He alth Ben efit s of Phy sica l Ac tivi ty

Du ring Chi ldho od a nd A dole scen ce

Od ed B ar-O r

MCMAS TER UNI VERS ITY

ORIGINALLY PUBLISHED AS SERIES 2, NUMBER 4, OF THE PCPFS RESEARCH DIGEST.

HI GHLI GHT

“C h ild ren a r e n o t li t t le a d u lt s . Th eir re sp on ses t o a c t ivi t y a r e

qu it e d i ffer en t fr om t h ose of a d u lt s . Ac t ivi t y p r ogra m s sh ou ld 

be p l a n n e d wi t h t h ese d i ffer en ce s in m i n d .” 

IN TROD UCTI ON

The beneficial effects to health of enhanced physical activity (PA) during adult years are

numerous. There is mounting evidence that such benefits include a reduction in morbidity

and mortality from diseases of several body systems (Bouchard et al., 1994). Much less

evidence is available regarding the effects of an active lifestyle during childhood and

adolescence on adult health.

The main reason for the paucity of information on the possible carryover of benefits

from childhood to adulthood is the lack of longitudinal studies that have followed the same

individuals over many years. Ideally, one would need randomly to assign children into those

who are given enhanced PA programs and those who remain sedentary over years and then

observe the long-term effects of PA or of inactivity. On ethical grounds, such studies are hard

to justify (it is unethical to demand that children not engage in PA for an extended period of

time). In addition, they are extremely expensive and logistically most complicated. A secondbest alternative would be to conduct controlled intervention studies that last shorter periods

and include several groups of subjects who span a wide age range (from childhood to middle

age). Such “mixed longitudinal” studies are feasible, but have yet to be launched. Another

approach is to identify adults with and without diseases and question them about their PA

during earlier years. Such “retrospective” studies are easier to perform, but their outcome

depends on the ability of people to correctly remember and report their PA behavior during

earlier years. Conclusions derived from retrospective studies are less valid than those derived

from longitudinal interventions.

The purpose of this article is to examine briefly the current evidence that enhanced PA

during childhood and adolescence imparts immediate health benefits, or reduces risk for

adult chronic disease. Emphasis will be given to the following conditions: obesity,

hypertension, abnormal plasma lipoprotein profile, and osteoporosis. Table 19.1 summarizes

the evidence attesting to such benefits.
SH ORT- TERM BEN EFIT S

Before analyzing the carryover effects of childhood PA, one should identify the immediate

effects of a training program (or an active lifestyle) on health-related risk factors. These are

measured while the program is still in progress, or immediately upon its conclusion. Evidence

for such benefits has been sought from intervention training programs that last a few weeks or

several months at the most. An alternative approach has been cross-sectional studies that

compare children (or youth) who habitually engage in athletic pursuit with those who lead a

sedentary lifestyle. The drawback of the latter approach is that differences in health-related

risk between groups might not be a result of the physical activity per se. They may instead

reflect heredity or events that took place before the child became physically active.

Bo d y fa t n es s. (See Bar-Or & Baranowski, 1994, for a review.) Many, although not all,

cross-sectional studies suggest that obese children and youth are less active than their leaner

peers. There is only scant evidence, though, that inactivity is a cause of juvenile obesity

(Roberts, 1993). Training studies with nonobese youth have shown little or no reduction in

body adiposity (Wilmore, 1983). However, enhanced PA with or without a low-calorie diet,

did reduce % body fat or excess body weight in obese children and youth.

Bl ood p r essu re. (See Alpert & Wilmore, 1994, for a review.) Some cross-sectional

studies show a slightly higher resting blood pressure among sedentary adolescents compared

with their active peers. Most studies, however, do not show such a difference, particularly if

the groups have the same adiposity level. Training of healthy, previously inactive children or

adolescents who have a normal blood pressure induces little (1-6 mmHg) or no drop in blood

pressure. However, in adolescents with hypertension, training over several months does induce

a reduction of both systolic and diastolic blood pressure. Even though such a reduction is

modest (around 10 mmHg), it may be beneficial for some individuals with mild hypertension

who otherwise may require medication to control their blood pressure. The training programs

that induced a decline in blood pressure were comprised mostly of aerobic activities. In one

study (Hagberg et al., 1984), the inclusion of a five-month weight training regimen following

a six-month aerobic program further reduced the blood pressure of adolescents with

hypertension. Such beneficial effects of exercise disappear within several months of

termination of the program.

