Example of moderate evidence: Time allotted for structured and unstructured time
Preschool-aged children are vigorously active in very short bursts (15-30 sec)*
Cannot sustain prolonged (>5 min) periods of vigorous activity
In adults, short bouts of vigorous activity (10 min) have health benefits (2008 PA Guidelines for Americans)
*Oliver, M. et al. Sports Med 37:1045-70.2007.