The arm musculature

Synonyms in the broadest sense

Arm muscles, arm muscle training, upper arm muscles


The arm muscles, or elbow joint muscles, which are mainly located on the upper arm, act on the elbow joint. While three muscles are responsible for flexion, the triceps alone acts as the three-headed extensor of the upper arm. As this muscle has three heads, it acts as a multijoint muscle and additionally causes adduction and retroversion in the shoulder joint.

Upper arm musculature

The upper arm muscles are divided into two groups, the flexors and the extensors. The flexors include the biceps brachii and brachialis muscles and the extensors include the triceps brachii and the anconeus muscles. The musculus biceps brachii has two parts.

The caput longum (long “head“) originates from a small protrusion (tuberculum supraglenoidale) at the upper end of the humerus (caput humeri). The caput breve (short “head“) has its origin at the projection of the shoulder blade (Processus coracoideus). Both arms start at a small projection (Tuberositas radii) on the radius (forearm bone).

The tendon of the biceps also pulls into the aponeurosis bicipitalis, a part of the fascia of the forearm. The biceps is responsible for bending (flexion) and outward rotation of the hand by turning the forearm (supination). It also causes the arm to be abducted from the body (abduction) and the arm to move forward (anteversion).

The biceps has a greater distance to the flexion/extension axis than the brachial muscle and therefore has a greater torque during flexion. When the elbow is bent at right angles, the biceps is also the strongest supinator. The musculus brachialis lies below the biceps and is therefore closer to the flexion/extension axis than the biceps.

Therefore even small changes in the length of the brachialis lead to large bending movements in the elbow. It is therefore the stronger flexor. In addition, a few fibres of the brachialis pull into the joint capsule of the elbow and tension it, therefore it is also called capsule tensioner.

The Musculus brachialis has its origin at the anterior lower third of the humerus (Corpus humeri) and pulls to a rough muscle attachment point (Tuberositas ulnae) at the upper end of the ulna. The triceps has three “heads”, the caput longum (long), lateral (lateral) and medial (towards the middle of the body). The caput longum begins at the outer edge of the shoulder blade (tuberculum infraglenoidale).

The lateral caput has its origin at the lateral upper third of the humerus (proximal sulcus nervus radialis). The medial caput originates from the lower third of the humerus (distal sulcus nervus radialis). All three parts move towards the elbow.

The triceps is responsible for the extension of the arm and also causes the arm to move sideways towards the body (adduction). The musculus anconeus starts at the lateral elbow and moves to the upper, rear end of the ulna. It also causes an extension and is also a capsule tensioner like the brachialis muscle.