Sedentary Image of Children and Adolescents Questioned

BUFFALO, N.Y. -- A review and analysis of 26 studies of physical activity levels of children, completed by University at Buffalo researchers, has found that children accumulate more physical activity than previously thought.

On average, adolescents get about 30 minutes of aerobic exercise and accumulate about 50 minutes of physical activity daily, results showed. Whether this is enough to provide substantial health benefits remains the central question.

Study results appear in the September electronic pages of Pediatrics.

These activity levels meet or exceed revised guidelines for children's activity set by the American College of Sports Medicine (ACSM) and the U.S. Centers for Disease Control (CDC). Original guidelines set by ACSM and CDC called for children and adults to accumulate 30 minutes or more of moderate to vigorous intensity physical activity most days of the week.

"Prior to this study, most people assumed that children were not getting enough exercise based on the amount of time they spend in continuous bouts of vigorous exercise, using the old ACSM definitions of 30 minutes or more of high-intensity exercise three days per week," said Leonard H. Epstein, Ph.D., UB professor of pediatrics and a specialist in treatment and prevention of childhood obesity who headed the study.

"If you use that definition, children in the studies reviewed still would not meet the definition of being active. However, the new guidelines focus on the accumulation of physical activity throughout the day. This is the first review to evaluate how much activity children get if you allow them to accumulate activity, rather than get it in sustained bouts."

Epstein said no one really knows the health benefits of accumulating activity throughout the day, or if 30 minutes accumulated is equivalent to 30 minutes in one bout.

"Physical activities at these low-to-moderate intensities may not improve aerobic fitness," he noted, "but they are far from the image of a television-watching couch potato and very sedentary child."

The studies in the review originated in differing nations and cultures: U.S (9), United Kingdom (4), Italy (2), Ireland (2), Estonia (2), plus one each in Belgium, Bolivia, France, Japan, Netherlands, Saudi Arabia and Singapore. The amount and intensity of physical activity was determined using heart-rate data registered and collected on heart monitors worn by the participants.

"We saw the same patterns all around the world," Epstein said. "Kids are more active than we thought."

Not that "more active" is necessarily active enough. Childhood obesity is a significant and growing health problem in the U.S. and, to a lesser extent, in the United Kingdom, France, Australia and China, Epstein said. Obesity and physical activity are directly linked in both children and adults.

"Few exercise scientists would suggest that children get enough activity, but you are not going to get more than two hours a day of physical activity from kids," Epstein said. "This is the quandary. If you decrease intensity, you need to spend more time at it to get a healthful benefit. For some children, we may need to go back to the idea of high-intensity, vigorous physical activity."

Rather than recommending a set amount of physical activity for all children, a better approach might be to develop guidelines based on the desired end result, Epstein suggested.

"The recommendation may be very different based on child age, baseline levels of physical activity or the reason for needing more activity. For example, the amount of physical activity needed to prevent obesity may be very different from the amount needed to treat obesity, which may be different from the amount needed to maintain weight loss.

"We need additional well-controlled, prospective randomized trials to provide solid evidence of the proper amount of activity required to reach specific goals."

Additional researchers on the study were Rocco Paluch; Lisa Kalakanis, Ph.D., and James Roemmich, Ph.D., from the UB Department of Pediatrics; Frank Cerny, Ph.D., professor and chair of the UB Department of Physical Therapy, Exercise and Nutrition Science, and Gary Goldfield, Ph.D., of the Children's Hospital of Eastern Ontario Research Institute.

The research was supported by grants from the National Institute of Child Health and Human Development.