The Best Rep Range for Muscle Growth
The “strength-endurance continuum” is a widely accepted concept in the field of exercise science. Simply stated, the theory asserts that training in different rep ranges elicits differential effects on muscular adaptations. From a practical standpoint, the continuum can be categorized into three distinct loading zones— heavy, moderate and light— whereby heavy loads (1-5 RM) promote maximal strength gains, moderate loads (6-12 RM) bring about maximal increases in muscle mass, and light loads (15+ RM) produce the greatest improvements in local muscular endurance.
A considerable amount of research has been conducted on the strength-endurance continuum, and there is now good evidence that heavy loads do indeed promote the greatest increases in strength while muscular endurance is optimized with the use of light loads.2,7,9 However, the claim that moderate-rep training is superior for maximizing muscle size has come under scrutiny, with a number of studies showing that training across a wide spectrum of rep ranges can be equally effective from a hypertrophy standpoint.6
A big issue with the body of research on the topic has been a paucity of studies carried out in individuals with resistance-training experience. It is well established that experienced lifters respond differently to training compared to non-lifters. This is due to a “ceiling effect,” whereby gaining muscle becomes progressively more difficult as you get closer to reaching your genetic potential.1
THE STUDY
Several years ago, I published the first study to investigate the effects of different rep ranges on strength and hypertrophy changes in resistance-trained men.5 In brief, the study randomized subjects to either a “bodybuilding-type” routine that trained with moderate reps or a “powerlifting-type” routine that trained heavy. The routines were equated for volume load (i.e., the total amount of weight lifted per session) so that the bodybuilding group performed three sets of 10 reps while the powerlifting group performed seven sets of three reps. Consistent with the “strength-endurance continuum,” the study found that the powerlifting-type routine produced the greatest strength increases. Contrary to the theory, however, both routines produced similar increases in hypertrophy of the biceps brachii.
It must be pointed out that the findings of that study are specific to the respective routines being equated for volume load. While this design helped to rule out potential confounding issues and thus isolate the impact of loading zones on hypertrophy, it is impractical to carry out long-term training with very heavy loads at the volumes used in that study (in fact, the majority of subjects in the powerlifting-type group displayed clear signs of overtraining by study’s end). So the question arises as to whether results would differ if an equal number of sets were performed between heavy and moderate loads?
Recently, I carried out a study that investigated this very topic.8 Here’s the lowdown on what we found.
Nineteen college-aged men, who had been lifting consistently for at least a year and regularly performed both the squat and bench press, were recruited to participate in the study. Subjects were randomized to either a group that trained in a heavy loading range of two to four repetitions per set (HEAVY) or a group that trained in a moderate loading range of eight to 12 repetitions per set (MODERATE). All other aspects of the routines were controlled between groups. The training protocol consisted of seven exercises that worked all the major muscles of the body each session, with three sets performed per exercise. Training was carried out on three non-consecutive days per week for eight weeks. Subjects were instructed to maintain their normal daily nutritional intake, and no differences in either calories or macronutrient consumption were found between groups over the course of the study.
Testing was carried out pre- and post-study. Ultrasound was used to measure muscle growth of the elbow flexors, elbow extensors and quads. Upper and lower body strength was assessed via the one-repetition maximum (RM) in the squat and bench press. Upper body local muscular endurance was determined by assessing the subject’s initial 1RM in the bench press for as many repetitions as possible to muscular failure.
Results showed that overall muscle growth was greater when performing a moderate-rep routine compared to heavy lifting. Increases in thickness of the elbow flexors (i.e., biceps brachii and brachialis) favored the use of moderate reps (~5% versus ~3%), while gains in the quads were markedly greater with moderate-rep training (10% versus 4%). Interestingly, growth of the triceps was similar between groups.
On the other hand, strength gains were superior for heavy-load training. In particular, improvements in the 1RM squat were decidedly greater in HEAVY compared to MODERATE (29% versus 16%). Changes in the 1RM bench press also favored the use of heavy weights, although the differences between HEAVY and MODERATE were less substantial (14% versus 10%). Muscle endurance increases were similar between rep ranges.
