HYPERTROPHY

Kassiano, W., et al. (2023). Journal of Strength & Conditioning Research, 37(9), 1746-1753.

Calf raises trained through a partial range of motion at long muscle length grew the medial gastrocnemius 15.2%, versus 6.7% for full range of motion, over the same training period.

Maeo, S., et al. (2021). Medicine and Science in Sports and Exercise, 53(4), 825-837.

Seated leg curls (long hamstring length at the working portion) grew the hamstrings 14%, versus 9% for prone leg curls (short muscle length), over 12 weeks.

Maeo, S., et al. (2023). European Journal of Sport Science, 23(7), 1240-1250.

Triceps cable extensions done in an overhead arm position (biases the long head into a longer stretched position at the shoulder) produced substantially greater long-head triceps growth than the same exercise in a neutral arm position, both performed through full range of motion. An arm-position manipulation, not a partial-vs-full-ROM comparison, but it supports the same underlying principle.

Pelland, J. C., Remmert, J. F., Robinson, Z. P., Hinson, S. R., Zourdos, M. C. (2026). Sports Medicine, 56(2), 481-505.

Meta-regression across 67 studies (2,058 participants) modeling weekly set volume and training frequency as separate variables, using a refined method that credited each set as direct, fractional, or indirect depending on how specifically it targeted the muscle being measured. Muscle size and strength both kept increasing as weekly volume went up, though with diminishing returns at higher set counts. Frequency showed a similar increasing-with-diminishing-returns pattern for strength, but its effect on hypertrophy specifically was far less consistent, weekly volume is the variable that matters most for growth.

Schoenfeld, B. J., Ogborn, D., Krieger, J. W. (2017). Journal of Sports Sciences, 35(11), 1073-1082.

The classic, widely-cited volume meta-analysis: 34 treatment groups from 15 studies, categorizing weekly sets per muscle group into low (under 5), moderate (5-9), and high (10+) volume groups. Muscle growth increased with volume across all three categories, with the biggest jump in hypertrophy showing up between the moderate and high groups, favorable results consistently showed up above roughly 9-10 weekly sets per muscle group. Doesn't identify a hard ceiling, higher volumes weren't tested extensively in the available studies at the time, but establishes the general shape of the dose-response curve behind this site's volume guidance.

Coskun, I. A., et al. (2026). BMC Sports Science, Medicine and Rehabilitation.

34 sedentary men randomized to a single set per exercise, 3 sets per exercise, or a non-training control group, 7 exercises, twice weekly, 8 weeks. Both training groups grew real muscle and got stronger than control, single-set training is not nothing, leg muscle cross-sectional area increased roughly 6-8% on one set per exercise alone. But 3 sets still won outright: 11.3% CSA growth versus the single-set group's 6-8%, plus larger strength gains (bench press +19.8%, squat +14.8%). A direct floor-vs-more test: a single set genuinely works, it just isn't the ceiling.

Robinson, Z. P., Pelland, J. C., Remmert, J. F., Refalo, M. C., Jukic, I., Steele, J., Zourdos, M. C. (2024). Sports Medicine, 54(9), 2209-2231.

Meta-regression found muscle hypertrophy meaningfully improved the closer working sets were taken to failure (lower reps in reserve), with growth declining more steeply once sets stopped well short of failure. Strength gains showed no meaningful relationship with proximity to failure at all, similar results across a wide range of reps in reserve. Training close to failure matters for growth, it doesn't matter much for getting stronger.

Hermann, T., Mohan, A. E., Enes, A., Sapuppo, M., Piñero, A., Zamanzadeh, A., Roberts, M., Coleman, M., Korakakis, P. A., Wolf, M., Refalo, M., Swinton, P. A., Schoenfeld, B. J. (2025). Medicine and Science in Sports and Exercise, 57(9), 2021-2031.

42 trained men and women did a single working set per exercise (9 exercises, all major muscle groups, twice weekly for 8 weeks), randomized to either train every set to true failure or stop at 2 reps in reserve. Training to failure produced slightly greater hypertrophy and slightly greater muscular endurance than 2-RIR, while strength gains came out similar between the two groups. A direct single-set test of the same pattern the Robinson et al. 2024 meta-regression found: failure helps growth a bit, it doesn't meaningfully help strength.

Robinson, Z., Macarilla, C., Juber, M., Cerminaro, R., Benitez, B., Pelland, J., Remmert, J., John, T., Hinson, S., Dinh, S., Elkins, E., Canteri, L., Meehan, C., Helms, E., Zourdos, M. (2025). International Journal of Strength and Conditioning, 5(1).

