How School Time Physical Activity Is the Big One for Daily Activity Among Schoolchildren: A Semi-Experimental Approach

Background: This study was designed to model the relationship between an ActiGraph-based in-school physical activity (PA) and the daily one among children and to quantify how school can contribute to the daily PA recommendations. Method: Fifty boys and 43 girls (aged 8 to 11 years) wore ActiGraph for 2 schooldays of no structured PA. The daily moderate-to-vigorous PA (MVPA(d)) was regressed on the school time MVPA (MVPA(s)). Then, a ROC analysis was computed to define the required MVPA(s). Results: Children spent 57% of their awaking time at school. School time PA opportunities (ie, recesses: similar to 18% of a child's awaking time) accounted for >70% of the MVPA(d) among children. Then, MVPA(d) (Y) could be predicted from MVPA, (X) using the equation: Y = 2.06 X-0.88; R-2 = .889, P < .0001. Although, this model was sex-specifically determined, cross-validations showed valid estimates of MVPA(d). Finally, with a sensitivity of 100% and a specificity of 90%, MVPA(s), a 34 min.d(-1) was required to prompt the daily recommendation. Conclusions: The current study shows the contribution of MVPA at school to recommended activity levels and suggests the value of activity performed during recesses. It also calls for encouraging both home- and community-based interventions, predominantly directed toward girls.