NETA Personal Trainer Practice Exam

The muscle that primarily assists with shoulder abduction within the first 30 degrees is the supraspinatus. This is because the supraspinatus muscle, which is one of the rotator cuff muscles, plays a crucial role in initiating the abduction of the arm at the shoulder joint. It acts to stabilize the humeral head in the glenoid cavity and allows the first part of the abduction movement, making it essential for raising the arm straight out to the side. While other muscles, such as the deltoid, become more active in shoulder abduction as the movement continues beyond the initial 30 degrees, the supraspinatus is specifically responsible for the first portion of this movement. It effectively engages before the deltoid takes over more completely, demonstrating the importance of the supraspinatus in the early phase of shoulder abduction.