Which muscle concentrically accelerates external rotation of the humerus?

The teres minor is the muscle that plays a significant role in the external rotation of the humerus. As a part of the rotator cuff group, the teres minor assists in stabilization and movement of the shoulder joint. When it contracts concentrically, it creates the necessary motion to rotate the humerus outward. This function is vital, especially in activities that require overhead motions or the throwing actions commonly seen in sports.

In contrast, while the infraspinatus also contributes to external rotation of the humerus, it was not the selected answer in this case. The deltoid muscle primarily functions in arm abduction and has anterior and posterior parts that facilitate various movements in the shoulder, but it is not the main muscle responsible for the concentric acceleration of external rotation specifically. Meanwhile, the teres major is involved primarily in internal rotation and extension of the humerus rather than external rotation.

Understanding the distinct roles of these muscles is crucial for corrective exercise specialists, as knowing which muscles to target for particular movements can greatly influence rehabilitation and performance training outcomes.