Biceps
Musculus biceps brachii
// Structure & location
The biceps has two heads. The long head arises by a thin tendon at the top of the socket and runs through the shoulder joint and a bony groove on the humerus. The short head comes from the coracoid process at the front of the shoulder blade. Both join into one muscle belly and insert via a tendon on the radius. Underneath lies the brachialis, which adds thickness to the arm.
// Function
The biceps bends the elbow and rotates the forearm so the palm faces up (supination). With the elbow bent it is the strongest supinator, the motion of driving in a screw with the right hand. Because both heads cross the shoulder joint, it also helps a little in raising the arm forward.
// For training & sport
- Dumbbell or barbell curls train it directly. With the palm turned up it works hardest.
- In hammer curls (thumb up) the brachialis and brachioradialis take over more work.
- Curls with the arm behind the body, for example on an incline bench, stretch the long head more because it crosses the shoulder.
- Chin-ups and rows train it as a helper.
// Good to know
If the long biceps tendon tears at the shoulder, the muscle belly slides down. This creates a typical bulge on the upper arm, known as the Popeye sign.