The Evolving Science of Rep Ranges for Hypertrophy: Challenging the 6–12 Rep Dogma
Brandon Hyatt, MS, CSCS
August 02, 2024 • 4 min read
Historically, the 6–12 repetition (rep) range was considered the foundational guideline for hypertrophy training; however, contemporary research challenges this long-held notion.
The Traditional Rep-Load Framework
A search for the optimal rep range for hypertrophy often yields standardized tables categorizing training goals by rep-load pairings:
Strength: 1–5 reps with high load
Hypertrophy: 6–12 reps with moderate load
Muscular endurance: ≥12 reps with low load
Notably, rep count inversely correlates with load magnitude. A more nuanced framing of this topic asks: Can both high- and low-load training induce hypertrophy, and if so, to similar extents?
From Textbook Dogma to Contemporary Evidence
These guidelines have long been fixtures in exercise science curricula and align with the American College of Sports Medicine’s (ACSM) 2009 position stand on resistance training (1). Yet, the landscape has shifted dramatically since 2009—an expanding body of research has refined our comprehension of the optimal rep range for hypertrophy. Let’s dissect the evidence.
The Case for High-Rep, Low-Load Training (Up to 35 Reps!)
A 2021 systematic review analyzed studies on rep schemes for hypertrophy and concluded that a broad spectrum of rep ranges is effective, with the minimum effective load identified as 30% of one-repetition maximum (1RM) (8).
In one study, 18 resistance-trained men were randomized 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 (e.g., volume, rest periods) were standardized across an 8-week intervention. Critically, both groups trained each set to muscular failure. Post-intervention measurements of elbow flexor, elbow extensor, and quadriceps cross-sectional area revealed comparable hypertrophy adaptations between groups. The authors noted, however, that the long-term sustainability of these findings (beyond 8 weeks) remains unestablished.
Numerous additional studies and meta-analyses—systematic syntheses of existing research—consistently demonstrate that hypertrophy can be achieved across a wide range of volume-matched loads (2, 5, 9).
High-Rep Sets and Muscle Fiber Specificity
Low-intensity exercise primarily stimulates type I (slow-twitch) muscle fibers, whereas moderate-to-high-intensity exercise targets type II (fast-twitch) fibers (6). Given that hypertrophy training prioritizes type II fiber growth—due to their greater hypertrophic potential—questions arise:
Do high-rep sets only activate type I fibers?
Would this limit muscle growth, as type I fibers exhibit less growth capacity than type II?
A meta-analysis addressing these questions found no statistically significant differences in type I or type II fiber hypertrophy in the lower body between low-rep and high-rep training—provided sets were taken to failure (3). The authors noted a wide confidence interval (i.e., greater uncertainty) in their findings, advocating for additional research before definitive conclusions can be drawn about the superiority of one rep scheme over another (3).
Limitations of High-Rep Training
While the idea of adopting 30-rep sets may seem appealing, high-rep (≥20) sets are associated with:
Greater discomfort
Higher ratings of perceived exertion (RPE)
Reduced enjoyment
...for most individuals compared to moderate-rep (8–12) sets (3, 8, 9).
Rather than overhauling an entire program to include ≥20-rep sets, a more practical approach is to integrate high-rep work selectively—for example, using a high-rep set as the final set for a given muscle group.
Is Training to Failure Necessary for Hypertrophy?
A consistent methodological feature across many load-scheme studies is the inclusion of training to failure. For high-rep sets to induce hypertrophy, training to failure (or within 1–2 reps of failure) is non-negotiable. To ensure appropriate load selection, individuals should periodically perform sets to failure to calibrate their understanding of failure and select weights that provide sufficient stimulus.
Notably:
Failure is less critical for high-load, low-rep training.
Failure is indispensable for low-load, high-rep training—where training to failure (or near-failure) is essential to elicit adaptive responses (4).
Don’t Fear Variation
Training in the 6–12 rep range for hypertrophy remains effective—so if that’s your current approach, you haven’t wasted time. However, if you’re plateaued or seeking variety, don’t hesitate to increase rep counts. Rest assured: exceeding 12 reps will not cause muscle loss—provided you train to near-failure.
Hypertrophy is achievable across a broad spectrum of rep ranges (2, 7). If strength is your primary goal, high-load, low-rep training remains optimal (4).
References
American College of Sports Medicine. American College of Sports Medicine Position Stand: Progression Models in Resistance Training for Healthy Adults. Medicine & Science in Sports & Exercise. 2009;41(3):687–708. doi:10.1249/MSS.0b013e3181915670
Carvalho L, et al. Muscle Hypertrophy and Strength Gains After Resistance Training With Different Volume-Matched Loads: A Systematic Review and Meta-Analysis. Applied Physiology, Nutrition, and Metabolism. 2022;47(4):357–368. doi:10.1139/apnm-2021-0515
Grgic J. The Effects of Low-Load Vs. High-Load Resistance Training on Muscle Fiber Hypertrophy: A Meta-Analysis. Journal of Human Kinetics. 2020;74:51–58. doi:10.2478/hukin-2020-0013
Lasevicius T, et al. Muscle Failure Promotes Greater Muscle Hypertrophy in Low-Load but Not in High-Load Resistance Training. Journal of Strength and Conditioning Research. 2022;36(2):346–351. doi:10.1519/JSC.0000000000003454
Morton RW, et al. Neither Load nor Systemic Hormones Determine Resistance Training-Mediated Hypertrophy or Strength Gains in Resistance-Trained Young Men. Journal of Applied Physiology. 2016;121(1):129–138. doi:10.1152/japplphysiol.00154.2016
Plotkin DL, et al. Muscle Fiber Type Transitions With Exercise Training: Shifting Perspectives. Sports. 2021;9(9):127. doi:10.3390/sports9090127
Schoenfeld BJ, et al. Strength and Hypertrophy Adaptations Between Low- vs. High-Load Resistance Training: A Systematic Review and Meta-Analysis. Journal of Strength and Conditioning Research. 2017;31(12):3508–3523. doi:10.1519/JSC.0000000000002200
Schoenfeld BJ, et al. Loading Recommendations for Muscle Strength, Hypertrophy, and Local Endurance: A Re-Examination of the Repetition Continuum. Sports. 2021;9(2):32. doi:10.3390/sports9020032
Schoenfeld BJ, et al. Effects of Low- vs. High-Load Resistance Training on Muscle Strength and Hypertrophy in Well-Trained Men. Journal of Strength and Conditioning Research. 2015;29(10):2954–2963. doi:10.1519/JSC.0000000000000958
