Which muscles show the clearest hypertrophy benefit from long-length training versus full ROM?

1. Calves: the strongest single signal for long‑length benefit

The most directly supportive single‑muscle finding comes from calf literature: a randomized trial found greater gastrocnemius hypertrophy when calf raises were performed in the initial (long‑muscle‑length) portion of the range of motion compared with training at the final, shortened portion, and this has been repeatedly cited in systematic summaries as evidence that calf training at longer lengths may optimize gastrocnemius growth in young women ^{[1] [4]}.

2. Quadriceps: regional gains favour long‑length or isometric long‑length work, but not uniformly

Multiple studies and a targeted trial comparing long‑length isometric training to full‑ROM isotonic work report preferential increases in particular quadriceps regions (often distal/proximal differences) after long‑length protocols, suggesting long‑length training may preferentially drive regional hypertrophy along the quad’s length, though uncertainty in effect estimates prevents a universal claim that whole‑muscle growth is greater across all conditions ^{[5] [6] [2]}.

3. Upper body: mixed results and often parity between lengthened partials and full ROM

Evidence for upper‑body muscles is more equivocal: within‑limb trials and a recent 8‑week study in trained participants reported that lengthened partials and full‑ROM produced similar hypertrophy for elbow flexors and extensors, and other analyses find trivial-to-small overall differences favoring full ROM, with some subgroups hinting at modest benefits for long‑length partials but without consistent, large effects ^{[7] [3] [8]}.

4. Biceps and triceps: hints, not confirmations

Selective studies and reviews report that biceps curls performed at lengthened partial ROM may produce more hypertrophy than shortened partial ROM and that some partial protocols can match full ROM, but the aggregate evidence does not yet establish a robust, muscle‑wide superiority for long lengths in these upper‑limb muscles—results depend heavily on study design, measure location, and whether the comparison is against short partials or true full ROM ^{[9] [7] [10]}.

5. How to read the mixed meta‑analyses: small effects, regional nuance, and methodological confounds

Systematic reviews and meta‑analyses converge on a few themes: full ROM often shows a modest overall advantage over partial ROM, but when partial ROM is performed at long muscle lengths the advantage can shift towards parity or slight superiority for hypertrophy in targeted muscles; these syntheses repeatedly flag that effects are small-to-moderate, region‑specific, potentially work‑dependent (total work differences can confound results), and sensitive to participants’ training status (novice vs trained) ^{[3] [2] [4]}.

6. Practical reading and limitations of the evidence base

The practical takeaway is that the clearest, reproducible hypertrophy benefit for long‑length training exists for the gastrocnemius and for certain quadriceps regions, while upper‑body results are inconsistent and often equivalent between lengthened partials and full ROM; major limitations across the literature include small sample sizes, regional (not whole‑muscle) measurements, variable control of total work, and a publication ecosystem (blogs and fitness media) that can overemphasize single‑study findings to sell training fads—readers should interpret claims of universal superiority for long‑length training with caution until larger, well‑controlled trials reconcile regional effects and control for workload ^{[1] [3] [11]}.