Which muscles comprise the shoulder muscle group?

The shoulder muscle group primarily includes the deltoid and trapezius muscles, which play crucial roles in shoulder movement and stabilization. The deltoid is a large, triangular muscle that forms the rounded contour of the shoulder; it is responsible for lifting the arm and gives the shoulder its range of motion. The trapezius, a large muscle extending down the back of the neck and upper spine, supports shoulder movement by aiding in elevation, retraction, and rotation of the scapula.

While other muscles mentioned in the options, such as the pectorals and latissimus dorsi, are important for upper body movement, they are not part of the shoulder muscle group specifically. The biceps, while they assist with certain arm movements, do not primarily function in the shoulder region. Similarly, spinal erectors have more to do with spinal stability and movement rather than shoulder mechanics.