Chizuko Mishima

Force–velocity, force–power relationships of bilateral and unilateral leg multi-joint movements in young and elderly women

The present study investigated force-velocity and force-power relationships of bilateral and unilateral knee-hip extension movement in young and elderly women. Twelve healthy young (age, 19-31 yr) and 12 healthy elderly (age, 60-82 yr) women performed bilateral and unilateral knee-hip extension movements on the dynamometer against loads controlled by the servo system. Under the isotonic force condition, force-velocity relationships were measured. The maximum isometric force (F(max)), unloaded velocity (V(max)) and power output (P(max)) of the movements were calculated from extrapolating force-velocity and force-power relationships. F(max) and P(max) of bilateral and unilateral knee-hip extension movements were 20-30% lower in elderly than in young women. On the other hand, there were no significant differences in V(max) between young and elderly women and between bilateral and unilateral movements. Bilateral deficit was larger as the generation of force was larger in both young and elderly women. Also, bilateral deficit of F(max) and P(max) were not different between young and elderly women. The results were that lower maximum power output of bilateral and unilateral leg multi-joint movements in elderly women did not depend on the intrinsic shortening velocity of muscle action, but largely on reduction in force generating capacity. This suggests the importance of preventing a loss of force generating capacity of muscles during leg multi-joint movements in elderly women.

Aging-Related Differences in Maximum Force, Unloaded Velocity and Power of Human Leg Multi-Joint Movement

Background: Because many of our movements of daily living are multi-joint movements and lower limb performance decreases with aging, it is important to understand the influence of aging on muscle functions of lower limb multi-joint movements. Objective: To investigate aging-related differences in the maximum force, unloaded velocity and power of muscles that control leg multi-joint movements. Methods: 285 recreationally active men (n = 142) and women (n = 143) aged between 18 and 82 years volunteered for the study. Lower limb muscle function was measured with a servo-controlled dynamometer and the maximum isometric force (Fmax), unloaded velocity (Vmax) and power (Pmax) were determined by the force-velocity and force-power relations. Results: With increasing age, Fmax/body mass significantly declines in both men (r = –0.400, p <0.001) and women (r = –0.587, p < 0.001), while Vmax/leg length does not change with age in either men (r = –0.033, p > 0.05) or women (r = –0.040, p > 0.05). Pmax significantly declines with age in both men (r = –0.370, p < 0.001) and women (r = –0.446, p < 0.001). Conclusions: Aging does not have effects on the shortening velocity, although it causes a decrease in maximum force and power of leg multi-joint movements. This finding suggests that decreases in muscle force-generating capacity and power may primarily lead to the loss of mobility and a reduced capability of accelerating and decelerating the body mass during the movements in elderly individuals.