Changes in mechanical properties of human plantar flexor muscles in ageing

Changes in contractile and elastic properties of human plantar flexor muscles in ageing, were investigated in 12 young (19-24 years, YG) and 11 old (61-74 year, OG) men. Maximal isometric and concentric voluntary torques, at several angular velocities, were measured to construct torque-angular velocity relationship. This led to the calculation of an index of maximal shorting velocity (VImax) at low torque. Two methods were then used to calculate musculotendinous (MT, quick-release movements) and musculoarticular (MA, sinusoidal perturbations) stiffness. In both cases, stiffness was linearly related to torque, leading to the calculation of a stiffness index (SI) as the slope of the stiffness…