Bl ood li p id s . (See Armstrong & Simons-Morton, 1994, for a review.) Based on some

cross-sectional studies, children and adolescents who are physically active, or whose aerobic

fitness is high, have a more favorable blood lipid profile than their sedentary, or less fit, peers.

This difference is particularly apparent in high-density lipoprotein cholesterol (HDL-C = the

“good” cholesterol), which is higher in the active groups. Other cross-sectional comparisons,

however, do not reveal such differences. In most of the cross-sectional studies it is impossible

to separate a high activity level from a high fitness level.

Training studies of several weeks’ duration have failed to show any beneficial effect on

the blood lipid profile in healthy children or adolescents. More beneficial responses have

been shown for groups who have a high coronary risk. These include children and

adolescents with insulin-dependent diabetes mellitus, obesity, or with at least one parent who

has three or more coronary risk factors.
Sk elet al h e alt h . (See Bailey & Martin, 1994, for a review.) The possible link between

skeletal health and PA has received attention in recent years with the finding that physically

active postmenopausal women, and elderly populations in general, have a higher bone

mineral density (BMD) and less osteoporosis than less active controls. One of the

determinants of bone health in old age is the “peak” BMD reached by young adulthood.

Bone mass and BMD subsequently (and inevitably) decline with the years, until the bones

become fragile.

This topic has an important pediatric relevance, because the great majority of bone buildup occurs during adolescence. A question of major public health relevance is whether

enhanced PA during childhood and adolescence will result in a higher peak BMD.

Cross-sectional comparisons have shown that young athletes in weight-bearing sports such

as gymnastics, soccer and volleyball (but not in non-weight-bearing sports such as swimming)

have a higher BMD than do nonathletes. Likewise, bones of the dominant limb in

“asymmetrical” sports, such as tennis or little-league pitching, have a higher BMD than the

nondominant limb. Conversely, bones of a limb immobilized for several weeks or months had

a lower BMD than in the contralateral, nonimmobilized limb.

Retrospective studies, in which adults were asked about their PA during childhood,

suggest that women who had been physically active during childhood had a higher BMD in

the third and fourth decades of life than women who had been less active as children.

Longitudinal results of weight-bearing training programs are equivocal. Most controlled

interventions yielded little or no increase in BMD or bone mass of exercising adolescents

(e.g., Blimkie et al., 1993).

CA RRYO VER TO A DULT LIF E

There are several models that may explain a possible link between an adult person’s health

and her or his activity behavior in earlier years. As suggested by Blair et al. (1989) there are

conceivably three avenues by which an enhanced PA level during childhood might improve

adult health:

1. Childhood activity improves child health which, in turn, is beneficial to adult health.

2. An active lifestyle during childhood has a direct benefit to health in later years.

3. An active child becomes an active adult who, in turn, has a lower risk for disease than an

inactive adult.

Research provides no proof, or disproof, for any of these links. However, because a

sedentary lifestyle in adults has been proven to entail a high risk for several chronic diseases

(Bouchard et al., 1994), the most plausible link is that an active lifestyle during childhood and

adolescence would be carried over through adulthood which, in turn, would reduce risk for

disease. There are, however, no prospective studies that have tracked activity patterns from

childhood to adulthood. Even though activity patterns and attitudes toward PA remain quite

stable during late adolescence (but less so around age 10–12 years) (Malina, 1990), there is a

low relationship between the two.
HO W MU CH P HYSI CAL ACTI VITY ?

There are practically no data as to the optimal dose of PA during childhood and adolescence

that might maintain and/or enhance health. However, a group of experts from various

countries has recently generated a consensus statement (Sallis & Patrick, 1994), which

includes the following guidelines for adolescents:

1. All adolescents should be physically active daily, or nearly every day, as part of play,

games, sports, work, transportation, recreation, physical education, or planned exercise; in

the context of family, school, and community activities.

2. Adolescents should engage in three or more sessions per week of activities that last 20

minutes or more at a time and that require moderate to vigorous levels of exertion.

