The deltoid is a large, thick, triangular muscle of the shoulder girdle (pectoral girdle) that assists in movements of the shoulder and arm. It consists of three heads: the anterior, or clavicular, head covers the front of the shoulder; the middle, or acromial, head covers the lateral part of the shoulder; and the posterior, or spinal, head covers the back of the shoulder. When these three heads contract together, they abduct the arm.
This muscle is responsible or assists with the following joint movement(s):
Exercises that involve this muscle: