muscle.
post compe
must be vie
atistical sig
ratio from
3 age group
se in the U1
d U17 age
e to dynam
ix 63
study on a
et al (2009
ue values, in
tion in FH/Q
ceps torque
ntial for the
Conflictingly
rtal children
(0.97) than
rained male
ent study o
hat all of the
m a seated
significantly
id supine o
from seated
gth –tension
, as used in
nship of the
is therefore
on the FH/Q
effects may
T90 contain
movements
ball specific
landing and
It would be
etitive match
ewed with a
nificance (P
pre to pos
p (0.02), bu
17’s (+0.38)
group, from
ic muscula
a
)
n
Q
e
e
y
n,
n
e
of
e
d
y
r
d
n
n
e
e
Q
y
n
s,
c
d
e
h
a
P
st
t
).
m
r
Theeffecto
stability cle
larger sam
biological m
explored th
angle spec
the study o
following a
EMG analy
muscle act
mechanism
study. Com
specific fat
footballers
angle or m
from male
compromis
stability is i
to this incre
quadriceps
There are d
effects are
for the diffe
FH/Q ratio
Horstmann
and lower
findings ten
eccentric m
based on th
an addition
This hypoth
in the curre
the increas
status and
discussed i
Other stud
decrease in
offootballsp
early has so
ple size. It
mechanisms
he influence
cific data. In
of Wright et
fatiguing pr
ysis indicat
tions signif
m that could
mparable da
igue using
and found
ovement ve
footballers
ed after foo
increased in
ease in the
torque pro
data that ha
more pron
erences be
reported in
et al., (200
lactate and
ntatively sug
muscle actio
he compara
al protectiv
hesis would
ent study di
e in the FH
training st
in the EMD
dies have r
n the FH/Q
pecificfatigu
ome practica
is difficult
s as well a
e of football
n support of
t al., (2009)
rotocol cons
ted that th
ficantly inc
d be attribut
ata from yo
the SAFT9
no statistica
elocity (Dav
to the U17
otball spec
n a fatigued
e FH/Q ratio
oduction pos
ave shown
ounced in f
etween the
previous fo
01) also sug
d ammonia
ggest that t
ons with ma
ative finding
e effect tha
d require ve
ffer in non-
/Q ratio pos
tatus to pr
section).
reported co
Q ratio when
ueondynam
al significan
to prescribe
s relate the
specific fat
f the U17 fi
) reported
sisting of 50
he co-activa
creased pos
ted to the g
outh player
90 protocol
ally significa
venport, 20
female gro
cific fatigue.
d state in fe
o post fatig
st fatigue co
that eccen
females com
findings of
ootball fatig
ggested tha
reaction th
there may b
aturation in
gs from our
at is develop
erification by
-trained you
st fatigue in
rotect the jo
onflicting fi
n fatigue is
mickneestab
nce and ma
e these find
em to previo
tigue on the
ndings of in
a significan
0 maximal c
ation of the
st fatigue
greater FH/Q
rs is limited
on angle s
ant change
11 ; Unpub
oup in the c
Indeed, o
emale footb
ue but it is
ompared w
tric actions
mpared to
f the curren
ue related s
at usually e
an concent
be developm
young girls
U18 male p
ped through
y exploring
ung girls. At
n the U17 ag
oint due to
ndings tha
s present (D
bilityinfem
ay have reac
dings to ph
ous studies
e FH/Q ratio
ncreased F
nt increase
concentric k
e hamstrin
(Wright et
Q ratio foun
d but we h
specific FH/
in the FH/Q
blished MSc
current stud
ur data sug
ballers. It is
s related to
with the decl
are more r
males (Hick
nt study an
studies that
eccentric ex
tric exercise
ment of fatig
s towards th
professiona
h football tra
whether th
t this point
ge group m
o diminishe
at would su
Delextrat et
maleyouthpl
Dr Mark D
ched statist
hysiological
s as this is
o in female
FH/Q ratio w
in the FH/
knee flexion
gs during
al., 2009)
nd in the U1
have previo
/Q ratio in
Q post fatig
c thesis). Th
dy suggests
ggest that
difficult to
a greater r
ine in ecce
resistant to
ks et al. 20
nd the signi
t have used
xercise lead
e at compa
gue resista
he adult sta
l players is
aining and to
e fatigue re
we would t
ay be relate
ed neuromu
upport the
t al. 2010;
layers
De Ste Cro
tical signific
and biome
the first stu
youth footb
when fatigue
/Q ratio (0.8
n/extension
concentric
) and this
17 group in
ously explo
U18 male p
ue, irrespec
hese compa
s that FH/Q
post pubert
prescribe m
reduction in
entric hamst
fatigue and
01). This m
ificant decr
d males as p
ds to less a
arable work
nce followin
te. Another
that there m
otal hours o
elated affec
tentatively s
ed to both m
uscular stab
U15 data
Rahnama
ix 64
cance with a
echanical o
udy to have
ballers using
e is presen
88 vs. 1.08
repetitions
quadriceps
may be a
the curren
ored footbal
professiona
ctive of join
arative data
Q ratio is no
ty muscula
mechanisms
n concentric
tring torque
d that these
may accoun
rease in the
participants
cute fatigue
levels. Ou
ng repeated
r suggestion
may also be
of exposure
cts observed
suggest tha
maturationa
bility (to be
showing a
et al. 2003
a
r
e
g
t
)
s.
s
a
nt
ll
al
t
a
ot
r
s
c
e.
e
t
e
s.
e
r
d
n
e
e.
d
at
al
e
a
3;
Theeffecto
Small et al.
protocols (
activation a
would influe
of studies
simulated
significant d
2003; Sma
to a signific
previously
determine t
It is well rec
generally, e
Therefore,
as found in
in the U15
(Delextrat
mechanism
in eccentric
stability of
during the
eccentric c
have focus
task that in
hamstring
related res
increase in
studies hav
their faster
possible th
being non-
muscular fa
and greater
U17 age g
combined w
with using
offootballsp
, 2010). Th
(including t
and the env
ence the m
that have
exercise. T
decrease in
ll et al. 2010
cantly great
stated thes
the FH/Q ra
cognized in
eccentric a
in a fatigue
the U17 ag
5 age group
et al. 2010
ms associate
c hamstring
the joint is
period of p
compared to
ed on ecce
ncluded ec
muscles. T
ponse in th
the U17s
ve suggeste
r oxygen u
at due to t
-specialists
atigue respo
r contributio
roup is mo
with extensi
predominan
pecificfatigu
e contradic
the mode a
vironment)
echanisms
explored ch
The finding
n the FH/Q
0). All of the
er extent th
se data sho
atio and test
adults that
ctions are
ed state the
ge group in
p and thes
0; Rahnam
ed with this
torque follo
compromis
puberty. In a
o concentri
entrically fat
ccentric act
Tentative sp
he FH/Q rat
may be du
ed that you
uptake kine
he puberta
to becomin
onse in the
on from aero
re difficult t
ive training,
ntly anaero
ueondynam
ctory finding
and intens
and propor
of fatigue (
hanges in
gs of thes
ratio when
ese studies
han the con
ould be vie
ting occurre
t fatigue affe
more fatigu
e FH/Q ratio
the current
se findings
a et al. 20
s decrease a
owing fatigu
sed during f
adults this h
c torque pr
iguing the m
ions but d
peculation o
tio from no
e to develo
ng children
etics compa
l nature of
ng metabol
e U13 age g
obic source
to describe
, these play
obic metabo
mickneestab
s may be a
ity of exer
rtion of con
(Maluf and
the FH/Q r
e studies
fatigue is p
s reported th
centric qua
ewed with a
ed with the h
ects eccent
ue resistant
o should inc
t study. How
are compa
003; Small
at this age
ue in the pre
forceful kne
has been p
roduction a
muscles. Th
id not spec
on the reas
change in
opmental ch
are metab
ared to ad
the U15 ag
lic specialis
group was
es. The lack
but potent
yers may ha
olism during
bilityinfem
attributed to
rcise, the n
ncentric vs.
