Best Rep Range to Build Muscle: Where is the Science Today?

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Upon searching on the internet for the ideal rep range to train in for hypertrophy, you’ll likely come across many tables that all lay down rep ranges the same way:

Strength: 1-5 reps at a high load
Hypertrophy: 6-12 reps at a moderate load
Muscular endurance: 12+ reps at a low load

It is important to note that the number of reps decreases as the load increases. Another way to examine this question is whether both high and low loads can elicit hypertrophy adaptations and to what degree.

The recommendations above have been staples in exercise science textbooks. They even align with the American College of Sports Medicine’s 2009 stance on resistance training (1). However, much has changed since 2009! In the last several years, an emerging body of literature has evolved our understanding of the ideal rep range for hypertrophy training. Let’s explore the research!

The Case for High Reps/Low Load (Up to 35!)

A 2021 review examined the literature on different rep schemes for hypertrophy training and found that a wide range of rep schemes can be effective, with the lowest effective load of 30% 1RM (8).

In a study, eighteen resistance-trained men were assigned to either a high-rep, low-load group (25-35 reps) or a low-rep, high-load group (8-12 reps) (9). All other training variables were equated in the eight-week program.

It is important to note that the load selected for both groups was trained to failure at the end of each set. At the end of the program, the elbow flexor, elbow extensor, and quad sizes were measured.

The results found that the high-rep and low-rep groups had similar hypertrophy adaptations. However, the study acknowledged that it is still unclear whether these results will continue beyond the eight-week program.

Many other studies and meta-analyses (studies that study multiple studies) continue to find that muscle hypertrophy can be achieved at many different volume-equated loads (2, 5, 9).

If High Rep Sets Work Just as Well, Which Muscle Fibers Are Being Adapted?

Low-intensity activity typically adapts type I muscle fibers, while moderate to high-intensity activity adapts type II (6). Since the benefits of hypertrophy training include growing the size of the type II fibers, will high-rep sets target only the type I fibers? Will this decrease muscle size potential since type I fibers don’t grow as big?

A meta-analysis examined these questions and found no significant differences between low-rep and high-rep on hypertrophy of type I or II fibers in the lower body, as long as each set was taken to failure (3). Their results had a large confidence interval or margin of error, so they recommended that more research be done before conclusively saying that one rep scheme is better than another (3).

Limitations of High Rep Training

You may think it’s a great idea to start doing 30-rep sets now. Compared to low-rep sets (8-12), high-rep (20+) sets cause more discomfort, a higher rating of perceived exertion, and less enjoyment for most people (3 8, 9). Instead of shifting your entire program to 20+ rep sets, you could make the last set of a muscle group’s workout a high-rep set or something similar.

Is Training to Failure Necessary for Hypertrophy, Regardless of the Rep Scheme?

One standard variable in many research articles on different load schemes was taking each set to failure. High rep sets will only be effective for hypertrophy if taking each set to failure or near failure. So make sure you know what point failure is by doing a set to failure every once in a while so that you start at a weight that will provide proper stimulus.

While training to failure is no longer as necessary when training at high load/low reps, it is essential to train to failure or very close to failure with lighter loads/higher reps (4).

Don’t Be Afraid To Change It Up

Training in the 6-12 rep range for hypertrophy can still yield great results, so don’t think you’ve been wasting your time if that’s the range you train in. However, don’t be shy about increasing those reps if you feel plateaued in your progress or need to change it up. Don’t worry. Your muscles won’t waste away if you go over 12 reps if you are near failure at the end of each set.

Muscle hypertrophy can be achieved with a large spectrum of rep ranges (2, 7). If strength is your primary goal, lift those high-load/low-rep sets (4)!

Sources

American College of Sports Medicine. American College of Sports Medicine position stand. Progression models in resistance training for healthy adults. Med Sci Sports Exerc. 2009 Mar;41(3):687-708. doi: 10.1249/MSS.0b013e3181915670. PMID: 19204579.
Carvalho L, Junior RM, Barreira J, Schoenfeld BJ, Orazem J, Barroso R. Muscle hypertrophy and strength gains after resistance training with different volume-matched loads: a systematic review and meta-analysis. Appl Physiol Nutr Metab. 2022 Apr;47(4):357-368. doi: 10.1139/apnm-2021-0515. Epub 2022 Jan 11. PMID: 35015560.
Grgic J. The Effects of Low-Load Vs. High-Load Resistance Training on Muscle Fiber Hypertrophy: A Meta-Analysis. J Hum Kinet. 2020 Aug 31;74:51-58. doi: 10.2478/hukin-2020-0013. PMID: 33312275; PMCID: PMC7706639.
Lasevicius T, Schoenfeld BJ, Silva-Batista C, Barros TS, Aihara AY, Brendon H, Longo AR, Tricoli V, Peres BA, Teixeira EL. Muscle Failure Promotes Greater Muscle Hypertrophy in Low-Load but Not in High-Load Resistance Training. J Strength Cond Res. 2022 Feb 1;36(2):346-351. doi: 10.1519/JSC.0000000000003454. PMID: 31895290.
Morton RW, Oikawa SY, Wavell CG, Mazara N, McGlory C, Quadrilatero J, Baechler BL, Baker SK, Phillips SM. Neither load nor systemic hormones determine resistance training-mediated hypertrophy or strength gains in resistance-trained young men. J Appl Physiol (1985). 2016 Jul 1;121(1):129-38. doi: 10.1152/japplphysiol.00154.2016. Epub 2016 May 12. PMID: 27174923; PMCID: PMC4967245.
Plotkin DL, Roberts MD, Haun CT, Schoenfeld BJ. Muscle Fiber Type Transitions with Exercise Training: Shifting Perspectives. Sports (Basel). 2021 Sep 10;9(9):127. doi: 10.3390/sports9090127. PMID: 34564332; PMCID: PMC8473039.
Schoenfeld BJ, Grgic J, Ogborn D, Krieger JW. Strength and Hypertrophy Adaptations Between Low- vs. High-Load Resistance Training: A Systematic Review and Meta-analysis. J Strength Cond Res. 2017 Dec;31(12):3508-3523. doi: 10.1519/JSC.0000000000002200. PMID: 28834797.
Schoenfeld BJ, Grgic J, Van Every DW, Plotkin DL. Loading Recommendations for Muscle Strength, Hypertrophy, and Local Endurance: A Re-Examination of the Repetition Continuum. Sports (Basel). 2021 Feb 22;9(2):32. doi: 10.3390/sports9020032. PMID: 33671664; PMCID: PMC7927075.
Schoenfeld BJ, Peterson MD, Ogborn D, Contreras B, Sonmez GT. Effects of Low- vs. High-Load Resistance Training on Muscle Strength and Hypertrophy in Well-Trained Men. J Strength Cond Res. 2015 Oct;29(10):2954-63. doi: 10.1519/JSC.0000000000000958. PMID: 25853914.