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Structure
Beginner
8 min read

Forearm muscles

The forearm muscles drive the wrist and fingers from a distance, through long tendons. They carry grip strength, which often gives out before the large muscles do.
3D scene
The forearm muscles
The scene shows the muscle masses gathered near the elbow and the long bellies running down towards the wrist. Without the 3D, picture two bundles wrapped around the bones, one in front that closes the hand, one behind that opens it.
Open in the explorer

Where the forearm muscles are

The forearm holds around twenty muscles, nearly all long and slender, arranged around its two bones, the radius and the ulna. What sets them apart is that they act far from their belly: the fleshy mass stays near the elbow, and long tendons run down to the wrist and fingers.
There is a mechanical reason for this. A hand whose muscles sat inside the hand itself would be thick and clumsy. By shifting the mass towards the elbow, the body gets slender fingers driven from a distance, like a puppet on strings.

Two compartments

The muscles fall into two groups, separated by the bones and by fibrous walls.
  • The anterior compartment holds the flexors of the wrist and fingers, plus the pronators. Most of it arises from the medial epicondyle of the humerus, the inner prominence of the elbow.
  • The posterior compartment holds the extensors and the supinator. Most of it arises from the lateral epicondyle, the outer prominence.
One muscle escapes this logic: brachioradialis, which arises above the lateral epicondyle but flexes the elbow instead of acting on the wrist.

Insertions

The tendons cross the wrist through narrow corridors, held down by transverse fibrous bands. They then attach to the carpal bones, the metacarpals or the phalanges, depending on their function. It is this tight passage that makes the region sensitive to repeated loading.

Nerve supply and palpable landmarks

Three nerves share the region: the median and ulnar for the anterior compartment, the radial for the posterior. The muscle masses are easy to feel on either side of the elbow, and harden noticeably when you clench your fist.

What the forearm muscles do

They produce every fine movement of the hand, and a force that is often underestimated.
  • Wrist flexion and extension: they orient the hand relative to the forearm.
  • Finger flexion: this is what produces grip strength, the ability to hold an object firmly.
  • Pronation and supination: they turn the radius around the ulna, which rolls the palm over.
Grip strength
The force a hand can exert by squeezing. It depends mainly on the finger flexors, not on hand size. In a heavy pull it is frequently the first thing to give way.
grip
That last observation has a practical consequence in training. In pulling movements, the load the latissimus dorsi could move often exceeds what the hand can hold. The limiting muscle is then not the one you set out to work.
Certainty level · Established
The forearm flexors produce grip strength, which can limit a pulling movement before the back muscles do.
Anatomy establishes the chain: the deep and superficial finger flexors are the only muscles able to close the hand around a bar. That grip gives out before the back is a common training observation, whose size depends on the grip used, the thickness of the bar and how long the effort lasts.
Standring S (2020) · Neumann DA (2016)

