KNEE EXTENSOR TORQUE AND CROSS-SECTIONAL AREA IN 20- TO 84-YR-OLD MEN AND WOMEN

Abstract

731 This study was conducted in an effort to assess the contribution of muscle atrophy to the low strength evident in older adults. One hundred fifty-five 20 to 84 year old volunteers (72 men and 83 women) participated. They were divided into 6 groups based on chronological age: 20s (20 and 30 yr), 40s, 50s, 60s, 70s, and 80s. Cross-sectional area (CSA) of the quadriceps femoris muscle group was measured using magnetic resonance imaging and torque during maximal voluntary isokinetic knee extensions was assessed at 4 different speeds (0, 60, 180, and 300°/sec). Peak torque was inversely related to age in both men and women. This was the case irrespective of the speed of contraction for both genders (men: r=−0.797 to −0.756, all p<0.001, women: r=−0.639 to −0.530, all p<0.001). The CSA was also inversely related to age in both men and women (men: r=−0.758, women: r=−0.564, both p<0.001). The ratio of peak torque to CSA, unlike its components, decreased linearly with age in men, but not women. Thus, apparent specific tension decreased with age in men (r=−0.518, p<0.001) but not women (r=0.070, ns). These results suggested that age-related muscle strength losses can be accounted for by muscle atrophy in women but not in men. The factors responsible for the decline in the ability to develop force per unit muscle mass in men but not women with advancing age are not clear.