Posted 10/02/2006

One-third of U.S. youth do not meet standards for physical fitness, USC researcher leads study

Approximately one-third of boys and girls age 12 to 19 in the United States do not meet standards for physical fitness, according to a report in the October issue of Archives of Pediatrics & Adolescent Medicine.

Dr. Russell R. Pate, a researcher at the University of South Carolina's Arnold School of Public Health, led the study that also found that physically fit young people are less likely to have high blood pressure, high cholesterol levels or other risk factors for chronic diseases.

"Between the 1950s and the 1980s, regular surveys of youth physical fitness were conducted in the United States.  An increasing proportion of children have become obese since the 1980s, which may be explained by a decrease in physical activity," Pate said.  "If so, it is likely that average physical fitness also has declined among youth in the same time period, since the last national survey."

Pate and colleagues from the Centers for Disease Control and Prevention and The Cooper Institute assessed the physical fitness of 3,287 youth ages 12 to 19 who participated in the government-conducted National Health and Nutrition Examination Survey between 1999 and 2002.  The participants were interviewed in their homes and then visited a mobile examination center, where they had a treadmill exercise test consisting of a two-minute warm-up, two three-minute periods of exercise and a two-minute cool-down.

During the test, researchers measured blood pressure, heart rate and rate of perceived exertion, determined by asking participants to rate how hard they feel their bodies are working.  Heart rate readings during the three-minute periods of exercise were used to estimate maximal oxygen uptake (VO2max), which is the amount of oxygen consumed by the body during maximum exertion.  Higher uptake levels mean an individual is more fit.

Estimated VO2max, and therefore physical fitness levels, were higher on average in males than in females and in youth of normal weight than those who were overweight. However, there were no differences across racial or ethnic groups. 

Older males were more physically fit than younger males, while the opposite was true for females.  Participants who reported more sedentary behavior, such as watching television or playing video games, and those who spent less time being physically active were more likely not to be physically fit.

"This represents a significant public health problem because low physical fitness during adolescence tends to track into adulthood, and adults who are less physically active are at a substantially increased risk for chronic disease morbidity (illness) and mortality (death)," the authors wrote in the study.

Because active youth tend to be more physically fit, experts recommend that physicians counsel children and parents about guidelines for physical activity, said Pate, who was the author of a recent report by the American Heart Association that called on schools to offer more physical education programs.

"This study is another indicator of the importance of physical activity in the lives of young people," Pate said.  "Clearly, we must do more as a nation to support fitness among all youth."

The study was funded by a grant from the National Heart, Lung and Blood Institute and the National Institute of Child Health and Human Development of the National Institutes of Health. The Archives of Pediatric and Adolescent Medicine is a publication of the Journal of the American Medical Association.