Seeing the forearm in movement

The forearm muscles

The scene shows the muscle masses gathered near the elbow and the long bellies running down towards the wrist. Without the 3D, picture two bundles wrapped around the bones, one in front that closes the hand, one behind that opens it.
Current step
Anterior view
The front of the body. Pectoralis major covers the upper chest, the deltoid caps the shoulder, the biceps fills the front of the arm, the abdominal wall links the ribs to the pelvis, and the quadriceps fills the front of the thigh. Further out on the limbs, the forearm muscles drive the wrist and hand, and tibialis anterior lifts the foot.
Scene description
A three-dimensional diagram of a standing human body, arms by the sides, built from simplified paper-coloured volumes. Twelve priority muscle groups are laid over this outline in terracotta: at the front, pectoralis major, the deltoid, biceps brachii, the abdominal wall and the quadriceps; at the back, the trapezius, latissimus dorsi, the erector spinae, triceps brachii, the glutes, the hamstrings and the calves. A simplified skeleton — skull, spine, ribcage, pelvis, humerus, femur and tibia — can be shown beneath the outline to reveal the bony levers these muscles pull on. Each group is selectable and opens its own reference page. This is a teaching diagram with stylised volumes, not an exact anatomical reconstruction.
Visible structures
  • Pectoralis major
    A thick sheet running from the clavicle, the sternum and the upper costal cartilages to the lateral lip of the bicipital groove of the humerus. It draws the arm towards the midline and forwards, and drives horizontal pushing.
  • Deltoids
    Three heads — anterior, lateral and posterior — running from the clavicle, the acromion and the spine of the scapula to the deltoid tuberosity of the humerus. Together they raise the arm; separately they carry it forwards, out to the side or backwards.
  • Biceps brachii
    Two heads arising from the scapula — the supraglenoid tubercle and the coracoid process — joining on the radial tuberosity. It flexes the elbow and supinates the forearm, and contributes to every pulling movement.
  • Abdominal wall
    Rectus abdominis, the external and internal obliques and transversus, running from the ribs and sternum to the pubis and iliac crest. They flex and rotate the trunk and, above all, stabilise the spine by regulating intra-abdominal pressure.
  • Quadriceps
    Four heads — rectus femoris, vastus lateralis, vastus medialis and vastus intermedius — joining through the quadriceps tendon onto the patella and then the tibial tuberosity. They extend the knee, and rectus femoris also flexes the hip.
  • Trapezius
    A diamond-shaped muscle spanning from the occiput and the cervical and thoracic spinous processes to the clavicle, the acromion and the spine of the scapula. Its upper, middle and lower portions elevate, retract and depress the scapula.
  • Latissimus dorsi
    A broad fan arising from the lower thoracic vertebrae, the thoracolumbar fascia, the iliac crest and the lowest ribs, converging on the bicipital groove of the humerus. It pulls the arm down and back, and drives vertical pulling.
  • Erector spinae
    Muscular columns — iliocostalis, longissimus and spinalis — running from the sacrum and iliac crest to the ribs, the vertebrae and the skull, on either side of the spinous processes. They extend the spine and control the trunk as it lowers.
  • Triceps brachii
    Three heads — long, lateral and medial — arising from the scapula and the back of the humerus and joining on the olecranon of the ulna. It extends the elbow, and its long head also assists shoulder extension.
  • Glutes
    Gluteus maximus, medius and minimus, arising from the iliac wing and the sacrum and inserting on the femur and the iliotibial tract. They extend, abduct and rotate the hip, and drive the pelvis upright in the hinge and the squat.
  • Hamstrings
    Biceps femoris, semitendinosus and semimembranosus, running from the ischial tuberosity to the tibia and fibula. They extend the hip and flex the knee, and control the trunk as it lowers in the hip hinge.
  • Calves
    The gastrocnemius and soleus, joining through the Achilles tendon onto the calcaneus. They plantarflex the ankle, and the gastrocnemius, which crosses the knee, also assists knee flexion.
  • Rotator cuff
    Four short muscles running from the shoulder blade to the top of the humerus. Their tendons merge into a sheet that holds the head of the bone against its socket while the deltoid moves the arm.
  • Serratus anterior
    A sheet hooked onto the upper ribs by triangular slips, passing under the shoulder blade and attaching to its inner border. It holds the blade against the ribcage and rotates it.
  • Iliopsoas
    The only muscle linking the lumbar spine directly to the femur. It descends from the vertebrae and the iliac fossa, curves around the rim of the pelvis and attaches to the lesser trochanter.
  • Hip adductors
    Five muscles running from the pubis to the back of the femur in overlapping layers. They draw the thigh towards the midline and control the pelvis in single-leg stance.
  • Forearm muscles
    Masses gathered near the elbow, continued by long tendons to the wrist and fingers. They drive the hand from a distance and carry grip strength.
  • Tibialis anterior
    A muscle pressed against the outer surface of the tibia, its tendon swinging towards the inside of the foot. It lifts the toes on every step and brakes the forefoot after heel strike.
  • Diaphragm
    A muscular dome running from the lower border of the ribs, the sternum and the lumbar vertebrae to a central tendon. As it contracts it descends, the chest gains volume and air enters: it is the engine of quiet breathing, and the ceiling of the abdominal cavity.
Guided steps
  • 1/5
    The front of the body. Pectoralis major covers the upper chest, the deltoid caps the shoulder, the biceps fills the front of the arm, the abdominal wall links the ribs to the pelvis, and the quadriceps fills the front of the thigh. Further out on the limbs, the forearm muscles drive the wrist and hand, and tibialis anterior lifts the foot.
  • 2/5
    The back of the body. The trapezius links the neck to the shoulder blades, the latissimus dorsi fans down to the pelvis, the erector spinae flank the spine, and the triceps fills the back of the arm. Glutes, hamstrings and calves form the posterior chain from hip to ankle.
  • 3/5
    Beneath the visible groups work muscles no silhouette shows. The rotator cuff holds the head of the humerus against the shoulder blade, serratus anterior keeps the shoulder blade flat on the ribcage, the iliopsoas links the lumbar spine to the femur, and the adductors fill the inner thigh. Deeper still, the diaphragm closes the trunk as a dome, inside the ribs. They orient and stabilise more than they move.
  • 4/5
    In a push, force starts at the ground, travels through the quadriceps and the abdominal wall, and then pectoralis major, the anterior deltoid and the triceps drive the load away from the trunk. The skeleton acts as the lever: no group works alone, and the quality of the movement comes from their sequencing.
  • 5/5
    In a pull, the latissimus dorsi and trapezius bring the arm and shoulder blade towards the trunk while the biceps flexes the elbow. Glutes, hamstrings and erector spinae hold the pelvis and spine so that force transfers without the trunk collapsing.
Model licence · Z-Anatomy et BodyParts3D — CC-BY-SA 4.0

