ACSM Personal Trainer Certification Practice Exam

Which joint motion is facilitated by the supraspinatus muscle?

1. Horizontal adduction

2. Abduction

3. Adduction

4. Medial rotation

The correct answer is: Abduction

The supraspinatus muscle plays a crucial role in the movement of the shoulder joint, specifically by facilitating abduction of the arm. This muscle is one of the four rotator cuff muscles and is primarily responsible for initiating the abduction of the arm, especially during the first 15 degrees of motion. When the supraspinatus contracts, it pulls the head of the humerus upward into the glenoid cavity, allowing for the arm to move away from the body in a lateral direction. In contrast, horizontal adduction involves moving the arm across the body, adduction refers to moving the arm back toward the body, and medial rotation involves rotating the arm toward the midline. None of these movements are primarily associated with the action of the supraspinatus muscle, as its main function is clearly linked to abduction. Therefore, recognizing the specific role of the supraspinatus in abduction is essential for understanding shoulder mechanics and the contributions of different muscles during various arm movements.