Muscle function in 164 men and women aged 20-84 yr

Purpose: The purpose of the present study was to investigate the effect of aging in men and women on muscle functional properties, i.e.. muscle force and force per unit of cross-sectional area (force/CSA). Methods: A total of 164 volunteers participated in this study and were divided into five group s according to their chronological age as follows: 20s (20-39 yr old), 40s, 50s, 60s, and 70s (70-84 yr old). Isokinetic (0, 60, 180, and 300 degreess (-1)) knee extensor and flexor peak torque, and CSA of the quadriceps femor is (QF) muscle of the mid-thigh were measured. Results: Peak torque during knee extension and flexion was inversely related to age in both men and wom en. This was the case irrespective of the speed of contraction in both gend ers (men: r = -0.797 to -0.756, all P < 0.001, women: r = -0.039 to -0.530, all P < 0.001). A significant correlation was observed between CSA of QF a nd peak torque during isometric knee extension in men (r = 0.827, P < 0.001 ) and women (r = 0.657, P < 0.001). During isometric contraction, the force /CSA exhibited a significant decrease with increasing age in men (r = -0.51 8, P < 0.001) but not in women (r = -0.207, NS). Conclusion: These results thus suggest that muscle strength losses would be mainly due to a decline i n muscle mass in both genders, whereas age-related decline in muscle functi on in men may also be the result of neural factors, such as muscle recruitm ent and/or specific tension.