Children and adolescents with Down syndrome, physical fitness and physical activity.pdf

8/10/2019 Children and adolescents with Down syndrome, physical fitness and physical activity.pdf

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Review

Children and adolescents with Down syndrome, physical fitnessand physical activity

Ken Pitetti a,*, Tracy Baynard b, Stamatis Agiovlasitis c

aDepartment of Physical Therapy, College of Health Professions, Wichita State University, Wichita, K S 67260-0043, USA

bDepartment of Kinesiology & Nutrition, University of Illinois at Chicago, Chicago, IL 60612, USA

cDepartment of Kinesiology, Mississippi State University, Mississippi State, MS 39762, USA

Received 8 July 2012; revised 7 September 2012; accepted 26 September 2012

Abstract

Children (5e12 years) and adolescents (13e19 years) with Down syndrome (DS) possess a set of health, anatomical, physiological,

cognitive, and psycho-social attributes predisposing them to limitations on their physical fitness and physical activity (PA) capacities. The

paucity of studies and their conflicting findings prevent a clear understanding and/or substantiation of these limitations. The purpose of this

article was to review the measurement, determinants and promotion of physical fitness and PA for youth (i.e., children and adolescents) with DS.

The existing body of research indicates that youth with DS: 1) have low cardiovascular and muscular fitness/exercise capacity; 2) demonstrate

a greater prevalence of overweight and obesity; 3) a large proportion do not meet the recommended amount of daily aerobic activity; and 4) their

PA likely declines through childhood and into adolescence. Future research should focus on: 1) strength testing and training protocols; 2)

methodologies to determine PA levels; and 3) practical interventions to increase PA.

Copyright 2012, Shanghai University of Sport. Production and hosting by Elsevier B.V. All rights reserved.

Keywords:Activity; Adolescents; Children; Down syndrome; Fitness

1. Introduction

1.1. Background and genetics

The condition of Down syndrome (DS) was first described in

a clinical lecture report delivered in 1866 by the British physi-

cian, John Langdon Down, entitled Observation on the ethnic

classification of Mongoloid idiots.1 Dr. Down used the

derogatory term Mongoloid because children with DS

displayed facial features (e.g., epicanthal fold) that shared

similarities with the prevailing erroneous ethnic theory estab-

lished by the German anatomist, Johann Friedrich Blu-

menbach.2 Catalyzed by editorials inThe Lancet, together with

political pressure by advocacy groups and parental organiza-

tions in the 1960s, the term mongolism was dropped from

medical references by the World Health Organization and

replaced by Down syndrome during the 1970s.3 The cause of

DS remained unknown until the 1950s when it became possibleto identify chromosomal abnormalities with the discovery of

karyotype techniques. In 1959 the French geneticist, Dr. Jerome

Lejeune, reported that DS was caused by an extra 21st chro-

mosome, an aneuploidy condition known as trisomy 21.4 The

vast majority of cases of DS are due to full trisomy 21, with

every somatic cell in the body having an extra 21st chromosome

(Table 1). A smaller percentage of persons with DS are due to

mosaic trisomy (2%e4%) and Robertsonian translocation

(3%e4%).5 Reports have suggested that children with mosaic

* Corresponding author.

E-mail address: [email protected](K. Pitetti)

Peer review under responsibility of Shanghai University of Sport

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Journal of Sport and Health Science 2 (2013) 47e57

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http://dx.doi.org/10.1016/j.jshs.2012.10.004
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DS have similar health and developmental difficulties as chil-

dren with full trisomy 21, but to a lesser degree6 and those with

DS caused by Robertsonian translocation have increased

frequency of psychiatric disorders.7

1.2. Demographics

In the United States the incidence of DS at birth from 1979

to 2003 increased from 9.0 to 11.8 per 10,000 births

(Table 1).8 It is suggested that the probable cause for the

increase in DS is related to the trend toward later child

bearing, with women over 35 being five times more likely than

younger women to have children with DS.5

1.3. The intellectual and health profiles of persons with

Down syndrome

Although about one-third of the causes of intellectual

disabilities (ID) remain unknown, the three major knowncauses of ID are DS, Fetal Alcohol Spectrum Disorder, and

