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Biceps curl

Also called arm curl

An exercise that bends the elbow against a weight. What the studies measured it loading, where they disagree about grip, and how the arm muscles changed with training.

Region
Upper arm
Muscles
biceps brachii, brachialis, brachioradialis, deltoid
Updated
October 23, 2026
Reviewed
October 23, 2026 · how entries are checked

Movement

What the elbow and shoulder do

The muscles that flex, or bend, the forearm at the elbow include the biceps brachii, the brachialis and the brachioradialis1. The biceps has two heads and crosses both the shoulder and the elbow1. It bends the elbow, helps turn the palm up, and helps raise the arm forward at the shoulder1.

Turning the palm up is called supination, and turning it down is pronation2,3. The biceps bends the forearm when the elbow is straight7. With the elbow bent, it becomes the forearm’s most powerful supinator7.

The versions studies have used

The studies on this page tested the curl in many forms2,8,9:

  • Cable curls with the palms up, palms down, or facing each other in a neutral (hammer) grip2.
  • Barbell curls with a straight bar or an EZ bar, with the upper arms kept still or allowed to move forward8.
  • Standing, incline and preacher curls with dumbbells, at 40% of maximum9.
  • A cable preacher curl with the shoulder flexed (arm raised forward), and a Bayesian cable curl with the shoulder extended10.
  • Curls done strictly, and curls that used momentum, or “cheating”11.

What it loads

How the elbow flexors share the work

In 15 young healthy men bending the elbow as hard as they could, the biceps, brachialis and brachioradialis were all very active throughout12. That held with the forearm neutral, fully turned down or fully turned up12.

The brachialis lies deep to the biceps and adds power to bending the elbow1. One cable curl study used electromyography (EMG), which picks up a muscle’s electrical signals, with sensors on the skin or in the muscle2. It did not measure the brachialis, which it notes can only be recorded with wire electrodes2. That study describes it as the most powerful forearm flexor2. It does not attach to the radius, a forearm bone, so it plays no part in supination2.

The brachioradialis is small but has good leverage13. In 10 arm specimens, its physiological cross-sectional area, a measure of muscle size across its fibres, was the smallest of the elbow muscles measured13. Its large moment arm, or leverage, still gave it a relatively large capacity to turn the elbow13.

What grip changes: the studies disagree

Studies disagree about whether grip changes how hard the biceps works2,3. They tested different people doing different tasks, as the table shows2,3:

Who was studiedWhat they didWhat grip changed for the biceps
10 competitive bodybuildersCable biceps curlsMore activity palms up than palms down (about 19%) or neutral (about 12%)2
16 healthy peopleElbow bending movementsNo significant change with hand position3

Other studies measured how grip changed the arm’s strength and leverage. In 11 young men, isometric elbow flexion was about 50% stronger with the forearm palms up or neutral than palms down14. In two anatomical specimens and a computer model, the biceps’ leverage for bending the elbow reached a higher peak with the forearm supinated15.

What grip does to the brachioradialis

Findings for the brachioradialis also vary between studies2,3. In the 16 healthy people, its activity differed significantly palms down compared with palms up and neutral3. In the ten bodybuilders doing cable curls, it was slightly more active palms up than palms down or neutral2. Those authors note this runs against the common belief that a hammer grip gives the brachioradialis a bigger role2.

In 15 young men bending the elbow as hard as they could, brachioradialis activity was slightly higher with the forearm supinated12. In 12 trained men doing barbell curls, it was more active than the biceps while lowering the bar16. That was most marked with supinated and semi-supinated grips16.

Where in the lift the biceps works hardest

Lifting the weight drew more activity than lowering it in two studies9,16. In 12 trained men doing barbell curls, the biceps and brachioradialis were more active in the concentric (lifting) phase than the eccentric (lowering) phase16. In 22 people doing dumbbell curls at 40% of maximum, lowering drew significantly less activity in all three versions tested9.

In that dumbbell study, incline and standing curls showed a similar pattern of activity in the long head of the biceps across the whole movement9. The preacher curl gave high activity only over a short range of elbow angle9. While lifting, activity reached up to 95% of its maximum late in incline and standing curls, and 80% early in the preacher curl9.

