The deltoid is a triangular-shaped muscle of the upper arm. It has three “heads,” hence the name. On the anterior (front) side of the body, it begins on the clavicle. The lateral (side) head begins on the acromial process, or
The sternocleidomastoid (SCM) is the large muscle in your neck that you can see when you turn your head to the side. It is a common cause of pain due to “tech neck.” This muscle is also prone to injury