Isometric training

What it is

Force without movement

An isometric contraction is one in which a muscle makes tension but the joint it crosses keeps the same angle¹. The joint stays still because the load is more than the muscle can move¹. A 2025 systematic review, which sums up the research on a question in a checkable way, contrasts two kinds of training². It describes isometric training as force with no joint movement, and dynamic training as force through a range of motion².

In daily life, isometric contractions help hold posture and keep bones and joints steady¹. Most body actions mix them with isotonic contractions, muscle work that moves a joint against a steady load¹.

The choices that shape it

A 2019 systematic review of 26 isometric training studies, each lasting 3 weeks or more, pointed to variables that change the results, such as⁷:

• The joint angle, which sets the muscle’s length⁷.
• How hard the muscle contracts, called intensity⁷.
• The intent: ballistic, meaning as fast and hard as possible, or not⁷.

The same review notes that athletes, special populations and the general public use it, with little agreement on guidelines for different outcomes⁷.

What it loads

Muscle force at different lengths

In one study, the joint angle changed how much force the muscle itself made⁸. It trained the quadriceps of 9 men at matched effort at two knee angles⁸. The quadriceps are the four muscles on the front of the thigh that straighten the knee. Internal muscle force was higher with the knee bent to 100 degrees, where the muscle is longer, than at 50 degrees⁸. The authors put this down to a difference in moment arm, a muscle’s leverage around the joint⁸.

A 2022 tendon review notes that eccentric contractions, done while the muscle lengthens, can make higher forces than concentric (shortening) or isometric ones⁹. A 2019 narrative review, a summary written without a set search method, reports that isometric training caused less fatigue than dynamic training¹⁰.

Tendons in held positions

A 2015 meta-analysis covered tendon training in healthy adults aged 18 to 50³. In it, 17 of 37 training programmes loaded the Achilles or patellar tendon through isometric contractions³.

Heart and circulation

In 23 people holding 2-minute wall sits, heart rate and blood pressure rose as the knee bent further, from 135 to 90 degrees¹¹. A 2021 meta-analysis of 24 trials covered adults with raised blood pressure¹². It found no significant rise in risk with isometric training, about one adverse event per 38,444 sessions¹².

How the body adapts

Strength, mostly in the way it was trained

A 2025 meta-analysis pooled 32 studies of 621 healthy adults². Isometric training raised isometric strength more than dynamic training did². The two gave similar gains in isokinetic strength, measured on a machine that holds a limb to a fixed speed².

Another 2025 meta-analysis, of 43 studies in 1,660 healthy people, looked the other way round¹³. Dynamic training raised dynamic strength about twice as much as isometric strength, which was not trained¹³.

Strength at the angle trained

Before a 2019 study, the idea that isometric training builds strength most at the trained angle was called disputed, with little rigorous evidence¹⁴. The studies are small^14,15:

• In 6 women training the calf at one ankle angle, strength rose only at that angle and the two beside it¹⁵. The authors linked this to the nerves¹⁵.
• In 13 people doing 4 weeks of knee-extension holds at one angle, strength rose 12% there and 5% to 11% at other angles¹⁴. The gains differed by angle compared with 9 people who did not train¹⁴.
• In that study, muscle activation rose, but not in an angle-specific way, so evidence for a nerve-based cause was weak¹⁴.

A 2019 narrative review reports that isometric training built more strength at the trained angle than dynamic training¹⁰. The same review reports benefits for running, jumping and cycling¹⁰.

Training at a long muscle length gave broader gains in some studies^7,8. In 9 men, short-length training raised strength near the trained angle, while long-length training raised it at every angle tested⁸. A 2019 systematic review found that long-length training carried over more to moving tasks⁷.

Fast force and intensity

A 2019 systematic review found ballistic intent gave larger gains in muscle activation and rapid force than non-ballistic holds⁷. On intensity, the same review reported substantial gains in muscle size and maximal force whatever the intensity⁷. In one trial of 31 male amateur rugby players, 8 weeks of unweighted Copenhagen adductor holds brought no significant strength change¹⁶. The weighted version raised hip adduction strength, pulling the leg inward, by 10%¹⁶.

Muscle size

Studies disagree on whether muscle length changes how much muscle grows¹⁷. A 2019 systematic review of 26 studies found more growth per week from long-length training than from equal short-length training⁷. In 9 men training for 12 weeks, muscle volume gains did not differ between short and long lengths⁸. A 2026 review found five studies on the question, some favouring long lengths and some finding no significant difference¹⁷.

Tendons

Tendon findings here come from lower-limb studies, mostly of the Achilles and patellar tendons^3,9. A 2015 meta-analysis of high-intensity training in adults aged 18 to 50 looked at tendon stiffness³. Stiffness is how much force it takes to stretch something by a given amount. Isometric, eccentric and concentric-eccentric training raised it by similar amounts³. The authors concluded that the size of the load matters more than the contraction type³.

