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MeasuringtheRiskofSustainingInjury-ANovelApproachNikunjVelani,OllieWilson,BenJ.Halkon,AndyR.HarlandSportsTechnologyInstitute,LoughboroughUniversity,1OakwoodDrive,Loughborough,LeicestershireLE113TU,UKAbstractDespite the possibilities offered by new approaches in design and advances in materials and
manufacturingmethods,fewitemsofPersonalProtectiveEquipment(PPE)usedinsporthaveseen
significant change for many decades. A major reason for this is the tradition and conservative
attitudesassociatedwithmanysports,althoughtheabsenceofappropriatetoolsandtechniquesto
assistthedesignanddevelopmentprocesshasalsoplayedalargepart.Theaimofthisstudywasto
developthefirststageofamethodofidentifyingspecificregionsofthehumananatomythatareat
thegreatestriskofsustaininginjuryduringparticipationinsportsinwhichtheplayerissubjectedto
multipleballisticimpacts.Itisproposedthatthefindingscouldbeusedtoconfirmfuturedesignsof
sportsPPE.Previousstudieshaveidentifiedtheamountandthelocationoftheprotectionprovided
by current commercially available products but, until now, no evidence has been reported to
determine what protection is required based on an understanding of the likely impact and the
anatomyoftheathlete.
Using the leg and cricket as examples of an anatomical feature and a sporting application
respectively,theseverityandprobabilityofinjuryduetoballimpactstypicallyobservedinplayare
quantified, with respect to their location on the leg, to estimate the level of risk in that region.
Resultsshowthatthelevelofriskisgreatestintheshinregionsofthefrontleg,suggestingthatthis
regionshouldbeofferedthegreatestdegreeofprotection,asisgenerallythecaseincommercially
availablelegguarddesigns.Conversely,however,theinnerregionofthemid-shinofthebacklegis
atthelowestrisk,suggestingthatprotectioninthisregionmightbesubstantiallyreduced,afeature
which is certainlynot included in currentproduct; sucha reductionmay significantly enhance the
ergonomicperformanceofthelegguarddesign.
Thefindingsofthispreliminarystudy indicatethatthemethodoffersthepotentialtoquantifythe
relativeriskofsustaininginjury,inasportsspecificapplication,asafunctionoflocationonthebody
andisthusapotentiallyusefuldesigntoolfordesignengineersofsportsPPE.Giventheembryonic
nature of this approach, however, a number of assumptions and additional considerations are
presentedwhichrevealthat,whilstthetechniqueoffersadditionaldesigninsight,furtherresearchis
requiredbeforeitshouldbeappliedtoequipmentdesign.
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1. IntroductionParticipation invirtuallyall sportcarries theriskofsustaining injury through impact,either froma
bat,ball, cluboranotherparticipant.Somesports, suchashockeyand football, carrya significant
riskof injuryand, asa result, the lawsof thegames stipulate thatPersonalProtectiveEquipment
(PPE)mustbeworn(e.g.shinguardsinfootball[FIFA,2010]andgoalkeepershandandlegguardsin
hockey[FIH,2011]).Athletes,however,oftenfeeltheneedtouseadditionalPPEtofurtherprotect
vulnerableareasdespitethelawsnotenforcetheirusage.Insomecases,suchasincricket,nolaws
existintheseniorgamethatenforceplayerstowearprotectiveequipmentyetcountlessPPEarticles
arestillworn.Whereit isdiscretionary,anathletewillmakeachoiceastowhichitemsofPPEare
wornbasedonacompromisebetweentheirpersonal safety (theprotectionaffordedby thePPE),
comfort (during and after wear) and performance (accounting for any detriment in performance
causedbywearingPPE).
