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Teenagers Drop The Ball On Exercise

Posted on: Wednesday, 16 July 2008, 00:30 CDT

American teenagers trade the regular exercise of their younger years for a more sedentary existence, according to a study highlighting a cause in the rise of youth obesity.

Ninety percent of 9-year-olds get two hours of exercise most days, fewer than 3 percent of 15-year-olds do.

The research, published on Tuesday in the Journal of the American Medical Association, noted an alarming decline in physical activity in 1,032 children. They looked at various spots around the United States and studied youths aged 9 to 15.

"We're dealing with an obesity epidemic," said pediatrician Dr. Philip Nader of the University of California at San Diego, who led the study. "I don't know what it will take for society to wake up and say, 'What's happening here and what can I do?'"

The study suggests that fewer than a third of 15 year old teens get even the minimum recommended hour long moderate exercise like cycling, brisk walking, swimming or jogging.

The authors of the study said the sharp drop in activity highlights concerns that their lack of exercise could continue throughout their lives. Inactivity contributes to an array of health problems, including heart disease, obesity, high blood pressure and diabetes.

"People don't recognize this as the crisis that it is," said Nader.

If an individual does not start good patterns in physical fitness early on, it is much harder to do so later in life, according to James Griffin of the U.S. National Institute of Child Health and Human Development, part of the National Institutes of Health, which backed the study.

"The concern is not only obesity, but also the lost opportunity to build muscle and bone. Those are both happening right around puberty. If you don't build it then, it's that much harder to do it later," he said during an interview.

The study hits the medical community just a week after an influential pediatricians group recommended that more children have their cholesterol checked and that some as young as 8 should be given cholesterol-lowering drugs. They were concerned over future levels of heart disease and other problems linked to an increase of childhood obesity.

The latest study used a special gadget called an accelerometer to record the youth's activity. It monitored physical activity, for one week at a time when they were ages 9, 11, 12 and 15. Average levels of moderate-to-vigorous activity fell from three hours a day at age 9 to less than an hour at age 15.

That method was slightly flawed because the accelerometer was not worn during swimming and contact sports. But researchers said it's unlikely that those activities happened enough among the children studied to skew the results.

Nader said he was "surprised by how dramatic the decline was," and blamed the numbers partly on schools dropping recess and gym classes and kids' increasing use of video games and computers.

The National Institute of Child Health and Human Development paid for the research, which they called one of the most comprehensive studies of its kind.

The science officer for the study, James Griffin, said that as children grow older, "You would expect somewhat of a decline (in activity), but nothing of this magnitude."

He said the research mirrored the rise in popularity of video games, DVDs and Internet use - "all of the types of things that take children from outside and put them on a couch or in front of a computer."

Griffin said the findings should raise a red flag for parents, so they teach their children to balance sedentary activities with more active pursuits, like walking the dog or playing basketball.

The children involved in the study were recruited from 10 hospitals around the country. Family income, race and ethnic background closely mirrored the U.S. population.

Well over half the children got at least the government-recommended amount of activity every day through age 12. However, just three years later, less than one-third were that active on weekdays, and only about 17 percent were on weekends.

Boys were more active than girls at every age. But by age 15, even boys' average activity levels fell short of recommendations, particularly on weekends.

Girls dipped below the recommended level of an hour a day at a younger age than boys. Girls were on average at age 13 for weekdays and age 12-1/2 for weekends, compared to boys who on average slipped below the recommended amount of exercise at age 14-1/2 for weekdays and age 13-1/2 on weekends.

Director of Washington University School of Medicine's human nutrition center in St. Louis Dr. Samuel Klein said the research provides a more in-depth snapshot compared to previous studies.

The rapid drop-off in exercise by age 15 shows that the preceding years are "really an area we should target," said Klein, who was not involved in the study.

Suburban Cleveland teenager Mary Lee, 13, said the results reflect her reality.

She says she spends more time on the computer now than she did a few years ago, particularly with online social networking sites. Lee also didn't have physical education class every day last year, and will only have it for half the upcoming school year in eighth grade.

Lee recently took classes that promote exercise and healthy choices at the Rainbow Babies and Children's Hospital in Cleveland.

She said she stays fit with help of track and volleyball, and has not gained weight due to tips from her class at the hospital.

"It really helps and it makes you feel better about yourself," Lee said.

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On the Net:

• Journal of the American Medical Association
• University of California at San Diego

Source: redOrbit Staff & Wire Reports

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