On current evidence, neither wins clearly: in the three direct trials so far, lengthened partials and full range of motion grew about the same amount of muscle346. One earlier trial in untrained women found the stretched partial ahead at some thigh sites2. What does grow less is a partial rep done only in the short, squeezed part of the movement26.
So the useful question is not "partial or full". It is which part of the movement a set spends its time in.
What the terms mean
Range of motion is how far a joint travels in one rep. A full-range rep goes the whole way, for example from a fully bent knee to a straight leg on a leg extension.
A lengthened partial is a rep that covers only the part of the movement where the working muscle is stretched long. On a leg extension that is the bent-knee half. On a biceps curl it is the bottom half, arm nearly straight.
A shortened partial is the opposite: only the part where the muscle is short and squeezed, such as the top of a leg extension.
Two measures of growth come up below. Muscle thickness is the depth of the muscle, usually measured by ultrasound at set points along the limb. Fascicle length is the length of the muscle's fibre bundles, a rough sign of the muscle growing longer rather than only thicker.
In plain terms: "lengthened" and "shortened" describe where in the rep the muscle is working, not how heavy the load is.
What was studied
Six studies frame the question. Three are direct trials of lengthened partials against full range, one compares partial ranges on a single exercise, and two pool many studies.
| Study | Design | Who | How long |
|---|---|---|---|
| Pallarés 2021 | Meta-analysis, 16 studies | Mixed | Varied |
| Pedrosa 2022 | Knee extension, 4 ranges plus control | 45 untrained women | Not in abstract |
| Wolf 2025 | One arm partial, other arm full | 25 trained adults (19 men, 6 women) | 8 weeks |
| Gschneidner 2025 | Randomised across 15 sites | 297 people | 12 weeks |
| Varovic 2025 | Meta-analysis, 12 studies | Young adults | Varied |
| McMahon 2026 | Knee extension, 3 ranges plus control | 45 people (details not in abstract) | 8 weeks |
The Wolf trial is the only one we could read in full. Its lifters had about 5 years of training behind them (4.9 ± 4.1). They trained twice a week, four upper-body exercises per session, four sets each, every set to failure (the point where another rep was impossible)3. Each person's two arms were randomly assigned: one did full reps, the other did half reps from the stretched end3.
What the studies found
Trained lifters, arms. After 8 weeks, biceps and triceps thickness grew by about the same amount on both arms3. The estimated differences at four measurement sites ran from −0.23 mm to 0.82 mm, and every 95% credible interval crossed zero3. A credible interval is the range the true difference most likely falls in. Here that range included "no difference" every time.
Difference in arm muscle growth, full range minus lengthened partials · mm
For scale, triceps thickness at one site went from 41.5 to 44.1 mm with partials and from 41.3 to 44.4 mm with full reps3. Both arms grew; the gap between them was a fraction of a millimetre.
A large multi-gym trial. The Gschneidner trial randomised 163 people to lengthened partials and 134 to full range, training for 12 weeks at 15 sites4. The estimated difference in thigh muscle area was 0 and in arm muscle area −0.032. The authors judged the two "practically equivalent", although with their strict statistical threshold they could not formally confirm equivalence4.
Knee extension, light stretched partial vs heavy full range. In the 2026 trial, one group trained only the bent-knee part (40–90° of knee bend) with 55% of their one-rep max, the heaviest load they could lift once. The full-range group (0–90°) and a shortened-partial group (0–50°) used 80%6. Growth in thickness of the outer quad (vastus lateralis) did not differ between the lengthened-partial and full-range groups at any of the three sites measured. Both grew more than the shortened partial at some sites6. The lengthened partial also increased fascicle length more than full range at two of three sites6.
Untrained women, knee extension. In an earlier trial of 45 untrained women, the group that trained only the initial, bent-knee part of the movement had greater relative growth than the full-range group at the 50%, 60% and 70% sites along the thigh2. The group training only the final, straight-leg part changed about as much as the non-training control group at two sites2.
In plain terms: stretched partials matched full range for size in trained and untrained people; squeezed partials trailed both.
