NETA Personal Trainer Practice Exam

Which muscle is primarily responsible for shoulder abduction?

1. Posterior Deltoid

2. Latissimus Dorsi

3. Middle Deltoid

4. Transverse Abdominis

The correct answer is: Middle Deltoid

The middle deltoid is the primary muscle responsible for shoulder abduction. This muscle is located on the outer aspect of the shoulder and plays a crucial role in lifting the arm away from the body, particularly from an initial position at the side. When the middle deltoid contracts, it creates a powerful force that elevates the arm, making it essential for various overhead and lateral movements. While other muscles, such as the posterior deltoid and the latissimus dorsi, contribute to shoulder movements, they do not primarily facilitate abduction. The posterior deltoid, for instance, is more involved in shoulder extension and external rotation. Similarly, the latissimus dorsi predominantly assists in shoulder adduction, extension, and internal rotation rather than abduction. The transverse abdominis, in contrast, is primarily a core muscle that stabilizes the pelvis and spine during various movements but does not participate in shoulder abduction. Understanding the specific functions of these muscles highlights why the middle deltoid is the key player in this particular movement.