Wrist curl

Movement

What the movement works

The studies on this page tested wrist curls and other wrist-flexion work, which bends the wrist against a load^2,6. In one study, six weeks of this training made the wrist flexors thicker². Studies of held efforts measured two wrist flexors, the flexor carpi radialis and the flexor carpi ulnaris¹. The flexor carpi ulnaris is a forearm muscle that bends the wrist toward the little finger¹.

In the studies here, bending the wrist was stronger than straightening it^1,7. Two studies measured the hardest isometric effort (the muscle works but the joint does not move) each way^1,7. Torque is a turning force, and a newton-metre is its unit:

Who was studied	Wrist flexion	Wrist extension
40 healthy arms, forearm in a neutral position	13.6 newton-metres1	8.2 newton-metres1
20 people	About 32 newton-metres7	About 17 newton-metres7

In the study of 20 people, flexion torque was also less variable than extension torque⁷.

The versions studies have used

The studies on this page tested wrist flexion in several forms^2,6,8,9:

• Wrist curls to exhaustion at 70%, 80% or 90% of the one-repetition maximum (the heaviest weight a person can lift once)⁶.
• Five sets of 8 at 70 to 80% of that maximum, three times a week².
• Twice-weekly dumbbell training that included wrist flexions¹⁰.
• Eccentric work, done while the muscle lengthens, as when lowering a weight slowly⁸.
• Home exercise with a water-filled bucket¹¹.
• Held efforts at a set share of maximum^1,7.
• Moving the wrist against a robot handle⁹.
• Elastic-band exercises that tilt the hand or turn the forearm¹².

What it loads

The wrist flexors

Most studies of muscle activity here used electromyography (EMG), which picks up a muscle’s electrical signals^1,9. The EMG studies here used held efforts, a robot handle or elastic bands^1,7,9,12.

In 40 healthy arms holding a wrist-flexion effort at 75% of maximum, forearm position changed the work¹. The flexor carpi radialis worked harder with the forearm in supination (palm up)¹. Flexor carpi ulnaris activity was lower in pronation (palm down) than in a neutral position¹.

A study with a moving wrist found something different⁹. In 12 young men moving against a robot handle, forearm rotation had little influence on the forearm muscles measured⁹. Whether the wrist was lifting or lowering set the activity of every one of those muscles⁹.

In 20 people doing held wrist efforts from 5% to 75% of maximum, flexor carpi ulnaris activity rose as flexion torque rose⁷.

How the flexor carpi radialis meets harder work

One study recorded single motor units (a nerve cell and the muscle fibres it switches on) in six subjects¹³. At 30% of maximum, flexor carpi radialis units fired about twice as fast while lifting as during a static hold¹³. Raising the intensity while lifting brought in more units, rather than making the same units fire faster¹³.

The finger flexors

The finger flexor tendons also pass through the wrist¹⁴, and wrist position changes what they can do¹⁵. In 50 people, finger flexion strength measured at the finger flexor tendons was lower with the wrist flexed¹⁵. The same study compared the flexor digitorum superficialis (the superficial finger flexor) with the flexor digitorum profundus (the deep one)¹⁵. The superficial one produced more force at the index, middle and ring fingers, and the deep one at the little finger¹⁵.

Two elastic-band exercises were tested in 10 healthy men¹²:

• Ulnar deviation (tilting the hand toward the little finger) worked the flexor carpi ulnaris, at about 40% of maximum¹². That was more than the superficial finger flexor or the pronator teres (a forearm muscle that turns the palm down)¹².
• Pronation gave high activity in the superficial finger flexor, about 64% of maximum¹².
• Pronation also gave high activity in the pronator teres, at about 73%¹².

The muscles on the other side

The muscles that straighten the wrist and fingers also work during wrist flexion^7,9. In 20 people making held efforts at 50% and 75% of maximum, the extensor digitorum (a forearm muscle that straightens the fingers) co-contracted during flexion⁷. Co-contraction is opposing muscles working at the same time⁷.

The extensor digitorum did so more than the flexor carpi ulnaris did during extension⁷. In the 12 young men using a robot handle, co-contraction was higher in flexion⁹. The authors read this as extra wrist-extensor activity to keep the joint stable⁹.