The movements they take part in

They work in every pull. In the vertical pull as in the horizontal pull, they form the link between the bar and the rest of the body: without them, no force produced by the back can be transmitted.
They are also involved in carrying anything, and in most everyday actions — writing, opening a jar, holding handlebars.

Synergists

  • The biceps brachii shares supination with the supinator, and elbow flexion with brachioradialis.
  • The latissimus dorsi and the trapezius produce the force that a firm grip lets you transmit.
  • The intrinsic muscles of the hand refine the grip that the forearm flexors have begun.

Antagonists

  • Wrist flexors and extensors are antagonists to each other, and their balance stabilises the joint.
  • Pronator teres and pronator quadratus oppose the supinator and the biceps.

What the 3D model simplifies

Limit
A superficial plane for a layered region
The scene shows the superficial muscles of the forearm. Beneath them lies a second layer, notably the deep finger flexors, which produce a large share of grip strength and do not appear.
More importantly, what does most of the work of the hand is not visible: the long tendons, the synovial sheaths they slide through and the fibrous bands that hold them at the wrist. The model gives the position of the muscle masses, not the transmission mechanism that links them to the fingers.

Sources

Main sources

  • Standring S (2020). Gray's Anatomy: The Anatomical Basis of Clinical Practice, 42nd edition. Elsevier.
  • Neumann DA (2016). Kinesiology of the Musculoskeletal System: Foundations for Rehabilitation, 3rd edition. Elsevier.
Put it into practice in Shapier

Practise the farmer's carry

The farmer's carry is practised in Shapier; Body Lab only explains why carrying a load works the forearm.
Practise the farmer's carry
Body Lab explains; Shapier lets you act and track.

Check my understanding

Where does grip strength mainly come from?
What does brachioradialis do, unlike the other muscles arising near the lateral epicondyle?
In a heavy pull, what is likely to give out first?
Choose an answer

Read next

  • Biceps brachii
    The biceps brachii sits on the front of the upper arm and crosses both the shoulder and the elbow. It flexes the elbow, but its most specific function is supination of the forearm.
    With a 3D scene
  • Triceps brachii
    The triceps brachii fills the whole back of the upper arm and extends the elbow. Its long head also crosses the shoulder, which changes its length depending on the position of the arm.
    With a 3D scene
  • Latissimus dorsi
    The latissimus dorsi is the broadest muscle of the back. It links the pelvis and the spine to the humerus, and draws the arm down and backward in every pulling movement.
    With a 3D scene

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Trust and method

Author
equipe-editoriale-shapier
Editorial review
Thanh Chau
Scientific review
Pending
Published on
August 2, 2026
Reviewed on August 2, 2026
Next review due August 2, 2027
Limits of this page
  • The forearm holds around twenty muscles in several layers: the scene shows only the superficial plane, and the deep finger flexors do not appear.
  • The long tendons crossing the wrist and the sheaths around them are not represented, although they do most of the work of the hand.
  • This page describes an anatomy. Elbow or wrist pain that persists calls for examination by a health professional.
Sources
  • Standring S (2020). Gray's Anatomy: The Anatomical Basis of Clinical Practice, 42nd edition. Elsevier.
  • Neumann DA (2016). Kinesiology of the Musculoskeletal System: Foundations for Rehabilitation, 3rd edition. Elsevier.
Educational content. Body Lab does not diagnose and does not replace professional advice.
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