Fragile X syndrome.6 As is the case for all persons with ID,

the degree of ID in persons with DS is determined by limi-

tations in both cognitive function and in adaptive behavior

(e.g., conceptual, social, and practical adaptive skills).7-9 The

degree of cognitive impairment is variable, with the majority

classified as mild (IQ: 50e55e69) or moderate (30e35 to

50e55) while a smaller percentage (


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a faster time to exhaustion (Table 2).27 Such findings were first

reported by Eberhard et al.28 in 1989, whereby they demon-

strated a 15% lower VO2peakusing bicycle ergometry compared

to age-matched children WOD. In 1990, Fernhall et al.,26 using

a validated treadmill protocol, reported lower VO2peak in

adolescents with DS when compared to adolescents WOD and

that lack of motivation or understanding protocol instructions inparticipants with DS did not contribute to their findings.

Following these initial contributions, the literature has

consistently demonstrated lower VO2peak values when indi-

viduals with DS are compared to individuals WOD and with

ID but without DS. In the largest sample to date (total n 635;

n 133 with DS, n 180 with ID, n 322 WOD), Baynard

et al.25 reported that VO2peak(absolute and relative values) is

lower in children and adolescents with DS through young

adulthood and into middle age, regardless of the comparison

group. Furthermore, the authors also demonstrated VO2peakdoes not significantly change after the age of w16 years.25

Interestingly, the average VO2peak at this age in individuals

with DS is similar to normative values found in middle-aged toolder persons WOD, yet individuals with DS do not appear to

experience the age-related decline in VO2peakas is expected in

those WOD (Table 2).25

Three physiologic factors that potentially contribute to low

VO2peakvalues in persons with DS are autonomic dysfunction,

reduced ventilatory capacity, and metabolic dysfunction.

When considering autonomic dysfunction, lower peak heart

rate (HR) responses have beenconsistently reported across all

age groups for persons with DS.25 The cause of lower peak HR

in persons with DS is still not completely understood at this

time, but Fernhall et al.29 demonstrated in a group of young

adults with DS (mean age 24 years) a blunted to non-existent

catecholamine response to peak exercise. This suggests that

some portion of the autonomic pathway is dysfunctional and

contributes to the lower HR response. Although diminished

sympathoexcitation in adults with DS has been reported,30,31

to date no studies have included youth with DS ( Table 2).

Further, with higher obesity levels generally observed inpersons with DS, the interaction between autonomic control

and obesity may be an important avenue to investigate in this

population.

It was also postulated that due to the relatively large

tongues (macroglossia) compared to the bony confines of the

oral cavity in persons with DS, ventilation would be restricted

at high work levels and thus limit peak performance. Indeed,

adolescents and young adults with DS have been reportedto

have low peak ventilation.26 However, Fernhall and Pitetti27

concluded that peak ventilatory parameters (e.g., ventilatory

equivalents, and peak minute ventialation) were appropriate

for a given VO2peak. In addition, imaging work has established

that children with DS do not have true macroglossia, althoughthey have relatively large tongues compared to their oral

cavity volume.32 Therefore, ventilation capacity does not

appear to restrict the peak performance of youth with DS.

However, gaps do exist in the literature with little to no data

available for additional ventilatory parameters, such as peak

minute ventilation/maximal ventilatory volume or peak tidal

volume/ventilatory capacity. This type of data would broaden

our understanding of potential limitations to exercise in

persons with DS.

Metabolic limitations have also been suggested to constrain

the physical capacity of youth and young adults with DS.

However, only two studies actually measured ventilatorythreshold in adolescents and young adults with DS.33,34

Collectively, these two studies reported that ventilatory

threshold was difficult to detect (e.g., V-slope method);

however, in those participants where it was detectable, normal

ventilatory thresholds were observed when expressed as

a percentage of VO2peak. Given that the respiratory exchange

ratio is related to substrate utilization and exercise intensity,

collection of blood lactate would assist in determining the role

that metabolic function may have in limiting exercise perfor-

mance in youth with DS. However, submaximal and maximal

exercise blood lactate levels have not been reported in the

literature for youth with DS. In line with this, supramaximal

testing (e.g., Wingate testing) is not reliable enough to date to

help complete a metabolic profile in youth with DS.35

It is important to note that several studies using field tests

also report lower predicted VO2peak and/or exercise perfor-

mance in youthand young adults with DS compared to peers

WOD (Table 2).36,37 The largest field study to date to measure

run performance (20-m shuttle run) had 119 youth (11e18

years) with DS, 394 youth with ID but without DS, and 80

youth WOD.38 Children and adolescents with ID but without

DS had better run performance than their peers with DS

independent of age, sex, and body mass index (BMI).38

Furthermore, those WOD had better run performance than

their peers with ID, again independent of age, sex, and BMI.38

Table 2

Physical fitness in youth with Down syndrome (DS).

