Based on the National Center for Education Statistics Fast Response Survey 2005, the average number of minutes per week of physical activity ranged from 85.4 minutes for first grade to 98.0 minutes to sixth grade. This includes schools with physical education classes, which vary by number of days per week and class length. From the National Institute of Child Health & Human Development study across 10 U.S. sites, as well as a Nader et al. study (2003), found that the average Metabolic Equivalent of Task (MET) expenditure at PE was approximately 3.4 for elementary school-aged students (also used for preschool). This METs expenditure is assumed to be the same for ages 2-5, as no data is currently available. Estimates of the average METs expended during PE for other grade levels are from various studies: 3.6 for middle school (McKenzie et al., 2004) and 3.7 for high school (Smith et al., in press)
According to the Centers for Disease Control and Prevention, in 2011, only 29 percent of high school students had participated in at least 60 minutes per day of physical activity—the U.S. Health & Human Services-recommended level of physical activity for youth people ages 6 to 17 years. Studies have also found a sharp decrease in the amount of time spent on physical activity once students enter high school. Johnston et al. (2007) found that the participation rate in physical education (PE) participation between 8th grade and 12th grade fell from 91 percent to 34 percent participation. The mean total number of minutes of PE per week were 172.3 min, 163.9 min, and 88.6 min for grades 8, 10, and 12, respectively.
A separate study on the impact of state laws and district policies on PE and recess in public elementary schools found that state policies that encourage daily recess had a significant effect on the odds of a school having daily recess. District policies, however, were not found to have a significant effect on the odds of having recess. Predominantly white schools and those with a lower percentage of students receiving free or reduced lunch were also found to have a greater odds of having recess. Finally, longer school days were associated with a greater odds of meeting national PE and recess standards.
On average, a school year is 180 days. The intervention assumes that the change is over the course of a school year (so if 10 minutes are added per day, it is added for 180 days). The total caloric impact is then averaged over 365 days to account for no change in activity on holidays, weekends, and summer vacation.
* The Average Caloric Impact (ACI) for this intervention is empirical, based on published estimates of METs expended, taken from trial data from McKenzie et al. (2004), Nader et al. (2003), and Smith (In Press), as listed below.
McKenzie TL, Sallis JF, Prochaska JJ, Conway TL, Marshall SJ, Rosengard P. Evaluation of a two-year middle-school physical education intervention: M-SPAN. Medicine and science in sports and exercise. Aug 2004;36(8):1382-1388.
Nader PR, The National Institute of Child Health and Human Development Study of Early Child Care and Youth Development Network. Frequency and Intensity of Activity of Third-Grade Children in Physical Activity. Archives of Pediatric and Adolescent Medicine 2003 Feb; 157:185-190.
Smith NJ, Lounsbery MA, McKenzie TL. Physical Activity in High School Physical Education: Impact of Lesson Context and Class Gender Composition. Journal of Physical Activity & Health. In Press.
Centers for Disease Control and Prevention. Adolescent and School Health: Physical Activity Facts. June 2, 2012.
Johnston LD, Delva J, O'Malley PM. Sports Participation and Physical Eduction in American Secondary Schools: Current Levels and Racial/Ethnic and Socioeconomic Disparities. American Journal of Preventive Medicine 2007; 33(4S):S195-S208.
Parsad B, Lewis L. Calories In, Calories Out: Food and Exercise in Public Elementary Schools, 2005 (NCES 2006-057). U.S. Department of Education. Washington, DC: National Center for Education Statistics, 2006.
Slater SJ, Nicholson L, Chriqui J, Turner L, Chaloupka F. The Impact of State Laws and District Policies on Physical Education and Recess Practices in a Nationally Representative Sample of US Public Elementary Schools. Archives of Pediatrics & Adolescent Medicine 2012 Apr; 166(4):311-316.