The inner elbow

In 30 volunteers, a repeated wrist-flexion exercise lowered wrist flexion strength by 7.5%¹⁶. Afterwards, the inner-elbow joint space widened by about 0.9 mm under a valgus stress test (a sideways push on the elbow)¹⁶. The authors of the 40-arm study suggested forearm positions that raise wrist-muscle activity may be a risk factor for tendinopathy¹. Tendinopathy is local pain in a tendon that comes with activities that load it¹. They noted their results fit with findings on tennis elbow and golfer’s elbow¹.

The median nerve and the carpal tunnel

The carpal tunnel is a passage at the front of the wrist¹⁷. The median nerve (a main nerve of the forearm and hand) runs through it with the tendons of both finger flexors¹⁴. Two lab studies in healthy people measured what wrist efforts did there^4,18:

• In 14 healthy people, carpal tunnel pressure typically did not rise during wrist flexion, and often fell⁴.
• In the same study, resisted wrist extension while pinching or gripping raised pressure more than wrist flexion movements did⁴.
• In 25 healthy adults holding flexion or extension at 50% of maximum, the nerve’s cross-section shrank during the hold¹⁸.
• It had not fully recovered 2 seconds after release¹⁸.
• The change did not differ significantly between flexion and extension, or with and without gripping¹⁸.

Blood flow in the forearm

In 14 college students doing three sets of wrist curls to exhaustion, forearm blood flow was measured after the sets⁶. It was generally lower after sets at 90% of the one-repetition maximum than at 70% or 80%⁶. At several points during recovery, it was higher after the third set than after the first⁶.

How the body adapts

Weeks of training

Several small studies trained the wrist flexors for four to six weeks^2,8,10,11:

Who was studied	What they did	What was found
14 men	Six weeks of wrist-flexion training2	Thicker wrist flexors and more local muscle endurance2
16 participants, each with the other forearm in a cast	Four weeks of eccentric wrist-flexion training of the free arm, or none8	The trained arm gained about 31% in strength and 7% in muscle thickness; controls lost a little8
11 men aged 70 to 80	Six weeks of dumbbell training that included wrist flexions10	Wrist flexion strength and control of finger-pinch force improved more than in controls10
30 amateur table tennis players	Six weeks of home wrist exercise with a bucket, or usual activity11	Wrist flexor and extensor strength ended higher than in controls; grip strength did not differ significantly between groups11

In the table tennis trial, counter-stroke performance did not improve more than with usual activity¹¹. In the study of 14 men, seven cooled the forearm in cold water after each session². They gained less wrist-flexor thickness and no maximal strength, while the group without cooling gained strength².

The arm that did not train

Two small studies found effects in an arm that did not train, while only the other arm trained^3,8. The first had 40 participants train either one wrist or one ankle³. Six weeks of one-sided wrist-flexion training raised strength in the untrained arm by 6%, which is called cross-education³. After a period without training, that gain had reached 15%³. The training response did not differ between the men and women in that study³.

A second study put one forearm of 16 participants in a cast for four weeks⁸. With eccentric training of the other arm, the casted arm lost less wrist-flexor strength: 2.4%, against 21.6% in controls⁸. That effect was limited to the trained flexors⁸.

What one hard bout does

One study used eccentric wrist work to cause muscle damage on purpose¹⁹. Its 10 healthy adults did ten sets of ten eccentric flexions, each at 70% of their one-repetition maximum¹⁹. In 25 healthy adults, eccentric wrist contractions lowered wrist flexion and extension force at 24 hours²⁰. Soreness and forearm girth rose too, and all had returned to normal by 7 days²⁰.

Studies in people with inner-elbow pain

Two systematic reviews looked for studies of exercise in inner-elbow pain^5,21. A 2013 systematic review looked for randomised trials in both inner- and outer-elbow epicondylitis²¹. It found 12, and every one was in lateral epicondylitis (tennis elbow)²¹.