Characteristic Description

Cardiovascular fitness 1. Low peak aerobic capacity/time to exhaustion

2. Low peak heart rate

3. Peak aerobic capacity does not change

significantly with age after w16 years

4. Autonomic dysfunction a primary factor

related to low fitness

5. Field tests largely support laboratory findings

6. Responsive to aerobic endurance training,

particularly with improvements in work

capacity

Muscular strength 1. Lower strength compared to individualswithout disabilities

2. Resistance training appears safe and beneficial

for improving strength

3. Improved leg strength does not appear

improve aerobic capacity

Body composition 1. Youth with DS in North America and Europe

are more obese/overweight vs. counterparts

without disabilities

2. Cause of high rate of overweight/obesity is

multifactorial (physiological, societal,

environmental, psychological, etc .)

3. Studies show no improvement in body

composition from exercise training alone,

likely due to lack of dietary control

Youth with DS: Fitness and activity 49


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Thus, poor running performance of children and adolescents

with ID, with and without DS, is not a consequence of age,

sex, or BMI.

Furthermore, Fernhall et al.39,40 produced a regression

equation from the results of the 20-m shuttle run to predict

VO2peakin children and adolescents with ID, with and without

DS. This equation was cross-validated in 2003 by Guerraet al.,41 however, this study consisted of a greater percentage

of children and adolescents with DS and they were not able to

validate Fernhalls39,40 original equation designed for persons

with ID to a sample with DS alone. The prediction of VO2peak,

from a 20-m shuttle run test, was further examined by

Agiovlasitis et al.,42 whereby they reported that while shuttle

performance was a predictor of VO2peakin youth with DS, the

equation had low predictability at the individual level.

Therefore, the use of the regression equation developed by

Fernhall et al.39,40 to predict VO2peakin persons with ID does

not appear to be specific for youth with DS.

2.1.2. Training studies

There are relatively very few longitudinal training studies

in persons with DS, particularly in youth. For this reason,

training studies in young adults with DS will be utilized here

with the understanding that it would be likely that youth with

DS would experience similar findings. A meta-analysis was

conducted by Dodd and Shields43 that included four papers,

which met their inclusion criteria.44e47 They reported that

aerobic training programs, which conformed to the American

College of Sports Medicine guidelines, were effective for

improving VO2peak, peakventilation, time to exhaustion, and/

or maximum workrate.43

One of the first trainingstudies in adolescents with DS wasconducted by Millar et al.,45 with 14 individuals participating

in a 10-week walking/jogging program, 3 days/week at 65%e

75% peak HR, which resulted in no change in VO2peak, but did

improve treadmill test time by 9%.45 Training studies that

have measured VO2peaksince the report by Millar et al.45 have

supported those initial findings, in that improvements have

been seen in exercise/work capacity without significant

improvements in VO2peak with training interventions lasting

12e16 weeks (Table 2).9,48 Further evidence of positive

training effects stems from an often overlooked study,

whereby HR recovery following a 3-min step test and resting

HR were decreased in a group of 10 individuals with DS

(8e18 years) after a 13-week training program.49 Lastly, an

interesting case study reported that a young 10.5-year-old

female with DS following 6 weeks of training did not alter her

estimated VO2peak, but her submaximal HR was lower during

the treadmill test, as was her respiratory rate, indicating

improved work capacity and capacity for change.50

While aerobic training studies are limited in persons with

DS, let alone youth, previous work suggests exercise training

is beneficial in youth with DS even if VO2peak itself is not

necessarily an expected outcome. It is especially important to

consider training studies in youth with DS in that early

intervention to improve their work/exercise capacity could

impact the health anomalies specific to the condition of DS.