Enoka, 200
ratio in ma
are relativ
resent (Del
hat the ecce
adriceps torq
a degree o
hip in a flex
tric and con
t than conc
crease and
wever, we fo
arable to th
et al. 201
are more d
esent study
ee extensio
prescribed t
and has bee
he current f
cifically foc
son why w
the U13s,
hanges in m
olic non-sp
ults (Fawk
ge group th
sts. This hy
negligible d
k of a notice
tially throug
ave adapted
g the footba
maleyouthpl
Dr Mark D
the nature
nature of l
eccentric w
05). Howev
ale adults a
vely consist
extrat et al.
entric hams
que when fa
of caution a
xed position
ncentric acti
centric actio
the knee s
ound a redu
he previous
0; Oliveira
difficult to pr
y would app
n movemen
to a relative
en more ap
fatigue task
cus on ecce
e observed
to a decrea
metabolic s
ecialists, w
ner and A
hat they are
ypothesis w
due to their
eable eccen
gh normal g
d to the neg
all related e
layers
De Ste Cro
of the varyi
oading dur
work perfor
er, there ar
after a bout
tent, demo
. 2010; Rah
string torque
atigue was
as they all
.
ons differen
ons (Roig e
should be m
uction in the
sly cited ad
et al. 200
rescribe. Th
pear to sugg
nt in female
ely greater
pparent in s
was a foot
entrically fa
d a shift in
ase in the U
specialisatio
which may b
Armstrong, 2
e in the tra
would sugge
non-specia
tric fatigue
growth and
gative effect
exercise. Ho
ix 65
ng fatiguing
ring muscle
rmed, which
re a numbe
t of footbal
onstrating a
hnama et al
e decreased
present. As
used PT to
ntly and tha
et al. 2009)
more stable
e FH/Q ratio
dult findings
09), but the
he decrease
gest that the
e footballers
decrease in
studies tha
tball specific
atiguing the
the fatigue
U15s, to an
on. Previous
be related to
2007). It is
nsition from
est that the
alists nature
effect in the
maturation
ts that come
owever, the
g
e
h
r
ll
a
l.
d
s
o
at
).
e,
o
s
e
e
e
s
n
at
c
e
e
n
s
o
s
m
e
e
e
,
e
e
Theeffecto
U15 group
anaerobic
effects that
younger ch
pathways q
children’s lo
resynthesis
Croix and D
in body we
of injury du
as a perce
contact loa
growth. Add
not allow th
intriguing in
actions is s
However, i
injury risk.
they require
A further ex
with to the
SAFT90 pr
group comp
hypothesis
protocol. T
10,590m) d
there was
compared w
this greater
the FH/Q in
it would ap
stability (se
greatest ris
significantly
Cronin (20
injuries/100
offootballsp
p may be
sources an
t come with
hildren are m
quicker tha
ower ability
s, improved
Deighan, 20
ight (peak w
ue to increa
ntage of bo
ding in this
ditionally th
hem to deve
n that in ver
seen as a
n this case
These prop
e further inv
xplanation f
U17 age gr
rotocol is se
pleted more
is partly su
he mean d
despite the
not a sign
with the U1
r Q angle c
n the curren
ppear that
ee EMD se
sk of knee
y greater ri
12). Rumpf
00h in 9-12
pecificfatigu
in the tran
nd have no
h anaerobic
more fatigue
an adults a
y to activate
d acid base
011). Anoth
weight velo
ased loading
ody weight
age group
here may be
elop large e
ry young ch
protective
e the inhibi
posed reaso
vestigation.
for why we
roup may be
elf regulated
e work than
upported by
ifference be
fact that th
nificant age
3 and U17
could be a
nt study. Ho
this reduc
ection) whe
e injury. O
isk of injury
f and Croni
2y-olds co
ueondynam
nsition from
ot yet deve
c metabolism
e resistance
and therefo
e their type
e regulation
er explanat
ocity [PWV])
g from incre
that occur
without the
e a protectiv
eccentric fo
hildren an in
mechanism
itory effect
ons for the
found a ne
e attributed
d and work
the U17 gr
the data w
etween the
he U15 perf
e effect for
7 respective
contributing
owever, this
ced muscul
n fatigue is
Our findings
y in the pu
in (2012) re
mpared to
mickneestab
m relying o
eloped meta
m. These a
e compared
ore lead to
II muscle f
and faster
tion of the U
) during this
eased body
during PW
e concomita
ve/inhibitory
orce in fatig
nhibitory fee
m during mu
is unwante
findings of
egative fatig
to the natu
load is not
roup, theref
we collected
U15 and U
formed for
the Q ang
ely (17° Vs
g factor to t
s hypothesis
ar stability
s present, p
s may sta
ubertal child
eported a s
65.8 injur
bilityinfem
on aerobic
abolic strat
assumptions
d with adults
o a lower
ibres and c
r removal o
U15 data m
s pubertal s
y mass. Dis
WV may mea
ant increase
y mechanis
ue conditio
edback cont
uscle lengt
ed and ma
the current
ue related
ure of the fo
matched it
fore inducin
on the dist
U17 age gr
10min less
gles the U
14.5° and 1
the negative
s requires fu
, combined
places the
rt to expla
d, as recen
significant in
ries/1000h
maleyouthpl
Dr Mark D
sources to
tegies to co
s are suppo
s due to: a)
accumulati
c) possible f
of metaboli
may be relat
stage and th
proportiona
an that ther
es in muscle
m in the U1
ons. This sp
trol in the m
hening to a
y potentiall
t study are
effect in the
ootball spec
may be tha
g a greater
tance travel
roups was o
s (80 V 90m
15 age gro
15.2° respe
e fatigue re
urther inves
d with a re
pubertal fe
ain the me
ntly demons
ncrease in
in 13-16y-
layers
De Ste Cro
o using pre
ope with th
orted by ev
) children us
on of by-p
faster phos
c by-produ
ted to the ra
he increase
al increases
re is increa
e strength f
15 age grou
peculation is
muscle durin
avoid musc
ly increase
provided te
e U15 group
cific fatigue
at on avera
fatigue res
led during t
only 65m (1
mins). Final
oup had la
ectively). It m
elated effec
stigation. Ne
educed neu
emale footb
echanisms
strated by
injury incid
-olds. They
ix 66
edominantly
he negative
vidence tha
se oxidative
products, b
phocreatine
cts (De Ste
apid change
ed likelihood
s in body fa
ased ground
from muscle
up that does
s somewha
ng eccentric
cle damage
anatomica
entatively as
p compared
task. As the
age the U15
sponse. This
the SAFT90
10,525m Vs
ly, although
rger angles
may be tha
cts found on
evertheless
uromuscula
baller at the
behind the
Rumpf and
ence of 8.0
y tentatively
y
e
at
e
)
e
e
e
d
at
d
e
s
at
c
e.
al
s
d
e
5
s
0
s
h
s
at
n
s,
r
e
e
d
0
y
Theeffecto
speculate t
(PHV). The
should hav
Croix and D
strength, w
had time to
This hypoth
neuromusc
did not set
used in the
4 players h
6.3: Influen
The import
(either from
is difficult t
study to ha
players. Th
slight decre
increase in
induces an
slight reduc
in the neur
This in tur
displaceme
during land
Adult studie
after fatigu
Comys et a
It is difficult
nature of
unpublished
45min of fo
changes in
0.94, r = 0.8
offootballsp
hat this dra
e girls in th
ve benefited
Deighan, 20
without conc
o ‘train’ this
hesis seem
cular functio
out to colle
e current stu
ad knee inj
nce of foot
tance of fe
m a jump or
o compare
ave explore
he significan
ease in stif
the U17s fr
inhibitory r
ction in stiff
ral control t
n would lik
ent during g
ing.
es have pro
e (Morin e
al. 2006) an
t to attribute
the fatigue
d data from
ootball spe
n both feed-
87 respectiv
pecificfatigu
amatic incre
he U15 age
d from peak
011). It may
comitant inc
s larger mu
ms plausible
oning aroun
ect incidenc
udy as the r
uries during
tball specif
eed-forward
during pivo
the finding
ed changes
nt time by g
ffness in th
rom pre to p
response in
fness in the
to a lower c
kely lead to
ground cont
ovided conf
t al., 2011)
nd some sho
e these find
e protocol,
m our resea
ecific exerci
-forward mu
vely) (Olive
ueondynam
ease seems
e group in t
k strength g
y potentially
reases in n
uscle mass
e, given ou
d PHV in g
ce data this
reason why
g the testing
fic fatigue o
mechanism
oting/twisting
gs from the
in leg stiff
roup interac
he U13s co
post fatigue
n younger p
U13 group
contribution
o more of
act and sub
flicting resu
), some sh
owing no ch
dings to me
and the
rch group h
ise in 16-ye
uscle activi
er, 2008). D
mickneestab
to coincide
the current
gains that o
y be a case
neuromuscu
to work ef
ur limited kn
girls, but req
s hypothesis
y the sample
g period.