Leverage also shifts as the elbow bends15. In two anatomical specimens, the moment arms of the elbow muscles varied by at least 30% over a 95-degree range of motion15. The biceps moment arm peaked with the elbow more straight15.

The bar, the upper arm and the shoulder

In ten competitive bodybuilders doing barbell curls, a straight bar gave a slight edge in biceps activity over an EZ bar8. Letting the upper arms move forward during the lift raised biceps activity by about 18 to 20%8. That held for both bars8.

The front of the deltoid, the rounded muscle that caps the shoulder, also worked2. In the bodybuilders’ cable curls, it was more active with palms-down and neutral grips than palms up2. The authors link this to holding the head of the humerus (upper arm bone) steady2.

The two biceps tendons

The distal biceps tendon attaches to the radial tuberosity, a bump on the radius near the elbow17. In 11 young men, it was measured with ultrasound during isometric elbow flexion, where the muscle works but the joint does not move14. Stress in the tendon was about 52% greater with the forearm palms up or neutral than palms down14. Tendon strain, how far it stretched, was about 36% greater in neutral than palms down14.

The long head of biceps tendon starts at the top of the shoulder socket18. In the middle third of the upper arm, it joins the short head, the biceps’ other head, as both become muscle18. In 13 healthy women with the elbow bent to 90 degrees, its tension was estimated with shear wave elastography19. Tension was lower palms up than palms down during a contraction without a weight19. While they held a weight, it did not differ between forearm positions19.

Injuries reported with the biceps curl

The injuries on this page reported during the curl itself come from single case reports5,6,20. Each describes one person5,6,20:

  • A recreational weightlifter ruptured (tore) both distal biceps tendons at once during a preacher curl5.
  • A young, active man with no earlier symptoms ruptured the long head of the biceps tendon during 25-pound curls6.
  • A healthy, recreationally trained woman aged 21 developed exertional rhabdomyolysis, a breakdown of muscle brought on by exercise20. It followed 143 repetitions of dumbbell curls in a research study20.

Two reviews point to lifting21,22. In one, of distal biceps tendon ruptures generally, heavy weight lifting was the most common way the injury happened, in 53.2% of people21. In the other, of 18 complete ruptures during sport in 16 athletes, weightlifting caused 56%22.

How the body adapts

The curl compared with a row

In 10 untrained men, one arm trained with the biceps curl and the other with the dumbbell row for eight weeks23. The elbow flexors of the curl arm grew more, 11.06% against 5.16%23.

Where along the arm the muscle grew

In a randomised trial of 63 young women over eight weeks, the incline curl thickened the elbow flexors more near the shoulder4. The preacher curl thickened them more near the elbow4. Each group gained more strength in the curl it had trained4.

Range of motion: findings differ

Several studies found more growth, at least at some sites along the arm, from the part of the lift with the elbow straighter24,25,26. In 32 young adults new to resistance training, five weeks of curls between 0 and 50 degrees of elbow bend grew muscle thickness 8.9%24. Curls between 80 and 130 degrees grew it 3.4%, and only the first group gained strength significantly24.

In 19 young women, one arm trained the first part of a preacher curl and the other the last part25. After eight weeks, the first-part arm grew more at 70% of biceps length, and gained more one-repetition maximum strength25. Growth at 50% of that length was similar25.

In 13 resistance-trained people, preacher curls over the first half of the range and over the full range gave similar mid-arm growth27. The half range had a trivial to small edge nearer the elbow27. The full range gave negligibly greater strength gains27.

Two systematic reviews differ on how firm this is26,28. One, of 11 studies, found full range or the elbow-straight part grew the biceps and brachialis more at distal sites, the ends nearer the hand26. That was compared with the final part of the range26. It concluded the evidence suggests some muscles, the biceps among them, tend to grow best when trained at a longer length26. Another systematic review, of six studies, found the upper-limb research on range of motion limited and conflicting28.

