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

To investigate the relationships between the age-associated decline in peak oxygen uptake (peak (V)over dot O-2), 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)over dot O-2 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)over dot O-2 . LS-1.46 (M) or -1.62 (F) adjustment but remained significant between peak (V)over dot O-2 . 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)over dot O-2 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)over dot O-2 . 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 fender differences are observed in peak (V)over dot O-2 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.