InordertobesoldintheUK,allPPEitemsmustpassspecificteststandardstocertifythattheyare
of an adequateprotective standard (McIntoshet al., 2003), for example theBS 6183-3:2000. The
majority of these standards have been developed focusing solely on the safety aspects. It has
thereforebeenverydifficultforadesignerormanufacturertoimprovethecomfortorperformance
aspectsofPPEwithoutcompromisingsafety,suchasisthecaseforthecricketlegguard,usedasan
exemplarinthisstudy,wherenosingleinjuryincidenthasbeenreportedinoveracenturyofuse.In
contrast, therearenostandards specificallydefiningdesign requirementsofPPE (McCrory,2002),
with reference to design only beingmade to state that the sports PPEmust allow typical athlete
movements (e.g.BS6183-3:2000,BSEN13061:2009).Asa result, thedesign isoftenneglected in
the development process andmodern sports PPE can be found to exhibit satisfactory protective
capabilitiesbutbeill-fitting,bulkyand/orheavy,ultimatelyinhibitingtheperformanceoftheathlete
using it (Akbar-Khanzadehetal.,1995;WebsterandRoberts,2009). Insomecases, thishas ledto
athletes modifying their own PPE in an attempt to make it more comfortable to wear or less
detrimentaltoperformancewithlittleconsiderationonhowitmayaffectthesafetycharacteristics
ofthePPE.Thelackofspecificationsconstrainingdesignsenablesthepossibilityofre-inventionthat
couldcountertheproblemsobservedinexistingPPEyet,despitethis,fewvariationsfromthenorm
arefound.Strivingtominimiseathleteinhibition(thusmaximiseperformancepotential),intoday’s
games,isofparticularimportancewheresuccessandfailureareoftenseparatedbythesmallestof
margins.
Thereisnoonecleardefinitionfor‘injury’butthecategorisationofinjuryinsportismostcommonly
performedbyusingtwomainclasses:‘medicalattentioninjuries’(i.e.thosewhichrequiretreatment
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by amedical practitioner) and ‘time-loss injuries’ (i.e. thosewhich cause athletes tomiss one or
more practice or game sessions) (Bahr and Engebretsen, 2009). Injuries that require the greatest
medicalattentionor thegreatest time lostarethosethataredeemedtobethemostsevereand,
ultimately, those that are themost undesirable. Of all injuries sustainable from impact in sports,
fracturescanbearguedtocarry thegreatestseverityandhavebeenreported tocauseup to240
playingdayslostduringrecoverytime(Oztekinetal.,2009).Theyoccurwhenthekineticenergyof
the impactor that is translated to the body exceeds the fracture energy of the bone (Ankrah and
Mills,2003).Clearlythefractureenergy ismost likelytobeexceededwhenthe impactenergyhas
the leastopportunitytobedissipated(i.e.wherebonesaresuperficialtotheskin).Bonesthatare
deep are typically protectedby soft tissue,which can absorb sufficient energy to ensure that the
energy translated to thebone is less likely to cause fracture. Impactwith regions that havedeep
lying bone, therefore, most commonly result in an injuries of lower severity, usually contusions
which, in the worst case, have been reported to cause only 60 playing days loss (Oztekin et al.,
2009).
PPEhasbeenobserved to reduce the injury rate ina rangeof sportsbutultimatelynoteliminate
injuries completely (Marshall et al., 2002; McIntosh and McCrory, 2005; Benson et al., 2009).
Furthermore,theseinjurieshaveoftenbeenreportedtobefocusedinparticularanatomicalregions
(LearyandWhite,2000;Marshalletal.,2002;Finch,2002;Stretch,2003)suggestingthat,ingeneral,
somepartsmaybeoverprotectedandothersunderprotected.Injuriessustainedduringbattingin
cricketprovideaprimeexampleofthistheory.Milsometal.,(2007)reportedthat10%ofallinjuries
during batting were phalangeal fractures, whilst there were no reported incidences of injuries
causedinthelowerlimbs.GiventhatbothregionsareprotectedbyPPE,itcanbearguedthatsome
protection in the leg can potentially be reduced without increasing injury occurrence, but that
protection in the fingers must be increased to reduce the number of injuries sustained. The
challengeinachievingthis,however,lieswiththedeterminationofwhereandtheextenttowhich
protection can be removed, or increased, in order to develop PPE that is injury risk minimising,
minimally performance inhibiting and ergonomic in design. To arrive at this balance it may be
acceptable,forexample,todevelopPPEthatshowsanincreasedleveloflowseverityinjuries,such
as contusions which do not prevent the athlete from playing if sustained, if the newer design
displays better ergonomic and performance characteristics than its predecessors. The lack of
required information,with respect to theareas inwhich theprotection ismostnecessaryandthe
sustainable injury levels that are acceptable, combinedwith the associated inertia tomove away
fromexistingdesigns,hasarguablynotallowedmoderntechnologicalandmaterialadvancestobe
fullyincorporatedintoPPEdesignstomakesuchchangespossible.
