Purpose: A linear dose-response relationship between resistance-training (RT) volume and hypertrophy/strength has been proposed when ≤10 to 12 weekly sets are implemented. The present study aimed to understand the impact of low to high weekly RT volume on muscular adaptations in trained young men over 6 wk of RT.
Methods: RT-experienced men (N = 49) were randomly allocated to a low (LOW; n = 17), moderate (MOD; n = 15), or high (HIGH, n = 17) -volume group, performing 9, 18, or 27 weekly sets of biceps RT, respectively, for 6 wk. RT was performed once (LOW) or twice (MOD and HIGH) weekly. Postexercise protein intake was controlled with both dietary intake and external training volume recorded. Before and after RT, assessments of biceps muscle thickness (MT) via ultrasound, isometric, and 1-repetition-maximum (1RM) strength were performed. Data were analyzed using 1-way analysis of variance (baseline characteristics) and repeated-measures analysis of variance (within- and between-groups pre-to-post change).
Results: MT significantly increased in all groups (4.3% [7.9%], 9.5% [11.8%], and 5.4% [6.3%] for LOW, MOD, and HIGH, respectively; P < .05), as did 1RM strength (P ≤ .001 for all). Isometric strength increased significantly in HIGH only (8.5% [15.1%], P < .05). There were no significant differences between groups in MT or indices of strength. However, effect-size estimates revealed that the magnitude of response was "moderate to large" for MOD and HIGH when compared with LOW.
Conclusion: The findings demonstrate that 9 weekly sets of biceps-focused RT, performed in 1 weekly session, are sufficient to increase MT, whereas 18-27 sets performed over 2 weekly sessions may confer greater strength increases.
Keywords: biceps thickness; isometric strength; isotonic strength; muscle hypertrophy.