2.2. Muscular strength

Few studies exist that have employed strength testing and/

or training in youth with DS. Strength decrements were first

characterized in youth with DS in 1994 by Cioni et al.,51 in

which children and adolescents with DS (n 25) exhibited

weak knee extensor strength compared to a WOD controlgroup. Furthermore, these authors concluded that adolescents

with DS generally do not show improvements in strength

beyond the age of 14 years.51 These findings can be extended

to thehip abductors as well.52 Interestingly, Pitetti and Fern-

hall53 explored the relationship between VO2peakand strength

in youths aged 10e17 years with ID (n 29), including eight

children with DS, and found a significant relationship between

knee flexion/extension strength and aerobic capacity

(r 0.56e0.62). Their data suggest that leg strength may be

a limiting factor in both work and aerobic capacity in persons

with DS, which is also supported by similar work in adults

(Table 2).54

There is a small body of literature in young adults with DS(mean age w24e25 years) that further extends the limited

findings in youth. Several studies have demonstrated lower

muscle strength in young adults with DS for both knee, and/or

elbow extensors/flexors compared to participants WOD.55e58

In those studies that distinguished between individuals with

ID with or without DS, no general differences in strength were

observed between these two groups, whereas the control group

WOD was always stronger (65%e225% stronger). However, it

should be noted that while not different, Croce et al.57 have

reported lower hamstring to quadriceps ratios in adults with

DS (20%)vs. those WOD and 10% lower compared to adults

with ID without DS. This may suggest reduced muscularperformance and knee joint stability.

The number of strength training intervention studies that

included individuals with DS is even smaller, withtwostudies

known to have specifically trained youth with DS.59,60 Weber

and French59 found that resistance training improved overall

muscular strength in adolescents with DS (e.g., 10 muscular

tests performed), yet this study lacked a control group.

Recently, Shields and Taylor60 demonstrated that a 10-week

community-based progressive resistance training intervention

was successful in increasing lower limb strength (as well as

muscle endurance) in 23 adolescents with DS, with no changes

in upper limb strength. Unfortunately, no measure of work

and/or aerobic capacity was performed in these studies.59,60

Lastly, a case study demonstrated that a young girl with DS

improved general muscle strength (e.g., trunk, hip, knee, and

shoulder) following a 10-week combined aerobic and resis-

tance program.50 These data collectively suggest that strength

training in youth is beneficial. Little to no data exist on the

relationship between strength training and improving work

capacity in youth with DS (Table 2). A recent study by Cowley

et al.61 reported a small, but significant increase in relative

VO2peak following a 10-week strength training program in

young adults with DS, yet no difference in absolute VO2 was

observed, suggesting this improvement was mediated by

weight loss (w5 kg).

50 K. Pitetti et al.


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A group of progressive resistance exercise training studies

clearly demonstrate that strength training is a safe and

important component of exercise prescription in young adults

with DS (24e29 years).61e64 These studies lasted 10e12

weeks and all employed a 2e3 days/week training of large

muscle groups, with improvements found in both upper- and/

or lower-body strength. Interestingly, Cowley et al.61

concomitantly measured aerobic capacity and reported no

change in absolute VO2peak and a small but significant

decrease in relative VO2peak(Table 2).

2.3. Body composition

Equivocal evidence exists regarding body composition in

persons with DS. The lack of consistency may involve meth-

odological issues for measuring body composition (e.g.,

skinfolds vs. dual energy X-ray absorptiometry) or perhaps

comparing weight status using different vehicles, such as

a laboratory measures versus BMI. Another possible contrib-

utor may be ethnic and/or environmental issues as well.Caution is urged when interpreting global statements on body

composition in DS for these reasons.

Numerous investigations have reported that the prevalence

of overweight and obesity are substantially higher in individ-

uals with DS comparedto their age-matched peers WOD and

with ID but without DS.65,66 Prasher67 reported that w48% of

adults with DS were obese, with w27% being overweight

(both sexes averaged) and that being overweight and/or obese

was associated with living at home compared togroup-home

situations. This is consistent with Rubin et als65 report of

w48% for men and w56% of women being overweight/

obese. Interestingly, BMI was found to decrease throughoutthe lifespan in males and females with DS, whereas BMI

increases through the lifespan in the general population.67 This

is in contrast to Baynard et al.,25 whereby they reported BMI

increases not only in the control group, but also in groups of

ID, with and without DS, up through middle-age. Prasher67

was unable to adequately explain why BMI would decrease

from young adulthood (16e19 years) through the 20 s into the

60 s. Perhaps the Alzheimers issues that individuals with DS

often experience could provide a possibleexplanation.

