Cardiorespiratory Fitness Levels Among US Youth 12 to 19 Years of Age

OBJECTIVES: To assess cardiorespiratory fitness levels in youth aged 12 to 19 years and to examine associations between fitness and age, sex, race/ethnicity, and self-reported physical activity in this age group. DESIGN: Cross-sectional study. SETTING: The National Health and Nutrition Examination Survey's mobile examination center, throughout the United States from 1999-2002. PARTICIPANTS: A representative sample of 4732 youth aged 12 to 19 years was examined; 3287 completed the treadmill test and were included in the analysis. The National Center for Health Statistics conducted the survey. Main Exposures Age, sex, race/ethnicity, weight status, self-reported physical activity, and television viewing. Main Outcome Measure Estimated maximal oxygen uptake (VO2max) determined by a submaximal treadmill exercise test. RESULTS: Estimated VO2max (mL.kg(-1) . min(-1)) was higher in males (mean +/- SE, 46.4 +/- 0.4) than in females (mean +/- SE, 38.7 +/- 0.3) but did not differ across race/ethnicity groups. Among males, older participants had higher VO2max values, while in females, younger participants had higher values. For both males and females, those in the normal weight group had higher fitness levels than those in the at risk for overweight and overweight groups. Approximately one third of both males and females failed to meet recommended standards for cardiorespiratory fitness. CONCLUSIONS: In US youth, cardiorespiratory fitness is lower in males and females who are overweight than in those of normal weight, but fitness is not related to race/ethnicity. Youth who have low levels of physical activity and high levels of sedentary behavior are also more likely to have lower cardiorespiratory fitness.