A recent study done on children in the U.S. found a sharp decline in the physical activity in the U.S. teens. The study findings published in the Journal of the American Medical Association showed that on an average activity levels that ranged from moderate to vigorous reduced from three hours a day to less than an hour as the child went from age 9 to 15 years. The change was more in the girls who by the age of 13.1 exercised less than the recommended time while in the case of boys it was by age 14.7.

As per the Department of Health and Human Service's Dietary Guidelines for Americans children and adolescents should ideally get a minimum of 60 minutes of physical activity, seven days a week."People don't recognize this as the crisis that it is," said lead author Dr. Philip Nader, a pediatrician and professor emeritus at the University of California at San Diego. The reason for the decline in activity level was not elaborated on but Dr Nader attributes it to "probably a combination of things."

Inactivity increases the risks for a number of health problems such as heart disease, high blood pressure, obesity and diabetes. One of the possible reasons for lessened outdoor physical activity feels Dr Nader is due to safety issues. "Teens today may have competing things, such as computers and other technology that keeps them inactive,” said Dr Nader.

"Here's the first time that we have a large group of kids, and it's the same kids from age 9 to 15," Nader said. "So, we are really seeing a culture and a societal decline in activity with age."

The decline in physical activity often means the children growing into unhealthy adults, and to counter this the study feels governmental action and programs which should ideally begin at the school level are needed to encourage physical activity in this age group.