The deltoid muscle is used in all side lifting movements and any movement of the humerus on the scapula. It is divided into three portions, anterior, middle and posterior, with the fibres having different roles due to their orientation.
The Supraspinatus muscle is one of the four muscles which make up the rotator cuff. Its main function is to stabilise the upper arm by holding the head of the humerus in position. It is important in throwing motions to control any forward motion of the head of humerus.