THIGH MUSCLE AREA AND STRENGTH LOSS OVER 12 YEARS IN OLDER MEN

Abstract

1979 Decline in muscle mass is a hallmark of aging, with most evidence derived from cross-sectional studies or longitudinal studies of whole body measures. This study investigates the twelve year (12.4±0.5 y) changes in thigh muscle cross sectional area and muscle strength in 7 men initially 60 to 70 y of age. CT scans of the mid-thigh region were performed. Isokinetic muscle strength of the knee extensors and flexors was measured at 60 deg/sec. The first CT was performed at the level of the first biopsy. Location of the follow-up CT site was identified by a muscle biopsy scar resulting from the first evaluation. Tissue areas (sq cm) were determined by planimetry. CT was obtained at 45% of the femur length above the distal femur. Average body weight (kg) did not change significantly over the follow-up period, 75.0±6.5 to 73.9±9.6. Tissue area changes are as follows: (Table)TableWeight change was associated with change in muscle cross-sectional area (r=0.73, p<0.06). Isokinetic knee extensor and flexor strength declined by 21±16% and 25±24% over the same period. Change in extensor strength was associated with change in extensor muscle area (r=0.73, p<0.06). No similar associations were observed for the flexor group. These data suggest that approximately 53% of the decline in strength can be accounted for by changes in muscle mass. Other factors affecting age related muscle strength changes may include alterations in single fiber contractile properties or neurologic alterations. Supported by USDA grant #53-1950-5-003 and NIH grant AG-15797.