Which muscle supports the arm in a position of 90 degrees of abduction?

Question

Quizplus · Accepted Answer

The middle deltoid is responsible for supporting the arm in a position of 90 degrees of abduction, as it is the primary muscle responsible for abduction of the arm in the horizontal plane. The anterior deltoid assists with flexion of the arm, while the posterior deltoid assists with extension of the arm. The pectoralis major assists with adduction and flexion of the arm, but not specifically in a position of 90 degrees of abduction.

Which Muscle Supports the Arm in a Position of 90