Effects of 4, 8, and 12 Repetition Maximum Resistance Training Protocols on Muscle Volume and Strength

<jats:title>Abstract</jats:title> <jats:p>Kubo, K, Ikebukuro, T, and Yata, H. Effects of 4, 8, and 12 repetition maximum resistance training protocols on muscle volume and strength. <jats:italic toggle="yes">J Strength Cond Res</jats:italic> 35(4): 879–885, 2021—The purpose of this study was to determine skeletal muscle adaptations (strength and hypertrophy) in response to volume-equated resistance training with divergent repetition strategies. Forty-two men were randomly assigned to 4 groups: higher load–lower repetition group performing 4 repetition maximum (RM) for 7 sets (4RM, <jats:italic toggle="yes">n</jats:italic> = 10), intermediate load–intermediate repetition group performing 8RM for 4 sets (8RM, <jats:italic toggle="yes">n</jats:italic> = 12), lower load–higher repetition group performing 12RM for 3 sets (12RM, <jats:italic toggle="yes">n</jats:italic> = 10), and nonexercising control group (CON, <jats:italic toggle="yes">n</jats:italic> = 10). The volume of the pectoralis major muscle (by magnetic resonance imaging) and 1RM of the bench press were measured before and after 10 weeks of training (2 times per week). No significant difference was observed in the relative increase in the muscle volume among the 4RM, 8RM, and 12RM groups. The relative increase in 1RM was significantly lower in the 12RM group than in the 4RM group (<jats:italic toggle="yes">p</jats:italic> = 0.029) and the 8RM group (<jats:italic toggle="yes">p</jats:italic> = 0.021). The relative increase in 1RM was significantly correlated with that in the muscle volume in the 12RM group (<jats:italic toggle="yes">r</jats:italic> = 0.684, <jats:italic toggle="yes">p</jats:italic> = 0.042), but not in the 4RM (<jats:italic toggle="yes">r</jats:italic> = −0.265, <jats:italic toggle="yes">p</jats:italic> = 0.777) or 8RM (<jats:italic toggle="yes">r</jats:italic> = −0.045, <jats:italic toggle="yes">p</jats:italic> = 0.889) groups. These results suggest that the increase in muscle size is similar among the 3 training protocols when the training volume was equated, whereas the increase in muscle strength is lower with the 12RM protocol than the other protocols.</jats:p>