on leg stiff
ms in prep
g actions) a
current stu
fness follow
ction effect
ompared to
e. These da
players and
p indicates l
n from pre-a
a yielding
bsequently
ults with so
owing a de
hange in sti
echanistic st
methods
has shown
ear-old boy
ty and ecce
ata has also
bilityinfem
e, especially
study were
occur aroun
that this gr
ular function
ffectively fro
nowledge o
quires furthe
s resonates
e is the sma
ness
paring the j
are crucial f
udy to the e
wing footbal
observed in
o relatively
ta would su
an excitato
longer grou
activation a
action with
increase th
me studies
ecrease in
iffness (Gira
tructures bu
used to c
an individua
ys, with str
entric musc
o shown tha
maleyouthpl
Dr Mark D
y in boys w
e, on avera
nd 0.5y afte
roup is expe
ning. Theref
om a neuro
on develop
er investiga
s with data
allest in the
joint for co
for dynamic
extant litera
ll specific fa
n the curren
no change
uggest that
ory respons
und contact
and short la
h an increa
he relative r
s showing a
stiffness (D
ard et al. 20
ut they coul
calculate le
alised respo
rong linear
cle activity
at differenc
layers
De Ste Cro
ith peak he
age 1y pos
er PHV in g
eriencing la
fore they m
omuscular p
ment of mu
ation. Also a
obtained fro
e U15 age g
ontact with
c stability of
ature as this
atigue in yo
nt study was
e in the U1
football spe
e in older p
times and
atency stret
ase in cent
risk of injury
an increase
Dutto and S
011; Morin e
ld be influe
eg stiffness
onse of leg
relationship
with leg sti
es in stiffne
ix 67
ight velocity
st PHV, and
girls (De Ste
rge gains in
ay not have
perspective
uscular and
although we
om the club
group is tha
the ground
the knee. I
s is the firs
outh female
s due to the
15s and an
ecific fatigue
players. The
a likely shif
ch reflexes
tre of mass
y, especially
in stiffness
Smith 2002
et al. 2006)
nced by the
s. Currently
g stiffness to
ps between
iffness ( r =
ess between
y
d
e
n
e
e.
d
e
b
at
d
t
st
e
e
n
e
e
ft
s.
s
y
s
2;
).
e
y
o
n
=
n
Theeffecto
children an
this needs
also be tak
studies hav
proportiona
and muscu
stiffness th
current stu
varying me
simply desc
forward me
The stiffnes
those previ
2010). Lloy
and 15 yea
(2012) and
control of
differences
groups. Th
maturationa
Lloyd et al
forward inp
found age
female foot
age related
from norma
significant m
The U13 d
detrimental
Importantly
stiffness wa
contact tim
pre-activati
suggest a
activity, but
offootballsp
d adults are
to be take
ken when
ve simply t
al changes
ular function
hat both bo
dy. Therefo
thod used t
cribe the ind
echanisms.
ss values r
ously found
yd et al (20
ar olds (49 v
d Oliver an
leg stiffnes
but the st
ese data a
al effect in
(2012a) su
put and sho
related ch
tballers, bu
d effects fou
al growth
maturation
data showin
l fatiguing
y there were
as reduced
es, shorter
on and sho
transition
t this hypot
pecificfatigu
e related to
n into cons
examining
taken body
in limb leng
ning. Thus
dy mass a
ore differen
to determin
dividualised
reported in
d using the
12) reporte
vs 46) to ou
d Smith (2
ss in boys
tiffness was
are difficult
leg stiffnes
ggest that a
ort latency s
anges that
t they are o
und in the c
and matura
effects in le
ng a small
effect on
e no individu
d post fatigu
flight times
ort latency
from fast
thesis requ
ueondynam
the speed
sideration w
data from
mass into
gth during g
it is import
nd limb len
nces in the
e relative s
d response
the current
same proto
d comparat
ur pre-fatigu
2010) have
with stiffne
s lower pre
to explain
ss that is re
as children
stretch refle
may supp
only eviden
current stud
ation. Ther
eg stiffness
l decrease
neuromus
ualised effe
ue. This red
s, and a like
stretch refl
stretch-sho
ires investig
mickneestab
of the move
when compa
studies th
account b
growth and
tant that wh
ngth are ta
findings o
tiffness. Ho
of fatigue to
t study for
ocol in youn
tive relative
ue data for
reported s
ess increas
e fatigue in
as others h
elated to gr
mature the
exes to regu
port this me
nt when fat
y are more
re is suppo
(Korff et al.
in leg stif
scular feed
cts of fatigu
duction in r
ely shift in th
exes. The
ortening cyc
gation using
bilityinfem
ement (Oliv
aring data
at have re
but this is n
maturation
hen explori
ken into ac
f previous
owever, the
o neuromus
the U13 an
ng boys (Llo
e leg stiffnes
U13 and U
significant a
sing with a
the U17 c
have propo
rowth and t
ey become m
ulate greate
echanism in
igue is pres
likely due
orting data
, 2010, Lloy
ffness from
d-forward m
ue on leg st
relative leg
he neural c
reduction in
cle activity
g contact ti
maleyouthpl
Dr Mark D
er and Smit
from differe
ported rela
not appropr
n play a key
ng age rela
ccount, as
studies ma
conflicting
scular functi
nd U15 age
oyd et al., 2
ss data for 1
U15s respec
age related
age. We a
compared w
osed that in
he develop
more relian
er levels of
n relation t
sent. It is li
to the effec
that has a
yd et al., 20
m pre to po
mechanisms
iffness and
stiffness in
ontrol to a
n angular d
to slow s
ime data. W
layers
De Ste Cro
th, 2010) an
ent studies.
ative stiffne
riate in chil
y role in bio
ated differe
has been d
ay be attrib
findings ma
ioning in ter
e groups ar
2012; Oliver
12 year olds
ctively. Both
d effects in
lso found a
with U15 an
n boys there
pment of mo
t on supra-
leg stiffnes
to maturatio
ikely therefo
ct of fatigue
also demo
012).
ost fatigue
s in this
all participa
ndicates lon
lower contr
displacemen
stretch-shor
What drives
ix 68
nd therefore
Care mus
ss as mos
dren where
omechanica
ences in leg
done in the
buted to the
ay of course
rms of feed
re similar to
r and Smith
s (44 vs 45
h Lloyd et a
the neura
age related
nd U13 age
e is a clea
otor control
spinal feed
ss. We have
on in youth
ore that the
rather than
nstrated no
indicates a
age group
ants relative
nger ground
ibution from
nt may also
rtening type
s this neura
e
st
st
e
al
g
e
e
e
-
o
h,
)
al
al
d
e
r
l.
-
e
h
e
n
o
a
p.
e
d
m
o
e
al
Theeffecto
response in
excessive r
is well reco
compared
protective
childhood m
developme
programme
propriocept
pre-program
The U15 da
that have s
45min of fo
individualis
fatigue whi
run have a
participants
and Smith,
stiffness pr
individuals
relatively s
pubertal sta
PHV was +
by individua
ways self r
do not exhi
but also do
group.
The U17 da
pubertal fe
explain but
some form
fatigue is p
has been s
been report
offootballsp
n this age
rapid overlo
ognised tha
to children
mechanism
may also d
nt is influen
ed comman
tive feedba
mmed comm
ata found in
shown no si
ootball spec
ed respons
lst others d
also demo
s increasing
, 2007). Ou
e-post fatig
but reduce
mall and in
atus of this
+0.41 – 1.9
als after the
regulated. T
ibit significa
o not use fee
ata was som
emale footb
t as with th
of compen
resent. This
shown in pre
ted that fem
pecificfatigu
group is un
oad of the r
at the Golgi
(Oliver an
m. It has a
dampen the
nced by fati
nds that pla
ck, our find
mands may
n the curre
gnificant ch
cific exercise
se to the fa
emonstrate
nstrated an
g stiffness,
ur data als
ue in the U
ed in others
n line with
group with
5y). These
e football s
These data
ant detrimen
ed-forward
mewhat une
ballers when
e enhance
nsatory mec
s finding ma
evious stud
males use a
ueondynam
nclear but c
relatively im
complex is
nd Smith, 2
lso been p
e excitatory
gue in child
y a decisiv
dings sugge
y not be opt
nt study are
hange in rel
e (Oliver, 2
atigue proto
ed a decrea
n individua
some show
so demonst
15 age gro
s post fatigu
our finding
h individuals
findings m
pecific fatig
suggest th
ntal effects
mechanism
expected an
n fatigue is
d FH/Q rat
chanism to
ay also sup
ies examini
an enhanced
mickneestab
could be re
mmature mu
s considera
2010) and
proposed th
y response
dren remain
ve role in st
est that you
imal when f
e in agreem
lative leg st
008). Howe
ocol with so
ase in leg st
alised respo
wing no cha
trated some
up, indicatin
ue. Howeve
s for the F
s at differin
ay also refl
gue task as
at female p
of fatigue o
ms in a com
nd suggests
s present.
