Suggested Repetition Ranges for Strength, Hypertrophy

Improving strength and increasing muscle mass are two prominent goals for exercisers. According to recent research, both goals require significantly different training protocols.

Published in the Journal of Sports Science & Medicine (2016; 15, 715–22), the small study involved 19 men (~23 years old) with experience in resistance training. They were assigned to one of two protocols—one aimed at building strength (heavy resistance), the other designed to build muscle (hypertrophy).

Prior to the intervention, each subject underwent tests to establish baseline 1-repetition maximum (1-RM) in the bench press and squat; upper-body muscle endurance; and muscle thickness of the upper arm and lateral thigh. Participants were asked to avoid nutrition supplementation and make no changes to their current diet. However, they were given a protein supplement to consume within 1 hour after their exercise bouts.

Both groups completed 3 sets of seven exercises for major muscle groups 3 days per week for 8 weeks. Target repetition range for the heavy-resistance group was 2–4 reps, with load set by a baseline 3-RM test. The hypertrophy group performed 8–12 reps, with load determined by a 10-RM baseline test.

Both groups experienced improvements in 1-RM for both test exercises. However, improvements were superior for the heavy-resistance group, especially in the squat, where the increase was nearly double what it was for the hypertrophy group. All men yielded similar improvements in muscle endurance—a point that raised questions for the researchers, as it seemed counterintuitive that the few repetitions completed by the heavy-resistance group would produce such results. Last, improvements in muscle thickness were greater among the hypertrophy group, most evidently in the quadriceps femoris.

“Our findings provide evidence that training in different loading zones elicits differential muscular adaptations in resistance-trained men when an equal number of sets are performed,” the authors said. “Although the mechanisms remain undetermined, we can infer that strength-related adaptations are maximized by training closer to one’s 1RM. Alternatively, increases in muscle size seem to be driven more by higher training volumes, at least up to a certain threshold. It is conceivable that combining loading strategies may have a synergistic effect on strength and hypertrophic improvements. This hypothesis warrants further investigation.”