IN CONCLUSION
At face value, the findings lend support to the concept of a strength-endurance continuum and reaffirms that a “hypertrophy range” of six to 12 reps per set maximizes muscle growth. This is consistent with what gym bros have been preaching for years. However, when the results are considered in conjunction with my previous study that equated volume load, an interesting hypothesis emerges. Since strength gains were greater with heavy loads in both studies, it can be concluded that low-rep training is best for maximizing strength regardless of volume load. On the other hand, since the previous study showed no differences in hypertrophy between conditions when volume load was equated, it can be inferred that volume load is a greater driver of muscle growth irrespective of the rep range. In other words, strength is maximized even with lower training volumes, provided heavy loads are used, but higher volumes are needed to maximize gains in size regardless of whether you train with moderate or heavy weights.
Take-home point: It appears that total training volume is the primary driver of muscle growth.
The study had several limitations including a relatively small sample size, the use of a single-site measurement for muscle growth on each of the respective muscles, and possible confounding from the “novelty factor” (i.e., virtually all the subjects trained with moderate loads, so it is possible that the novel stimulus for those in the heavy-load group might have impacted results). These issues must be taken into account when attempting to draw evidence-based conclusions. Most importantly, one study is never the be-all and end-all when it comes to answering questions on an applied science topic. Rather, each study should be considered a piece in a puzzle that lends support to a given theory; with respect to the strength-endurance continuum, more research is certainly needed to fully understand its practical implications for program design. For now, though, the evidence suggests to train heavy if your goal is maximal strength, and to focus on accumulating volume for maximal gains in muscle mass. Moreover, there is evidence that training across the full spectrum of rep ranges might promote the greatest increases in growth3,4, so systematically vary your loading zones over time.
Brad Schoenfeld, Ph.D., CSCS, FNSCA is widely regarded as one of the leading authorities on training for muscle development and fat loss. He has published over 100 peer-reviewed studies on various exercise- and nutrition-related topics. He is also the author of the best-selling book, The M.A.X. Muscle Plan and the seminal textbook, Science and Development of Muscle Hypertrophy. Check out is website and blog at www.lookgreatnaked.com
References:
1. American College of Sports Medicine. American College of Sports Medicine position stand. Progression models in resistance training for healthy adults. Med Sci Sports Exerc2009;41: 687-708.
2. Campos GER, Luecke TJ, et al. Muscular adaptations in response to three different resistance-training regimens: specificity of repetition maximum training zones. Eur J Appl Physiol 2002;88: 50-60.
3. Ogborn D and Schoenfeld BJ. The role of fber types in muscle hypertrophy: Implications for loading strategies. Strength Cond 2014;J36: 20-25.
4. Schoenfeld BJ, Contreras B, et al. Effects of varied versus constant loading zones on muscular adaptations in well-trained men. Int J Sports Med 2016;DOI: 10.1055/s-0035-1569369.
5. Schoenfeld BJ, Ratamess NA, et al. Effects of different volume-equated resistance training loading strategies on muscular adaptations in well-trained men. J Strength Cond Res2014;28: 2909-2918.
6. Schoenfeld BJ, Wilson JM, et al. Muscular adaptations in low- versus high-load resistance training: A meta-analysis. Eur J Sport Sci2014: 1-10.
7. Schoenfeld BJ, Peterson MD, et al. Effects of Low- Versus High-Load Resistance Training on Muscle Strength and Hypertrophy in Well-Trained Men. J Strength Cond Res2015;29: 2954-2963.
8. Schoenfeld BJ, Contreras B, et al. Differential Effects of Heavy Versus Moderate Loads on Measures of Strength and Hypertrophy in Resistance-Trained Men. J Sports Sci Med2016;15: 715-722.
9. Stone MH and Coulter SP. Strength/endurance effects from three resistance training protocols with women. J Strength Cond Res1994;8: 231-234.
