what muscles do shoulder flexion
Pectoralis Major. The petoralis major is a large, strong muscle that produces shoulder flexion. It is located in the front of the chest and attaches by tendon to the humerus, or upper arm bone.ectoralis Major. The petoralis major is a large, strong muscle that produces shoulder flexion. It is located in the front of the chest and attaches by tendon to the humerus, or upper arm bone.