Biceps brachii at a glance
| Feature | Detail |
|---|---|
| Short head origin | Coracoid process of the scapula |
| Long head origin | Supraglenoid tubercle of the scapula, with its tendon running through the bicipital groove of the humerus |
| Insertion | Radial tuberosity of the radius, plus the bicipital aponeurosis into the forearm fascia |
| Nerve | Musculocutaneous nerve (mainly C5 and C6) |
| Blood supply | Brachial artery |
| Main actions | Elbow flexion, forearm supination; assists shoulder flexion and stability |
Biceps anatomy: heads, tendons, and neighbors
The two heads start separately on the shoulder blade and merge into one muscle belly in the middle of the upper arm. The short head attaches to the coracoid process. The long head attaches to the supraglenoid tubercle, then its tendon passes through the groove at the front of the upper arm bone before joining the short head's tendon. Near the elbow, both heads form a single tendon that attaches to the radial tuberosity, a bump on the radius. A flat sheet of tissue, the bicipital aponeurosis, branches off and blends into the forearm fascia, passing over the brachial artery and median nerve at the inner elbow.
Muscles that work with the biceps
Two muscles lie underneath it. The brachialis attaches to the ulna and flexes the elbow in every forearm position, and the coracobrachialis sits near the short head at the shoulder. The brachioradialis in the forearm also helps flex the elbow. Because these muscles share the work, a curl never trains the biceps alone.
Anatomical variation
Some people have a third head arising from the humerus. Reported rates vary between studies and populations; anatomy references cite roughly 10%, and one cadaver study found two heads in 93% of specimens. A third head does not change how you should train.
What the biceps does
Elbow flexion and forearm supination
Elbow flexion brings your hand toward your shoulder, as in lifting a bag or a mug. Supination rotates the forearm so your palm turns up. The biceps is a powerful supinator, especially when the elbow is bent, which is why it works hard when you twist a screwdriver or turn a stubborn jar lid with your elbow bent.
Why grip changes the exercise
With your palm facing up, the biceps is in its strongest position. With your palm facing down, as in a reverse curl, the biceps contributes less and more of the load shifts to the brachialis and brachioradialis. A neutral grip, as in a hammer curl, falls in between.
At the shoulder
Because the biceps crosses the shoulder joint, it assists with raising the arm forward and helps stabilize the joint. Its long-head tendon runs through the bicipital groove, a common spot for tendon irritation and front-of-shoulder pain.
Best exercises for the biceps
| Exercise | Grip | What it is good for |
|---|---|---|
| Dumbbell curl | Palms up, or start neutral and rotate up | Trains flexion and supination; each arm works independently. |
| Barbell or EZ-bar curl | Palms up | Easy to load heavier; the EZ-bar can be more comfortable on the wrists. |
| Hammer curl | Neutral | Shifts more work to the brachialis and brachioradialis. |
| Incline dumbbell curl | Palms up | Puts the arm behind the body, so the biceps is stretched at the bottom. |
| Chin-up | Palms facing you | A compound pull in which the biceps assists the lats. |
No curl variation reliably isolates the long or short head, so there is little reason to build a program around "training each head." Pick a few curl variations that feel good on your shoulders and elbows, and cover the elbow flexors with at least one neutral-grip option such as hammer curls.
How to train the biceps
A simple starting plan
This is a practical starting point, not a prescription:
- Frequency: twice a week, on non-consecutive days, including indirect work from rows and pull-ups.
- Volume: 2 to 3 sets of a curl variation, plus 1 to 2 sets of a second variation.
- Reps: 8 to 15 per set, stopping 1 to 3 reps short of failure.
- Progression: when you can complete the top of the range on every set with clean form, add the smallest weight increment and drop back to the lower end of the range.
The rep range isn't fragile. In a 2015 trial of well-trained men, elbow-flexor thickness increased in both a group doing 8 to 12 reps and a group doing 25 to 35 reps to failure (Schoenfeld et al.), and a later review of low-load and high-load training concluded that growth is broadly similar when sets are taken close to failure. Heavier loads were better for maximal strength. Choose a range you can perform with control and keep doing consistently.
Form cues
- Keep your elbows near your sides and your torso still; don't swing the weight up.
- Lower the weight under control instead of dropping it.
- Use a range of motion that doesn't force your shoulders forward.
- If a curl hurts at the front of the shoulder or in the elbow crease, change the grip or angle or stop.
What about partial reps?
Partial reps in the stretched half of the curl can work. An 8-week trial in 30 resistance-trained adults found that lengthened partial reps and full-range reps produced similar upper-body adaptations (Wolf et al., PeerJ, 2025). In that trial the partials replaced full reps instead of being added after them, so use them as a variation and not a guaranteed extra.
Biceps and triceps work as a pair
The biceps flexes the elbow and the triceps on the back of the arm extends it. The biceps has two heads, and the triceps has three. Curls alone leave out the elbow extensors, so pair them with pressing and extension exercises.
Common mistakes and when to get help
- Swinging the weight. Reduce the load until your torso stays still.
- Ignoring tendon pain. Pain at the front of the shoulder can come from the long-head tendon; persistent pain deserves an evaluation.
- Missing the signs of a rupture. A sudden pop, a new bulge in the upper arm, bruising, or sudden weakness in bending or turning the forearm need prompt assessment. Tendon ruptures are uncommon, but treatment options can depend on how quickly one is identified.
FAQ
Do I need to train the long and short heads separately?
What is the difference between the biceps and the brachialis?
How often should I train my biceps?
Are chin-ups a good biceps exercise?
Bottom line
The biceps brachii is a two-headed elbow flexor and forearm supinator that also assists the shoulder. Train it with a few controlled curl variations, use a rep range you can sustain, and increase the load gradually. Pay attention to tendon pain or a sudden change in the arm, and get it checked.
References
- StatPearls: Anatomy, Shoulder and Upper Limb, Biceps Muscle
- Elsevier Anatomy: Biceps Brachii Muscle
- Radiopaedia: Biceps brachii
- Schoenfeld BJ et al. Effects of low- vs. high-load resistance training on muscle strength and hypertrophy in well-trained men. J Strength Cond Res. 2015
- Wolf M et al. Lengthened partial repetitions elicit similar muscular adaptations as full range of motion repetitions (PeerJ, 2025)
This article is general education, not medical advice. See a clinician for persistent pain or any sudden change in arm strength or shape.
