Maximal aerobic power and leg muscle mass and strength related to age in non-athletic males and females

Abstract

To investigate the relationships between the age-associated decline in peak oxygen uptake (peak V˙O₂), leg muscle mass (LMM) and leg strength (LS) under the modulating effect of gender and level of physical activity (LPA, as assessed by questionnaire), we evaluated 71 sedentary subjects [males(M):females(F), 34:37], aged 20–80 years. Peak V˙O₂ at maximum cycle ergometry was related to LMM (dual energy X-ray absorptiometry) and LS (isokinetic dynamometry) using both standard (y · x ⁻¹) and power function ratios (allometry). Absolute values of all variables were higher in males and declined with age (P < 0.01). Differences between the genders disappeared after peak V˙O₂·LS^{−1.46 (M) or −1.62 (F)} adjustment but remained significant between peak V˙O₂·LMM-^{−0.51 (M) or −0.45 (F)} and LS·LMM-^{−0.91 (M) or −1.10 (F)} corrected values. Allometric correction of peak V˙O₂ and LS by LMM slowed their age-related declines; the flattening effect however, was more evident in the females. Interestingly, while no age-related decrement in peak V˙O₂·LS⁻¹ was found, power function ratio values also declined with age, and at a slower rate in females. These findings are consistent with those obtained following a multiple regression analysis using LPA as an independent covariate (P < 0.01). We conclude that using adequate scaling methods and controlling by LPA: (1) no gender differences are observed in peak V˙O₂ adjusted for LS, (2) loss of LS and LMM are important determinants of the age-associated reduction in physical fitness in both genders but (3) age per se has an LS- and LMM-independent influence on the functional decline, although this intrinsic effect of senescence is less pronounced in females.