Left Upper Trap & Left Scalene Overactivity

I know this is a broad question but was wondering what you all feel contributes most to tight left scalenes and upper trap. Would this be from poor ZOA and left abs, or would you maybe see this more with pathological patients?

Whenever I hear patients complain of left upper trapezius tightness, I think of their possible limitation of right hip abduction, either passively or actively. They are attempting to pull more into right thoracic abduction with their right lateral abdominal and lateral intercostals, and in the process of doing so compensate and integrate with their left upper traps to help “pull” the head over to the left, in addition to their entire upper thorax. So these patients lack frontal plane alternation with appropriate abdominals. Whenever I hear patients complain of or feel left scalene tightness, I think of a Superior T4 Syndrome pattern of respiration, where they are having difficulty getting air into their left apex because of left upper three ribs being in a state of internal rotation and their inability to expand the left upper apical lung region requires the left scalenes to help “pull” air into this region. The failed attempt to externally rotate the upper three ribs on the left because of the over active subclavius on the right, reinforces these left scalenes to become over used for both respiration and cervical stabilization during Superior T4 respiration. It is very common to find scalenes and upper trap tightness on the left with patients who are chronically engaged in respiratory challenge at the pelvis and thorax, as you mentioned, that results in compensation patterns that are not always necessarily associated with pathology, but could be.  
–Ron Hruska