Population-based reference standards for cardiovascular fitness among US adults: NHANES 1999-2000 and 2001-2002

Purpose: To provide reference standards for cardiovascular fitness levels, using population-based estimates of estimated maximal oxygen uptake (VO2max) from a diverse sample of U.S. adults. Methods: Analysis of data from adults (20-49 yr) who completed a submaximal exercise test in the National Health and Nutrition Examination Survey 1999-2000 and 2001-2002. Estimated VO2max was categorized as low (< 20th percentile), moderate (between 20th and 59th percentiles), or high (>= 60th percentile) fitness using age- and sex-specific cut-points. Results: There were 1978 subjects, roughly 29% Mexican-American, 20% non-Hispanic black, and 51% non-Hispanic white. Using population-based sample weights, this was equivalent to 54,078.766 persons with mean (+/- SE) age, 34.4 +/- 0.3 yr; body mass index (BMI), 27.0 +/- 0.2 kg(.)m(-2); and estimated VO2max, 40.4 +/- 0.3 mL(.)min(-1.)kg(-1). There was a significant association between race and fitness level and between race and fitness level by sex (P < 0.0001). Low fitness was highest among non-Hispanic blacks (percentage (95% confidence interval): (32%, (26-38%)) compared with Mexican-Americans (22% (18-27%)) and non-Hispanic whites (18% (15-21%)), particularly among females, where 35% (28-42%) non-Hispanic black women had low fitness compared with 22% (16.3-27.4%) Mexican-American and 18% (13.7-22.4%) non-Hispanic white women. Conclusions: Non-Hispanic black adults have the highest percentage of low cardiovascular fitness among major race groups in the United States. On a population basis, over one third of non-Hispanic black women have low cardiovascular fitness, suggesting this group in particular may be at increased health fisk due to poor fitness.