Answer: supraspinatus Muscle causing impingement issues

The supraspinatus muscle in the shoulder is a quite small muscle and it may not be the only muscle that is tightened in the joint.
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As with any muscular rigidity, we have to ask ourselves, what is the cause of involuntary tightened muscles in the body? They are induced by a reaction triggered by the autonomic nervous system (ANS), specifically the Sympathetic component of the nervous system.
There is no other mechanism for this condition in the body.

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