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Areasthatarethemostsusceptibletosustainingasevereinjuryarethosethattheoreticallyrequire
thegreatestprotection fromPPE.Areas thatmaybe likely to sustain severe injury,however,may
not require any protection should the region have little chance of sustaining an impact. This
relationshipbetweenprobabilityandseverityand its influenceonsustaining injuryhasoftenbeen
defined as ameasure of the ‘risk of injury’ (Anthony Cox, 2008; Bahr and Engebretsen, 2009; BS
OHSAS18001:2007).Riskestimationhasmostcommonlybeenconductedusingthreequantitative
techniques: 1) Risk matrix (estimation of risk by considering the consequence [or severity] and
probability of injury), 2) Fine andKinney’smethod (estimationof risk basedon the consequence,
exposurerateandtheprobability)and3)Quantitativeriskmeasuresofsocietalrisk (estimationof
risk based on the accident category, frequency and consequence) (Marhavilas and Koulouriotis,
2008). Of the three approaches the risk matrix approach presents the simplest, and broadest,
methodofestimation suggestingwhy ithasbeenused in theHSE (2010)andwidelyemployed in
studies,suchasthosebyDrawerandFuller(2002)andGreenwaldetal.,(2008),toestimatetherisk
ofsustaininganinjury.
Withinthesportingdomain,riskhasbeenestimatedasafunctionoftheperceptionofoccurrence
(Rundmo, 1996) or, more commonly, the frequency of injury over an extended period of time
(Woods,1996; LearyandWhite,2000;Finch,2002;Stretch,2003;Marshalletal., 2005;McIntosh
andMcCrory,2005).Littlework,however,hasbeenconductedonanalysingtheriskasafunctionof
thehumananatomy.Woods (1996) successfullypresentedamethodofdeterminingwhat typeof
protectionwas required in certain regionsbasedon theoccurrence rates of the typesof damage
thatprevailedonmotorcyclesuitsafteraccidents.Althoughthemethodallowedmodernmotorcycle
protectivesuitstobetailoredtopreventtheseformsofdamage,henceminimisingtheriskofinjury
at that anatomical location, the study also suggested that some of the injuries were sustained
irrespective of whether that additional protection was present or not. The method presented,
therefore, may not necessarily be the optimal means to analyse sports PPE to aid designers in
makingprotectivemodifications,especiallywheremostsportingimpactscauselittlevisibledamage
toPPE.More recent studieshave focusedon theanalysisof the capabilitiesof currentprotection
basedonthetypeofinjurythatcouldbesustained(Marshalletal.,2005;Milsometal.,2007),but
haveeluded tostatehowprotectioncouldbeadapted toalter the risk.Theyhavenot, therefore,
provided designers with the information that is required to make modifications to counter the
drawbacksofcurrentsportsPPE.
This study aims to present a method in order to identify where the greatest relative risks of
sustaining injury lieacrossa regionusing the riskmatrixmethod fora single sample right-handed
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batsman, with the leg and cricket leg guard as examples of a potential anatomical feature and
sporting application respectively. Understanding where the greatest risks lie and how they vary
couldformausefuldesigntoolthatcouldbeimplementedintothedesignprocesstoaiddesigners
in understanding where protection could be reduced or increased to optimise PPE design. By its
nature, themethod is specific to the user, application and the nature of the injurydeemedmost
severe.
2. MethodDevelopmentTheriskofsustaininganinjuryhaspreviouslybeendescribedasaproductofthepotentialseverity
ofinjuryandtheprobabilityofimpactinacertainregion(Equation1)(AnthonyCox,2008;Bahrand
Engebretsen, 2009; BS OHSAS 18001:2007). If either the probability of impact or the severity of
injuryislowatalocationtheriskofsustaininganinjuryatthatlocationislow.Similarly,ifbothare
high the risk is high.Understanding this balance between the potential severity of injury and the
probabilityofimpactisofgreatimportancewhenattemptingtodeterminewhereandwhatdegree
ofprotectionisneeded.
