Individualized Volume Increases Versus Prior Training Volume Maintenance: Effects On Muscular Adaptations In Trained Males

PURPOSE: This study investigated the effects of increasing resistance training (RT) volume by 30% (G30) and 60% (G60) compared to a control (CON), which maintained volume on quadriceps regional fat-free mass (ROI-FFM), muscle thickness (MT) and strength adaptations. METHODS: Fifty-five resistance-trained men were randomly allocated to the experimental groups, and twenty-nine completed the study: CON: n = 10, G30: n = 10, and G60: n = 9. Subjects underwent a lower body RT program twice a week for eight weeks. We assessed pre- and post-study measures of ROI-FFM, anterior thigh MT at two sites: proximal (PMT) and distal (DMT), and their sum (ΣMT), one-repetition maximum (1RM), and strength-endurance via repetitions to failure (RTF) at 70% of 1RM. RESULTS: ROI-FFM and MT showed a main effect of time (p < 0.001) but no significant group x time interaction (ROI-FFM estimated differences: CON: 1.57 kg, G30: 0.47 kg, G60: 1.55 kg; ΣMT estimated differences: CON: 1.07 cm, G30: 0.76 cm, G60: 0.70 cm). All groups increased back squat 1RM (p < 0.0001). However, there was a main group effect (p < 0.0268), with the CON group exhibiting a greater overall 1RM (Estimated 1RM: CON: 174.7 kg, G30: 159.0 kg, G60: 149.0 kg). For RTF, a significant group x time interaction (p < 0.0263) revealed that only the G30 group increased RTF (RTF estimated differences: CON: 0.13reps, G30: 5.45reps, G60: -0.41reps). CONCLUSIONS: Our findings suggest that, above a certain weekly set volume, trained males can experience substantial muscle growth while maintaining their previous weekly set number. However, aggregate maximum strength was superior when maintaining RT volume compared to increases of 30% or 60%. Additionally, a 30% increase in volume appeared to enhance strength-endurance performance.