Isometric training means producing force without the muscle changing length. Two 2019 reviews summarise what is known about its long-term effects. This article reports what each says, notes how their methods differ, and identifies what remains uncertain. It covers general findings on training in healthy people and is not advice for anyone with an injury or health condition.
Two different kinds of review
The reviews are not equivalent in strength of evidence. Oranchuk, Storey, Nelson and Cronin (Scandinavian Journal of Medicine and Science in Sports) conducted a systematic review of medium- to long-term adaptations, searching MEDLINE, PubMed, SPORTDiscus and CINAHL. It included 26 research outputs of at least three weeks. Lum and Barbosa (International Journal of Sports Medicine) describe their paper as a brief review with a narrative summary of findings on isometric strength training and its effects on strength and dynamic performance. A narrative summary does not pool results statistically, so its training figures are the authors’ synthesis and not a measured optimum.
Muscle length: the systematic review’s clearest signal
Oranchuk and colleagues report that isometric training at longer muscle lengths produced greater muscular hypertrophy than equal volumes of training at shorter muscle lengths. The figures they give are weekly gains of 0.86 to 1.69% at longer lengths, against 0.08 to 0.83% at shorter lengths. They also report that long-muscle-length training resulted in greater transference to dynamic performance. The review says relatively few studies met its inclusion criteria, so these figures come from a small evidence base.
Intensity and intent
The systematic review reports several other findings:
- ballistic intent, meaning trying to produce force as quickly as possible, gave greater neuromuscular activation and greater rapid force production than non-ballistic intent, for example weekly gains in rapid force production of 1.2 to 13.4% against 1.01 to 8.13%;
- substantial improvements in muscular hypertrophy and maximal force production were reported regardless of training intensity;
- high-intensity contractions, at about 70%, were required to improve tendon structure and function.
The intensity result is worth reading carefully: it says intensity was not critical for hypertrophy or maximal force in the included studies, while the tendon finding is specific to the tendon outcome measured.
Practical figures from the narrative review
Lum and Barbosa state that isometric training has been shown to induce less fatigue and to give superior joint-angle-specific strength compared with dynamic strength training, and to benefit sports-related dynamic performance such as running, jumping and cycling. Their suggested parameters are:
- To increase muscle hypertrophy: contractions at 70 to 75% of maximum voluntary contraction, held for 3 to 30 seconds per repetition, with a total contraction duration of more than 80 to 150 seconds per session, for more than 36 sessions;
- To increase maximum strength: contractions at 80 to 100% of maximum voluntary contraction, held for 1 to 5 seconds, with total contraction time of 30 to 90 seconds per session, using multiple joint angles or a targeted angle;
- To improve rate of force development: performing the contractions in a ballistic manner.
Because the two reviews are different kinds of evidence, the second set of figures should be read as the authors’ summary of the literature and not as prescriptions tested against one another. The two reviews agree on a general direction: ballistic intent helps rapid force production, and the joint angle used matters.
What the reviews do not say about equipment
Neither review evaluates products, and neither compares isometric holds against dynamic training as an equipment strategy. Any suggestion that isometric work saves money or space is outside what these papers show. The reviews are relevant mainly as a guide to how isometric sessions might be structured for someone who already has an anchor point or a loaded position to hold against. For readers comparing isometric holds with lifting through a range of motion, the related article on this site about full against partial repetitions covers a neighbouring question.
Limits of the evidence
- The systematic review found relatively few studies, so its hypertrophy and transfer figures rest on small numbers.
- The narrative review does not pool data and its parameter ranges are wide.
- Both concern healthy training populations and neither replaces individual medical or coaching advice.
- Comparisons of isometric training with dynamic training on equal terms are limited in these papers, which is why they do not support claims that one is superior.
Frequently asked questions
Does isometric training build muscle?
The systematic review reports substantial improvements in muscular hypertrophy across the included studies, with larger gains at longer muscle lengths.
Does the joint angle matter?
Both reviews indicate it does: the systematic review found greater hypertrophy and transfer at longer muscle lengths, and the narrative review recommends multiple or targeted joint angles for maximum strength.
The bottom line
Two 2019 reviews indicate that isometric training can produce meaningful gains in size and force, that longer muscle lengths appear to favour hypertrophy and transfer, and that ballistic intent favours rapid force production. The systematic review is based on 26 research outputs and the narrative review supplies broad, non-pooled parameter ranges. Neither compares products or establishes that isometric work is better than dynamic training.
Sources
- Oranchuk DJ, Storey AG, Nelson AR, Cronin JB, “Isometric training and long-term adaptations: Effects of muscle length, intensity, and intent: A systematic review”, Scandinavian Journal of Medicine and Science in Sports, 2019
- Lum D, Barbosa TM, “Brief Review: Effects of Isometric Strength Training on Strength and Dynamic Performance”, International Journal of Sports Medicine, 2019