Risk=Wsev·SevxWprob·Prob (Equation1)
Where:Wsev=SeverityWeightingFunction
Wprob=ProbabilityWeightingFunction
InaccordancetoEquation1,boththeseverityandprobabilityarerequiredtobecriticallyweighted
toarriveataprecisequantifiedinjuryriskvalueforaspecificlocationbut,duetotheinfancyofthis
approachandtheconsequentlackofavailabledatatojustifydifferentweightings,thisstudyutilises
anequalweighting.
2.1 SourceDataCollectionForty-one magnetic resonance imagery ‘slices’ of a person’s right leg, taken at 21 mm intervals
betweentheankleandthehip,wereobtainedforanalysisfromtheVisibleHumanServerdataset
(EPFL,2000).Each‘slice’wasextractedfromthedatasetasa400x400pixelJPEGimagefromwhich
bothhardtissues(bone)andsoftertissues(skin,fatandmuscle)couldeasilybeidentified.
2.2 PotentialSeverityofInjuryEstimationWiththefrontofthelegfacingupwards,thecentrepointofeach‘slice’wasfoundbylocatingthe
intersectionofthexandybisectorofthemaximumandminimumhorizontalandverticalpixels,as
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showninFigure1a.Thisenabled24equi-spacedpositions(15Ointervals)tobemarkedaroundthe
perimeteroftheleg,asshowninFigure1b.Fromeachofthesepositionstheshortestdistancetoa
bone was measured and recorded, as can be seen graphically in Figure 1c. A smaller ‘distance’
representsanareathathasahighpotentialseverityofinjuryandviceversa.
The‘distances’forallsliceswerecollatedandnormalisedbysubtractingtheminimumvalue(from
theentirecollation [2]) fromeach individualvalueandthendividing theresultantby therangeof
values (88). Consequently a value close to 1 represented a lower severity of injury. The scale,
however,wasreversed,bysubtractingeachvaluefrom1,toarriveatdatathatwasintuitivelyeasier
to interpret (highervalues representahigher severity).Newvalueswere thenplottedona single
‘grey-scale’map,asshowninFigure2,suchthatthevarianceinthepotentialseverityofinjurycould
beobservedbothgraphicallyandnumericallyasa functionof the locationonthe leg.Thedarkest
regions are indicative of areas that are considered susceptible to injuries of high severity, whilst
lightestregionsrepresentthoseleastlikelytosustainsevereinjury.Duringthisanalysisitwasfound
that,atthetransitionbetweenthelegandadjacentanatomicalfeatures,determiningtheperimeter
ofthelegfromtheimagebecameincreasinglydifficult.Tomaintainthevalidityintheresultsslices1
(lowerleg/foottransition)and39-41(upperleg/hiptransition)wereeliminatedfromanalysisforthis
reason.
TheresultspresentedinFigure2revealthatthepotentialseverityofinjuryisgreatestinthecentral
regions on the leg in the mid to lower areas. Simple analysis of the slice numbers enables the
determinationoftheseareastorepresentthekneeandshinregions.Measurementsbetweenslices
20and24 (approximately theknee region) revealawide region inwhich thepotential severityof
injuryishigh,suggestingthatprotectionrequirementsaregreatestwithintheareaextendingfrom
themedialtothelateralthrougharangeof180ocentredaroundthepatella.Theshinandcalfregion
showa largerangeofmeasureddistances.Whilstthepresenceofthetibiaproximaltotheskinat
thefrontofthelegrevealsareasofhighinjuryrisk;thelargeamountofsofttissueatthebackofthe
legisinfluentialinreducingtheriskrating.
2.3 ProbabilityofImpactEstimationInordertocontinuetheanalysis,anestimationofthelikelihoodofanimpactoccurringataspecific
positionisrequired.Thelegwasthereforedividedintofifteenregionsofinterest,asshowninFigure
3. 15 shots (individual methods used to facilitate bat-ball impacts for different types of ball
deliveries) typically played during batting were selected for analysis, for which images would be
required. Ten of these shots were selected from Palmer (1999): the forward defence, front foot
off/ondrive,backfootdefence,backfootoff/ondrive,thesweep,front/backfootlegglanceandthe
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leave.Afurtherfive:thereversesweep,legside‘slog’,‘paddingup’toaballontheoff/legsideand
Yorker, were added to broaden the scope and better reflect shots played in contemporary
professionalcricket.
