The is a prime mover of the glenohumeral joint during flexion. the is a prime mover of the glenohumeral joint during flexion. biceps brachii coracobrachialis deltoid teres major

THe answer to this question would be: deltoid

The glenohumeral joint is the join of upper arms(humerus) bones with the shoulder. Deltoid is the muscle in your upper arm near the shoulder. If this muscle contract, the upper arm will be doing flexion. Teres major is used in extension and adduction. Biceph brachii is muscle for lower arm.

Coracobrachialis. The coracobrachialis is responsible for contracting during flexion of the glenohumeral joint because of that it is the prime mover. When relaxed it places the arm in anatomical position.