GLOSSARY

The serratus anterior is a broad muscle on the lateral chest wall that arises from the ribs by saw-like digitations and holds the scapula against the rib cage; it is also called the “boxer’s muscle”.

Attachments and Innervation

• Origin: the outer surfaces of ribs one to eight or nine.
• Insertion: the anterior surface of the medial border of the scapula, beneath the scapula between it and the rib cage.
• Nerve: the long thoracic nerve (C5–C7), which runs superficially on the outer surface of the muscle.

Actions

• Protraction of the scapula: as in punching and pushing.
• Upward rotation of the scapula: with the trapezius, essential for raising the arm overhead.
• Posterior tilt of the scapula.
• Holding the scapula against the chest wall and preventing winging.

Clinical Application

Medial scapular winging: injury to the long thoracic nerve, for example from a direct blow, carrying a heavy backpack, or surgery, makes the medial border of the scapula protrude, especially when pushing against a wall.

Relevance to Sport

• Boxing and throwing: maximising reach by protracting the scapula.
• Overhead sports: its weakness is associated with shoulder impingement.
• Exercises: the push-up plus, cable punches, wall slides, and the overhead press.