Beneath the clavicle, lies a small, rather demure muscle often left out of discussion when it comes to overall shoulder health. The subclavius, triangular in shape, is like a distant relative – it has its connection to the pectoral family and surrounding shoulder muscles, but its level of participation in the family affairs seems a bit ambiguous. “Sub” meaning under and “clavius” referring to the clavicle, the muscle name cleverly reflects its precise location within the chest cavity. This secondary muscle may seem to have little impact on shoulder health, but as you read further, the integrative role of the subclavius is quite impressive.
The subclavius originates high on the front of the chest, at the first rib and junction of the costal cartilage. It extends up a little posteriorly along the underside of the clavicle and inserts specifically to a groove on the inferior surface, middle one-third section of the clavicle known as the subclavian groove. In humans, this muscle is not only challenging to see, but it is also very difficult to isolate. But in four legged animals, such as a horse, the subclavius is larger and much more defined as it stabilizes the clavicle and shoulder girdle. This stability allows the animal to power from one move to the next, place to place.
So what does the subclavius muscle do and how does it integrate within the shoulder girdle?
Let’s first consider the primary objective of the shoulder girdle and our challenges with it. In the article, “Pivotal Places: Help for Problem Shoulders, “by Tom Meyers, he explains that, “the human shoulder was designed primarily for mobility and not stability…various problems such as hypermobility, friction and displacement are common problems. In addition, even slight displacements of the pelvis, lumbars, ribs, spine, neck or head may have a deleterious effect on shoulder function, especially when multiplied over months or years.” Meyers also discusses that there are three major points in the shoulder where certain muscles act as “pivots” in facilitating shoulder movement. The imbalances between these pivotal muscles can often lead to trigger points, faulty shoulder patterns and general dysfunction. These three crucial “pivotal muscles” are the subclavius, pectoralis minor, and teres minor, which I now visualize as the “Bermuda triangle” of the shoulder girdle.
Check back on Friday to learn how our daily habits may impact the subclavius and learn valuable self-care strategies to maintain healthy shoulder function.