The subscapularis is a muscle located in the shoulder region, specifically on the underside of the scapula, or shoulder blade. It is one of the four rotator cuff muscles, which play a crucial role in stabilizing the shoulder joint and allowing for a range of arm movements. The subscapularis primarily helps in the internal rotation of the arm. This muscle is innervated by the upper and lower subscapular nerves, which branch from the brachial plexus. Strengthening the subscapularis can improve shoulder function and reduce the risk of injuries, making it important for athletes and individuals engaged in physical activities.