Muscle size responses to strength training in young and older men and women.

To examine the possible influences of age and gender on muscle volume responses to strength training (ST). Prospective intervention study. University of Maryland Exercise Science and Wellness Research Laboratories. Eight young men (age 20-30 years), six young women (age 20-30 years), nine older men (age 65-75 years), and ten older women (age 65-75 years). A 6-month whole-body ST program that exercised all major muscle groups of the upper and lower body 3 days/week. Thigh and quadriceps muscle volumes and mid-thigh muscle cross-sectional area (CSA) were assessed by magnetic resonance imaging before and after the ST program. Thigh and quadriceps muscle volume increased significantly in all age and gender groups as a result of ST (P < .001), with no significant differences between the groups. Modest correlations were observed between both the change in quadriceps versus the change in total thigh muscle volume (r = 0.65; P < .001) and the change in thigh muscle volume versus the change in mid-thigh CSA (r = 0.76, P < .001). The results indicate that neither age nor gender affects muscle volume response to whole-body ST. Muscle volume, rather than muscle CSA, is recommended for studying muscle mass responses to ST.