Imagesof the first ten shotsbeingplayedbya right-handedbatsmanwereobtained fromPalmer
(1999). The remaining five, which were not depicted in Palmer (1999), were captured from an
alternative right-handedbatsman,of the sameexperience,ator close to thepointofball impact.
Fromtheseimages,regionsthatweredeterminedtobethemostlikelytosustainimpactweregiven
ascoreof2,regionsthatwerelikelytosustainimpactduetounexpectedbounceorballmovement
weregivenascoreof1,whilstareasthathadlittleornolikelihoodofbeingimpactedweregivena
scoreof0.Regionswereassignedscoresbasedonthelocationofthe‘middle’(optimalpositionon
batforball impact)ofthebatpriortoballstrike(aswereshowninimages).Regionsclosesttothe
‘middle’ofthebatwereassumedtohaveagreaterprobabilityofimpact(assignedscoresof2)over
thosefurtherawayfromthe‘middle’ofthebat(givenscoresof1or0).Boththefrontandrearlegs
weretakenintoconsiderationgiventheinherentlegpositionsnecessarytoplayalltheshotsinvolve
bothlegsbeingexposedtoimpactbyvaryingdegrees.Unlikethecaseofthepotentialseverity,the
probability of impact is not symmetrical hence the necessity of both legs being consideredwhen
assigning values to various regions. For simplicity, this initialwork excluded potential changes in
possibleimpactedregionsduetoindividualbatsmenstyle,pitchandenvironmentalconditions,etc.
indeterminingwhethertheprocesswasaviablemethodtoestimatetheriskofsustaininganinjury.
Impactprobabilityratingswerecollatedforall15shots,normalised(usingtheprocessdescribedin
section2.2)andpresentedinasingleprobability‘grey-scale’map,asshowninFigure4.Thisenables
theareasofgreatestprobabilityofimpacttobereadilyviewedasafunctionofboththelocationon
the legand the legof interest (frontor rear).Darkerareasand larger valueson themap indicate
regionsthathavethegreatestprobabilityofimpactand,conversely,lighterregionsandlowervalues
indicatethoseleastlikelytosustainimpact.
The combined data unsurprisingly, but reassuringly, show the front leg to have a substantially
greaterprobabilityofimpactthantherearlegthusindicatingthatthefrontlegshouldbeprovided
withgreaterprotectionthantherear.Thehighestprobabilitiesarefoundtobeconcentratedinthe
central and inner regionsof the kneeand shin regionsof the front leg.Conversely, the innermid
region of the rear leg shows a zero probability of impact suggesting that minimal protection is
requiredinthisregion.
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2.4 RiskofInjuryDeterminationQuantificationof thepotential severityof injury and theprobability of impact enabled the riskof
sustainingimpacttobeestimatedbasedontheriskmatrixrelationshipgiveninEquation1.
Priortoestimatingtherisk,however,thefifteenregionsdefinedintheprobabilityofimpacthadto
bemirrored onto the potential severity on injury ‘grey-scale’map, such that the relevant regions
corresponded.Keyanatomical landmarkswereused inordertodeterminetherangeofslicesthat
representedtheheightsoftheprobabilityregions.Forexample,thethighregionwasdeterminedby
the identifying where the slices last showed features solely found in the upper leg (i.e. only the
femurobserved),andsubsequentlythekneeregionfromwhereinitialkneefeatureswereobserved
totheslicepriortowheretheywerenolongerseen(i.e.onlytibiaobserved).Slicesthatrepresented
the remaininguppershin,midshinand lowershin regionsweredeterminedbymakingcalculated
estimations based on the number of slices that represented the heights of the thigh and knee
regions.Thus,thethighwasdefinedasslices24-38,theknee:20-23,uppershin:14-19,midshin:8-
13andlowershin:2-7.
Lateralcoveragewasestablishedsuchthattheinner,centralandouterregionswerecoveredbyan
equal numberof equi-spacedpositions. The inner legwas consequentlydefinedbypositionsA-H,
thecentrallegbypositionsI-PandtheouterlegbypositionsQ-X.Thisisshownforthefrontlegfora
right-handedbatsmaninfigure5.
