The more physically fit a young person, the less likely he or she is to have high blood pressure, high cholesterol levels or a number of other risk factors for chronic diseases, according to background information in the article. 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. If so, it is likely that average physical fitness has also declined among youth in the same time period, since the last national survey.
Russell R. Pate, Ph.D., Arnold School of Public Health, University of South Carolina, Columbia, and colleagues assessed the physical fitness of 3,287 individuals age 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 home and then visited a mobile examination center, where they performed 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), the amount of oxygen consumed by the body during maximum exertion; the higher the VO2max, the better the individual's fitness level.
Estimated VO2max, and therefore physical fitness levels, were higher on average in males than in females and in youth of normal weight compared with overweight youth but were no different 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.
Based on standards developed by experts and used by schools and school districts nationally, about 65 percent of youth met criteria for being physically fit. "This represents a significant public health problem because low physical fitness during adolescence tends to track into adulthood, and low-fit adults are at substantially increased risk for chronic disease morbidity [illness] and mortality [death]," the authors write. Because active youth tend to be more physically fit, experts recommend that physicians counsel children and parents about guidelines for physical activity, they conclude.
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