Changes that made little or no difference to growth

Four other studies compared two versions of the curl and found growth alike, or not clearly different10,11,29,30:

  • Cable against barbell preacher curls: in 35 young adults over 10 weeks, biceps thickness gains were similar, at 7% and 8%29.
  • Preacher against Bayesian cable curls: in 15 young men over 10 weeks, biceps and brachialis thickness did not differ significantly between arms10.
  • Shoulder angle in cable curls: in 24 untrained men over 10 weeks, both arms grew about 7 to 9%30. The authors concluded that, with resistance profile, elbow range of motion and effort matched, shoulder angle alone did not appear to make a meaningful difference30.
  • Strict form against momentum: in 30 young adults over eight weeks, one arm did strict biceps curls and triceps pushdowns and the other used momentum11. Muscle thickness rose similarly, though the momentum arm lifted far more total load11.

Progressive overload

A 2026 position stand describes progressive overload as the need to increase the stimulus placed on the muscle throughout a training programme31. Most of the curl studies below raised the load, the number of sets, or both10,25,30,32.

How the studies raised the load

Four studies set the next load by the repetitions done, and one raised it over ten sessions24,25,27,29,30:

Who trained, and howHow the load changed
19 young women, dumbbell arm curls three times a week for eight weeksEach set went to failure, the point where another repetition isn’t possible25. The load rose 1 kg after a last set of more than 10 repetitions, and fell 1 kg after fewer than 825
13 resistance-trained people, one-arm preacher curls twice a week for 8 weeksEach arm started at 65% of its one-repetition maximum, the heaviest load it could lift once, for five sets to failure27. The load rose 1 kg after a set of more than 15 repetitions27. It fell 0.5 kg per missing repetition below 1027
24 untrained men, one-arm cable curls for 10 weeksA double progression: sets of 10 to 20 repetitions to failure, with 0.25 kg added once the first set passed 2030
35 young adults, preacher curls three times a week for 10 weeksSets of 8 to 12, with loads raised about 5% a week by the repetitions done, to keep sets at or very near failure29
32 young adults new to resistance training, dumbbell curls on a preacher bench twice a week for 5 weeksThree sets of 10, with intensity raised over ten sessions from 30% to 100% of the maximal isometric torque (turning force) measured before training24

How the studies added sets

Four studies added sets, groups of repetitions done one after another, partway through10,25,30,32:

  • In 19 young women doing arm curls, each arm did four sets per session at first, and five from the fifth week25.
  • In 15 young men doing one-arm cable curls for 10 weeks, sets rose from 3 to 4 to 510.
  • In 24 untrained men doing cable curls, each arm did six sets a week, then eight from the second session of week 530.
  • In 19 resistance-trained adults doing preacher curls, the number of sets went up midway32. The load rose about 1 to 2 kg at the next session after a set of 12 or more repetitions32.

Effort, lighter weeks and speed

In 19 resistance-trained adults doing one-arm preacher curls at 70 to 80% of one-repetition maximum, one arm trained to failure32. The other stopped with 1 to 3 repetitions in reserve, the number more it could have done32. After eight weeks, both arms gained muscle thickness and strength32. The ranges for the difference between arms spanned zero32.

In 19 untrained young men, some arms did biceps curls twice a week for 8 weeks33. Others dropped to one session of 2 sets in weeks 4 and 8, a deload (a planned spell of lighter training)33. The study found no time-by-condition interaction for muscle thickness or 10-repetition maximum33. The curl 10-repetition maximum rose by about 3.6 kg and 3.4 kg in the two conditions33.

One three-week study of 27 subjects compared load and speed in barbell biceps curls, three times a week34:

  • High load, fast: maximal isometric strength rose 9.7%34.
  • High load, slow: slow isokinetic strength, tested on a machine held to a fixed speed, rose 8.5%34.
  • Low load, fast: force performance showed no improvement34.

Connections

The tendons it loads

One study of isometric elbow flexion measured stress in the distal biceps tendon, which attaches to the radial tuberosity of the radius14,17. Another estimated tension in the long head of biceps tendon, which starts at the top of the shoulder socket18,19.

The muscles it works

  • The biceps brachii, the two-headed muscle on the front of the upper arm1,2.
  • The brachialis, which lies deep to the biceps1,12.
  • The brachioradialis, a forearm muscle that bends the elbow1,2.
  • The front of the deltoid, which was active during cable curls2.

Biceps curl loads

Biceps curl is progressed by

Sources

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Every source the library cites

Changes

  • Added a Progressive overload section.
  • Tidy pass: minor review findings fixed, glosses aligned with the reviewed glossary.
  • First published.