Comparison of muscle mechanical and histochemical properties between young and elderly subjects

We examined age-related human muscle fiber changes and their relation with maximal power scaled to muscle volume (specific power). Fiber type distribution and cross sectional area (CSA) were determined from m. vastus lateralis in 7 young (YS; 29.6 +/- 5 years) and 7 elderly subjects (ES; 74.3 +/- 3 years). Muscle volume and mean CSA of the thigh were anthropometrically measured. Muscle power was assessed by a series of accelerations on a cycle ergometer. Specific power was 35 % lower in ES than YS. Area ratios of IIa/I and IIx/I fibers were lower in ES than YS. By including single fiber power data from the literature to the present results, the decline in the specific power between YS and ES was 34 %, when data of both IIa and IIx fibers were considered. The decrease of the specific power with age on the whole muscle would be compatible with the age-induced changes in the muscle histochemical characteristics.