Cardiorespiratory Fitness’ Indirect Assessment With Running Metabolic Equations Among Healthy Active Men

Abstract

VO2max is defined as the highest amount of oxygen the cardiovascular and pulmonary systems can supply and the highest amount of oxygen the muscular system can use during intense physical exertion. It is widely accepted as the criterion measure of cardiorespiratory fitness. Unfortunately, accessibility to VO2max’s direct measurement is restricted. 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 Sports Medicine (ACSM) and recently, the research group of Fitness Registry and the Importance of Exercise National Database developed a new metabolic equation (FRIEND). PURPOSE: The aim of this study is to evaluate the accuracy of the ACSM and FRIEND equations to estimate VO2max comparatively to direct O2 consumption measurement in healthy active men. METHODS: 54 healthy active men aged between 19-60y.o. (36,6±5,4)(BMI: 24,1±2,6kg/m2) performed a maximal treadmill test using a metabolic cart (Vyntus CPX) to measure direct VO2max (mL O2/kg*min-1). VO2max estimation was then calculated using ACSM and FRIEND running metabolic equations. For analysis, they were separated in two age groups (18-34 vs 35-60y.o.) to evaluate if it has an impact on the metabolic equations used. Results were compared using a two-way ANOVA. RESULTS: When compared to the direct measurement (53,9±7,2 (18-34y.o.) and 49,8±4,4 (35-60y.o.)), both ACSM and FRIEND equations showed significantly higher results in both age group (mean overestimation: 12,7; p<0,001 and 3,7; p=0,005, respectively). However, the FRIEND equation was significantly lower than the ACSM equation (mean difference: 9,0; p<0,001). Moreover, ACSM showed a very large effect size (Hedge’s g=1,84) while FRIEND showed a medium effect size (Hedge’s g=0,58). As for the two age groups, results varied similarly using the two equations (p=0,781). CONCLUSIONS: The VO2max calculated with the metabolic equations for running showed overestimated values in our male 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 levels to optimize the VO2 estimation formula.