ACE Personal Trainer Practice Exam

The primary action of the supraspinatus muscle is to abduct the arm. This muscle is one of the four rotator cuff muscles located in the shoulder and is specifically responsible for initiating the first 15 degrees of arm abduction. After this initial movement, the deltoid muscle takes over to continue abduction beyond this point.

Understanding this role is important, especially in the context of shoulder stability and mobility. The supraspinatus helps maintain the position of the humeral head in the glenoid cavity during arm movements, which is crucial for shoulder joint function. Its role in abduction is vital for various overhead activities, making this muscle a key player in movements such as reaching and lifting.