The activity level of a large group of American children dropped sharply between age 9 and age 15, when most failed to reach the daily recommended activity level, according to the latest findings from a long-term study by the National Institutes of Health.
The analysis is one of the largest, most comprehensive of its kind to date.
The researchers evaluated the children to determine whether they achieved the minimum 60 minutes per day of moderate to vigorous physical activity (MVPA) recommended for children.
At age 9, the children averaged roughly three hours of MVPA on weekdays and weekends. By age 15, however, they averaged only 40 minutes per weekday, and 35 minutes per weekend.
"Lack of physical activity in childhood raises the risk for obesity and its attendant health problems later in life," said Duane Alexander, M.D., Director of NIH's Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD). "Helping American children maintain appropriate activity levels is a major public health goal requiring immediate action."
The analysis was conducted on data collected for the NICHD Study of Early Child Care and Youth Development, a long term study of more than 1,000 children from ethnically and economically diverse backgrounds. The study collected information on various other aspects of children's health and development. It was geared toward gathering information on children's experience in various child care arrangements but did not constitute a nationally representative sample of the United States as a whole.
The analysis, appearing in the July 16 Journal of the American Medical Association, was undertaken by Philip Nader, M.D., Emeritus Professor of Pediatrics at the University of California San Diego, and other coauthors from the study.
Beginning at age 9, the researchers recorded the activity levels of more than 800 children for four to seven days. The children's activity was recorded with an accelerometer, a device that records movement, which the children wore on a belt. The researchers conducted follow up tracking at ages 11, 12, and 15.
The 2005 Dietary Guidelines for Americans recommends that children and adolescents engage in at least 60 minutes of physical activity on most, preferably all, days of the week. (See http://www.health.gov/dietaryguidelines/dga2005/document/default.htm.)
As examples of moderate physical activity, the Centers for Disease Control and Prevention list walking briskly, dancing, swimming, or bicycling on level terrain. Vigorous physical activity includes such activities as jogging, high-impact aerobic dancing, swimming continuous laps, or bicycling uphill. Additional information is available at http://www.cdc.gov/nccdphp/dnpa/physical/everyone/recommendations/children.htm