Peak O₂ Uptake Correlates with Fat Free Mass in Athletes but Not in Sedentary Subjects

Abstract

Objective: To characterize relationships between peak O 2 uptake (VO 2 max) and fat free mass (FFM) in adult sedentary and in young and adult athletes. Methods: Healthy adult male sedentary workers or students reporting no regular physical activity in the last six months (n = 61, 31.0 ± 0.95 years) and young (n = 63, 15.8 ± 0.16 years) or adult (n = 85, 25.9 ± 0.48 years) males athletes were studied. Sports were classified according to their MET intensity. Bruce’s treadmill protocol served to measure VO 2 max. Weight and seven skin-fold thicknesses were used to estimate body density and FFM. Subjects signed informed-consent forms before the tests. Results: The significant correlations (R 2 = 0.48, p < 0.01) between FFM and VO 2 max or of log FFM with log VO 2 max (R 2 = 0.53, p < 0.01) in young athletes were lower in adult athletes (R 2 = 0.34 & 0.30), and not significant (R 2 = 0.19 & 0.17, p > 0.05) in sedentary subjects. Stepwise multiple regression analysis (R 2 = 0.65) indicated that VO 2 max depended on FFM, heart rates and MET intensity of practiced sport in athletes. In sedentary subjects VO 2 max was insignificantly (R 2 = 0.18) related to flexibility. Discussion: Skin-fold based FFM reliably reflects maximally active muscle mass in young athletes, to a lesser extent in adult athletes but not in adult sedentary subjects. In sedentary, VO 2 max is often limited by local pain and fatigue and does not reflect the capacity of the oxygen extraction system. In sedentary, varying proportions of surface fat, muscle and bone increase variability in the relationship between skinfolds and FFM.