What muscle is engaged in the shoulder of the arm that is resting on the floor during the quadruped t-spine rotation?

During the quadruped T-spine rotation, the muscle that is primarily engaged in the shoulder of the arm resting on the floor is the serratus anterior. This muscle plays a key role in stabilizing the scapula against the rib cage during movements that involve upper body rotation and arm positioning.

As the individual rotates their thoracic spine, the serratus anterior assists in maintaining proper shoulder alignment and control. It helps facilitate the movement of the scapula as the upper body turns, ensuring that the shoulder remains stable and does not collapse, which is crucial for effective movement and injury prevention.

While the subscapularis, deltoid, and rotator cuff muscles all contribute to shoulder function, they do not have the same primary role in this specific exercise as the serratus anterior does. The subscapularis is involved in internal rotation of the shoulder, the deltoid primarily facilitates arm elevation, and the rotator cuff collectively stabilizes the shoulder joint but is not directly responsible for the shoulder positioning during the rotation.