Early work by Sharav and Bowman68 demonstrated that

young children with DS (w4e5 years) were not different from

their siblings WOD in BMI. Additionally, Luke et al.69 reported

non-significant but higher BMI and lower fat-free mass in

children with DS (9 years old) versus a control group WOD,

whereas other investigators have observed higher BMIs and/or

percentage of body fat in youth with DS compared to peers

WOD.52,70 However, these studies also included adults in their

samples.52,70

In contrast to Luke et al.,69 others have observed lower total

muscle mass in persons with DS versus individuals WOD.70

This has been further substantiated recently in Spanish youth

with DS that did exhibit higher body fat content and lower lean

mass than peers WOD.71 In Greece, researchers observed that

22% of adolescents in their sample were obese and that percent

body fat, BMI, fat mass and fat-free mass were also greater in

adolescentswith DS (10e18 years) than in children with DS

(2e9 years).72 It is important to note that several studies do

suggest that children and adults with developmental disabilities

in the United States and Australia have greater prevalence rates

of overweight and obesity compared to non-disabled age-

matched controls. Yet these studiesonly have a small portion of

individuals with DS included.65,66

However, the prevalence ofoverweight/obesity has recently been questioned and it may not

be as high as previously thought.73 It is also possible interna-

tional differences exist that need further examination. More

work will need to be conducted not only at the physiological

level, but work at the environmental, community, societal and

psychological levels to fully delineate the numerous factors

involved in obesity (Table 2).

3. Physical activity (PA) in youth with DS

Apart from physical fitness, PA has the potential to improve

health in youth with DS. Although the relationship of PA and

health outcomes has not been directly examined in youth withDS, it is reasonable to assume that the findings in the general

population of youth also apply to those with DS. PA may

improve the cardiovascular, metabolic, musculo-skeletal, and

psychosocial health profiles of all youth.74e76

For this reason, the 2008 Physical Activity Guidelines for

Americans devoted a section to children and adolescents.76

Specifically, it is recommended that youth older than 6 years

perform 60 min of PA daily. Most of aerobic activity should be

of either moderate or vigorous intensity, defined as 3.0e5.9

and >5.9 metabolic equivalent units (METs), respectively;

however, vigorous-intensity activity should be performed at

least 3 days/week. Muscle- and bone-strengthening activitiesare important components of the recommended 60 min of

daily activity and each should be performed at least 3 days/

week. Importantly, the Guidelines call for the promotion of

physical activities that are age-appropriate, enjoyable, and

offer variety. Recent evidence, however, suggests that most

American youthdespecially adolescentsddo not meet the

required amount of daily PA and that their activity levels

decline as they grow.77 The issues of interest therefore are: (a)

whether the PA levels of youth with DS differ from those of

youth WOD, and (b) whether youth with DS meet the current

recommendations for PA.

Answering these questions is difficult because research on

PA in youth with DSis limited. In a review of research pub-

lished prior to 2008,78 the authors could not conclude whether

the PA levels of youth with ID, including those of youth with

DS, are different from those of children WOD. As the authors

explained, this was due to methodological problems of

previous research such as insufficient description of samples

and questionable applicability of objective or subjective

measurements of PA to youth with ID.

3.1. Measurement of PA in youth with DS

Subjective PA assessments using questionnaires are not as

accurate as objective ones.77 This difficulty is magnified in



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youth with DSby the need to use parental or caregiver/teacher

proxy reports.78 One study demonstrated questionable accu-

racy of PA measurement by proxy reports for adults with ID.79

It is possible that subjective assessment of PA in youth with

DS may benefit if questionnaires are obtained from both

parents and teachers or caregivers; such practice may offer

a more accurate representation of the activities youths with DSengage in throughout the day. Nevertheless, to our knowledge,

the psychometric properties of subjective measures have not

been examined in youth with DS. Finally, in-depth inter-

viewsdtypically with parentsddo not allow for a quantifica-

tion of the amount of PA performed by youth with DS.

