February 28 — 29, 2008 Advisory Committee Meeting
Subcommittee Report: Youth
Russell Pate, Ph.D., presented the subcommittee report on youth.
Dr. Pate noted the challenge the youth subcommittee faced was different then
what many of the other subcommittees faced as the group researched a wide range
of health outcomes relative to physical activity and youth. Overall, the
following questions were asked:
Among children or youth — is physical activity
significantly related to this outcome?
If the above is yes, is there an established dose-response
pattern? Is it influenced by age and/or developmental status? Is it influenced
by gender? Is it influenced by race/ethnicity and/or SES?
The following health outcomes were researched: Physical
fitness, body mass and composition, cardiovascular and metabolic health, bone
health and mental health.
Cardio-respiratory Fitness Conclusion
Physical activity is positively related to cardio-respiratory fitness (CRF) in
youth. Endurance training increases VO2 max by 5 to 15%. The optimal dose needed
to attain improvements cannot be stratified. A recent review concluded that an
intensity of 80% or more of maximal heart rate done 3 – 4 days per week with
duration of 30 – 60 minutes per session with a length of 1 – 3 months improved
CRF. Endurance training increases CRF among children and adolescents and men and
women. The research cannot come to any conclusions about race/ethnicity or SES.
Muscular Strength and Endurance Conclusion
Physical activity is positively related to muscular strength. Resistance
training 2 or 3 times per week significantly improved muscle strength in
children as well as in both males and females. As before, there is not enough
data surrounding race/ethnicity or SES.
Body Mass and Composition Conclusion
Non-obese youth who have relatively high levels of physical activity tend to
have less adiposity; however, programs that increase activity in normal weight
youth typically have little effect on adiposity. Controlled studies with obese
youth have resulted in reductions in overall adiposity with exposure to
moderate-to-vigorous activity 3 – 5 times per week for 30 – 60 minutes. There is
no consistent evidence for a dose-response pattern in the studies reviewed.
Additionally no data can support conclusions on age, race/ethnicity or SES.
Cardiovascular and Metabolic Health Conclusion
Physical Activity is positively related to cardiovascular and metabolic health
in youth. There appears to be a dose-response relationship; however, the precise
pattern cannot be determined. Very little is known about the effects of age,
maturity, gender, race/ethnicity and SES on the relationship of physical
activity to cardiovascular and metabolic health.
Bone Health Conclusion
Physical activity is positively related to bone health. Targeted weight loading
activities that simultaneously influence muscular strength, done on a daily
basis, are most effective. It is challenging to compare mode and dose due to
variability across studies. Additional studies on dose-response are needed. The
relationship between physical activity and bone health is influenced by age and
developmental status and the bone health of both boys and girls are improved by
physical activity. There is inadequate data on race/ethnicity and SES.
Mental Health Conclusion
Physical activity during childhood and adolescence exerts a beneficial effect on
symptoms of anxiety and depression. The varying methodologies and insufficient
numbers of intervention trials preclude inferences about dose-response patters.
The research is not adequate for conclusions about age, race/ethnicity and SES.
Overall Summary of Health Benefits of Physical Activity
The types and amounts of activity required to produce health benefits vary
across health outcomes. It is not possible to draw definitive conclusions
regarding the minimal or optimal doses of physical activity needed for provision
of health benefits in young people. Important health benefits can be expected to
accrue to most children and youth who participate daily in 60 or more minutes of
moderate to vigorous physical activity.