REF-1158 · Oranchuk et al., 2019 · Scandinavian Journal of Medicine & Science in Sports · Paper · PubMed
Long or short muscle length for isometric holds?
In 26 small trials in non-athletes, long-length holds grew muscle faster (1.16 vs 0.47%/week, 3 studies) and spread strength to more angles; over 9 studies the gap shrank (0.88 vs 0.61).
Oranchuk et al. searched four databases to March 2018 for studies of at least three weeks that compared two or more variants of isometric training. They found 26 (713 participants, 8.4 weeks on average, 3.5 sessions a week).
Three studies compared muscle size after holds at long versus short muscle length; all three favoured long lengths (about 1.16 vs 0.47% muscle size gain per week). Holds at long lengths also raised maximal force at more of the untrained joint angles, while gains at the trained angle were similar either way.
Explosive ("ballistic") intent improved early rapid force and early muscle activation more than slow ramped contractions, while ramped and sustained contractions gave equal or more hypertrophy. Across studies, contraction intensity explained little of the gain in muscle size or maximal force.
Tendon stiffness and size rose only with high-intensity holds (about 90% vs 55% MVC in two calf studies), so the authors set about 70% MVC as the likely threshold. When all nine studies reporting both joint angle and muscle size are pooled, the long-length advantage shrinks to 0.88 vs 0.61% per week and the effect size per week is identical (0.046 vs 0.045).
The authors conclude that isometric training should be done mainly at long muscle lengths, with sustained contractions for morphology, ballistic intent for rapid force, and at least 70% MVC for tendon.
Included studies
Search: MEDLINE, SPORTDiscus, PubMed and CINAHL, inception to March 2018; English peer-reviewed papers and doctoral dissertations; at least two isometric variants compared; at least 3 weeks; excluded small muscles (fingers, toes), cardiovascular outcomes, blood flow restriction, vibration and electrical stimulation. Quality scored 0-20 on a scale adapted from Brughelli; mean 14.3/20 (range 10-18).
Participants: 713 (463 male, 250 female), mean age 24.3 years; mean sample 27.4 ± 28.1 (4-120). 16/26 studies untrained, the rest active or recreational.
Training: 8.4 ± 3.6 weeks (3-14), 3.5 ± 0.96 sessions a week, 28.6 ± 13.2 sessions; volume equated in 17/26; a non-exercise control in 10/26; 23/26 single-joint, 2 closed-chain.
Kind of isometric: almost all overcoming ("pushing") contractions against a dynamometer or fixed lever. Variables compared: joint angle / muscle length (10 studies, 8 knee extensor, 2 elbow flexor; "long" = more than 70 degrees of knee flexion, "short" = 70 or less), intensity (6 studies, 25% to 100% MVC), intent (ramped vs ballistic, 5 studies), total volume, contraction duration (1 to 30 s), rest between contractions, periodisation.
Contraction prescriptions in the cited trials (examples): 40 x 3-s at 75% MVC vs 40 x 1-s explosive (Balshaw REF-1161); 4 x 30-s vs 4 x 10 x 3-s maximal; 20-s vs ~1-s holds load-equated; ~55% vs ~90% MVC plantar flexion for 14 weeks; 25%, 50% or 100% MVC for 15 sessions.
Not included: holding ("yielding") vs pushing training, which the authors flag as unstudied in the long term (see REF-1163).
Key Results
| Comparison (k = studies) | Long length / high / ballistic | Short length / low / ramped | Source |
|---|---|---|---|
| Muscle size, long vs short muscle length (k=3) | 1.16 ± 0.46%/week, 0.067 ES/week | 0.47 ± 0.48%/week, 0.032 ES/week | full text, Figure 2 |
| Muscle size, long vs short, all studies reporting angle (k=9) | 0.88 ± 0.8%/week, 0.046 ES/week | 0.61 ± 0.42%/week, 0.045 ES/week | full text, Supplementary 3 |
| Muscle size, abstract ranges | 0.86-1.69%/week (ES 0.03-0.09/week) | 0.08-0.83%/week | abstract |
| Muscle size, intensity (>70% vs ≤70% MVC) | 0.70 ± 0.55%/week | 0.77 ± 0.26%/week | full text, Figure 3 |
| Maximal isometric force, trained angle (k=7) | no difference long vs short | full text | |
| Transfer to untrained angles | long length: gains at 7, 8 and 6/6 tested angles in three studies | short length: 4, 5 and 2 angles | full text (Bandy, Kubo, Bogdanis) |
| Rapid force (RFD), ballistic vs ramped | 1.2-13.4%/week (ES 0.05-0.61) | 1.01-8.13%/week (ES 0.06-0.22) | abstract |
| Tendon CSA and stiffness, ~90% vs ~55% MVC, 14 weeks (k=2) | +17.1 to 36%, p < 0.05 | +5.2 to 7.9%, p > 0.05 | full text |
| Tendon stiffness, long vs short length (k=1, Kubo) | +50.9% | +6.7% | between groups p = 0.021 |
| Quadriceps volume, sustained 3-s vs explosive 1-s (k=1, Balshaw) | 8.1% sustained | 2.6% explosive | between groups p < 0.05 |
| Dynamic outcomes (k=1, Bogdanis leg press) | 1RM squat +11.9%, CMJ +8.4% (long) | +9.6%, +7.2% (short) | full text |
Across all studies, significant muscle-size gains were 5-19.7% (0.84%/week, 9 studies) and significant maximal isometric force gains 8-60.3% (4.34%/week, 14 studies).
