Purpose: To compare the effect of 4 velocity-loss (VL) thresholds-0% (VL0), 15% (VL15), 25% (VL25), and 50% (VL50)-on strength gains, neuromuscular adaptations, and muscle hypertrophy during the bench press (BP) exercise using intensities ranging from 55% to 70% of 1-repetition maximum (1RM).
Methods: Fifty resistance-trained men were randomly assigned to 4 groups that followed an 8-week (16 sessions) BP training program at 55% to 70% 1RM but differed in the VL allowed in each set (VL0, VL15, VL25, and VL50). Assessments performed before (pre) and after (post) the training program included (1) cross-sectional area of pectoralis major muscle, (2) maximal isometric test, (3) progressive loading test, and (4) fatigue test in the BP exercise.
Results: A significant group × time interaction was found for 1RM (P = .01), where all groups except VL0 showed significant gains in 1RM strength (P < .001). The VL25 group attained the greatest gains in 1RM strength and most load-velocity relationship parameters analyzed. A significant group × time interaction was observed for EMG root mean square in pectoralis major (P = .03) where only the VL25 group showed significant increases (P = .02). VL50 showed decreased EMG root mean square in triceps brachii (P = .006). Only the VL50 group showed significant increases in cross-sectional area (P < .001).
Conclusions: These findings indicate that a VL threshold of about 25% with intensities from 55% to 70% 1RM in BP provides an optimal training stimulus to maximize dynamic strength performance and neuromuscular adaptations, while higher VL thresholds promote higher muscle hypertrophy.
Keywords: muscle hypertrophy; muscle strength; neuromuscular; resistance training; training volume; velocity-based training.