VO₂max is simply defined by the body’s ability to use oxygen during physical exercise and is widely used as an indicator of cardiorespiratory fitness. Lower VO2max is associated with higher risk of morbidity and mortality as well as low performance while higher VO2max predict good performance in aerobic sports. Direct measurement of VO2max is still the gold standard, however this method presents high cost and required sophisticated equipment. Therefore, several metabolic equations have been developed to estimate VO₂max using indirect calculation. The most commonly used equations are those developed by the American College of Sport Medicine (ACSM) and the research group of Fitness Registry and the Importance of Exercise National Database (FRIEND).
PURPOSE: The aim of this study is to evaluate the accuracy of these two equations to estimate VO₂max comparatively to direct O₂ consumption measurement.
METHODS: 21 healthy active women aged between 22-50y.o. (mean: 37,1±7,4)(BMI: 23,0±2,5kg/m²) performed a maximal treadmill test using a metabolic cart (Vyntus CPX) to measure direct VO₂max (mlO₂/kg/min). VO₂max estimation was then calculated using ACSM and FRIEND running metabolic equations. Results were compared using repeated measures T-test. These preliminary results are part of a larger study which includes 180 men and women of all age group and fitness level (18-34, 35-54 and ≥ 55y.o.).
RESULTS: When compared to the direct measurement (Vyntus: 44,9±4,9), only the ACSM equation showed significantly higher results 53,0±6,6)(mean difference: 8,1; p<0,01). The FRIEND equation did not significantly differ from the metabolic cart result (45,5±4,7)(mean difference: 0,56; p=0,5). In the same direction, ACSM showed a large effect size (Hedge’s g = 1,29) while Friend only showed a small effect size (g = 0,11).
CONCLUSION: The VO₂max calculated with the ACSM equation for running showed overestimated values in our female sample. The average difference between direct and indirect measurement when using the FRIEND equation suggests a better accuracy. More research is needed to evaluate the accuracy in different populations and different fitness level to optimize the VO₂ estimation formula.