Specific Adaptations to 0%, 15%, 25%, and 50% Velocity-Loss Thresholds During Bench Press Training

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) crosssectional 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 x 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 x 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.