38 trained men split into 4 groups over 8 weeks: 4-6 RIR, 1-3 RIR, 0-3 RIR (final set only to failure), or every set to true failure (0 RIR), tracking squat/bench strength, muscle thickness, and fatigue (subjective soreness plus blood biomarkers for muscle damage). Strength gains were comparable between the 4-6 and 1-3 RIR groups, with slightly worse outcomes in the two failure-based groups. Hypertrophy data was too variable to draw a strong conclusion either way. The genuine surprise: fatigue and soreness markers were largely comparable across all four groups, no strong evidence that training closer to failure accumulates meaningfully more fatigue over 8 weeks, contrary to what most lifters (and most training programs) assume.

Augustin, F., Piñero, A., Enes, A., Mohan, A. E., Sapuppo, M., Coleman, M., Wolf, M., Androulakis Korakakis, P., Swinton, P. A., Nippard, J., Schoenfeld, B. J. (2025). International Journal of Exercise Science, 18(3), 329-342.

8-week trial comparing strict form against deliberately "cheated" reps (momentum, body swinging, leg drive) on biceps curls and triceps pushdowns trained to failure. The cheat-rep condition let lifters move roughly double the total weekly volume load, but produced no meaningful difference in muscle growth versus strict form. The authors still flagged a real, separate injury-risk concern from persistent momentum use on muscles, tendons, and ligaments, something an 8-week study in standard exercises through a normal range of motion wasn't positioned to rule out.

Sola, O. M., Christensen, D. L., Martin, A. W. (1973). Experimental Neurology, 41, 76-100.

A classic, genuinely extreme animal model: researchers attached a weight to one wing of a chicken, holding a back muscle (the anterior latissimus dorsi) in a chronic, continuous stretch, day and night, for weeks straight, not intermittent training sets. The result was dramatic hypertrophy plus real hyperplasia, a measured 16% increase in the actual number of muscle fibers, and this happened even in muscle that had been surgically denervated. A fascinating demonstration that hyperplasia is mechanically possible under extreme conditions, but nothing like resistance training: constant passive stretch with no contraction, not a stimulus any human would tolerate or want.

Barton, N. V., Gowda, H. N., Dankel, S. J. (2025). Journal of Sports Medicine and Physical Fitness, 65.

Meta-analysis pooling 11 studies (biceps brachii and vastus lateralis, the two muscles hyperplasia research has actually measured) found resistance exercise did not meaningfully change the estimated number of muscle fibers, a 95% confidence interval crossing zero. Training experience, program length (up to 6 months), and which muscle group was trained didn't change that result. The direct answer to whether ordinary resistance training makes new muscle fibers: no, not to any meaningful extent, growth from lifting is fiber enlargement, not fiber creation.

Velloso, C. P. (2008). British Journal of Pharmacology, 154(3), 557-568.

Review establishing that the number of muscle fibers in a muscle is fixed during the perinatal period, and that an increase in muscle size in adulthood comes from fiber cross-sectional area growing (hypertrophy), not from new fibers forming. Growth hormone and IGF-I drive their muscle-building effect by causing satellite cells to fuse with already-existing fibers, adding nuclei that support a bigger fiber, not by creating new fibers. The mechanistic case against the common gym rumor that growth hormone use causes hyperplasia: it doesn't, it just supercharges the same fiber-enlargement process normal training uses.

Maeo, S., Balshaw, T. G., März, B., Zhou, Z., Haug, B., Martin, N. R. W., Maffulli, N., Folland, J. P. (2024). Medicine and Science in Sports and Exercise, 56(10), 1906-1915.

Cross-sectional comparison of 16 long-term resistance-trained men (5.9 ± 3.5 years' experience) against 13 untrained men found the trained group's biceps were 70% larger and, measured via muscle biopsy, contained 34% more muscle fibers in cross-section, on top of larger individual fibers with denser myofibril packing. A striking number, but the design can't establish cause: it compares two groups at a single point in time, so it can't rule out that people who already had more fibers were more likely to become successful long-term lifters in the first place (a selection effect) rather than years of training itself adding fibers. The field still treats human training-induced hyperplasia as genuinely unresolved, this reopens the question rather than closing it, it doesn't overturn the controlled evidence above finding no fiber-number change over shorter, directly-tracked training periods.

Haugen, M. E., Vårvik, F. T., Larsen, S., Haugen, A. S., van den Tillaar, R., Bjørnsen, T. (2023). BMC Sports Science, Medicine and Rehabilitation, 15, 103.

Meta-analysis of 13 studies (1,016 participants) comparing free-weight against machine-based resistance training. Each modality showed a testing-specificity effect (free-weight training produced better results on free-weight strength tests, machines showed a similar tendency on machine tests), but in a direct, apples-to-apples comparison of training outcomes, there was no meaningful difference between free-weight and machine training for strength, jump performance, or muscle hypertrophy. When load and volume are matched, machines aren't an inferior hypertrophy tool, the choice comes down to preference and goals, not growth potential.

