Knowing the major muscle groups (Pt3)
Let’s move on to some of the major muscle groups found in the front of the body. In this post we’ll discuss the location and action of four muscles: Pectoralis Major, Pectoralis Minor, Biceps Brachii, and Serratus Anterior.
Pectoralis Major: The “Pecs” as they’re collectively known are the large, broad muscle of the chest. Its muscle fibers are divided into three segments: upper (clavicular), middle (sternal), and lower (costal). All three segments help to: adduct the shoulder, medially rotate the shoulder, and aid in forced inhalation by lifting up the ribcage. Its upper and lower segments however are capable of performing opposing actions. The upper fibers can flex and horizontally adduct the shoulder, while the lower fibers can extend the shoulder.
When the Pecs are tight they can create a whole host of undesirable side effects. Tight Pec muscles can pull the shoulders forward putting the muscles of the upper back on a perpetual stretch. This can lead to a rounded shoulder posture and can force the head and neck to pitch forward, creating a further postural imbalance. This upper crossed posture has been known to compress nerves, constrict blood vessels, restrict breathing, and lead to chronic head, neck and jaw pain.
Pectoralis Minor: Underneath Pec Major lies the smaller Pec Minor muscle. This muscle originates along ribs 3-5 and converges upward to attach on a part of the scapula known as the coracoid process. As a result Pec Minor acts predominantly on the scapula. It serves to: depress the scapula – moving downward along the ribcage, abduct the scapula – moving it away from the spine, and tilt the scapula anteriorly – shifting the scapula forward. Pec Minor also assists Pec Major in forced inhalation.
A tight Pec Minor can also contribute to a rounded shoulder posture. More importantly it can constrict the major blood vessels and nerves that supply the arm due to its direct placement over them. This type of neurovascular compression can lead to shooting nerve pain, numbness and tingling, and weakness of the arm and hand.
Biceps Brachii: Just about everyone knows where their Biceps are. From an early age when we’re taught to “make a muscle”, we automatically flex our Biceps. And as the name implies, the Biceps consist of two muscle bellies – the long head, which is the outermost belly and the short head, which lies closest to the chest.
Both heads of the Biceps help to: flex the elbow, flex the shoulder, and supinate the forearm – that is, turn the forearm so the hand is face up. The Biceps also play a big part in stabilizing the shoulder joint. Without the biceps, the shoulder joint would not be able to maintain any significant weight without being pulled apart.
We rarely feeling pain along the Biceps themselves, but when they’re in trouble, fully extending the elbow with hand face down can be difficult and painful. Trigger points in this muscle will most often refer pain to the front of the shoulder jointand along the elbow crease.
Serratus Anterior: Although not as well known as the Biceps, Serratus Anterior is often very well developed in superheroes. Yes, superheroes! Located just below the armpit along the side of the ribs, its serrated ends are distinctly outlined in some of our most beloved action heroes. One end of the muscle attaches to the underside of the scapula, while the other end attaches to the upper nine ribs. It’s this small portion of the muscle which is actually visible, most of it lies hidden beneath the scapula, the Lats, and Pec Major.
Despite its placement, Serratus Anterior is a shoulder muscle. It serves to abduct and depress the scapula. It also helps to stabilize the scapula and aid in forced inhalation. Runners may be familiar with the all too common “side stitch” pain, which can result from a spasming of this muscle.
