Scapulohumeral rhythm is the way the upper arm (humerus), and the shoulder blade (scapula), work together to move the arm. The “rhythm” is referring to the timing of these two parts of the body, that allow for smooth and coordinated movements of the arms. For example, when the arm is lifted up, the scapula also moves upwards and slightly rotates. This coordination allows for a smooth, full range of motion of the arm. In a healthy shoulder, the arm and shoulder blade move together in a balanced way—for every 2 degrees your arm moves up, your shoulder blade moves 1 degree. This synchronised movement helps keep everything aligned and functioning properly.
A good scapulohumeral rhythm also allows muscles of the upper back to stay in positions that can support the arm through its full range of motion. This will help avoid muscle strain or injury while moving. Scapulohumeral rhythm is also very important for maintaining the shoulder muscles length-tension relationship. This is a fancy way of saying that muscles work best when they are neither too stretched or too shortened. When they are at their correct length, they can produce the most strength. This allows for a stable shoulder while doing movements like overhead reaching or lifting in the gym.
Changes in this rhythm can affect the control and movement of this joint. Poor shoulder blade movement is often seen as forward tipping and rotation of the shoulder blade. This can cause pressure on the muscles that sit underneath the shoulder blade. This is typically felt as a pinch or pain around the shoulder blade. This incoordination of the arm and shoulder blade will eventually lead to shoulder impingement, instability, or injury to the supporting muscles. Scapulohumeral rhythm can be assessed for better performance through an increased range of motion as well as injury avoidance. Keys to look for to ensure proper shoulder rhythm are:
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