While trolling the internet for information about this post I came across “teres major steaks” sold online by a beef company. They report that teres major “a seldom used muscle in the shoulder,” is the hot new cut in fine dining, second only to the tenderloin (the psoas major) in tenderness.
Teres major is one of a number of muscles connecting the scapula to the humerus or arm bone (The other muscles that connect the shoulder blade to the arm are the four rotator cuff muscles and the deltoid).
Teres Major rotates the arm inwards (medial) and extends the arm slightly behind from the body. Additionally, the teres major helps the latisimus dorsi pull the arm down from over head. The latissimus dorsi (our swinging from the trees muscle) connects the arm to the spine and to the pelvis through the thoraco-lumbar fascia. The teres major and the latissimus dorsi tendons insert onto the arm bone right next to each other and actually connect for a bit.
Any time you clasp your hands behind your back you are employing teres major.