The nuance
"Full range beats partials" and "partials match full range" are both true, for different partials. The 2021 meta-analysis found full range produced more lower-body growth than partial range, with an effect size of 0.881. An effect size expresses a difference in units of spread, so 0.88 is large. But that analysis pooled partials of any kind, and the abstract does not split them by where in the movement they were done. The trials that compared stretched and squeezed partials directly found the squeezed one was the weak link26.
Muscle length is not the whole story either. A 2025 meta-analysis of 12 studies compared training at longer against shorter average muscle lengths, measured at points along the muscle5. The differences were small everywhere, with a slight trend favouring longer lengths toward the distal end of the muscle (the end farther from the trunk).
Training at longer vs shorter muscle lengths, by site along the muscle · SMD
The authors add a caution: the "long" and "short" conditions in those studies differed by only about 22% of muscle length on average, so bigger contrasts might show more5.
Equal growth does not mean equal strength. In the Wolf trial, strength over 10 reps on a lat pulldown improved similarly with both methods3. The 2021 meta-analysis found full range produced more strength overall1. The 2026 knee-extension trial did not report strength in its abstract6.
Longer fibre bundles are a proxy. Fascicle length hints at a muscle adding length along its fibres. It is not the same thing as more muscle, and the 2026 abstract does not say how it was measured6.
In plain terms: the stretched part of the movement seems to carry most of the growth signal, and a full rep already includes it.
What this means in practice
This is a description of what the trials did, not a programme. In the trials, both full reps and stretched-half reps were taken close to or to failure, and both grew muscle3. A full-range rep already includes the stretched position, which may be why the two methods keep coming out even.
Some lifters use lengthened partials after full reps run out, to extend a set. None of the trials here tested that pattern directly, so it remains an open question rather than a finding. For how sets and effort fit together, see how many sets per muscle group per week, RIR vs RPE and set types explained. Adding load or reps over time still matters more than rep range; see what progressive overload is.
The studies at a glance
| Study | Who was studied | Key result | Year |
|---|---|---|---|
| Pallarés et al., *Scand J Med Sci Sports*1 | 16 studies pooled | Full range grew more lower-body muscle than partials of any kind (effect size 0.88) | 2021 |
| Pedrosa et al., *Eur J Sport Sci*2 | 45 untrained women, knee extension | Bent-knee partial grew more than full range at 3 thigh sites; straight-leg partial lagged | 2022 |
| Wolf et al., *PeerJ*3 | 25 trained adults, arms, 8 weeks | Arm thickness differences within about 1 mm of zero at all 4 sites | 2025 |
| Gschneidner et al., *J Sports Sci*4 | 297 people, 15 sites, 12 weeks | Arm and thigh muscle area differences near zero | 2025 |
| Varovic et al., *Int J Sports Med*5 | 12 studies, young adults | Trivial differences between longer and shorter muscle lengths | 2025 |
| McMahon et al., *J Strength Cond Res*6 | 45 people, knee extension, 8 weeks | Light stretched partial matched heavy full range for thickness; longer fibre bundles | 2026 |
Limits worth knowing
- Small trials. Most direct comparisons have 25 to 45 people. The largest (297 people) reports an estimated muscle area; its abstract does not describe the method4.
- Few exercises. Two trials used only the knee extension; one used only upper-body exercises.
- Short. Eight to twelve weeks. Nothing here says what happens over years.
- Abstract only for five of six papers. We read the Wolf trial in full; for the others we cite only what the abstract states. The 2026 trial's abstract gives directions of change but no sizes and does not say who the 45 were6.
- Different definitions. "Partial" meant about half the range in one trial and specific degree ranges in others.
- Growth, not appearance or strength. Thickness and area are what was measured.
Latest research
The newest study is the 2026 knee-extension trial, published online in July 20266. It adds one new wrinkle: the stretched-partial group used a clearly lighter load (55% vs 80% of max) and still matched full range for thickness. Its authors argue the finding challenges how resistance training is traditionally programmed. That is their reading. It is one 8-week trial on one muscle, and we have seen only the abstract.
The short version
- Lengthened partials and full range of motion grew about the same muscle in the three direct trials so far.
- Partials in the short, squeezed range grew less in the knee-extension trials.
- The stretched part of a rep seems to matter most, and a full rep includes it.
- Strength may favour full range; the evidence is mixed.
- Trials are small and short, so read this as the current picture, not a final answer.
Educational overview only — not medical advice.
