Models of school recess for combatting overweight in the United States

The aim of the study was to quantify and compare potential energy expenditure associated with school recess in the U.S. based on four scenarios: professional recommendations and state policies for the conduct of recess, previous studies that measured physical activity intensity during recess (i.e., reality), and no daily recess.

Estimated energy expenditure (kcal) was modeled using secondary data over six years of elementary school for boys and girls using a standard formula: Intensity × duration × frequency × mass .

Boys and girls would expend similar energy under the professional recommendation (boys, 69,146 kcal; girls, 63,993 kcal) and state policy (boys, 69,532 kcal; girls, 64,351 kcal) scenarios. These values are significantly greater than a no recess scenario (boys, 26,974 kcal; girls, 24,821 kcal). The greatest energy expenditure was found for the reality scenario, based on actual studies that measured physical activity intensity (boys, 82,208 kcal; girls, 75,628 kcal).

Professional recommendations and state policies for recess duration may be overly conservative and recommendations for percentage of MVPA may be overly liberal compared to the reality of energy expended during recess. Both potential and real estimates dwarf a scenario of withholding recess (i.e., no recess), which is discouraged in only six state policies. Mandated reporting with "groundtruthing" is needed to determine true recess frequency/duration and state policy compliance.