Maximal power across the lifespan

Background. Previous investigators have reported that maximal power increases during growth and decreases with aging. These age-related differences have been reported to persist even when power is scaled to body mass or muscle size. We hypothesized that age-related differences in maximal power were primarily related to differences in muscle size and fiber-type distribution rather than to age per se. Methods. Maximum cycling power (P-max) and optimal pedaling rate (V-opt, a surrogate measure for muscle fiber type) were determined for 195 boys and men, 8-70 years of age, by using inertial load cycle ergometry. Anthropometric dimensions were used to estimate lean thigh volume (LTVest) of all subjects, and magnetic resonance imagery was used to determine thigh and hip muscle volume (MRIvol) for 24 subjects. Results. P-max was highly related to the product of LTVest and V-opt (LTVest X V-opt; r(2) = .83). Multiple regression revealed that P-max was significantly related to both LTVest X V-opt, and age (R-2 = .84). Power scaled by LTVest X V-opt was stable during growth and exhibited a small but significant decrease with aging. MRIvol was highly correlated with LTVest and the ratio of LTVest to MRIvol was independent of age. Conclusions. These results suggest that muscle volume and optimal pedaling rate are the main determinants of maximal power across the lifespan and that the contractile properties of muscle are developed early in childhood and remain nearly intact late into the lifespan.