io post fatig
counteract
pport some
ing fatigue e
d feed-forw
bilityinfem
elated to a
usculotendo
ably diminis
this in part
hat intrafus
to a stretc
ns to be inv
tiffness regu
ung female
fatigue is pr
ment with p
tiffness in U
ever, the Ol
ome individ
tiffness. Ad
onse to a
ange and so
e individua
ng that pre-
er, the incre
FH/Q ratio t
ng stages o
lect differing
s the worklo
players who
on feed-forw
mpensatory m
s enhanced
The propos
gue we ten
t the reduce
form of qua
effects in fe
ward strategy
maleyouthpl
Dr Mark D
protective
on system u
hed in size
t may acco
sal fibre de
ch stimulus
vestigated. A
ulation toge
footballers
resent.
revious unp
U16 year old
iver (2008)
uals increa
ult data foll
fatigue rel
ome showin
lised respo
-activation w
ease or dec
this variabil
f maturatio
g amounts
oad was no
o are progre
ward neuro
manner, as
feed-forwa
sed reason
ntatively sug
ed feedbac
adriceps-do
emales (Pad
y of the qua
layers
De Ste Cro
mechanism
upon ground
e and numb
ount for the
evelopment
s in children
As it is likel
ether with a
s (U13) abi
published o
d male foot
data demo
asing leg st
lowing a 1h
ated task,
ng a decrea
onse to the
was enhanc
crease in st
ity may be
n (range in
of fatigue e
t set and w
essing throu
omuscular m
s shown in t
ard mechan
n for this is
ggest that t
ck system (E
ominant stra
dua et al., 2
adriceps wh
ix 69
m to preven
d contact. I
ber in adults
e increased
throughou
n. How this
y to be pre
a barrage o
lity to recal
observations
ballers afte
onstrated an
tiffness pos
h exhaustive
with some
ase (Hunte
e change in
ced in some
tiffness was
due to the
offset from
experienced
was in some
ugh puberty
mechanisms
the U17 age
isms in pos
s difficult to
this may be
EMD) when
ategy, which
2006). It has
hen fatigued
t
t
s
d
ut
s
-
of
ll
s
r
n
st
e
e
r
n
e
s
e
m
d
e
y
s
e
st
o
e
n
h
s
d
Theeffecto
by activatin
(Padua et a
and/or foot
times (long
(FH/Q ratio
demonstrat
greater rela
greater ext
al. (2012)
greater abs
findings ma
stiffness in
simply to a
youth footb
exposure to
response a
pre-activati
decrease c
and skill ma
of Laffaye e
increased s
in the curr
performanc
Therefore,
above chan
course spe
therefore th
flexibility tra
al., 1992).
weeks of p
Although L
study explo
an increase
findings su
properties
study. Pote
offootballsp
ng the quad
al., 2006). O
tball specifi
ger EMD) by
o) and feed
ted that me
ative stiffne
ensor activ
reported si
solute and
ay support
female you
age and ma
ballers requ
o football tr
and musculo
on (Lazarid
co-contractio
astery asso
et al (2005)
stiffness to
rent study
ce and this m
our data m
nges that w
eculation as
his should
aining have
There is ve
plyometric tr
loyd et al (
oring the eff
e in Achilles
uggest that
in children
entially the
pecificfatigu
driceps 45%
Our finding
ic training t
y moving to
-forward m
en were ab
ess compa
vity and abil
imilar findin
relative leg
our data in
uth footballe
aturation, o
uires further
raining may
oarticular st
dis et al.,
on ratios. T
ociated with
) indicated t
maximise ju
have ‘lear
mastery ma
may potentia
we would e
s we do not
be an ave
e been show
ery little dat
raining impr
2012) did n
ffects of 10
s tendon st
training m
through ph
change fro
ueondynam
% more tha
s tentatively
that post p
o a quadrice
echanisms
ble to incre
red to boy
lity to use r
ngs in 9, 1
stiffness in
ndicating tha
ers, but only
or is further
r investigat
y develop th
tiffness (Gro
2010), im
There may a
h the ability
that those in
ump height
rned’ to inc
ay also help
ally demons
expect to se
t have any c
enue for fu
wn to lead t
ta on childr
roved leg s
not find any
weeks of r
tiffness (Wa
may be abl
hysical train
m an inhib
mickneestab
an male co
y suggest t
pubertal fem
eps domina
(stiffness)
ease their f
ys at faster
reflex musc
2 and 15y
n 15 year o
at there ma
y when fati
r enhanced
ion using n
he ability, w
osset et al.,
prove spin
also potent
to increase
ndividual cla
compared
crease stiff
p to reduce t
strate some
ee through
control grou
rther study
to both incr
ren howeve
tiffness in 1
y training re
resistance t
augh et al.,
e to influe
ning and ma
itory effect
bilityinfem
unterparts
that via eith
male player
ant strategy
to protect t
feed-forwar
r hopping v
cle activity (
year old bo
olds compa
ay be an ag
gue is pres
d through fo
non-trained
when fatigue
, 2007), inc
ndle sensiti
tially be som
e stiffness w
assified as
to novices.
fness when
the relative
form of tra
normal gro
up data to c
y. In adults
eases or de
er, one rece
12 and 15-y
elated effec
training in p
2011; cited
ence both r
ay in part e
of fatigue i
maleyouthpl
Dr Mark D
in preparat
her normal
rs compens
y and increa
the joint. O
d mechanis
velocities. E
Oliver and
oys, demon
red to 12 a
ge related
sent. Wheth
ootball spec
controls. It
e is present
crease and
ivity (Gross
me form of
when fatigu
experts we
It may be t
n fatigue is
risk of injur
aining effect
owth and d
compare ou
certain for
ecrease in
ent study ha
year old bo
cts in 9-yea
prepubertal
d in Blazvic
relative leg
explain the
in the U13
layers
De Ste Cro
tion for grou
growth and
sate for lon
asing muscu
liver and S
sms by de
EMG also
Smith, 201
nstrating a
and 9 year
effect in en
her this effe
cific training
t could be
t, to increas
produce ea
set et al.,
training/lea
e is presen
re able to d
that the U17
s present
ry.
t that may b
evelopment
ur findings
rms of resi
leg stiffness
as indicated
ys (Lloyd e
ar old childr
children de
ch et al., 20
stiffness a
findings of
group to a
ix 70
und contac
d maturation
nger latency
ular stability
Smith (2010
monstrating
indicated a
0). Lloyd e
significantly
olds. These
nhanced leg
ct is related
g in female
that greate
se the reflex
arlier muscle
2007) and
arning effec
nt. The work
demonstrate
7 age group
to maintain
be over and
t. This is o
against and
istance and
s (Wilson e
d that just 4
et al., 2012)
ren a recen
emonstrated
011). These
and tendon
the curren
n excitatory
ct
n
y
y
)
g
a
et
y
e
g
d
e
r
x
e
d
ct
k
e
p
n
d
of
d
d
et
4
).
t
d
e
n
t
y
Theeffecto
response in
compensat
through tra
systematic
be related t
6.4: Influen
The EMD,
muscle res
tendon unit
muscle ten
during phys
the organiz
through its
The signific
that footbal
demonstrat
compromis
neuromusc
affected mo
for all musc
number of m
coupling fa
(Pasquet e
corroboratin
reduced ca
loading of
present. S
represent a
which may
under great
It is difficult
changes in
offootballsp
n the U17 g
te for a redu
aining. It sh
plyometric
to football s
nce of foot
which is a c
ponse to su
t compromi
nsion to the
sical activiti
zation of th
relationship
cant group b
ll specific fa
te that irre
ed with foo
cular system
ost in youn
cles assess
mechanism
ilure as wel
et al., 2000,
ng findings
apability of t
the knee f
Such fatigue
an increase
be amplifie
test mecha
t to compar
n EMD bef
pecificfatigu
group could
uction in oth
ould be no
, resistance
specific train
tball specif
component
udden move
se knee int
tibia. Prev
es. Vos et a
he moveme
p with the re
by time inte
atigue signif
espective o
otball perfo
m to contrib
ger age gro
sed was lon
ms such as m
ll as structu
Gibala et
from other
the dynamic
from a neu
e-related c
ed risk of inj
ed particula
nical strain
re our data
fore and a
ueondynam
d be attribu
her stability
oted that no
e or eccent
ning effects
fic fatigue o
of the refle
ements. Cli
tegrity and/o
vious studie
al., (1991) o
ent and pro
eflex time.
eraction effe
ficantly incr
of age ne
rmance in
bute to the
oups. The s
nger post-fa
metabolic in
ral changes
al., 1995, B
r studies (e
c stabilisers
uromuscular
changes in
jury (Chan
arly at knee
(e.g., near
to the wor
after fatigue
mickneestab
uted to som
mechanism
one of the g
tric conditio
.