Anderson, K. G., Behm, D. G. (2004). Journal of Strength and Conditioning Research, 18(3), 637-640.

Measured force output and muscle activation (EMG) for the pectoralis major, anterior deltoid, triceps, latissimus dorsi, and rectus abdominis under stable versus unstable conditions. Maximum force output under instability was roughly 60% lower than under stable conditions, even though overall EMG activity in the target muscles didn't differ significantly between conditions. Instability doesn't necessarily reduce how hard the target muscle works per se, but it sharply limits how much force and load you can actually apply, which matters directly for progressive overload.

Schoenfeld, B. J., Pope, Z. K., Benik, F. M., Hester, G. M., Sellers, J., Nooner, J. L., Schnaiter, J. A., Bond-Williams, K. E., Carter, A. S., Ross, C. L., Just, B. L., Henselmans, M., Krieger, J. W. (2016). Journal of Strength and Conditioning Research, 30(7), 1805-1812.

21 resistance-trained men trained 3x/week for 8 weeks with identical programming (7 exercises, 3 sets of 8-12 reps) except rest between sets: 1 minute versus 3 minutes. The 3-minute group's quad thickness grew roughly double the 1-minute group's (13.3% vs 6.9%), alongside meaningfully bigger 1RM strength gains on bench and squat. A real, substantial difference from rest length alone, on otherwise identical training. Broader meta-analytic evidence since this trial shows a smaller, less consistent hypertrophy edge from longer rest on average (strength/power benefits more reliably), with the leading explanation being that longer rest preserves more of your strength set-to-set, it's that preserved training output doing the work, not rest itself.

Andrews, M. H., Pai, A. S., Gurchiek, R. D., et al. (2024). Journal of Sport and Health Science, 14, 100996.

12 healthy adults did 9 weeks of Nordic hamstring exercise (eccentric-only, 3x/week), with sarcomere number measured directly inside living muscle tissue via second harmonic generation microendoscopy, not estimated. Serial sarcomere number (sarcomeres added end-to-end along the fiber, distinct from fibers getting thicker) increased 25% in the central biceps femoris and 49% in the distal region, alongside a 33% fascicle length increase, an 8% muscle volume increase, and a 40% strength increase. After 3 weeks of detraining, sarcomere number and fascicle length both declined, though not fully back to baseline. The first direct, unambiguous demonstration in humans that deliberate training can add real sarcomeres in series, not just make existing muscle bigger.

Blazevich, A. J., Herzog, W., Nunes, J. P. (2025). Journal of Sport and Health Science, 14, 101073.

A historical review plus a meta-analysis (mostly animal data) directly testing what actually triggers serial sarcomere addition. Conclusion: high active or passive muscle force applied at long fiber length appears to be the real trigger, not eccentric muscle action itself. In their meta-analysis, eccentric resistance training alone showed a negligible, statistically null effect on sarcomere number in animal models (a 1% change, p = 0.449). The authors explicitly note too few human studies exist to draw firm conclusions in people. A genuinely provocative claim: it may be training a muscle at long, stretched lengths under load that matters, not the eccentric contraction itself, which lines up closely with SEHT's own stretch-position philosophy even though the two are separate lines of research.

Power, G. A., Franchi, M. V., Hinks, A. (2025). Journal of Sport and Health Science, 15, 101089.

A direct rebuttal to the Blazevich et al. 2025 review above. Argues the meta-analysis it responds to pooled in studies that weren't actually optimized to detect sarcomerogenesis (too-short training durations, poorly timed muscle activation, dysfunctional aged animals) alongside well-designed ones, diluting a real effect, and that it excluded muscles showing larger responses based on limited measurement evidence. When Power's team reran the analysis using only well-designed eccentric protocols, the effect sizes were moderate-to-large (0.76 for downhill running, 1.05 for electrical stimulation), not null. A live, current scientific disagreement, not a settled question, both sides publishing in the same journal within months of each other.

Hinks, A., Hawke, T. J., Franchi, M. V., Power, G. A. (2023). Journal of Applied Physiology, 135(2), 375-393.

Review covering why serial sarcomere number matters for real-world muscle function (force production across a wider range of motion, injury resilience, especially in the hamstrings) and what actually regulates it at the molecular level: mechanotransduction pathways involving IGF-1/Akt/mTOR signaling and myostatin (a growth suppressor whose inhibition is linked to stretch-induced sarcomere addition). These pathways are real drug targets in muscle-wasting disease research (myostatin inhibitors, activin receptor blockers), but remain investigational treatments for disease and injury, not an available performance intervention for a healthy lifter. Also notes serial sarcomerogenesis still occurs with training in older age, but to a smaller degree than in young muscle, likely due to age-related blunting of these same signaling pathways.