Gender differences in human muscle and joint mechanical properties during plantar flexion in old age

Muscle and joint mechanical properties during plantar flexion were investigated in 13 elderly women (EW) (age range 73-83 years) and 15 elderly men (EM) (age range 74-81 years). Maximal torque, at several angular velocities, was measured to construct torque-velocity relationship. This led to the calculation of an index of maximal shortening velocity (VI_max) at 10% of maximal isometric torque. Two methods were then used to calculate musculotendinous (quick-release movements) and musculoarticular (sinusoidal perturbations) stiffness. In both cases, stiffness was linearly related to torque, and the slope was defined as a stiffness index (SI): SI_MT and SI_MA, respectively. Maximal torques as well as VI_max (p < .05) were lower in EW compared with EM. Furthermore, SI_MT and SI_MA values were higher for EW than for EM (p < .05). These results are interpreted in terms of possible differences in the muscle mass, fiber-type distribution, and tendons. They may also have implications for daily motor behavior.