Comparative Analysis of Direct and Indirect Methods for the Determination of Maximal Oxygen Uptake in Sedentary Young Adults

Background: Maximal oxygen uptake is a powerful prognostic indicator and a reliable measure of physical conditioning. It can be measured directly by cardiopulmonary exercise testing (CPET) or indirectly by formulas derived from conventional protocols. Objective: We compared the VO2 max obtained by formula using exercise testing with Bruce protocol (BP) with the VO2 max obtained by CPET on the treadmill. Methods: We selected 41 healthy, non-obese, physically inactive young volunteers, aged between 21 and 50 years, residents of Florianópolis, Brazil. Results: Twenty-one women (52%) with mean age of 35.62 ± 8.83 years, and 20 males, with mean age of 32.5 ± 7.18 years participated in the study. Statistically significant differences were found for VO2 max between the two methods (BP - 42.31 ± 5.21 ml/kg.min vs. CPET - 30.46 ± 5.50 ml/kg.min., p < 0.0001). The Bruce formula overestimated the result by 34.1% (BP - 45.95 ± 3.94 ml/kg.min vs. CPX - 34.27 ± 4.20 ml/kg.min, p < 0.0001) for men, and by 44.8% (BP - 38.84 ± 3.72 ml/kg.min vs. CPX - 26.83 ± 3.90, p < 0.0001) for women. A moderate correlation was observed between the methods (r = 0.65). When classifying the results according to the table of aerobic capacity of the American Heart Association, the agreement was null (kappa = 0.0034; Pearson chi2 = 0.001). Conclusion: VO2 estimated by BP is not capable of demonstrating the true aerobic capacity in these individuals, while CPET is an important tool for early detection of diminished functional capacity in sedentary young men and women.