There is no formal consensus statement for preadolescents although Corbin, Pangrazi, and

Welk (1994) have made recommendations for physical activity levels for this group in a

previous issue of the President’s Council on Physical Fitness and Sports Physical Activity and

Fitness Research Digest.

TA BLE 1 9 .1

Po ssib le ef f ect s of en h an c ed p h y sic al ac tiv i ty du r in g ch ildh ood an d

ad oles cen c e on r i sk f o r ch r on i c di seas e.

Ob serv ed V aria ble/ Risk 

Ad ipos ity/ Obe sity 

Re stin g Bl ood Pres sure /Hyp erte nsio n

Bl ood Lipi d Pr ofil e

Bo ne M iner al D ensi ty/ Oste opor osis 

Cr oss- Sect iona l Co mpar ison s

Ob esit y is ass ocia ted with hyp oact ivit y.

Le ss a ctiv e gr oups hav e si mila r or sli ghtl y hi gher BP comp ared wit h ac tive gro ups. 

Yo ung athl etes som etim es h ave a be tter pro file tha n se dent ary cont rols (mo stly in HDL- chol este rol) .

At hlet es ( weig ht-b eari ng a ctiv itie s) h ave high er B MD t han nona thle tes. 

Sh ort- Term Eff ects of Inte rven tion Pro gram s

Ge nera l Po pula tion : L ittl e or not red ucti on i n % fat

Ob ese: r educ tion in % fa t

Ge nera l Po pula tion : L ittl e or no redu ctio n in blo od p ress ure

Hy pert ensi ves: 5 –12 mmHg red ucti on i n SB P an d le ss i n DB P

Ge nera l Po pula tion : N o im prov emen t in pro file 

Hi gh-r isk Popu lati on: I mpro ved prof ile

Im mobi lity ind uces los s of BMD . Tr aini ng o ver seve ral mont hs i nduc es n o in crea se i n BM D.

Ge nera l Po pula tion : No inf orma tion 

Ob ese: % fat ret urns to pret rain ing leve ls i n mo st p atie nts

Ca rryo ver to A dult Lif e
Ge nera l Po pula tion : No inf orma tion 

Hy pert ensi ves: B P re turn s to pre trai ning val ues with in w eeks 

Ge nera l Po pula tion : No inf orma tion 

Hi gh-r isk Popu lati on: No inf orma tion 

Re tros pect ive data sug gest a p ossi ble carr yove r.

C ON CL US IO N

Based on current information, no long-term studies exist that support or reject the notion that

physical activity during childhood and adolescence is beneficial to adult health. There is,

however, some evidence for short-term benefits of enhanced PA during the early years,

particularly among children and youth who are at a high risk for chronic illness in later years.

Much more research is needed to study this important issue further. In particular, it is

essential to identify means of keeping young people motivated to maintain an active lifestyle

as they reach young adulthood and middle age.

Th e co ntra st be twee n cr oss- sect iona l da ta an d th ose ge nera ted th roug h tr aini ng

st udie s is in trig uing . Th e fo rmer su gges t fa vora ble he alth ch arac teri stic s am ong ac tive 

ch ildr en an d yo uth, co mpar ed wi th se dent ary co ntro ls. Tr aini ng st udie s, on th e ot her

ha nd, sh ow li ttle or no be nefi cial ef fect of tr aini ng am ong he alth y ch ildr en an d yo uth. 

Th is co ntra st ma y re flec t a pr esel ecti on of th ose wh o be come ac tive , an d ar e he alth ier to 

st art wi th, ve rsus th ose wh o ch oose to pu rsue a se dent ary li fest yle. It is po ssib le, th ough ,

th at in terv enti ons mo re vi goro us th an th ose co mmon ly us ed in re sear ch wo uld yi eld

gr eate r ef fect s. It ha s be en sh own, fo r ex ampl e, th at ar my re crui ts wh o un derg o an 

in tens e ei ght ho urs pe r da y tr aini ng re gime n fo r se vera l mo nths re spon d wi th an in crea se

in bo ne mi nera l co nten t (M argu lies et al ., 19 86) an d an im prov ed li pid pr ofil e

(R ubin stei n et al ., 19 95). Li kewi se, it is po ssib le th at lo nger in terv enti ons (e .g., 1– 2

ye ars) th an th ose us ed in mo st st udie s wo uld yi eld mo re po siti ve tr aini ng-i nduc ed

re sult s.

