Physically active academic lessons and time on task: the moderating effect of body mass index

Med Sci Sports Exerc. 2009 Oct;41(10):1921-6. doi: 10.1249/MSS.0b013e3181a61495.


Physically active classroom lessons have been found to increase on-task behavior in children. Given that physical activity has been associated with an increased time on task (TOT) and that overweight children take fewer steps than normal weight children do, it was expected that benefits of the physical activity would differentially impact those children of higher weight status.

Purpose: To examine the effects of a physically active classroom lesson and body mass index (BMI) category on TOT in a sample of elementary-aged children (N = 97).

Methods: Behavior was assessed through direct observations before and after a physically active classroom lesson and before and after a traditional inactive classroom lesson. TOT was calculated through momentary time sampling for each student by dividing the number of on-task observations by the total number of observations per student (interrater reliability = 94%).

Results: TOT decreased significantly from before to after the lesson for all BMI categories in the inactive control condition, with no change for the active condition. Post hoc analyses found a significant linear effect for the reduction in TOT with each level of BMI in the inactive condition, with the greatest magnitude of effect for the overweight group.

Conclusions: Physically active classroom lessons provide a buffer to prevent the steep reduction in TOT experienced after a period of inactivity in all children, especially those who are overweight.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Analysis of Variance
  • Body Mass Index*
  • Child
  • Female
  • Humans
  • Male
  • Motor Activity*
  • Overweight
  • Random Allocation
  • Schools
  • Single-Blind Method
  • Task Performance and Analysis*
  • Teaching / methods*
  • Time Factors