Riskwas finallyestimated,according toEquation1,bymultiplying thepotential severityvaluesby
the probability of impact values of their respective regions, as displayed in Figure 5. Calculated
valuesarepresentedgraphicallyandnumericallyona ‘grey-scale’mapforboththefrontandrear
legs of a right-handed batsman, as shown in Figures 6 and 7,where darkest regions in themaps
representareasofhighriskandthelighterregionsareasoflowrisk.
Figure 5a displays the segregated regions of a single leg and the corresponding normalised
probabilityvaluesforboththefrontandrearleg(Figures5band5c)ofaright-handedbatsman.In
thecaseofaleft-handedbatsman,however,toestimatetheriskofsustaininganinjury,valuesfor
thefrontandrearlegs,fortheprobabilityofimpact,wouldberequiredtobeinterchangeddueto
thechangeinorientationofbatsmanstance.So,forexample,theinnermidshinregionoftherear
legforaright-handedbatsmanisequivalenttotheinnermidshinregionofthefrontlegforaleft-
handed batsman and thus should be assigned a value of 0.71. Potential severity of injury values
would remain consistent between right and left-handed batsmen because anatomically players
wouldbealike.
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3. Discussion
3.1 ValidityofApproachThisprimaryaimofthisstudywastodevelopanovelconceptualmethodofquantifyingtheriskof
sustaininginjurythatparticipantsfaceduringasportingdiscipline-inthiscasebattingincricket.The
motivation for this approach was to provide equipment designers with data that might be used
withinthedesignprocessinordertocreateequipmentthatbetterfulfilstheneedsoftheenduser.
Previous studies have yielded little information regarding the risk of injury as a function of
anatomical features, as they have in the main focused on the locations of the injuries. This has
provideddesignerswithlittleusefulinformationwithregardstohowmodificationsmightbemade
to manage risk and safeguard against serious injury whilst ensuring the PPE minimally inhibits
performance and is ergonomic in design. It is anticipated that themethodology proposed in this
studyovercomesthisshortcomingandcould, intheory,beappliedtoanypartoftheanatomy,for
anysportingapplication,providedthatappropriateinputdatacouldbesourced.
The findings of this study have suggested there to be a substantially greater risk of sustaining an
injuryduringbatting in cricket in the front leg than in the rear leg,with the greatest riskpresent
within the central mid shin region of the front leg. Regions of high risk were found to be
concentratedintheupperandmidshinregionsofthefrontlegandthelowerthighandkneeregions
oftherearleg,detailingwheretheprotectionmightbeconcentratedoneach.Giventheproximity
ofthebonetotheskinandthelegpositionsrequiredtoplaythefifteenshotsanalysed,thisfinding
is likely to align with any experienced athletes perceptions, and adds justification to the British
Standard (BS 6183-3:2000, 2010), which requires additional protection within the shin regions.
Individualmeasurementshaveshownthatboththepotentialseverityandtheprobabilityofimpact
werefoundtobegreatestinthecentralshinregion,therebyleadingtothegreatestriskbeingfound
in this region,correctwithprevious reported findings.Thesameregionontheback leg,however,
was shown to be exposed to a considerably lower risk, suggesting that theobserved symmetrical
natureof the frontand rear legprotectionaffordedwithin commerciallyavailable legguardsmay
notnecessarilybejustified.Thelowestriskofinjurywasfoundtobeintheinnermidshinregionof
the rear leg which was estimated to be completely free from risk due to the zero probability of
impact in this region for the range of shots studied. This suggests that it may be possible to
substantiallyreducetheamountofprotection,withoutsubstantiallyincreasingtheriskofinjuryfor
thebatsman.
Analysisof the risk in thismannerwouldenablePPEdesigners to visualise the relativeprotection
needsofdifferentregionsoftheprotectiveequipment.Whilstthecalculatedvaluesdonotindicate
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theabsoluteamountandexacttypeofprotectionthatshouldbeaffordedinnoveldesigns,theydo,
however,provideinvaluableinformationwithrespecttomanufacturinga‘functionallygraded’PPE
(i.e. one that exhibits different protection properties in different areas). For the purpose of
convertingthevaluesintodesignelements,understandingallthemechanisms(peakforce,pressure,
strain,etc.) that lead to severe injurywithin thebodyand the completearrayofdesignelements
(stiffness, strain rate, fracture toughness, mass, density etc.) that lead to a design being able to
mitigatetheriskofsustaininginjurymoreeffectivelythanpreviousversions,isfundamental.Bythis
mechanism,themethodwouldbecomeaneffectivetoolfortheredesignofsportsPPE.
