The main purpose of this study was to examine the effect of training intensity on muscle deoxygenation, which may be an indicator of muscle tissue damage that is thought to be essential for increases in muscle size (hypertrophy) and strength. Eleven male athletes experienced in strength training performed four sets of barbell squats using either a lower-intensity and higher volume protocol (15 repetitions with 60 percent of their maximum weightload) or a higher-intensity and lower volume protocol (4 repetitions with 90 percent of their maximum weightload). The results showed no apparent difference in muscle deoxygenation between the lower-intensity (15 repetitions) exercise protocol and the higher-intensity (4 repetitions) exercise protocol. However, time-dependent postexercise reoxygenation was significantly longer in the lower intensity (15 repetitions) training protocol. Both testosterone and growth hormone concentrations were elevated immediately after the exercise sessions, and at 20 minutes and 40 minutes post exercise. Although there were no differnces in testosterone levels, growth hormone was significantly higher at 20 and 40 minutes post exercise for the lower intensity (15 repetitions) training protocol.
Training to muscle fatigue with a heavier weightload (90 percent maximum) and fewer repetitions (4 reps) produced similar effects on muscle deoxygenation as training to muscle fatigue with a lighter weightload (60 percent maximum) and more repetitions (15 reps). However, the longer set of resistance exercise did require a longer time for muscle reoxygenation, and produced higher growth hormone concentrations during the post exercise period.
Hoffman, J. J. Im, K. Rundell, J. Kang, S. Nioka, B. Speiring, R. Kime, and B. Chance. Effects of muscle oxygenation during resistance exercise on anabolic hormone response. Medicine and Science in Sports and Exercise, 35 (11): 1929-1934, 2003.
This study compared the effects of two strength training modalities (free-weights and a unique interim elastomer resistive device used on the International Space Station), and two exercise protocols (3 sets of 6 to 12 repetitions each and 6 sets of 6 to 12 repetitions each) on muscle strength, muscle volume, lean body mass, and bone mineral density. Twenty-eight untrained males were assigned to one of the following exercise groups: (1) control; (2) 3 sets of free-weights; (3) 3 sets of elastomer device; (4) 6 sets of elastomer device; and trained 3 days a week for 16 weeks. Results showed similar increases in muscle strength and muscle volume for all three groups that performed resistance exercise. However, only the free-weight group experienced significant increases in lean body mass and bone mineral density. Doubling the training volume (6 sets vs. 3 sets) did not produce any additional improvement in any of the training responses.
Although the softer resistance supplied by the elastomer device produced similar muscle strength and muscle volume increases to the harder resistance supplied by the free weights, only the latter training modality resulted in greater lean body mass and bone mineral density. Doubling the number of exercise sets did not elicit any further training benefits, but may have contributed to overtraining injuries that occurred in half of the 6-set subjects.
Schneider, S., W. Amonette, K. Blazine, J. Bentley, S. Lee, J. Loehr, A. Moore, M. Rapley, E. Mulder, and S. Smith. Training with the international space station interim resistive exercise device. Medicine and Science in Sports and Exercise, 35 (11): 1935-1945, 2003.