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NEW YORK (Reuters Health) - Australian researchers have found that young teens who spend more than two hours in front of the TV or computer each day showed less endurance during a standard running test than their peers.
The findings do not prove that TV and computer time is leading to out- of-shape kids, the researchers note in the American Journal of Preventive Medicine. However, the study does lend support to advice from the American Academy of Pediatrics (AAP) that parents limit their kids' screen time to a maximum of two hours per day.
That advice has been based on "prudence," rather than direct measures of kids' fitness levels, Dr. Louise L. Hardy, the lead researcher on the new study, told Reuters Health.
These latest findings suggest the recommendation is "pretty much spot-on," said Hardy, a researcher at the New South Wales Center for Overweight and Obesity at the University of Sydney.
The study, in the American Journal of Preventive Medicine, included 2,750 11- to 15-year-old students at schools in New South Wales who were surveyed about various sedentary activities -- including how much time they spent reading, doing homework, using a computer for "fun" and watching TV.
In general, students who sat in front of the TV or computer for more than two hours a day performed more poorly on fitness testing. There was no clear effect, however, on the oldest boys.
That latter finding, Hardy explained, may reflect the boys' stage of maturation. At the age of 15, they may have had enough muscle mass that extra screen time did not affect their fitness levels as much as it did girls and younger boys.
However, Hardy said, the same message still applies to older boys: limit TV and computer time in favor of physical activity.
She suggested that parents make clear rules about their kids' small-screen time, remove TVs from their children's bedrooms or even designate "no-screen" days for the whole family.
SOURCE: American Journal of Preventive Medicine, February 2009.