Muscular hypertrophy in young versus older men and women:
The effect of age on the magnitude of hypertrophy response was examined in 9 young (22-31 yr, 5 male and 4 female) and 8 old (62-72 yr, 4 male and 4 female) subjects. Muscle hypertrophy is an increase in the size of a muscle through an increase in the size of cells. Muscle in the thigh and upper arm were examined before and after 3 months of progressive resistance training by magnetic resonance imaging (MRI). Strength was determined by 3-repetition-maximum (3RM) testing. Results showed that an average increase in muscle cross-sectional areas (CSA) were lower in the older group for elbow flexors (22% in young, 9% in old, p < .05) and knee flexors (8% vs 1% in old, p < 0.01), but not for knee extensors (4% vs 6% in old). Mean increases in specific tension (ratio of 3RM strength to CSA) were similar in young (21%) and old groups (19%) for elbow flexors and knee extensors (38% vs 32 % in old), but were greater in the older group for knee flexors (28% vs 64% in old, p < 0.02). In conclusion, aging can reduce the effect of hypertrophic muscle response to resistance training, but the older subjects are able to continue to develop increase in strength and muscle size despite aging. (8)