R EF ER EN CE S

Alpert, B.S., & Wilmore, J.H. (1994). Physical activity and blood pressure in adolescents. Pediatric Exercise

Science, 6, 361–380.

Armstrong, N., & Simons-Morton, B. (1994). Physical activity and blood lipids in adolescents. Pediatric

Exercise Science, 6, 381–405.

Bailey, D.A., & Martin, D.A. (1994). Physical activity and skeletal health in adolescents. Pediatric Exercise

Science, 6, 330–347.

Bar-Or, O. (1994). Childhood and adolescent physical activity and fitness and adult risk profile. In C. Bouchard,

R.J. Shephard, & T. Stephens (Eds.), Physical activity, fitness, and health. International proceedings and

consensus statement (pp. 931–942). Champaign, IL: Human Kinetics Publishers.

Bar-Or, O., & Baranowski, T. (1994). Physical activity, adiposity, and obesity among adolescents. Pediatric

Exercise Science, 6, 348–360.

Bar-Or, O., & Malina, R.M. (1995). Exercise during childhood and adolescence. In L.W.Y. Cheung & J.B.

Richmond (Eds.), Child health, nutrition, and physical activity (pp. 79–123). Champaign, IL: Human Kinetics

Publishers.

Blair, S.N., Clark, D.B., & Cureton, K.J. (1989). Exercise and fitness in childhood: Implications for a lifetime of

health. In C.V. Gisolfi & D.L. Lamb (Eds.), Perspectives in exercise science and sports medicine, Vol 2 .

Youth, exercise and sport (pp. 401–430). Indianapolis: Benchmark Press.

Blimkie, C., Rice, S., Webber, C., Martin, J., Levy, D., & Gordon, C. (1993). Effects of resistance training on

bone mass and density in females. Medicine and Science in Sports & Exercise, 25, S48.
Bouchard, C., Shephard, R.J., & Stephens, T. (Eds.) (1994). Physical activity, fitness and health. International

proceedings and consensus statement. Champaign, IL: Human Kinetics Publishers.

Calfas, K.J., & Taylor, W.C. (1994). Effects of physical activity on psychological variables in adolescents.

Pediatric Exercise Science, 6, 406–423.

Corbin, C.B., Pangrazi, R.P., & Welk, G.J. (1994). Toward an understanding of appropriate physical activity

levels for youth. President’s Council on Physical Fitness and Sports Physical Activity and Fitness Research

Digest, 1(8), 1–8.

Hagberg, J.M., Ehsani, A.A., Goldring, D., Hernandez, A., Sinacore, D.R., & Holloszy, J.O. (1984). Effect of

weight training on blood pressure and hemodynamics in hypertensive adolescents. Journal of Pediatrics, 104,

147–151.

Malina, R.M. (1990). Growth, exercise, fitness and later outcomes. In C. Bouchard, R.J. Shephard, T. Stephens,

J.R. Sutton, & B.D. McPherson (Eds.), Exercise, fitness and health: A consensus of current knowledge (pp.

637–653). Champaign, IL: Human Kinetics Publishers.

Margulies, J.Y., Simkin, A., Leichter, I., Bivas, A., Steinberg, R., Giladi, M., Stein, M., Kashtan, H., &

Milgrom, C. (1986). Effect of intense physical activity on the bone-mineral content in the lower limbs of

young adults. Journal of Bone and Joint Surgery, 68, 1090–1093.

Roberts, S.B. (1993). Energy expenditure and the development of early obesity. Annals of the New York Academy

of Medicine, 699, 18–25.

Rubinstein, A., Burstein, R., Lubin, F., Chetrit, A., Dann, E.J., Levtov, O., Geter, R., Deuster,

P.A., & Dolev, E. (1995). Lipoprotein profile changes during intense training of Israeli

military recruits. Medicine and Science in Sports and Exercise, 27, 480–484.

Sallis, J.F., & Patrick, K. (1994). Physical activity guidelines for adolescents: Consensus statement. Pediatric

Exercise Science, 6, 302–314.

Wilmore, J.H. (1983). The 1983 C.H. McCloy Research Lecture. Appetite and body composition consequent to

physical activity. Research Quarterly of Exercise and Sport, 54, 415–425.