Researchers from Japan studied the effects of training volume—one versus three sets per exercise—on muscular strength and hypertrophy (muscle growth) in the biceps muscles (i.e., the elbow flexor muscles) in sedentary and untrained young men. Training sessions were completed two times per week, for 12 weeks, using the seated dumbbell preacher curl exercise. Training intensity/load was set at 80 percent of a one-rep-etition maximum for all sets. The three-set protocol was shown to result in significantly greater increases in muscle size, compared to the one-set protocol. In addition, the gains in strength experienced with the three-set protocol tended to be greater than the strength gains achieved with the one-set protocol. Based on these findings, for beginner lifters, three sets per exercise using moderate loads, when targeting relatively small muscle groups, is an excellent place to start to maximize gains.
[Sooneste, Heiki, et al. “Effects of training volume on strength and hy-pertrophy in young men.” The Journal of Strength & Conditioning Research27.1 (2013): 8-13.]