University Relations
GREENSBORO, NC - The average activity level of American children drops sharply between age 9 and age 15, when most failed to reach the minimum recommended daily activity level of one hour per day, according to a new study co-authored by Dr. Marion O’Brien, a professor in the UNCG Department of Human Development and Family Studies.
The study, one of the largest and most comprehensive of its kind, found that the children averaged about three hours of moderate to vigorous physical activity per day on weekdays and weekends. By age 15, however, they averaged only 49 minutes per weekday and 35 minutes per weekend day.
“We anticipated that children would become less active as they got older,” O’Brien said, “but we were surprised at the extent of the change and the low level of activity among the older children, especially after the age of 13.”
The results of the long-term study by the National Institutes of Health are published in today’s issue of the Journal of the American Medical Association. In addition to O’Brien, the study’s authors are Dr. Philip R. Nader of the University of California San Diego; Dr. Robert H. Bradley of the University of Arkansas, Little Rock; Dr. Renate M. Houts and Susan McRitchie of RTI International, Research Triangle Park.
The researchers tracked the activity levels of more than 800 children from ethnically and economically diverse backgrounds when the children were 9, 11, 12 and 15. Each child wore an accelerometer, a device that records movement, for four to seven days at those intervals. Data was collected at 10 locations: Little Rock, Ark.; Irvine, Calif.; Lawrence, Kan.; Boston, Mass.; Philadelphia, Penn; Charlottesville, VA.; Seattle, Wash.; Hickory and Morganton, N.C.; and Madison, Wis.
“Lack of physical activity in childhood raises the risk for obesity and its attendant health problems later in life,” said Dr. Duane Alexander, director of NIH’s Eunice Kennedy Shriver National Institute of Child Health and Human Development. “Helping American children maintain appropriate activity levels is a major public health goal requiring immediate action.”
More than 90 percent of the children were active for at least an hour per day at the ages of 9 and 11. But by age 15, only 31 percent met that recommended activity level on weekdays, and only 17 percent did so on weekends.
On average, boys were more active than girls. The researchers estimate that the average age at which girls drop below the recommended activity level on weekdays is 13.1 years, compared to 14.7 years for boys. For weekends, girls dropped below the recommended level at 12.6 years, and boys at 13.4 years.
“This decline augurs poorly for levels of physical activity in American adults and potentially for health over the life-course,” the study authors wrote.
“Consequently, there is 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.”
Schools should ensure children have recess breaks and daily active physical education, the authors say. Local governments can do more to provide safe biking and walking routes around schools. Families should make an effort to be active together.
“We need to become more aware of the amount of activity we engage in,” O’Brien said. “This is undoubtedly true for adults as well as children. Parents can go for walks and bike rides with children.”
The federal Centers for Disease Control and Prevention lists walking briskly, dancing, swimming or bicycling on level terrain as examples of moderate physical activity. Vigorous physical activity includes jogging, high-impact aerobic dancing, swimming continuous laps or bicycling uphill.
