Show shoulder width. When the humerus moves forward, you will see that your shoulder protrudes forward, much like a serious round shoulder, which is shoulder-width. When the humerus moves forward, the humeral head moves forward relative to its original position. When the humerus moves forward, the tissues on the front side of the shoulder joint, including the front of the joint capsule and the deltoid muscle, will be pulled, resulting in tension and pain.