Objective PA measurements with accelerometers or

pedometers are preferable, but they should be used carefully in

youth with DS. Pedometers appear valid and reliable during

locomotion in youth with intellectual or developmental

disabilities,80,81 but their accuracy may be compromised

during games and sport activities conducted in physical

education.82 Additionally, spring-levered pedometers are less

accurate than piezoelectric in people with DS.83 Furthermore,using step-rate cut-points to estimate moderate- and vigorous-

intensity activity in youth with DS may be problematic. Adults

with DS have lower step-rate cut-points for activity intensity

even when accounting for their shorter height compared to

adults without DS84dthis may potentially apply to youth with

DS. Similarly, accelerometry-determined cut-points for

moderate- and vigorous-intensity activity developed for youth

WOD may not be applicable to youth with DS. This has been

demonstrated for adults with DS85 and it has been suggested to

be partially due to an altered gait pattern that increases the

energy expenditure.86 It is possible that this also applies to

youth with DS who also exhibit altered gait patterns,87,88

potentially duedat least in partdto deficits of the cere-

bellum.89 Additionally, cut-offs developed in youth WOD may

be inappropriate for those with DS because the latter have very

low cardiovascular fitness. Finally, there have been some

reports of compliance issues with accelerometers secured at

the hip in youth with DS.90,91 Although these difficulties are

not extensive, they highlight the need for adequate familiar-

ization and parental supervision. Alternately, researchers could

consider other placement sites, such as the wrist, where the

accelerometer could be secured with an irremovable strap.

These measurement issues should be collectively considered

when evaluating previous reports of PA in youth with DS.

3.2. What are the PA levels of youth with DS?

In infants with DS, movementdespecially of the

legsdmay be important for motor development. Children with

DS appear to reach stages in motor development with some

delay.92 A notable example is the onset of independent

walking which occurs about a year later (wage 2) in children

with DS than children with typical development.93,94 It is

possible that low levels of motor activity during early infancy

may contribute to this phenomenon. One study found that,

during the first 6 months of life, infants with DS show lower

levels of general movements as measured by observation than

infants with typical development.95 In contrast, analyzing

video recordings, others reported no differences between

infants with and without DS in the total amount of leg

movements93 which are presumably more relevant for the

development of walking. Subsequently, infants with DS were

found to show more low-intensity and less high-intensity leg

motor activity than infants with typical development.96,97

Furthermore, greater amount of high-intensity activity at

about 1 year of age was associated with earlier walking onset

in infants with DS.96,97 Finally, a randomized controlled study

showed that infants with DS, who underwent home-based

stepping training while supported over customized treadmills,

achieved independent walking by an average of 101 days

earlier than infants with DS not undertaking this intervention;

the intervention was initiated once infants with DS could sit

independently and it was conducted 5 days/week, 8 min/day,

until the onset of independent walking.94 Taken together, these

data suggest that alterations in PA patterns in infants with DS

are associated with their motor development, thus supporting

the need for early interventions.96

The objective data on PA levels of children and adolescents

with DS are limited and provide somewhat conflicting results.

Non-resting total energy expenditure measured with doubly-

labeled water did not differ between 5- and 11-year-old chil-

drenwith DS from the U.S. and peers WOD of similar age and

BMI.98 In another U.S. study, the amounts of total, low-

intensity, and moderateeintensity activity, as well as time

spent sedentary measured with hip-accelerometry over 7 days

did not differ between childrenwith DS aged 3e10 years and

similarly-aged siblings WOD;90 however, the children with DS

participated in less and shorter bouts of vigorous-intensity

activity than their siblings. Notably, children both with andwithout DS in that study exceeded the recommendations for

total and vigorous-intensity aerobic activity. Similarly,

Australian children and adolescents with DS met on average

the recommended amounts of moderate- and vigorous-inten-

sity activity as measured by hip-accelerometry91 and also

appeared more active than U.S. youth.77 But there was large

between-person variability in activity levels and 58% of the

children with DS did not meet the recommended amount. In

the same study, youths with DS aged 13e17 years showed

lower total, moderate-, and vigorous-intensity activity than

those aged 7e12 years, indicating a possible age-associated

decline in PA. Recent acceleromety-derived data from the U.S.

demonstrated that, on average, children and adolescents with

DS did not engage in moderate-to-vigorous PA for 60 min/

day.99 Furthermore, PA was lower and sedentary behavior was

higher in older youths with DS compared to younger ones.

