Effects of Strength Training on Muscle Hypertrophy and Muscle Cell Disruption in Older Men

To determine whether a total body, heavy resistance, strength training (ST) program can significantly increase muscle strength and hypertrophy without muscle cell disruption and soreness in older men, 35 sedentary male subjects between the ages of 50 and 69 years of age (60 ± 5, X ± SD) were studied. Twelve served as inactive controls. Muscular strength, cross-sectional muscle area, serum creatine kinase (CK) activity and perceived soreness were assessed before and after a 16 wk heavy resistance ST program. The ST program resulted in a 43 % increase in muscular strength (p < 0.001), and a 7.2 % increase in midthigh muscle area (153 ± 24 vs 164 ± 23 cm2, p < 0.001). There were no significant changes in strength or muscle area in the inactive control group. Peak serum CK levels were approximately twofold above baseline (278 ± 175 vs 133 ± 88 U/I, p < 0.01) 8 h after the first regular training session. At the end of training, the peak rise in CK levels was also reached 8 h after exercise, but was reduced substantially at the same absolute (p < 0.01) and relative resistance loads (p < 0.01) compared to the first training session. Muscle soreness after exercise was only occasionally reported at the beginning of training and was almost nonexistent after training. These results indicate that middle-aged and older men can safely participate in a total body strength training program, intense enough to produce substantial increases in muscle strength and hypertrophy, without promoting muscle soreness or significant muscle cell disruption. Furthermore, the risk of muscle cell disruption during acute resistive exercise is reduced at the end of a strength training program in older individuals similarly to that reported in younger individuals.

Key words

Weight training - aging - muscle mass - muscle injury - creatine kinase