It is inserted by means of a tendon on the largest part of the radius (lower arm bone). The movable end is pulled toward the origin when it contracts and the arm bends the elbow.  Both heads arise on the scapula and join to form a single body called a muscle belly which is attached to the upper forearm.

The biceps (two heads) cross the shoulder and the elbow joints, but its’ main function is to flex the elbow and supinate the forearm. There have been observations of more than two heads in the biceps and their head usually  arises from the humerus and then the muscle joins the short head and this is considered normal.

The biceps work across three joints  making it tri-articulate. The most important of these functions is considered to be supinating (palm side of the hand toward the shoulder) and elbow flexion.

 These joints  are listed and their actions are listed as follows along with the order  of their importance:

Functions of the Biceps:

• Proximal radioulnar joint (upper forearm) -  brings palms up when elbow is bent.

• Humeroulnar joint (elbow) - flexor of the  forearm with palms down.

• Glenohumeral joint (shoulder) - assists bringing the arm forward and upward and may help to bring the arm out to the side. The short head of the biceps brachii also assists in bringing the arm across the body and for assisting the shoulder to stabilize when supporting heavy weight carried in the arm.  This is due to it being attached to the scapula (shoulder blade).

In order to strengthen the biceps  it is understood that to  target the long head one must place the elbows behind the body and to target the short head one must keep the elbows in front of the body.