Maximal oxygen uptake at the same fat-free mass is greater in men than women

Summary Maximal oxygen uptake (V̄O2max) is commonly divided by body mass or fat‐free mass (body mass minus fat mass) in order to make it size independent so that comparisons among persons of different size can be made. However, numerous studies have shown that the ratio created is not size‐independent. Analysis of covariance (ANCOVA) allows a dependent variable to be compared between groups at a common value of a covariate. The purpose of this study was to compare V̄O2max at the same fat‐free mass (FFM) in 230 sedentary subjects (half men) who ranged in age from 20 to 70 years. The subjects underwent maximal cardiopulmonary exercise testing on a cycle ergometer as ventilation and the expired gas fractions were being measured. Two ANCOVA models were evaluated. The dependent variable, fixed factor and covariate(s) in the linear model were V̄O2max, sex and FFM, respectively. The corresponding terms in the log‐linear model were ln V̄O2max, sex, and ln FFM and age. Sex made a significant contribution to both models. In the linear model, the mean V̄O2max at the same FFM was 27% higher in men (2444 versus 1929 ml min−1; P