Effects of a resistance training program on muscular performance adaptations: comparing three vs. four times per week

Study aim: The aim of this study was to examine the effects of 8 weeks of resistance training (RT) with three vs. four sessions per week and equated training volume on muscular adaptations in men. Materials and methods: Thirty-three healthy young men volunteered to participate in the study and were randomly assigned to three times per week whole-body RT (RT3, n = 11), four times per week whole-body RT (RT4, n = 11) or a control group (CG, n = 11). Before and after training, participants were evaluated for one-repetition maximum (1RM) and muscular endurance (i.e., 60% of 1RM to failure) for the leg press and bench press. In addition, thigh, arm, chest, and calf circumferences, and percent body fat were assessed before and after training. Results: The findings revealed significant main effects of time for chest and thigh circumferences (p <= 0.05). There were no significant group x time interactions for chest and thigh circumferences (p > 0.05), but the RT4 showed greater changes (effect size [ES]: 0.48 vs. 0.15) in chest circumference, while the RT3 showed greater changes (ES: 0.77 vs. 0.35) in thigh circumference. Significant group x time interactions were observed for the 1RM of leg and bench presses (p < 0.05). Post-hoc analyses showed greater improvements for RT3 in comparison to RT4 in 1RM bench press (p = 0.01, ES: 0.77 vs. 0.6) and leg presses (p = 0.009, ES: 0.94 vs. 0.86). Conclusions: These results suggest that RT induces meaningful adaptive effects to improve strength and muscle size in men and RT3 appears to be more effective to induce muscular adaptations.