A progressive decline in levels of physical activity has been documented in children, with less than one third able to meet the recommended physical activity guidelines when they are 15 years old, according to an article released on July 15, 2008 in JAMA.
Physical activity has been associated with obesity and associated illnesses as well as chronic diseases among young people. Expert opinion corroborates studies in suggesting that children maintain a minimum of 60 minutes of moderate-to-vigorous physical activity (MVPA) each day, but it has not been thoroughly examined how many youth actually meet this standard.
To further explore this issue, Philip R. Nader, M.D., of the University of California San Diego, La Jolla, and colleagues examined physical activity data in a group of 1,032 children in 10 geographic locations between 2000 and 2006, beginning at the age of 9 and continuing through age 15. The children wore accelerometers to monitor their movements minute by minute for one week each year at ages 9, 11, 12, 15. The study was composed of boys and girls in approximately equal numbers. The study group was approximately three-quarters white, and one-quarter lived in low-income families.
It was found that the average minutes of MVPA and the range of minutes spent engaging in MVPA decreased steadily as the children moved into adolescence. Beginning at 9 years, approximately 3 hours were spent in MVPA per day on both weekends and weekdays. Almost all children at this time met the recommended guidelines. However, by the age of 15, the adolescents were spending 49 minutes each weekday and 35 minutes each weekend day in this level of activity. Both the weekday and weekend MVPA thus showed significant decreases between these years, as they dropped 38 and 41 minutes per year respectively.
By the researchers’ estimation, girls fell below the recommended 60 minutes of MVPA per day during the week at 13.1 years, in comparison with boys who made this transition at 14.7 years. For weekend activity, girls crossed at 12.6 years in comparison to boys at 13.4 years.
According to the authors, the reasons for these decreases are not clear. “More research is … needed to understand the reasons for such substantial decreases in youth activity. Further study and more precise descriptions of the immediate activity environment, such as whether youth are located in urban, suburban, or rural areas; availability of safe places to be active; and quality of school-based physical education may explain some of the individual and regional differences noted in this and other studies.” They say.
They continue, warning against the troubling trend this could indicate for the future. They conclude: “This decrease augurs poorly for levels of physical activity in U.S. adults and potentially for health over the course of a lifetime. Consequently, there is a need for program and policy action as early as possible at the family, community, school, health care, and governmental levels to address the problem of decreasing physical activity with increasing age.”
Moderate-to-Vigorous Physical Activity From Ages 9 to 15 Years
Philip R. Nader; Robert H. Bradley; Renate M. Houts; Susan L. McRitchie; Marion O’Brien
JAMA. 2008;300(3):295-305.
Written by Anna Sophia McKenney