TRAPEZIUS MUSCLE (Traps)
The trapezius (or trapezoid) is a large surface muscle originating, running vertically from the back of the head (occipital bone) to the lower portion of the thoracic spine. It has a horizontal aspect, moving from the spine laterally, along the top to the farthest edge of the scapula (shoulder blade).
The trapezius has three functions: The upper region supports the weight of the arm. The middle region retracks the shoulder blade. The lower part rotates and lowers the scapula.
Muscle imbalances in the trapezius significantly affect posture and disrupt normal shoulder motion leaving the shoulder vulnerable to injury.
Rounded shoulders and a stooped posture overstretches, thins, and eventually weakens the trapezius making it difficult to pull the shoulders back and down.
Many people with weak trapezius muscles complain of tightness and "knots" on the top of their shoulders, between their shoulder blades and at the base of their skull.