Which muscle eccentrically decelerates humeral external rotation, abduction, and flexion?

The muscle that eccentrically decelerates humeral external rotation, abduction, and flexion is the infraspinatus. This muscle plays a crucial role in the stabilization of the shoulder joint by assisting in the deceleration phase of shoulder movements. When the arm is raised externally or abducted, the infraspinatus works eccentrically to control and slow down the movement, thereby preventing excessive motion that could lead to injury.

The teres minor and teres major do have roles in shoulder movement and stabilization, but they are not primarily responsible for the deceleration of external rotation, abduction, and flexion in the same way the infraspinatus does. The latissimus dorsi also contributes to arm movements but is more associated with pulling actions rather than deceleration of the specific movements mentioned. Understanding the specific actions of these muscles is essential for effective exercise programming and corrective strategies, particularly in managing shoulder health and function.