The serratus anterior muscles are located on your rib cage under your arms. They are anchored to the top eight or nine ribs. They attach to the scapula -- or shoulder blade -- between the ribs and scapula, on the edge near the spine. When you tighten the serratus anterior muscles, they can look like ribs, but if you feel them you'll realize they are muscular.
Action
The serratus anterior pulls your scapula forward when you roll your shoulders forward or make a move like a jab in boxing. It's the opposite to squeezing your shoulder blades together in the back. The serratus anterior muscles stabilizes the scapula, holding it against your ribs. One of the symptoms of a weak serratus anterior muscle is "winging," when the medial edge of the scapula, the edge closest to the spine, stands out like a wing because the serratus anterior isn't pulling it into place on your ribs.
Injury
The serratus anterior muscle is susceptible to injury due to overuse when you participate in work or sports that rely on the arm and shoulder, such as tennis, swimming or chin-ups. It can spasm through forced inhalation, for instance when you run. The serratus is a secondary breathing muscle -- the diaphragm is the primary breathing muscle -- and the "stitch" or pain you feel in your side when you are breathing too hard is a spasm in the serratus anterior muscle.
Fascial Binding
The serratus anterior is one of a band of muscles connected by fascia. The rhomboid muscles are anchored close to the spine and attach to the scapula right next to the serratus anterior. The connective tissue of the rhomboids blends into the connective tissue of the serratus anterior and then merges into the connective tissue of the external oblique muscle, which extends from the serratus anterior to the front of the hip. It's as if the three muscles are actually one long muscle that starts at the spine and wraps around the ribs, ending up at the front of the hip bone. So if you have a spasm or trigger points in one of these muscles, you may have some in the other two muscles, too.
Exercises
To exercise the serratus anterior muscles, just think of their actions. They pull the scapulae forward, so exercises that require you to move your arms forward -- hitting a punching bag, for instance -- will work the serratus anterior muscles. Doing the opposite movement -- squeezing your shoulder blades together in the back -- stretches the serratus anterior muscles. Raising your arms over your head with hand weights works the top fibers of the serratus anterior.
References
- ExRx.net; Serratus Anterior; 1999
- "J Brachial Plex Peripher Nerve Inj"; Rapid Recovery of Serratus Anterior Muscle Function...; R. Nath, et al.; February 2007
- Duke University; Wheeless' Textbook of Orthopaedics -- Serratus Anterior; Clifford Wheeless
- "The Trigger Point Therapy Workbook"; Clair Davies; 2004