A 2022 meta-analysis of 61 studies found every high-intensity mode, isometric included, raised tendon stiffness and modulus⁹. Modulus is how stiff a material is in itself, regardless of its size. The modes did not differ significantly⁹. Only eccentric training increased tendon cross-sectional area, the size of a slice across it⁹. That difference went away when the analysis kept only studies that compared modes directly⁹.

A 2019 systematic review found contractions of 70% of maximum or more were needed to change tendon structure and function⁷.

Single small studies add detail^18,19:

• In 8 people after 12 weeks of holds at 70% of maximum, outer-thigh tendon stiffness rose from about 67.5 to 106.2 N/mm¹⁸.
• In 8 young men training at 70% of maximum, stiffness rose in the leg trained with 20-second holds, not the 1-second leg²⁰.
• In 11 people training the calf for 12 weeks, tendon stiffness rose after isometric but not plyometric training¹⁹.
• In the same 11 people, active muscle stiffness rose after plyometric but not isometric training¹⁹.

Resting blood pressure

Several meta-analyses found isometric training lowered resting blood pressure^12,21. The table gives the drop in systolic blood pressure, the upper number in a reading. The reviews studied different people.

Review	Drop in systolic pressure (mm Hg)
2016, 302 healthy adults	about 5.221
2021, 1,143 adults with raised blood pressure (office)	about 7.012
2023 network meta-analysis, 270 trials across exercise types	about 8.24
2022, 38 trials, short-term training	about 8.5, against 2.9 for interval training22

The 2021 review found no significant drop in 24-hour systolic pressure¹². It rated the certainty of evidence, how sure reviewers are that a finding is right, as very low to low¹². The 2023 network meta-analysis ranked isometric training highest of the exercise types it studied for systolic pressure⁴. Within that analysis, the wall squat ranked highest of the isometric forms⁴.

A 2022 meta-analysis of 18 trials looked at why pressure fell²³. The main cause was lower total peripheral resistance, how hard the blood vessels resist blood flow²³. Better nerve control of the blood vessels may explain it²³.

Pain after a hold

A 2012 meta-analysis found a large drop in lab-induced pain in healthy adults²⁴. In people with chronic pain, the effects were highly variable²⁴. A 2021 meta-analysis of randomised studies found no drop in either group, but its studies were small and their risk of bias unclear²⁵. Another 2021 review of 346 people found no consistent effect in people with local muscle or joint pain²⁶.

Tendon pain

Studies in tendinopathy have reached different answers^5,6. One crossover trial, a study in which each person tries every option in turn, involved 6 volleyball players with patellar tendinopathy⁵. After one session of holds, pain during a decline squat fell from about 7.0 to 0.2 out of 10⁵. The drop lasted at least 45 minutes, and after isotonic exercise pain fell from 6.3 to 3.8⁵.

Other trials in people with patellar tendinopathy found mixed results^27,28:

• In 20 jumping athletes training for 4 weeks, holds gave more immediate pain relief than isotonic leg extensions²⁷.
• In another trial of 29 jumping athletes, pain fell over 4 weeks in both groups, with no significant difference²⁸.
• In a crossover trial of 21 people, one session of heavy holds or moving exercise eased pain slightly, and the effect faded by 45 minutes²⁹.
• In that trial, the drop was about 0.9 out of 10 and did not differ between the two²⁹.

In an exploratory study of 16 people with Achilles tendinopathy, one 45-second heavy calf hold did not meaningfully change pain, and responses varied³⁰.

A 2020 review of 10 trials across five tendon sites found limited evidence that holds were no better than isotonic exercise, up to 12 weeks⁶. A 2026 review of 13 trials found holds appeared tolerable and may ease pain short term³¹. Their long-term effect against eccentric or isotonic exercise remains uncertain³¹.

Injury

One retrospective study, looking back at past records, covered 27 players in one professional rugby squad³². It compared a season with a 26-week isometric neck programme against one without³². The programme season had fewer match injuries, 2 against 11³². The number of neck spine injuries did not differ significantly³². The injury evidence on this page for isometric training comes from this one retrospective analysis of 27 players from one professional rugby union squad³².

Connections

Isometric training loads muscle and tendon^1,9. Several studies above trained the quadriceps^8,14. Several tested holds in people with patellar tendon pain^5,27,28,29. One 2025 meta-analysis above compares it with dynamic resistance training². Another looked at how much dynamic training raises isometric strength¹³. In one trial of 180 female office workers with neck pain, the holds used an elastic band³³.

Library exercises studied as holds^11,34:

• Wall sit: isometric wall squats held at set knee angles¹¹.
• Plank and hollow hold: the prone plank and v-sit, studied as isometric trunk endurance postures³⁵.
• Side plank: an isometric side support on one elbow and both feet³⁴.
• Glute bridge hold: once the hips are raised, the bridge can be held for a set time³⁶.
• Neck isometric hold: isometric neck training raised held neck strength by 69% to 110% in those office workers³³.
• Copenhagen adductor plank: in 44 male rugby players, weighted holds made up to 48.3% more hip adduction (inward) turning force than body-mass holds³⁷.

Sources

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Every source the library cites

Changes

• September 30, 2026 First published.