There is a muscle that sits underneath your arm pit called the Serratus Anterior (SA) which originates from the inners side (nearest spine) of the underside of the scapula (shoulder blade) and attaches to numerous ribs on the same side of the body – see picture for clarity!
Serratus Anterior muscle
The SA is a scapula prime mover, meaning it is vitally important in both moving the shoulder. It also vital in controlling the shoulder blade’s movement. It is a key upward rotator and posterior tilter, creating room for the arm to move freely. In order to reach higher than about 90° (shoulder level) the scapula must upwardly rotate. If the SA is weak, and so not adequately rotating, the shoulder blade can not get out of the way of the arm, and that leads to “pinching” at the top of the shoulder, which can lead to shoulder impingement type syndromes or subacromial bursitis. Over time, it can even lead to secondary issues, as the other important role of the SA is to anchor/hug the scapula to the thorax when using the arm. If the scapula doesn’t have that stability, then the rotator cuff must work much harder, which – again – can lead to pain and/or injury.
When contracting, it pulls the scapula forward around the thorax (ribs) – pulling the shoulder blades away from each other – and so is in a tug of war with the rhomboid muscles, a muscle group that is often worked in isolation the gym pulling the shoulder blades together…
The SA is sometimes called the boxer’s muscle because of this movement, and its significant role in throwing a punch. During a punch, this muscle quickly brings the scapula forward and around – and almost hugging – the rib cage. Because of this action it is also essential in sports that involve throwing and catching, or bringing the arms overhead, or any daily activity that requires the arm to be raised or extended outward. The SA is mostly hidden from view, so it is easy for people to forget about this vital muscle (NOT Superheroes, however…)
Batman; definitely doing his Push-Up Plus’
It is important to have a healthy, strong SA for everyone, but particularly for those lifting heavy weights in the gym, or with postural shoulder issues. Below is a chart by Sports Physiotherapist Adam Meakins (https://thesportsphysio.wordpress.com/) which shows electro-myographical readings for SA exercises, the best exercises being Resisted Scap. Raise and Push Up Plus.
Serratus Anterior Muscle Activity, by @AdamMeakins (twitter)
The shoulder is the most mobile joint in the body; because of this it needs controlling. Muscle strength and timing are another two variables in the equation. Sometimes strength and timing can become inhibited, for a multitude of reasons. Is it time to back away from the bench press?
N.B. There are no ‘one size fits all’ style quick fixes in most injury scenarios, so these article shouldn’t be seen as such. They are merely guides to a better understanding of how our bodies work.