Inaccordancetothepresentedanalysis,wheretheestimatedriskofinjuryis1thegreatestamount
ofprotectionisrequiredandwheretheestimatedriskis0protectioncantheoreticallybealleviated
on that particular article of PPE. As a result, scales ranging frommaximum tominimum could be
developedtoindicatetherequiredquantityofaparticularmaterial,thatisrequiredtominimisethe
riskofsevereinjuryoccurringforaparticularregion.
The method also lends itself to the possible manufacture using multiple materials that display
varying ‘protective capabilities’. For example, in cricket leg guards, different amounts of a single
material can be selected for various regions such that both protection and design element
requirements are met. Furthermore, combinations of materials can be selected such that each
material provides sufficient protection to individual regions, whilst also adhering to the required
design element requirements of that particular region. This will further reduce the risk of a
cumbersome solution being developed, the like of which may be observed in a single material
design.
PPEshouldideallyminimisetheinhibitiontoperformancewhilstkeepingtheathleteinjuryriskfree.
The developedmethod also potentially allows PPE to be tailored for individual athletes based on
theiri)specificbattingtechniqueortherangeofshotsthattheymostcommonlyplay,ii)thegeneral
pitchcondition,iii)whereintheworldthematchisplayed,iv)theformatofthegameetc.,.One,or
all,ofthesevariablesmayresultinsignificantdifferencesinthearea(s)ofgreatestinjuryrisk.
3.2 LimitationsoftheStudyWith the adventof shorter formsof the game, the rangeof shotsbeingplayed is ever increasing
withmany batsmen adopting unconventional techniques in an attempt to scoremore runsmore
rapidly. In these cases, whilst the method of estimating the risk from an assessment of the
probabilityandseverityofimpactremainsavalidapproach,thebodypositionsassumedtoplaythe
fifteen identified shotswouldalmost certainlynotbeappropriate.Accommodatingmatch specific
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scenarioswhereathletesinnovatenewtechniquesandmethodstogainacompetitiveadvantage,or
takingintoaccountthefrequencywithwhichdifferentshotsareplayedorthosedeliverieswhichare
notsuccessfullyplayedbythebatsman,wouldrequire furtheranalysisof individualapproaches.A
similar situation exists in the case of a left-handed batsman. The angle of ball delivery (and shot
selection,asaresult)maygeneratedifferentregionsofpossibleimpactwhencomparedtoaright-
handedcounterpart.Consequently, themethodshouldnotbeusedtodevelopsymmetricalsports
PPEfor left-handedplayersbasedonthefindingsofaright-handedplayerbut, instead,serveasa
tooltoenablePPEtobetailoredforthisalternate, left-handedbattingscenario. Asaasageneral
toolforconventionalmatchplay,however,theapproachpresentedisconsideredvalid.
Inorder toquantify theseverityof injury itwasassumedthatboth legswereperfectlysymmetric
andthattheseverityvariedlinearlywiththedistancefromthebonesurfacetotheskin;bonethat
wasdeepwasassumedtobeatlessriskthanthatwhichwassuperficial.Muscle,however,canexist
in both relaxed and tense form, with the differences between them severely influencing impact
energy absorption characteristics (Tsui and Pain, 2008). Muscle that is tensed has a significantly
lower ability to absorb energy, thus translating a greater amount to the bone and potentially
resulting in a greater potential severity of injury. Furthermore, the property of bone and its
susceptibility to damagewas considered to be homogenous, something that is unlikely to be the
case due to both the structure of the skeletal arrangement and the localised bone material
properties.Consequently,themethoddescribedshouldnotbeusedasanindicatoroflikelydamage
foraspecificimpact,ratherageneralisedmethodofdescribingrelativerisk.Furtherresearchwould
also be required to allow the method to account for other causes of significant injury, such as
contusions.