on EMD
ex time, is i
nically, alte
or impair pe
es have hig
observed th
obably resu
ect and main
reases EMD
euromuscula
youth fema
stabilisatio
significant m
atigue com
nhibition of t
s that have
Baker et al
e.g., Gleeso
s to provide
r perspectiv
neuromus
et al., 2001
e angles wh
full knee ex
k of others
e in young
bilityinfem
me form of t
ms with fatig
groups in th
oning progra
mportant fo
erations in t
erformance
hlighted the
hat changes
ult in impa
n effect for
D post fatig
ar feedbac
ale footballe
on of the kn
main effect
pared to pr
the contract
been sugg
., 1993). Th
on et al. 19
e forceful co
ve (feedba
scular perfo
1; Gleeson
here key lig
xtension) (B
as there ar
girls, and
maleyouthpl
Dr Mark D
training effe
gue (eg long
he current
ammes, so
or sports pe
he EMD of
e by modifyi
e importanc
s in EMD pl
irment of n
time and gr
ue for all ag
ck mechan
ers. Import
nee when f
for time, in
re-fatigue c
tile process
ested to ex
he present
998; Zhou e
orrective res
ck mechan
ormance m
et al., 1998
gamentous
Beynnon an
re no studie
during ec
layers
De Ste Cro
ect where t
ger EMD) is
study have
this hypoth
erformance
the hamstr
ing the tran
ce of chang
lay an impo
neuromuscu
roup for EM
ge groups.
isms are
tantly the a
fatigue is p
ndicating th
can be attrib
s; excitation
plain periph
findings, to
et al. 1996)
sponses to
nisms) whe
may be int
8; Mercer e
structures
d Johnson,
es that hav
ccentric act
ix 71
he ability to
s developed
e undergone
hesis would
as it affects
ring muscle
nsfer time o
ges in EMD
ortant role in
ular control
MD indicated
These data
significantly
ability of the
present was
at the EMD
butable to a
-contraction
heral fatigue
ogether with
), suggest a
mechanica
n fatigue is
terpreted to
et al., 1998)
are already
1996).
e examined
tions of the
o
d
e
d
s
-
of
D
n
l,
d
a
y
e
s
D
a
n
e
h
a
al
s
o
),
y
d
e
Theeffecto
hamstrings
mainly duri
influenced
the level of
the age an
the majority
2012; Nilss
Nilsson et
concentric
The study
component
production
implications
even after m
of football s
study it m
compromis
This hypoth
on both mu
coaches w
population.
To our kno
eccentric m
have show
female adu
with the fin
compromis
than that o
influence n
adulthood.
There are n
or females
isometric a
2010; Zhou
triceps sura
offootballsp
. There are
ng isometri
by the type
f effort (Gra
d sex of the
y of adult s
son et al., 19
al. (1977)
muscle acti
of Howats
t that EMD
returns to
s for injury
muscular co
specific exe
may be tha
ed until the
hesis requir
uscular and
with importa
owledge no
muscle actio
wn a signific
ults, with the
ndings of th
ed when fa
observed fo
neuromuscu
no paediatr
. The limite
actions and
u et al. 1995
ae in norma
pecificfatigu
e a numbe
ic muscle a
e of muscle
abiner, 1986
e participan
studies have
977, Horita
reported a
ions from 95
son (2010)
D remains
o pre fatig
risk as neu
omponents
ercise on EM
at youth fe
ir next train
res further
d neuromus
ant informa
o studies h
ons of the h
cant increas
e effects si
he current s
atigue is pre
or adults, in
ular stability
ric studies t
ed EMD da
in a non-fa
5). The work
al and dise
ueondynam
er of adult
actions. The
e action (Ca
6; Vos et a
nts (Clarkso
e shown a s
and Ishiko,
an increase
5ms at rest
) indicated
compromis
ue levels.
romuscular
have recov
MD, howev
emale footb
ning session
investigatio
scular com
ation regar
have exami
amstrings.
se in EMD
gnificantly g
study indica
esent. The
ndicating tha
y to a grea
hat have ex
ata in childr
atigued sta
k of Gosset
eased childr
mickneestab
studies tha
ere is an ac
avanagh an
al., 1991), fa
on and Krol
significant i
, 1987; How
e in EMD
to 121ms a
that after
sed 96h a
These da
r feedback
vered. We d
ver given the
ballers neu
n or game w
on plotting t
ponents in
rding neuro
ined the ef
However, u
during ecc
greater in f
ating that E
absolute ch
at football
ater extent
xplored the
ren have be
te (Cohen
t et al. (2010
ren. They r
bilityinfem
at have exp
cknowledge
nd Komi, 19
atigue (Nils
l, 1978, Be
increase in
watson 2010
of the vas
after 100 ma
r fatiguing
after the fa
ata from ad
mechanism
did not expl
e large incr
uromuscula
which could
the chronic
youth fem
omuscular
ffect of fati
unpublished
centric ham
females (El
EMD during
hange in EM
specific fat
t in female
e influence o
een exclusi
et al. 2010
0) focused
reported a g
maleyouthpl
Dr Mark D
plored fatig
ment in the
979), joint a
son et al.,
ll and Jaco
EMD follow
0; Zhou et a
stus laterali
aximal isok
exercise w
atiguing tas
dult partici
ms appear to
ore the chro
rease in EM
r feedback
increase th
effects of f
ale football
readiness
gue on ch
d observatio
mstring exer
Nagar, 20
g eccentric
MD in the c
igue effects
s during c
of fatigue o
ively on ma
0; Falk et a
on ankle st
greater EM
layers
De Ste Cro
ue effect o
e literature t
angle (Grab
1977, Kroll
bs, 1986).
wing fatigue
al., 1996). F
is muscle
inetic knee
with a larg
sk even th
pants have
o remain co
onic effects
MD found in
k mechanis
he relative r
football spe
lers. This m
to re-perfo
anges in E
ons from ou
rcise in bot
12). These
hamstring
current stud
s appear to
hildhood co
n EMD in e
ale participa
al. 2009; Gr
iffness and
MD in childre
ix 72
on EMD bu
that EMD is
biner, 1986)
, 1974) and
Despite this
e (El Nagar
For example
(VL) during
extensions
e eccentric
hough force
e importan
ompromised
s of the bou
the curren
sms remain
isk of injury
ecific fatigue
may provide
orm in this
EMD during
ur laboratory
h male and
data agree
actions are
dy is greate
o negatively
ompared to
either males
ants, during
rosset et al
EMD of the
en suffering
ut
s
),
d
s
r,
e
g
s.
c
e
t
d
t
t
n
y.
e
e
s
g
y
d
e
e
r
y
o
s
g
l.
e
g
Theeffecto
with Legg-C
children. C
longer EMD
as a result
differences
Therefore d
conduction
developme
Our data s
actions. Th
with the U1
are longer
(Cohen et a
the muscle
that compa
shown to v
muscle act
study by M
angles prox
specific ch
(McComas
activation (
(Muraoka e
Additionally
present. Th
reduced ab
response o
girls have a
girls and th
observed a
in fibre type
shorter forc
with matura
(2010) did
suggesting
may challe
offootballsp
Calve_Pert
ohen et al.
D in young c
of differen
in muscle
differences
velocity ha
nt may redu
support this
e U13 had
15 (93ms) a
than those
al. 2010; Fa
e group, mu
arison of EM
vary betwee
ion, joint an
Minshull et a
ximal to ful
ange in EM
, 1996), th
Komi et al.
et al., 2004)
y the curren
he significan
bility of yo
or that they
a more com
his requires
age differen
e distributio
ce-developi
ation althou
not show a
that level o
enge this co
pecificfatigu
hes diseas
(2010), Fa
children (8-
ces in mus
e compositi
in muscle a
ave been i
uce muscle
s age relat
significantly
and U17 (92
e previously
alk et al. 200
uscle action
MD data be
en 30 to 50
ngle and m
al. (2011) d
l knee exte
MD is likel
he discharg
, 2000) and
.
