Study: As Children Grow, Activity Slows

New York Times – July 16, 2008
By Tara Parker-Pope

Young children spend an extraordinary amount of time moving about: an average of three hours a day at age 9, new research shows.

But in just a few short years, all that childhood energy disappears. By the age of 15, daily physical activity is down to just 49 minutes on weekdays and about a half-hour on weekends, according to the research, being published Wednesday in The Journal of the American Medical Association.

Experts have long believed that activity wanes as children enter their teenage years. This study affirming that belief, one of the largest and longest ever undertaken on the subject, followed about 1,000 children from around the country and, unlike many previous studies, used monitoring devices to track the activity carefully rather than relying on reports from parents.

The findings, which measured everything from moderate walking to vigorous athletic pursuits, show clearly that even the most energetic young children experience a precipitous drop in physical activity as they reach puberty.

“I was surprised by the degree of the drop; it’s a dramatic shift,” said the lead author, Dr. Philip R. Nader, emeritus professor of pediatrics at the University of California, San Diego. “Younger children appear to be naturally active, but as kids get older, they find fewer opportunities to be active.”

The research was part of the continuing Study of Early Child Care and Youth Development, a look at the health of American children that was begun in 1991 and is financed by the National Institutes of Health.

The authors had the children wear accelerometers, devices that measure movement, for a week at each of four ages: 9, 11, 12 and 15.

Over all, boys were more active than girls, moving an average of 18 more minutes a day.

Age 13 appeared to be a particularly vulnerable time. Though activity was not measured at that age, mathematical modeling showed it was at that point that daily weekend activity, for boys and girls alike, dropped below 60 minutes.

The percentage of children who met the government’s recommendation of one hour of moderate daily activity shifted markedly over time. At 9 and 11, almost every child in the study was moving at least an hour a day. But by 15, only 31 percent met the guideline during the week, and just 17 percent on the weekend.

The study did not measure reasons for the decline, but researchers noted that schools often curtail physical activity as children get older. Not only does recess stop, but many schools drop physical education as well. In addition, sports become more exclusive as children grow, allowing only the best athletes to compete.

“When you are younger, it’s much easier to go out and do things spontaneously,” said James A. Griffin, deputy chief of the Child Development and Behavior Branch at the national institutes’ Center for Research for Mothers and Children. “But when you get older, kids tend to play a video game or watch television with their friends. Parents need to be aware to help them balance that out a little better.”

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