Concern about the increase in obesity in children and adolescents has spurred research into their activity levels. Data garnered from girls' reports of their activity, for example, indicates that as girls mature, their participation in leisure-time and total exercise appears to decrease. Because these studies are based on participants' reports of their activities, it is hard to know how accurate they are.
A new study, published in the July 16 issue of the Journal of the American Medical Association (JAMA 2008; 300:295-305) confirms and extends the earlier reports with a more quantitatively...