nt study is t
ntly longer E
unger child
y have a les
mpliant mus
more time
ce in the pr
on (Viitasalo
ng times th
ugh the ev
any signific
of training st
onclusion a
ueondynam
se (a hip di
alk et al (20
-12 years) c
scle compos
ion are no
activation, s
mplicated i
-tendinous
ted differen
y longer EM
2ms) age g
y reported
09; Grosset
n and move
etween stud
0ms up to a
ovement ve
emonstrate
ension were
y to reflec
ge propertie
d the compl
the first to d
EMD both p
dren to qui
ss stiff mus
scle–tendon
to produce
resent study
o and Komi
an type I fib
vidence to s
cant differen
tatus did no
and sugges
mickneestab
isorder) com
009) and Z
compared to
sition. How
t sufficient
such as exc
in this long
stiffness an
nce in EMD
MD for all m
groups. The
in the litera
t et al. 2010
ement veloc
dies is prob
a few hundr
elocity (Shu
ed that volit
e shortened
ct the influe
es of the
iance chara
demonstrate
pre and pos
ickly activa
sculo-tendin
n system w
e a mechan
y in relation
, 1981, Wo
bres. It may
support this
nce betwee
ot have an e
st that num
bilityinfem
mpared to
Zhou et al (
o adults. Th
wever, curre
to accoun
citation-cont
ger EMD. T
nd increase
D of the ha
uscles asse
pre-fatigue
ature for is
0; Zhou et a
city used. It
blematic as
red ms dep
ultz and Pe
ional EMD
d by increas
ence of the
motoneuron
acteristics o
e age relate
t fatigue in
ate their m
nous system
when fatigue
ical respon
ns to fatigue
oledge et al
y be that th
s view is li
en enduranc
effect on EM
mber of tota
maleyouthpl
Dr Mark D
healthy co
1995) have
his longer E
ent limited e
nt for the c
traction cou
Therefore th
the potenti
amstring du
essed (aver
e EMD valu
sometric act
al. 1995) bu
t has been
EMD value
pending on
rrin, 1999).
of the quad
sed knee fl
e degree o
ns and the
of the musc
ed effects in
the U13 ag
uscles unti
m. It is pos
e is presen
se, given th
e could also
., 1985), wi
ere is an in
imited. Inte
ce trained a
MD in 9-12
al hours of
layers
De Ste Cro
ntrols, albe
e all found
EMD in child
evidence su
child-adult
upling and m
his lower ra
ial for injury
uring eccen
rage 119ms
es in the cu
tions (rang
t this may b
previously
es in adults
the muscle
For examp
driceps fem
lexion. This
of myofilam
e capability
culo-tendino
n EMD whe
e group ma
il the first
ssible that t
nt compared
he same st
o represent
ith type II fi
ncrease of t
erestingly, C
and untrain
year olds. O
athlete exp
ix 73
eit only in 6
significantly
dren may be
uggests tha
differences
muscle fibre
ate of force
y in children
ntric muscle
s) compared
urrent study
e 44-65ms
be related to
recognised
s have been
e examined
ple a recen
moris at join
s joint angle
ent overlap
y for neura
ous complex
en fatigue is
ay indicate a
mechanica
the younge
d with olde
imulus. The
t differences
bres having
ype II fibres
Cohen et a
ned children
Our findings
posure may
6
y
e
at
s.
e
e
.
e
d
y
)
o
d
n
,
t
t
e
p
al
x
s
a
al
r
r
e
s
g
s
al
n
s
y
Theeffecto
influence E
growth and
hypothesis
participants
The main
excitation-c
component
ions (Ca2+)
reach its pe
time of 40m
(SR) Ca2+ r
EMD during
intense mu
peak), Ca2+
Ishiko, 198
during fatig
mechanism
U13 age g
fatigue (eg
Arnstrong,
specific tra
anaerobic
detrimental
the contrac
et al., 1996
EMD is the
increases i
alter the EM
likely that t
reduction in
EMD during
the current
properties a
In response
the ability to
offootballsp
EMD by red
d maturation
requires f
s at each ag
proposed m
contraction
ts (SEC), re
) release fr
eak level (Z
ms. Impaired
release and
g fatigue (W
uscle action+ sensitivity
87b, Maclar
gue may be
m we would
roup. Curre
g acidosis o
1997). We
ining, which
metabolism
l by-produc
ctile compon
6, Viitasalo
e time for
n the perce
MD time. Th
this reflects
n muscle fi
g fatigue is
t study cou
and require
e to muscul
o detect joi
pecificfatigu
ucing the d
n (as show
further inve
ge group.
mechanism
coupling c
esulting in
rom the sar
Zhou et al.,
d membran
d therefore,
Westerblad e
s may redu
y and force
en et al., 1
e largely att
not have e
ent data on
or accumul
can only sp
h includes l
m in this ag
ts of anaer
nent to stret
and Komi,
the contrac
entage of ty
he current s
s impaired c
ibre conduc
s not clear.
uld be due
s further stu
lar fatigue,
nt motion m
ueondynam
detrimental
wn in the U1
estigation i
m for the le
contractile
prolonged
rcoplasmic
1996), whic
e conductiv
, contribute
et al., 1991
uce SR Ca2
production,
989). It wo
tributed to t
expected to
children su
ation of Pi
peculate tha
large eleme
ge group b
robic metab
tch the SEC
1980, Winte
ctile compo
ype II fibres
study clearl
contractile m
ction veloci
The mecha
to the det
udy.
Rozzi et al.
moving into
mickneestab
effects of fa
17 compare
investigatin
engthening
mechanism
EMD (Shi,
reticulum (
ch would ac
vity with fati
to the redu
). Thus, it h+ release (c
, and prolon
ould appear
the failure o
o observe g
uggest that
) due to fa
at possibly
ents of ana
but they are
bolism. It ha
C probably
er and Broo
onents to s
s, contracti
ly demonstr
mechanism
ty. But how
anisms invo
terioration
., (1999) ind
the directio
bilityinfem
atigue, ove
ed with the
g fatigue
of EMD w
ms and the
1996). Afte
(SR) has b
ccount for a
gue could r
uced rate o
has been su
consequent
ng EMD (W
r therefore
of the musc
greater fatig
younger c
aster oxyge
even in the
erobic work
e not traine
as been sug
accounts fo
okes, 1991)
stretch the
le force an
rated an elo
ms, increase
w the elasti
olved in the
in muscle
dicated that
on of extens
maleyouthpl
Dr Mark D
r and above
U13 age g
effects on
with fatigue
stretching
er stimulatio
been shown
pproximate
reduce the s
of force gen
uggested th
tly increasin
Westerblad e
that the pro
cle contract
gue related
hildren exp
en uptake
e youngest
k, may have
ed enough
ggested tha
or the major
). If the maj
series elas
d rate of fo
ongation of
ed complian
ic propertie
e increase i
conductive
t there was
sion, an incr
layers
De Ste Cro
e the effect
groups). Ho
EMD in n
in adults
of the se
on, the rate
n to require
ly 5%-7.5%
sarcoplasm
neration and
hat acidosis
ng the time
et al., 1991
olongation
tile process
effects in
erience les
kinetics (Fa
age group
e increased
to effectiv
at the time
r portion of
jor influenci
stic compon
orce develo
EMD with
nce of the S
es of the m
n EMD afte
, contractile
an overall
rease in the
ix 74
ts of norma
owever, this
non trained
is from the
eries elastic
e of calcium
e 2-3 ms to
% of an EMD
mic reticulum
d prolonged
s induced by
to reach its
, Horita and
of the EMD
s. Given this
EMD in the
ss metabolic
awkner and
that footbal
d the use o
vely remove
required fo
EMD (Zhou
ing factor o
nent (SEC)
opment may
fatigue. It is
SEC, with a
uscle affec
er fatigue in
e or elastic
decrease in
e onset time
al
s
d
e
c
m
o
D
m
d
y
s
d
D
s
e
c
d
ll
of
e
r
u
of
),
y
s
a
ct
n
c
n
e
Theeffecto
of contracti
task. Muscu
research h
and efferen
propriocept
consequen
respond qu
input to the
protection
conditions
this was du
stresses in
propriocept
findings su
youth footb
specifically
injury. Our
control are
more studie
sense, whic
We found
current stud
that there
medial ham
away from
et al., 200
demonstrat
the joint wh
current stud
ankle domi
findings sug
no differen
This would
when fatigu
al. (2006) w
possible tha
offootballsp
on for the m
ular fatigue
has demons
nt neuromu
tion due to
ce of the i
uickly enoug
e alpha mot
of the join
participants
ue to eithe
the joint c
tion due to
pport the v
ballers pote
differences
findings of
e altered wh
es are need
ch may alte
no significa
dy. These f
are no diffe
mstrings or
a knee dom
6). Using p
ted that fem
hen fatigue
dy is the fir
nant strateg
ggest that a
ces in the
suggest th
ue is presen
we acknow
at the footb
pecificfatigu
medial ham
is consider
strated its d
uscular path
fatigue is
ncreased la
gh to protec
tor neurons
ts (Rizzu e
s had signif
er altered a
capsule as
o fatigue m
iew that the
ntially influe
s in muscle
increased
hen fatigue
ded to explo
er landing m
ant muscle
findings sug
erences in
the calf mu
minant strat
peak EMG
males shift t
is present
rst study to
gy is evide
at least for f
feedback r
hat female y
nt, irrespect
wledge that
all specific
ueondynam
mstring and
red an impo
deleterious
hways (Ribe
a decreas
atency peri
ct a joint fro
can potent
et al., 2000
ficantly dec
afferent imp
a result of
may impact
e influence
ences dyna
recruitmen
EMD with
e is presen
ore the influ
mechanics, w
specific dif
ggest that in
the respon
uscles. Prev
tegy to an a
determine
towards gre
as these m
have exam
nt is any ag
female yout
esponse ra
youth footba
tive of age,
we did not
fatigue prot
mickneestab
lateral gast
ortant factor
effects on
eiro et al.,
e in neuro
ods during
m injury es
tially affect
0). Skinner
creased pro
pulses from
the muscle
on neurom
of fatigue o
amic muscu
t and EMD
fatigue tent
t, due to d
ence of fati
when individ
fferences in
n youth fem
nse rate of
vious studie
ankle domin
ed during th
eater relianc
muscles ten
mined chang
ge group/se
th footballe
ate between
allers do no
maturation
t explore th
tocol used i
bilityinfem
trocnemius
r in impaire
knee joint
2007). A im
muscular c
the fatigue
pecially in f
reactive mu
r et al. (19
oprioceptive
the muscl
e fatigue (S
muscular co
on the EMD
ular control
may be pa
tatively sug
decreased
gue on prop
duals youth
n the EMD
male footbal
feedback m
es have su
nant strateg
he prepara
ce of the a
nd to be les
ged in EMD
ex, let alone
rs that after
n the musc
ot move tow
nal status or
e role of th
n the curre
maleyouthpl
Dr Mark D
muscles in
d neuromus
laxity as we
mportance
control (Rizz
ed state m
females. Alt
uscular func
986) reporte
abilities. T
es themsel
Skinner et a
ontrol (Rizz
D on hamst
of knee jo
rtly respons
ggest that p
neuromusc
prioception
female foo
either pre
lers, and du
mechanism
uggested th
gy when fat
tory phase
nkle muscu
ss fatigued.
