Infraspinatus / Teres Minor
These two muscles do the same things, together.
• They work with the latissimus dorsi--your mid-back muscles--to perform movements like chin ups where the upper arm is drawn from the front horizontal position down toward your sides.
• They also work with the rear deltoid to pull the upper arm back from the front horizontal position to the side horizontal position.
• They turn the arm outward.
• And, they counteract the upward pull of the middle deltoid on the humerus, keeping it from being jammed into the top of the shoulder joint.
ORIGIN:
Most of the back of the shoulder blade, beneath its spine.INSERTION:
Greater tubercle of the humerus, posterior side.ACTION:
Horizontal abduction of the shoulder joint.Extension of the shoulder joint.
External rotation of the shoulder joint.
example exercise