The “strength-endurance continuum” is a widely accepted concept in the field of exercise science. Simply stated, the theory asserts that training in different rep ranges elicits differential effects on muscular adaptations. From a practical standpoint, the continuum can be categorized into three distinct loading zones— heavy, moderate and light— whereby heavy loads (1-5 RM) promote maximal strength gains, moderate loads (6-12 RM) bring about maximal increases in muscle mass, and light loads (15+ RM) produce the greatest improvements in local muscular endurance.
A considerable amount of research has been conducted on the strength-endurance continuum, and there is now good evidence that heavy loads do indeed promote the greatest increases in strength while muscular endurance is optimized with the use of light loads.2,7,9 However, the claim that moderate-rep training is superior for maximizing muscle size has come under scrutiny, with a number of studies showing that training across a wide spectrum of rep ranges can be equally effective from a hypertrophy standpoint.6
A big issue with the body of research on the topic has been a paucity of studies carried out in individuals with resistance-training experience. It is well established that experienced lifters respond differently to training compared to non-lifters. This is due to a “ceiling effect,” whereby gaining muscle becomes progressively more difficult as you get closer to reaching your genetic potential.1
THE STUDY
Several years ago, I published the first study to investigate the effects of different rep ranges on strength and hypertrophy changes in resistance-trained men.5 In brief, the study randomized subjects to either a “bodybuilding-type” routine that trained with moderate reps or a “powerlifting-type” routine that trained heavy. The routines were equated for volume load (i.e., the total amount of weight lifted per session) so that the bodybuilding group performed three sets of 10 reps while the powerlifting group performed seven sets of three reps. Consistent with the “strength-endurance continuum,” the study found that the powerlifting-type routine produced the greatest strength increases. Contrary to the theory, however, both routines produced similar increases in hypertrophy of the biceps brachii.
It must be pointed out that the findings of that study are specific to the respective routines being equated for volume load. While this design helped to rule out potential confounding issues and thus isolate the impact of loading zones on hypertrophy, it is impractical to carry out long-term training with very heavy loads at the volumes used in that study (in fact, the majority of subjects in the powerlifting-type group displayed clear signs of overtraining by study’s end). So the question arises as to whether results would differ if an equal number of sets were performed between heavy and moderate loads?
Recently, I carried out a study that investigated this very topic.8 Here’s the lowdown on what we found.
Nineteen college-aged men, who had been lifting consistently for at least a year and regularly performed both the squat and bench press, were recruited to participate in the study. Subjects were randomized to either a group that trained in a heavy loading range of two to four repetitions per set (HEAVY) or a group that trained in a moderate loading range of eight to 12 repetitions per set (MODERATE). All other aspects of the routines were controlled between groups. The training protocol consisted of seven exercises that worked all the major muscles of the body each session, with three sets performed per exercise. Training was carried out on three non-consecutive days per week for eight weeks. Subjects were instructed to maintain their normal daily nutritional intake, and no differences in either calories or macronutrient consumption were found between groups over the course of the study.
Testing was carried out pre- and post-study. Ultrasound was used to measure muscle growth of the elbow flexors, elbow extensors and quads. Upper and lower body strength was assessed via the one-repetition maximum (RM) in the squat and bench press. Upper body local muscular endurance was determined by assessing the subject’s initial 1RM in the bench press for as many repetitions as possible to muscular failure.
Results showed that overall muscle growth was greater when performing a moderate-rep routine compared to heavy lifting. Increases in thickness of the elbow flexors (i.e., biceps brachii and brachialis) favored the use of moderate reps (~5% versus ~3%), while gains in the quads were markedly greater with moderate-rep training (10% versus 4%). Interestingly, growth of the triceps was similar between groups.
On the other hand, strength gains were superior for heavy-load training. In particular, improvements in the 1RM squat were decidedly greater in HEAVY compared to MODERATE (29% versus 16%). Changes in the 1RM bench press also favored the use of heavy weights, although the differences between HEAVY and MODERATE were less substantial (14% versus 10%). Muscle endurance increases were similar between rep ranges.