D pre-post f
e in youth f
r football sp
cles of the h
wards an an
r training st
he gluteal m
nt study ma
layers
De Ste Cro
response t
scular mech
ell as both
aspect of a
zu et al., 2
uscles are
terations in
ction and d
ed that du
They hypoth
lves or from
al., 1986). A
zu et al., 2
ring muscle
int alignme
sible for the
proprioceptio
ular contro
and knee jo
otballers are
or post fa
uring eccen
ms between
at adult fem
igue is pres
e Padua et
ulature to he
To our kno
fatigue to e
female foot
pecific fatigu
hamstrings
nkle domina
tatus. As wi
muscles an
ay have alte
ix 75
to a landing
hanisms, as
the afferen
altered join
2000). As a
not able to
the afferen
ecrease the
ring fatigue
hesized tha
m abnorma
Altered join
2000). Ou
es in female
nt, and tha
risk of ACL
on and join
ol. However
oint position
e fatigued.
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elp stabilise
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explore the
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ix 76
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vements
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ix 77
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s present a
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onsistent de
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studies hav
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ix 78
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neuromusc
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ix 79
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et al. 2009)
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ons in injury
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2004) also
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ix 80
metric versus
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onson dynamic
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2010), future
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Theeffecto
Aagaard, P
concept for
Medicine, 2
Aagaard, P
hamstring/q
contraction
Ahmad, C.
Effect of G
Ligament. L
Baker, A. J
duration ex
74: 2294-3
Bamac, B.
performanc
Bangsbo, J
Journal of S
Bartlett, R.
Routeledge
Bell, D.G. a
in males an
Beynnon, B
Biomechan
offootballsp
P., Simonse
r isokinetic h
26: 231-7.
P., Simonse
quadriceps
mode’, Act
S., Clark,
Gender and
Laxity.The A
., Kostov, K
xercise: met
00
., Çolak, T
ce in elite vo
J., Iaia, F, K
Sports Phys
. (1999). S
e.
and Jacobs,
nd females’,
B. D. and Jo
nical conside
pecificfatigu
Rn, E.B., Ma
hamstring:q
n, E.B., Tro
strength rat
ta Physiolog
A.M., Heil
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Appendix
Protect he
I have had and benefitcompleted Participant Name:…… Signed:……
Miss Abiga MSc by ReApplied SpoSchool of SUniversity o e-mail: AbigProject mob
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B: Particip
er knees - E
full detailsts involved, a health qu
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bilityinfem
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Dr Mark
Lead RReader
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e-mail:
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Dr Mark D
gue on dyna
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ned to me. s at any poiertake the r
……...
k De Ste Cr
Researcher/r in ChildrenSchool of S
sity of Glouc
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layers
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amic knee
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roix
Project mann’s PhysioloSport and Ecestershire
ix 103
stability in
nd the risksm that I haveercise.
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n
s e
Theeffecto
Appendix
Protect he
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……………
Dr Mark
Lead RReader
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maleyouthpl
Dr Mark D
gue on dyna
party and wed on to the
e your coachat could be
gement plea
……………
k De Ste Cr
Researcher/r in ChildrenSchool of S
sity of Glouc
ecroix@glos
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amic knee
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……
roix
Project mann’s PhysioloSport and Ecestershire
s.ac.uk
ix 104
stability in
anonymous members of
t use the through an
elow.
nager ogy Exercise
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Theeffecto
Appendix
Protect he
I have had risks and bchild has cexercise. Parent/ gua Name:…… Signed:……
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Dr Mark D
gue on dyna
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k De Ste Cr
Researcher/r in ChildrenSchool of S
sity of Glouc
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layers
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o me. I undany point. I
undertake t
roix
Project mann’s PhysioloSport and Ecestershire
ix 105
stability in
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Theeffecto
Appendix
Protect her kfootball play
After attendamendmentapproved. Thank you fo Best wishes Dr Malcolm Chair ‐ Resea
Associate DeUniversity ofThe Park Cheltenham
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Approval
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bility in fema
nd making thou that it ha
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ix 106
ale youth
he suggesteds now been
d
Theeffecto
Appendix
About th
The purposuse this infovolunteeredbe treated idestroyed.
Section 1, wwhich you hresponse oand 10 will
1.1 Secti
To complet
Mo
do
Vigorounabl
The testing
Wa
Ru
Cy
Ro
SwimJump
1.2 Secti Name: ...... Height (app
offootballsp
F: Pre-test
his questio
se of this quormation tod. It is impoin confidenc
which has bhave volunt
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ion 1: The
te the testin
oderate exe
at rest but
ous exercise to mainta
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alking
unning
ycling
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ming
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ion 2: Gen
..................
prox.): ........
pecificfatigu
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SPORT
H
onnaire:
uestionnaire decide whe
ortant that yce. Your co
been complteered. Secr answer in ted by the te
testing (co
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ercise (i.e., e
not so heav
se (i.e., exerain a conver
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neral inform
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questionn
T & EXER
Health Qu
e is to gatheether you ayou answer ompleted fo
eted by thections 2 to 7the space pester, after
ompleted by
you have v
exercise tha
vily that you
rcise that mrsation)
enerating o
enerating o
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enerating o
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mation
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tester, prov7 are for youprovided. Pyou have c
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g high forces
g high forces
g high forces
g high forces
g high forces
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pprox.):
maleyouthpl
Dr Mark D
TORIES
our health anin the testiny. The inforrely for 5 ye
informationete: please complete sections 2 to
e required to
more heavil
in a convers
eavily that y
s through yo
s through yo
s through yo
s through yo
s through yo
F Age
layers
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nd lifestyle.ng for whichrmation youears and the
n about the circle the a
section 8. So 8.
o undertake
ly than you
sation)
ou are
our arms
our shoulde
our trunk
our hips
our legs
e:
ix 107
We will h you have u give will en
testing for appropriate Sections 9
e:
ers
Theeffecto
1.2.1 Sec
1. Do any
a) b) c)
d) e)
2a. Do you
for 20 m
2b. Have y 3a. Do you
at leas
3b. Have y
1.6
1.7 Secti
4. Do any
a) I hb) I hc) I ha
5. Have y 6. Has yo 7. Do bot
a) I takb) I ha
with 8. Do you
offootballsp
ction 3: Ini
y of the follo
I have HI am preI have aby the tI am feeI have h
u typically p
minutes or
you perform
u typically p
t once a we
you perform
ion 5: Kno
y of the follo
have had inshave insulin-ve non-insu
you ever ha
our doctor e
th of the fol
ke asthma mve experien
h breathing
u have any o
pecificfatigu
tial consid
owing apply
HIV, Hepatiegnant a muscle oresting desceling unwelhad a fever
1.3
1.4
1.5
erform mod
longer at le
med this type
erform vigo
eek?
med this type
own medica
owing apply
sulin-depen-dependentulin-depend
d a stroke?
ever said yo
lowing appl
medication nced shortnin the last 4
of the follow
ueondynam
derations
y to you?
