Lats

The latissimus dorsi is a stronger shoulder adductor when the shoulder is somewhat externally rotated. It is a stronger shoulder extensor when the shoulder is in anatomical position. Incidentally, the latissimus dorsi does not extend the shoulder beyond anatomical position (shoulder hyperextension). In strict transverse extension, the latissimus dorsi is weak. The posterior deltoid is strongly involved in both shoulder hyperextension and transverse extension.