IN CONCLUSION
At face value, the findings lend support to the concept of a strength-endurance continuum and reaffirms that a “hypertrophy range” of six to 12 reps per set maximizes muscle growth. This is consistent with what gym bros have been preaching for years. However, when the results are considered in conjunction with my previous study that equated volume load, an interesting hypothesis emerges. Since strength gains were greater with heavy loads in both studies, it can be concluded that low-rep training is best for maximizing strength regardless of volume load. On the other hand, since the previous study showed no differences in hypertrophy between conditions when volume load was equated, it can be inferred that volume load is a greater driver of muscle growth irrespective of the rep range. In other words, strength is maximized even with lower training volumes, provided heavy loads are used, but higher volumes are needed to maximize gains in size regardless of whether you train with moderate or heavy weights.
Take-home point: It appears that total training volume is the primary driver of muscle growth.
The study had several limitations including a relatively small sample size, the use of a single-site measurement for muscle growth on each of the respective muscles, and possible confounding from the “novelty factor” (i.e., virtually all the subjects trained with moderate loads, so it is possible that the novel stimulus for those in the heavy-load group might have impacted results). These issues must be taken into account when attempting to draw evidence-based conclusions. Most importantly, one study is never the be-all and end-all when it comes to answering questions on an applied science topic. Rather, each study should be considered a piece in a puzzle that lends support to a given theory; with respect to the strength-endurance continuum, more research is certainly needed to fully understand its practical implications for program design. For now, though, the evidence suggests to train heavy if your goal is maximal strength, and to focus on accumulating volume for maximal gains in muscle mass. Moreover, there is evidence that training across the full spectrum of rep ranges might promote the greatest increases in growth3,4, so systematically vary your loading zones over time.
Brad Schoenfeld, Ph.D., CSCS, FNSCA is widely regarded as one of the leading authorities on training for muscle development and fat loss. He has published over 100 peer-reviewed studies on various exercise- and nutrition-related topics. He is also the author of the best-selling book, The M.A.X. Muscle Plan and the seminal textbook, Science and Development of Muscle Hypertrophy. Check out is website and blog at www.lookgreatnaked.com
References:
1. American College of Sports Medicine. American College of Sports Medicine position stand. Progression models in resistance training for healthy adults. Med Sci Sports Exerc2009;41: 687-708.
2. Campos GER, Luecke TJ, et al. Muscular adaptations in response to three different resistance-training regimens: specificity of repetition maximum training zones. Eur J Appl Physiol 2002;88: 50-60.
3. Ogborn D and Schoenfeld BJ. The role of fber types in muscle hypertrophy: Implications for loading strategies. Strength Cond 2014;J36: 20-25.
4. Schoenfeld BJ, Contreras B, et al. Effects of varied versus constant loading zones on muscular adaptations in well-trained men. Int J Sports Med 2016;DOI: 10.1055/s-0035-1569369.
5. Schoenfeld BJ, Ratamess NA, et al. Effects of different volume-equated resistance training loading strategies on muscular adaptations in well-trained men. J Strength Cond Res2014;28: 2909-2918.
6. Schoenfeld BJ, Wilson JM, et al. Muscular adaptations in low- versus high-load resistance training: A meta-analysis. Eur J Sport Sci2014: 1-10.
7. Schoenfeld BJ, Peterson MD, et al. Effects of Low- Versus High-Load Resistance Training on Muscle Strength and Hypertrophy in Well-Trained Men. J Strength Cond Res2015;29: 2954-2963.
8. Schoenfeld BJ, Contreras B, et al. Differential Effects of Heavy Versus Moderate Loads on Measures of Strength and Hypertrophy in Resistance-Trained Men. J Sports Sci Med2016;15: 715-722.
9. Stone MH and Coulter SP. Strength/endurance effects from three resistance training protocols with women. J Strength Cond Res1994;8: 231-234.
