The Effects of Full Range of Motion and Lengthened Partial Range of Motion on Chest Hypertrophy and Strength

Purpose: This study investigated the effects of full versus partial range of motion (ROM) resistance training on hypertrophy and strength adaptations in untrained individuals. Emphasis was placed on hypertrophic outcomes in the pectoralis major across multiple anatomical sites. Methods: Eleven untrained males completed an 8-week unilateral within-subject design using the benchpress. One arm was randomly assigned to a full ROM and another using partial ROM at long muscle lengths. Pre- and post-intervention assessments included muscle thickness of the triceps brachii, anterior deltoid, and five sites of the pectoralis major using B-mode ultrasound, 1RM bench press and maximal isometric voluntary contraction (MVC) torque. Results: Significant muscle thickness increases were found in the triceps (full: Δ = 0.30 cm, p = 0.001; partial: Δ = 0.15 cm, p = 0.004) and anterior deltoid (full: Δ = 0.10 cm, p = 0.053; partial: Δ = 0.08 cm, p = 0.017). For the pectoralis major, only the mid-region (1/2 site) in the partial ROM condition increased significantly (Δ = 0.215 cm, p = 0.022). 1RM increased in both conditions but no significant effect of ROM (p = 0.841, η2 = 0.002) or time × ROM interaction (p = 0.365, η2 = 0.041) was observed. MVC significantly improved over time (p < 0.001, η2 = 0.752) but improvements over time did not differ significantly between test positions or ROM conditions. Conclusion: Both full and partial ROM training can effectively hypertrophy the chest. MVC and 1RM strength gains were comparable between conditions with no significant differences detected between conditions. Although no clear superiority was found, the small sample size limits firm conclusions. Practitioners should interpret the results cautiously and adopt a contextually individualised approach to training.