Weight-training with slow and super-slow repetitions has been promoted in some quarters as superior to normal-speed weight training. An article by Tanimoto et al. in the Journal of Strength and Conditioning Research (vol. 23, no. 8, 2009) tested this hypothesis.
Twenty-four young men performed 3 sets of barbell squat exercise, twice a week for 13 weeks, and were equally distributed among the following 3 groups:
- Control Group: no organized exercise
- Slow-Repetition Group: 3 sec descending, 3 sec ascending, no rest between reps
- Normal-Speed-Repetitions: 1 sec descending, 1 sec ascending, 1 sec between reps
The two lifting groups each did 8 reps with the most weight they could handle for that number of reps and the assigned speed (metronome-timed). Because slow reps are more difficult, the weight used was about 60% of max for the slow group and about 85% of max for the fast group.
Both training groups significantly improved both their max squatting strength (Slow: 34%, Fast: 28%) and their lean thigh muscle volume (Slow: 2.5%, Fast 3.6%). However the groups did not differ significantly in their percent gains in these two parameters. The authors concluded that slow resistance-training is just as effective as normal-speed training for improving muscle strength and size, and has the additional advantage of being safer because of lower musculoskeletal forces and less elevation of blood pressure.
One area in which the groups differed was in their muscle electrical activity while riding a bicycle at a typical speed and resistance. The slow-trained group developed a more unusual pattern of muscle activation and force application. The authors felt this indicated that slow-speed strength-training may have some unfavorable effects on dynamic physical activities, like those typical of sports. However, they felt that, because of the safety advantages of slow-speed weight-training, the method can be combined for sport training with some fast and exposive lifts (e.g. cleans), “cheating technique”, and plyometrics (e.g. jumping).