Effects of different intensities of resistance training with equated volume load on muscle strength and hypertrophy.

The present study investigated the effects of different intensities of resistance training (RT) on elbow flexion and leg press one-repetition maximum (1RM) and muscle cross-sectional area (CSA). Thirty men volunteered to participate in an RT programme, performed twice a week for 12 weeks. The study employed a within-subject design, in which one leg and arm trained at 20% 1RM (G20) and the contralateral limb was randomly assigned to one of the three conditions: 40% (G40); 60% (G60), and 80% 1RM (G80). The G20 started RT session with three sets to failure. After G20 training, the number of sets was adjusted for the other contralateral limb conditions with volume-matched. CSA and 1RM were assessed at pre, post-6 weeks, and post-12 weeks. There was time effect for CSA for the vastus lateralis (VL) (8.9%, 20.5%, 20.4%, and 19.5%) and elbow flexors (EF) (11.4%, 25.3%, 25.1%, and 25%) in G20, G40, G60, and G80, respectively (p > .05). G80 showed higher CSA than G20 for VL (19.5% vs. 8.9%) and EF (25% vs. 11.4%) at post-12 weeks (p < .05). There was time effect for elbow flexion and unilateral leg press strength for all groups post-12 weeks (p < .05). However, the magnitude of increase was higher in G60 and G80. In conclusion, when low to high intensities of RT are performed with volume-matched, all intensities were effective for increasing muscle strength and size; however, 20% 1RM was suboptimal in this regard, and only the heavier RT intensity (80% 1RM) was shown superior for increasing strength and CSA compared to low intensities.