tis A, Hepa
r joint problecribed in secl today in the last 7
(If you hav
Section
derate exerc
ast twice a
e of exercis
orous exerci
e of exercis
al condition
y to you?
ndent diabett diabetes a
dent diabete
?
u have hea
ly to you?
ness of brea4 weeks?
wing: cance
mickneestab
titis B or He
em that couction 1
7 days
e answered
n 4: Habitu
cise (as def
week?
e within the
ise (as defin
e within the
ns
tes for moreand am overes and am o
art trouble?
ath or difficu
er, COPD, c
bilityinfem
epatitis C
uld be aggra
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ual physica
fined in sect
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ned in secti
e last 10 day
e than 15 yer 30 years oover 35 yea
ulty
cystic fibros
maleyouthpl
Dr Mark D
No
avated
uestion 1, g
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tion 1)
ys?
on 1)
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ears old rs old
sis,
layers
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go straight t
No
No
No
No
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No
No
No
No
ix 108
to section 8
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
)
Theeffecto
other luosteop
1.8 Secti
9. Do you 10. Do you 11. Do you 12. Have y
when ly 13. Do you 14. Do you
beats, 15. Do you
that are 16. Has yo 17. Do you
everyd
18. Does e
a) I smb) I sto
19. Has yo 20. Has yo 21. Has yo
heart s 22. Has yo
heart s
23. Do any
a) I hab) I hac) I ha
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(If yo
ion 6: Sign
u often have
u experience
u often feel
you, in the laying down o
u experience
u often get teither at res
u regularly ge not due to
our doctor e
u experienceay activities
(If yo
either of the
moke cigareopped smok
our doctor e
our doctor e
our father orsurgery, or a
our mother osurgery, or a
y of the follo
ve had insuve insulin-dve non-insu
pecificfatigu
e, liver diseaere arthritis
ou have ans
ns and sym
e pains in yo
e shortness
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ast 12 montor been awa
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the feeling tst or during
get pains in o soreness
ever told you
e unusual fas?
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ttes on a daking cigaret
ever told you
ever told you
r any of youa stroke bef
or any of yoa stroke bef
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ulin-dependdependent dulin-depend
ueondynam
ase, kidneys, a thyroid p
swered “Yes
mptoms
our heart, c
s of breath,
ve spells of s
ths, experieakened at n
or a build up
that your he exercise?
your calvesor stiffness?
u that you h
atigue or sh
swered “Yes
1.9
1.10
apply to you
aily basis ttes on a da
u that you h
u that you h
ur brothers hfore the age
our sisters hfore the age
y to you?
ent diabetediabetes andent diabete
mickneestab
y disease, mproblem?
s” to any qu
chest, or the
either at re
severe dizz
enced difficunight by sho
p of fluid in
eart is racing
s and lower?
have a heart
hortness of
s” to any qu
Section 7:
u?
aily basis les
have high bl
have high ch
had a hearte of 55?
had a heart e of 65?
es for less thd am 30 or
es and am 3
bilityinfem
mental illnes
uestions in s
e surroundin
st or with m
ziness?
ulty with breortness of b
or around y
g or skippin
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t murmur?
breath duri
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Risk facto
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t attack,
attack,
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35 or young
maleyouthpl
Dr Mark D
ss,
section 5, g
ng areas?
mild exertion
eathing reath?
your ankles?
ng
g exercise
ng
section 6, g
ors
months ago
ure?
rs
er
layers
De Ste Cro
o straight to
No
n? No
No
No
? No
No
No
No
No
o straight to
No
No
No
No
No
No
ix 109
o section 8.
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
o section 8.
Yes
Yes
Yes
Yes
Yes
Yes
)
)
Theeffecto
1.11 Secti
Participant:
Guardian*: (*Required o Section 9:
24. Is the p
25. Has the Section 10
26. Is the p Name (of te
Signature:
offootballsp
ion 8: Sign
: ……………
.................only if the pa
Additiona
participant’s
e participan
0: Eligibilit
participant e
ester): .......
……………
pecificfatigu
natures
………………
..................rticipant is u
al risk facto
s body mass
nt answered
ty (to be com
eligible for t
...........……
……………
ueondynam
………………
.....….………nder 18 year
ors (to be co
s index >30
d no to ques
mpleted by
the testing?
……............…
………………
mickneestab
………………
…….….......rs of age.)
ompleted b
0 kg/m2?
stions 2a an
the tester)
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……………
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….. Date
. Date
y the tester
nd 3a?
………
Date: .…
maleyouthpl
Dr Mark D
e: ........……
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r if relevant)
………....…
layers
De Ste Cro
….……........
…….…........
)
No
No
No
.…….…...
ix 110
Yes
Yes
Yes
Theeffecto
Appendix F Table 1: U1
Q = Quadric Table 2: U1
Q = Quadric
Concentric Q at 60°/s Concentric Q at 120°/sConcentric Q at 180°/sEccentric Hat 60°/s Eccentric Hat 120°/s Eccentric Hat 180°/s
Concentric Q at 60°/s Concentric Q at 120°/s Concentric Q at 180°/s Eccentric H at 60°/s Eccentric H at 120°/s Eccentric H at 180°/s
offootballsp
F: Concentri
3 Eccentric
ceps
15 Eccentric
ceps
0-10°21 ± 7
s 18 ± 7
s 19 ± 6
H 33 ± 2
H 33 ± 2
H 31 ± 2
0-10° 17 ± 9
17 ± 6
23 ± 7
26 ± 9
30 ± 14
24 ± 15
pecificfatigu
c and Eccen
and Conce
H = Hamstr
c and Conce
H = Hamstr
Pr
° 10-27 32 ±
7 30 ±
6 28 ±
2 44 ±
1 46 ±
0 46 ±
Pr
10-29 33 ±
6 33 ±
7 31 ±
9 51 ±
4 55 ±
5 50 ±
ueondynam
ntric torque
ntric torque
ings
entric torque
ings
re
20° 2± 11 42
± 8 3
± 8 3
± 20 52
± 19 50
± 19 51
re
20° 2± 8 46
± 8 44
± 8 4
± 13 54
± 10 57
± 14 52
mickneestab
values pre
e pre and po
e pre and po
20-30° 2 ± 11
37 ± 9
35 ± 9
2 ± 18
0 ± 17
1 ± 17
20-30° 6 ± 10
4 ± 10
40 ± 9
4 ± 13
7 ± 12
2 ± 13
bilityinfem
and post fa
ost fatigue b
ost fatigue b
0-10° 14 ± 8
16 ± 5
18 ± 9
34 ± 18
24 ± 16
48 ±18
0-10° 18 ± 6
19 ± 7
22 ± 6
23 ± 17
22 ± 11
22 ± 7
maleyouthpl
Dr Mark D
atigue
by joint angl
by joint ang
Post
10-20°27 ± 12
23 ± 9
24 ± 9
47 ± 23
50 ± 23
24 ±16
Post
10-20°34 ± 12
33 ± 8
31 ± 9
39 ± 21
44 ± 13
49 ± 14
layers
De Ste Cro
e
le
20-3036 ± 1
31 ± 1
30 ± 1
50 ± 2
54 ± 2
52 ± 2
20-3046 ±1
42 ±
40 ±
45 ± 1
50 ± 1
52 ± 1
ix 111
0° 12
11
10
25
25
21
0° 10
9
8
18
12
12
Theeffecto
Table 3: U1
Q = Quadric
Concentric Q at 60°/s Concentric Q at 120°/s Concentric Q at 180°/s Eccentric H at 60°/s Eccentric H at 120°/sEccentric H at 180°/s
offootballsp
7 Eccentric
ceps
0-10°26 ± 10
24 ± 10
26 ± 9
35 ± 13
s 34 ± 15
s 30 ± 13
pecificfatigu
and Conce
H = Hamstr
Pr
° 10-0 48 ±
0 41 ±
9 39 ±
3 67 ±
5 75 ±
3 67 ±
ueondynam
ntric torque
rings
re
20° 2± 15 6
± 13 54
± 13 5
± 21 7
± 24 8
± 27 7
mickneestab
e pre and po
20-30° 62 ±17
4 ± 15
1 ± 15
1 ± 23
0 ± 20
7 ± 23
bilityinfem
ost fatigue b
0-10° 24 ± 6
23 ± 7
25 ± 6
31 ± 19
25 ± 22
28 ± 28
maleyouthpl
Dr Mark D
by joint angl
Post
10-20°39 ± 9
33 ± 8
27 ± 10
85 ± 48
49 ± 34
65 ± 39
layers
De Ste Cro
e
20-342 ±
39 ±
33 ±
93 ±
66 ±
75 ±
ix 112
0° 12
9
9
43
28
28
