A 9-year-old moves, jumps, skates, bikes, runs, and walks about three hours a day.
Fast forward to the age of 15, when a child slows down their energy output to about 49 minutes per weekday and 30 minutes on a weekend day.
Those numbers come from the largest study of childhood exercise published Wednesday in the Journal of the American Medical Association (JAMA).
This was a fairly large study with about 1,000 participants, school age children from around the country followed for six years. They were tracked for their physical activity at various ages, races and socio-economic backgrounds.
The magic age of puberty, around age 13, seems to be the benchmark where exercise drops off as other activities begin to ramp up.
"I was surprised by the degree of the drop – it’s a dramatic shift,” said Dr. Philip R. Nader, emeritus professor of pediatrics at the University of California-San Diego tells the New York Times. "Younger children appear to be naturally active, but as kids get older, they find fewer opportunities to be active.”
The decline amounts to about 40 minutes per day each year up until the age of 15.
The same kids were measured at ages 9, 11, 12 and 15 when they wore accelerometers that collected data on movement for a full week, instead of relying on parents to recount a child’s activity.
Overall boys did more activity than girls, about 18 more minutes a day, but the rate of decline was the same for boys and girls and race or income seemed to have no bearing.
It’s recommended that children get one-hour of moderate activity a day. By the age of 15, only about a third met the guidelines during the week. On weekends that dropped to just 17 percent.
Many school systems have curtailed physical activity programs, assuming that athletes will join teams and after school programs.
Parents need to be aware of this dramatic drop, researchers say, and encourage children to go out and play.
"I think we thought there would be a drop but nowhere near this magnitude,” says James A. Griffin, deputy chief of the NIH’s Child Development & Behavior Branch at the Center for Research for Mothers and Children.
Children raised in a digital age are increasingly socialized with electronics such as televisions, cell phones, videogames and computers and are paying the price with childhood obesity now and its accompanying health problems in the future, say researchers. #