The New York Times  reports that "[y]oung children spend an extraordinary amount of time moving about: an average of three hours a day at age nine," but "all that childhood energy disappears" as they get older, according to a study published in the July 16 issue of the Journal of the American Medical Association. Lead author Philip R. Nader, M.D., of the University of California San Diego, and colleagues, found that "[b]y the age of 15, daily physical activity is down to just 49 minutes on weekdays, and about a half-hour on weekend[s]."

        For the study, "researchers measured and analyzed the activity of more than 1,000 children from 10 different cities from 2000 to 2006," . Participants "wore monitors called accelerometers for four to seven days during the school year when they were nine, 11, 12, and 15. The accelerometer, which measures movement, tracked activities such as playing tag, biking, jumping rope, dancing, walking briskly and running, and playing non-contact sports."

        Study data showed that about "90 percent of nine-year-olds get a couple of hours of exercise most days, [while] fewer than three percent of 15-year-olds do," the AP (7/16, Tanner) reports. This "suggests that fewer than a third of teens" aged 15 "get even the minimum recommended by the government -- an hour of moderate-to-vigorous exercise, like cycling, brisk walking, swimming, or jogging." According to Dr. Nader, "People don't recognize this as the crisis that it is." In fact, "[i]nactivity is linked with greater risks for many health problems, including heart disease, obesity, high blood pressure, and diabetes."

        Currently, approximately "25 million U.S. children and teens are estimated to be overweight or obese, leaving them at a higher risk for diabetes and heart disease, including high blood pressure,". Dr. Nader hypothesized that "[c]hanges in the home, in which more children stay indoors after school as part of parent-working families, and at school, as physical education classes are reduced or eliminated, may account for some of the drop in exercise as kids become teenagers."

        Focusing on the study's details, Gordon pointed out that "[b]oys stayed more active than girls, averaging an extra 18 minutes on weekdays, and 13 more minutes on the weekends." In addition, "[g]irls dropped to less than one hour of activity daily on weekdays at about 13.1 years old, while boys didn't reach that mark until 14.7 years."

       Dr. Nader said "'Teens today may have competing things,'...such as computers and other technology, that keeps them inactive." He added, however, that "the study results should be a wake-up call to pediatricians, parents, and policy makers."