Excerpted from: (Page, Frank, Lardner. Assessment and Treatment of Muscle Imbalance, The Janda Approach. 2010, Human Kinetics, Champagne IL.)
Thoracic outlet syndrome (TOS) is characterized by compression of the neurovascular structures between the neck and the shoulder— specifically, between the scalenes and the first rib or between the pectoralis minor and the coricoid process. Symptoms include parethesia, numbness, and pain in the upper extremity. Obviously, muscle tightness and imbalance play a role in TOS.
Poor posture or repetitive overhead work can contribute to TOS. Abnormal posture and compensated movement patterns cause an imbalance in muscle tightness and weakness in the upper back, neck, and shoulder contributing to increased mechanical pressure around the nerves.
The postural deviations that result from muscle imbalance in TOS include: tightness of the SCM leading to a forward head position, tightness of the upper trapezius and levator scapula causing elevation and protraction of the shoulder girdle. Janda recommends releasing the short/tight ‘tonic’ structures (upper trapezius, levator scapula, scalenes, SCM, and suboccipitals). The ‘phasic’ muscles (middle and lower trapezius and serratus anterior) will easily recover their strength, on their own.
Some schools of therapy (?), who shy away from hands-on bodywork, mistakenly attempt to strengthen (with exercise) the weak phasic muscles first. From a neuromuscular perspective, this is ‘putting the cart before the horse’. A basic understanding of Sherrington’s Law of Reciprocal Inhibition will clarify why the short/tight ‘tonic’ structures must be released first.