In accordance with Equation 1, both the severity and the probability values should include a
weighting factor. In this study, however, the weightings for both the potential severity and the
probabilitywerekeptatonebecauseofalackofpreviousstudiesordatasupporting,andjustifying,
analternatelybalancedweighting.Themannerinwhichlikelihoodandseverityareweightedislikely
to be influenced by the aspirations of the athlete. Different athleteswill place different value on
stayingfreeofinjury,remainingcomfortablewhilstusingPPEoroptimisingtheirperformance.This
may also change depending uponwhether an athlete is playing a short, twenty overmatch or a
longermatchplayedoverseveraldays.Therefore,someathletesmaybemoretoleranttorepeated
impactsoflowseverity,whereasothersmaynot.Inaccommodatingthisrangeofcircumstancesitis
likelythattheweightingswillbeadjusted.
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4. ConclusionsandFurtherWorkMinimisingtheriskofinjuryistheprimarydesigncriterionforPPE.However,toolstoidentifywhere
protection ismost requiredandwhere itmightbe reducedsuch thatusers remain injury risk free
butalsominimallyinhibitedaresparse.Themethodreportedinthisstudyallowstheriskofinjuryto
be quantified in different anatomical regions based upon their potential severity of injury and
probability of being impacted. In turn, this would allow designers to achieve a different balance
betweenathletesafety,comfortandperformanceinhibitionwhererequired.Theproposedmethod
is suitable in scenarios where current PPE arguably offers excessive or inadequate amounts of
protection.Thisstudyfocussedmainlyontheformersituationbutthemethodproposedwouldalso
allowdesignerstoaddprotectionwhererequired.
In order to validate this method, continuation of the work should aim to use the data to
manufactureaphysicalprototype legguard,possiblyusingtheapproachsuggesting insection3.1,
thusenablingbothlaboratoryandplayertestingtobecompleted.Aphysicalmodelwouldaidinthe
eliminationof someof the limitationsdescribed in section3.2 (andpotentially reveal some that s
havesofarbeenoverlooked)infutureiterationsthroughdirect inputfrombothlaboratorytesting
resultsandplayerfeedback.Throughthedevelopmentandevaluationofaphysicalmodel,boththe
valuesandshortcomingsoftheriskassessmenttechniquecanbereadilydetermined.
To maximise the value of the approach outlined, further research is also required to better
characterise the damagemechanisms leading to playing days lost and the likelihood of particular
impact types. Further research is also likely to allow specific applications or individuals to be
considered based on bespoke input data and also consider scenarios where athletes may not
necessarilybeperformingoptimallyorconventionally.Whilstthisstudyonlyfocussedonthelegand
cricketlegguardsthemethodologyisbelievedtobeeasilyemployableintoallsportsforanytypeof
PPEtoaidinthedevelopmentofnewdesignsprovidingthesourcedataisavailable.
13
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15
Figure1.a)Calculationofthecentrepointofeachslice.b)15oincrementtoobtainpositionsaroundperimeterofleg.c)
Shortestdistancetonearestbone(solidwhitelinetopositionXandsolidblacklinetopositionM).
a b
c
Y-MaxX-MaxX-Min X-Bisector
Y-Min
Y-Bisector Intersection
15o
Increments
Front
16
Figure2.Normalisedpotentialseverityofinjury‘grey-scale’mapforasinglelegwithrespectto‘height’ontheleg
17
Figure3.15regionsofeachleg
Figure4.Normalised‘grey-scale’mapoftheprobabilityofbeingimpactedwithincertainregionsforall15shotsfora)thefrontandb)backleg.
IT IT OTCT
OLS CLS ILS
IK CK OK
IUS CUS OUS
IMS CMS OMS
ILS CLS OLS
CKOK
CT
IK
IUSCUSOUS
OMS CMS IMS
OT
18
Figure5.a)Normalisedpotentialseverityvaluesforasingleleg.b)Norm
alisedprobabilityofimpactvaluesforfrontlegofaright-handedbatsm
an.c)Normalisedprobabilityvalueforrearlegofa
right-handedbatsman.
InnerCentral
OuterThigh
0.430.286
0.14Knee
0.710.643
0.29UpperShin
0.640.857
0.36MidShin
0.711
0.36LowerShin
0.570.643
0.29X
OuterCentral
InnerThigh
0.140.5
0.14Knee
0.070.429
0.29UpperShin
0.140.143
0.07MidShin
0.140.143
0LowerShin
0.070.071
0.07
Front
OR
Rear
a
bc