Which muscle is involved in the abduction of the humerus?

The medial deltoid is primarily responsible for the abduction of the humerus, which is the movement that raises the arm away from the body. Located on the outer shoulder, the medial deltoid specifically assists in lifting the arm when the humerus is positioned in the anatomical position.

During the initial stages of arm abduction, the medial deltoid engages effectively. The muscle fibers run laterally from the shoulder joint, allowing for the effective upward movement of the arm. This action is crucial for various functional movements such as reaching overhead or performing exercises that involve raising the arms.

In contrast, the anterior deltoid is involved primarily in shoulder flexion and medial rotation rather than abduction. The latissimus dorsi plays a role in adduction and extension of the shoulder rather than abduction, while the rectus abdominis, being a core muscle, does not assist in shoulder movements at all. Understanding the specific roles of these muscles is essential in both fitness training and rehabilitation contexts.