A 2026 systematic review found five studies, with 143 patients, of eccentric wrist flexor-pronator exercise in medial epicondylitis⁵. They were too varied and too small to pool in a meta-analysis⁵. Pain and function improved within the groups doing the exercise⁵. Only one randomised trial showed it doing better than a comparison⁵. The authors judged the certainty of the evidence low and called for larger, high-quality trials⁵.

One study added a new eccentric wrist-flexor exercise to standard care²². Its 20 patients had long-standing medial epicondylosis and had not improved with earlier care²². Their scores on the DASH, an arm and hand disability questionnaire, improved from 34.7 to 7.9²². Golf brought on symptoms for 14 of the 20, and weight lifting for one²².

Progressive overload

A 2026 position stand describes progressive overload as the need to increase the stimulus placed on the muscle throughout a training programme²³. Three of the small wrist-flexion studies below raised the work, each in its own way^3,8,24. The fourth compared lowering with lifting²⁵.

Retesting and raising the weight

In one study, 40 men and women were randomly assigned to train either one wrist or one ankle³. The wrist group lifted a dumbbell set at 80% of maximal voluntary contraction, the hardest effort a person can make with a muscle³. They did 3 sets of 10 to 12, four times a week, for six weeks³. At week 3 they retested their strength, and the weight was raised to 80% of the new value³. Trained-arm strength rose 24%, and was still 16% above baseline after six weeks without training³.

Adding sets

In the four-week cast study, 8 people trained on an isokinetic dynamometer, a machine that holds the limb to a fixed speed⁸. They made maximal eccentric wrist flexions three times a week, with 1 minute of rest between sets⁸. Volume rose from 2 sets of 8 to 6 sets of 8, then tapered to 2 sets in the last session⁸. The trained arm gained about 31% in strength⁸.

Lowering or lifting

In one study, 9 young adults trained the right wrist flexors with eccentric contractions and 9 with concentric ones, for 12 sessions over four weeks²⁵. Concentric work is done while the muscle shortens, as when lifting a weight. Concentric strength rose 64% in the concentric group, and eccentric strength rose 62% in the eccentric group²⁵. Strength carried over to the untrained arm by 47% after eccentric training and 28% after concentric, a difference between the groups²⁵.

Faster contractions for endurance

In 9 healthy college-aged men and women, one arm did 30 minutes of nonstop dumbbell wrist flexion, five days a week for four weeks²⁴. The dumbbell was set at about 30% of a maximal voluntary isometric contraction (a muscle’s hardest effort while the joint stays still)²⁴. It was reset each week from a new maximal test²⁴. The pace rose as tolerated, from 0.3–0.5 to 1.0–1.2 contractions a second²⁴. Contractions per session rose from about 800 in the first session to about 1,800 in the twentieth²⁴.

Muscle mitochondrial capacity rose by an average of 64%, while the trained arm’s maximal isometric strength did not change²⁴. Mitochondria are the small parts inside a cell that release energy from food. Five weeks after training stopped, mitochondrial capacity did not differ from the starting value²⁴.

Connections

The nerve near the work

The median nerve sends branches to the flexor carpi radialis and the superficial finger flexor²⁶. A review describes it as, classically, the nerve of wrist flexion, among other movements²⁷. In 25 healthy adults, its cross-section shrank during held wrist-flexion efforts¹⁸.

Related exercise and stretch pages

The wrist extension page covers the opposite movement, lifting the back of the hand²⁸. In 40 healthy arms, flexion torque was higher than extension torque¹. The wrist flexor stretch page covers stretching the same muscles²⁹. In one study of 26 healthy men, stretching these muscles was followed by signs the authors read as faster fatigue in a held grip²⁹.

The muscles it works

• The flexor carpi radialis, more active palm-up in held flexion¹.
• The flexor carpi ulnaris, whose activity rose with flexion torque⁷.
• The flexor digitorum superficialis, the superficial finger flexor, highly active, in 10 healthy men, during an elastic-band exercise that turns the forearm palm-down¹².
• The extensor digitorum, which co-contracted during held flexion⁷.

Sources

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Every source the library cites

Changes

• October 23, 2026 Added a Progressive overload section.
• September 29, 2026 First published.