Physical Activity and Time on Task: The Moderating Effect of BMI

Abstract

Physical activity has been found to increase on-task behavior in children (Mahar et al., 2006). BMI has been associated with many health outcomes. A paucity of research exists examining the effects of physical activity on on-task behavior in relation to BMI. PURPOSE: To examine the effects of physical activity and BMI on on-task behavior in a sample of elementary aged children (N=137). METHOD: On-task behavior was assessed through observations before and after a period of academically oriented physical activity or inactivity and calculated as a percentage of time spent on-task (IRR=94%). Heights and weights were collected and BMI calculated for each student. Activity level was assessed through pedometry and calculated as average steps per day. RESULTS: A three-way (pre- vs. post-observation x lesson type [active vs. control] x BMI category [on-weight, at-risk of overweight, overweight]) repeated measures analysis of variance compared time on-task between observation periods and revealed a significant three-way interaction [F(3, 94)=3.64, p<.05]. Pre-post change scores and separate repeated measures ANOVAs revealed significant differences between intervention and control days for each of the BMI categories: on-weight [F(1,61)=8.38, p<.01], at-risk [F(1,18)=8.00, p<.05], and overweight [F(1,15)=21.30, p<.001]. The magnitude of these effects differed by BMI category, specifically on-weight (ES=.49), at-risk (ES=1.14), and overweight (ES=1.69). This occurred despite significantly less steps at each increasing level of BMI [F(2,92)=3.09, p=.05]. CONCLUSION: Although children in higher BMI categories take fewer steps, they derive a greater benefit from physical activity with regard to time on-task. Specifically, physical activity provides a buffer to prevent the steep reduction in time on-task experienced following a period of inactivity.