Another U.S. study using accelerometry100 showed that, prior

to an intervention, youth with DS aged 8e15 years were active

at moderate-to-vigorous levels for an average of about 43 min,

although there was significant between-people variation in this

value. Finally, cross-sectional accelerometry-determined data

from England demonstrated lower amount and faster age-

associated decline of moderate-to-vigorous activity in people

with DS thanpeople with ID but without DS across the life-

span (Table 3).101



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Some subjective datad

obtained with parental reports or in-depth interviewsdsupplement the literature on PA of youth

with DS. Canadian children with DS aged 2e14 years were

rated by their parents as less active and as spending more time

indoors compared to siblings without DS,68 although all youth

in this study withDS participated in organized sports at least

once per week.69 Among 38 Australian youth with DS aged

11e18 years, only two engaged in PA more than 3 days/

weekda finding suggestive of low PA levels.102 In a second

Australian study, less than one third of 208 youth with DS

aged 5e18 years were found to be active at moderate-to-

vigorousintensity for 60 min/day, although most participated

in sports.103 Finally, during in-depth interviews, parents of

U.S. preschoolers with DS perceived their children as natu-

rally active. In contrast, parents of elementary-school students

perceived a gradual decrease in their childrens interest for PA,

supporting thepossibility for an age-associated decline among

youth with DS.104

The existing objective and subjective data do not allow us

to conclude with confidence whether youth with DS have

lower PA levels than youth WOD, but this appears likely.

Additionally, it is not known if youth with DS meet the

required amounts of muscle- and bone-strengthening activi-

ties. Although there are no longitudinal data on the develop-

mental course of PA in youth with DS, it is likely that PA

declines with age in this population. Furthermore, a large

proportion of children and adolescents with DS may not meet

the recommended amount of daily aerobic activity.

3.3. Determinants of PA

The study of the determinants of PA in youth with DS is

still in its infancy. Following the approach of the InternationalClassification of Functioning, Disability and Health,105 PA

may be influenced by a childs health status, functional profile,

participation in life activities, and contextual factorsdeither

within the person or in the environment. DS is associated with

many health conditions, but there is great variability in the

number and extent of conditions that youth with DS exhibit. In

one study, medical issues were not associated with function

among youth with DS.106 It is reasonable, however, to assume

that acute health problems might present barriers to PA for

youth with DS and that, when medical issues are efficiently

overcome, PA may be facilitated.

The functional profiles of youth with DS may also be

related to their PA levels. Quantitative and qualitative datasuggest that lower cognitive, behavioral, and motor skills may

present barriers to PA of youth with DS.103,104,107,108 Some

theorists also argue that people with DS may have a tendency

for slower, safer, and more accurate movement patterns due to

interactions between neurological, environmental, and task-

associated constraints.109 Additionally, the very low aerobic

and muscular fitness of youth with DS may potentially affect

their involvement in physical activities, especially of higher

intensities, but this has not been directly examined (Table 3).

Contextual factors within the person may also be at play. In

support of this argument, the aforementioned lower partici-

pation in vigorous-intensity activities of children with DScompared to their siblings90 was collectively explained by age,

sex, race, ethnicity, income, maternal education, and BMI. It is

difficult, however, to determine the individual contributions of

these factors to PA of the children in that study. As previously

discussed, PA in youth with DS may decline with age,91,101,104

although one study did not find differences in sport partici-

pation between children and adolescents with DS.103

Furthermore, whether PA differs between sexes in youth

with DS, as in youth WOD,74,77 is not known. Data from

Taiwan, China showed no difference in recreational and sport

participation between boys and girls with DS.108 In contrast,

another study conducted in Taiwan, China demonstrated that,

among youth with ID including DS, boys and those who had

positive attitudes towards exercise were more likely to be

regularly active after school.110

It is also very likely that the social and physical environ-

ment contributes to the PA levels of children and adolescents

with DS (Table 3). This is supported by a wide variation in

typesof leisure participation among youth with DS around the

world.68,102,103,108,110,111 Furthermore, it has been argued that

inactivity among youth with DS may be a learned behavior

partially resulting from exclusionary practices.112 Importantly,

lack of accessible, inclusive, and appropriately-designed

programs, as well as negative attitudes, transportation prob-

lems, competing family responsibilities, parental education

Table 3

Physical activity in youth with Down syndrome (DS).

