Forearms

Dozens of small muscles that move the wrist and fingers and, above all, deliver grip. Grip strength is one of the best simple markers of overall strength and even longevity.

This muscle in 3D

Drag to rotate · scroll to zoom — see the shape, origin and insertion of the forearms. 3D model via Sketchfab (CC-BY).

Anatomy

Muscles: Wrist/finger flexors (anterior), wrist/finger extensors (posterior), brachioradialis

Origin: Flexors: medial epicondyle of the humerus (inner elbow). Extensors: lateral epicondyle (outer elbow).

Insertion: Bones of the wrist, hand and fingers via long tendons.

Actions:

Wrist flexion / extension
Finger flexion (grip) and extension
Radial & ulnar deviation
Brachioradialis: elbow flexion in neutral grip

How the muscle works

Long tendons run from muscles in the forearm all the way to the fingers, so the fingers are moved by 'remote control'. Grip is mostly isometric — sustained finger-flexor contraction against a bar or load.

Fibre-type bias: Endurance-biased (type I) — built to sustain grip and posture over time.

Functional role: Grip and carry; controlling every hand task and every pulling lift.

Common problems

Lateral epicondylitis ('tennis elbow', extensors)
Medial epicondylitis ('golfer's elbow', flexors)
Carpal tunnel / overuse strain

Training & stretching

Dead hangs, farmer's carries, wrist curls and extensions, reverse curls.

Wrist flexor stretch (palm up, gently pull fingers back) and extensor stretch (palm down).