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 wide range of arm movements. The subscapularis primarily functions to internally rotate the arm and assist in adduction. This muscle is innervated by the upper and lower subscapular nerves, which branch from the brachial plexus. Strengthening the subscapularis can help prevent shoulder injuries and improve overall shoulder function, making it important for athletes and individuals engaged in physical activities.