Characteristic Description

Physical activity 1. Likely declines during the growing years

2. A large proportion of youth with DS does

not meet the recommendation for daily

aerobic activity

3. Youth with DS participate in a wide varietyof culturally-relevant leisure activities

Barriers to physical activity

Within the person 1. Health problems

2. Low fitness levels

3. Low motor skills

Environmental 1. Lack of accessible, inclusive, and properly

designed programs

2. Transportation difficulties

3. Negative attitudes towards people with

disabilities

4. Competing family responsibilities

5. Parental education and income

6. Lack of friends

Facilitators of physical activity

Within the person 1. Knowledge on physical activity and health

2. Positive attitude towards exercise

3. Determination to succeed

Environmental 1. Positive social and familial attitudes

2. Knowledgeable professionals

3. Structured programs that .

1) Are adapted to the needs of youth with DS

2) Provide knowledge on physical activity

and health

3) Are inclusive

4) Promote social interaction and enjoyment



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and income, and lack of friends, all reportedly present barriers

to PA for youth with DS.90,104,107

3.4. PA promotion

Youth with DS reportedly participate in a wide range of

recreational activities. Examples include walking, swimming,bowling, dancing, and team sports.68,102,103,108,110,111 The

types of leisure participation among youth with DS likely vary

around the world; for example, swimmingappears common in

Australia,102,103 ice-skating in Canada,68 and bicycling in

Taiwan, China.108 Notably, walking is one of the most

commonly performed activities among youth with

DS,108,110,111 suggesting that their altered gait pattern87,88 may

not present a barrier to PA. Supporting this proposition, chil-

dren and adolescentswith DS exhibit functional independence

in locomotion tasks.106 Therefore, youth with DS have the

potential to participate in all types of culturally-relevant

physical activities.

Unfortunately, very little data exist on interventions topromote PA in youth with DS. A randomized-controlled study

found that youth with DS who learned to ride a bicycle

increased their PA levels about 1 year after the intervention,100

suggesting that motor skill development may improve long-

term PA. Furthermore, well-designed school programs allow

students with ID including those with DS to meet the PA

recommendations.113 It should also be considered that 12

weeks of exercise training, combined with health education,

improves the attitudes towards exercise and psycho-social well

being of adults with DS,114 but, to our knowledge, similar

studies in youth with DS have not been conducted (Table 3).

It has been recommended that PA promotion in all youthaimed at ameliorating the age-associated decline in PA, sup-

pressing the development of pathological processes, and

creating life-long PA habits.74 To achieve these goals in youth

with DS, PA promotion should be multi-factorial. Well-

designed programs should take into account the physical,

cognitive, and psycho-social health profiles of children with

DS as well as their need for enjoyment and participation. But

at the same time, the environmental contexts in which PA,

exercise, and recreation occur must be appropriately designed.

Parents tell us that the PA of their children with DS may be

facilitated by positive familial and social attitudes, and struc-

tured programsdones that are adapted to the abilities of their

children, offer youth with DS knowledge on PA and health,

utilize their determination to succeed, and promote social

interactions and enjoyment.104,107,111

4. Summary and future directions

4.1. Physical fitness

Youth with DS have low peak aerobic capacity coupled

with low peak HR, suggesting autonomic dysfunction may be

a primary reason explaining low work performance in this

population. Furthermore, persons with DS also have low

muscular strength compared to individuals WOD. Exercise

training utilizing endurance and/or resistance exercise appears

beneficial for youth with DS. The role of overweight/obesity

in youth with DS does not currently explain lower aerobic

capacities in persons with DS, yet more work needs to be

conducted to completely understand its role with regards to

aerobic capacity and PA in this population. Studies involving

multi-factorial issues (e.g., physiological, environmental, etc.)common to youth with DS are necessary to understand how to

optimize quality of life in this population.

4.2. PA

Cross-sectional data suggest that PA likely declines with

growth in youth with DS and that a large proportion of these

youths do not meet the recommended amount of daily aerobic

activity. Effective PA promotion should be multi-factorialdit

should be adapted to the physiological, cognitive, and psycho-

social profiles of youth with DS, but should also consider

environmental modifications. There is a need to improve theassessment of PA with objective and subjective approaches.

Furthermore, longitudinal research is needed to examine how

PA levels change and what factors contribute to them during

growth in youth with DS. Finally, it is also important to

examine the effectiveness of specific interventions aimed at

increasing PA.

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