Mechanisms
Measured (in the included trials): EMG amplitude rose by more and over more joint angles after long-length training in two studies (one study showed the reverse); ballistic training raised early EMG (first 100-150 ms) and voluntary activation, ramped training raised EMG at peak force.
Authors' interpretation: long-length holds produce more mechanical tension, muscle damage, blood-flow occlusion, oxygen use and metabolite build-up than short-length holds, which drives the hypertrophy advantage; sustained contractions add metabolic stress at equal time under tension.
Authors' interpretation: tendon responds to a threshold of strain, so low-intensity holds (around 55% MVC) leave stiffness unchanged even when total load is matched.
Authors' interpretation: stiffer tendons after long-length training should shorten electromechanical delay and help rapid force. Inference, not measured in the reviewed trials.
Inference: the pooled per-week numbers mix studies of different muscles, volumes and durations; they describe tendencies, not a dose-response.
Practical Application
Long or short muscle length for isometric holds? In 26 small trials in non-athletes, long-length holds grew muscle faster (1.16 vs 0.47%/week, 3 studies) and spread strength to more angles; over 9 studies the gap shrank (0.88 vs 0.61).
The trained-angle strength gain was the same either way. Use long lengths when size or strength through the range is the goal; use the specific angle only when a sticking point is the target.
For tendon, intensity is the variable to protect. Holds at about 90% MVC thickened and stiffened the Achilles tendon over 14 weeks, about 55% did not; the authors put the floor near 70% MVC. For a runner's Achilles or patellar tendon this matches REF-517; the threshold is the authors' estimate from two calf studies, not a tested cut-off.
For rapid force, contract "as fast and hard as possible". Only the ballistic groups improved force in the first 50-100 ms; slow ramped holds did not, even when they built more maximal force (see REF-1161).
For size and maximal force, intensity mattered little in these studies; volume, contraction duration and muscle length mattered more. The authors suggest progressing holds by lengthening contractions, adding volume or moving to longer lengths rather than by raising %MVC. This conflicts with the dynamic-lifting rule that heavier loads build more maximal strength (REF-677); treat it as weak and specific to isometrics in untrained people.
Base's practice, not the paper's: for an endurance athlete isometric work is a supplement or a low-fatigue phase, not a replacement for the heavy dynamic lifting that has endurance-performance trials behind it (SYNTH-43, SYNTH-44). None of the 26 studies tested an endurance outcome; later trials did (heavy isometric calf training and running economy, REF-1155, REF-1156; isometric training and 2.4-km time, REF-1157).
Limitations
No meta-analysis: "pooled" values are averages of per-study percent changes and effect sizes per week, without weighting, confidence intervals or heterogeneity. The headline long-length advantage rests on three studies; in the nine-study comparison the effect size per week is the same (0.046 vs 0.045).
Populations untrained or recreational; mostly young men; mostly single-joint dynamometer holds. No study tested competitive athletes, multi-joint dynamic performance in a game or race, or an endurance outcome.
The accepted manuscript is internally inconsistent: its abstract says 23 research outputs, its results 26 studies; one comparison is labelled "n=?" and one sentence reports isometric-force gains as "muscle size". The published abstract says 26.
Hypertrophy measures mixed (girth, ultrasound thickness, MRI volume, cross-sectional area); intensity groups were not always volume-matched (for example, time under tension, not total load, was matched in Szeto et al.).
A later Bayesian meta-analysis of 12 trials (REF-1168, Varovic 2025; mostly dynamic training, plus two of the isometric knee trials behind this review's long-length finding) found no meaningful regional-hypertrophy advantage for training at longer mean muscle lengths (SMD 0.05-0.09, mostly inside the equivalence region). It disagrees with the direction here.
Funding: none for the review; the first author held an Auckland University of Technology doctoral scholarship; no conflicts declared.
How this entry was checked and changed
Why this level
systematic review of mostly small trials (mean n 27, range 4-120), descriptive pooling only, every comparison of muscle length, intensity or intent rests on 2-10 studies; read from the accepted manuscript (full text)
Full text (checked 2026-10-16)
A total of 26 studies with a mean quality score of 14.3/20 (range = 10-18); 713 participants (463 male, 250 female), average sample size of 27.4 ± 28.1 (4-120) (full text).
Most studies (16/26) recruited untrained participants; none examined competitive athletes or well-trained participants (full text).
Intervention 8.4 ± 3.6 (range = 3-14) weeks, 3.5 ± 0.96 sessions per week, 28.6 ± 13.2 total sessions; volume equated in 17/26 studies (full text).
Joint angles ≤ 70º improved muscle size by 0.47 ± 0.48%/week vs 1.16 ± 0.46%/week at > 70º of flexion (3 studies) (full text).
Nine studies: ≤ 70º 0.61 ± 0.42%/week and 0.045 ES/week vs > 70º 0.88 ± 0.8%/week and 0.046 ES/week (full text).
Intensity ≤ 70% of MVIC 0.77 ± 0.26%/week vs > 70% 0.70 ± 0.55%/week for muscle size (full text).
Achilles tendon CSA and stiffness rose after high (17.1-36%, p < 0.05) but not low (5.2-7.9%, p > 0.05) intensity training (full text).
Kubo: tendon stiffness +50.9% after long muscle length vs +6.7% after short (between groups p = 0.021) (full text).
Bandy and Hanten: improvements at four, five and seven tested angles after short, medium and long muscle length training; Kubo: five vs eight angles (full text).
Bogdanis: 1RM squat 9.6% vs 11.9% and CMJ 7.2% vs 8.4% after short vs long muscle length leg press training (full text).
Abstract of the accepted manuscript: "Twenty-three research outputs were reviewed" (full text).
No funding was received for this review; no conflicts of interest (full text).