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Evidence for increased neuromuscular drive following spinal manipulation in individuals with subacromial pain syndrome


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Structural and chiropractic

Clin Biomech (Bristol, Avon).2021 Dec;90:105485.


A K Hegarty, M Hsu, J Roy, J R Kardouni, J J Kutch, L A Michener


Background: Thoracic spinal manipulation can improve pain and function in individuals with shoulder pain; however, the mechanisms underlying these benefits remain unclear. Here, we evaluated the effects of thoracic spinal manipulation on muscle activity, as alteration in muscle activity is a key impairment for those with shoulder pain. We also evaluated the relationship between changes in muscle activity and clinical outcomes, to characterize the meaningful context of a change in neuromuscular drive. Methods: Participants with shoulder pain related to subacromial pain syndrome (n = 28) received thoracic manipulation of low amplitude high velocity thrusts to the lower, middle and upper thoracic spine. Electromyographic muscle activity (trapezius-upper, middle, lower; serratus anterior; deltoid; infraspinatus) and shoulder pain (11-point scale) was collected pre and post-manipulation during arm elevation, and normalized to a reference contraction. Clinical benefits were assessed using the Pennsylvania Shoulder Score (Penn) at baseline and 2-3 days post-intervention. Findings: A significant increase in muscle activity was observed during arm ascent (p = 0.002). Using backward stepwise regression analysis, a specific increase in the serratus anterior muscle activity during arm elevation explained improved Penn scores following post-manipulation (p < 0.05). Interpretation: Thoracic spinal manipulation immediately increases neuromuscular drive. In addition, increased serratus anterior muscle activity, a key muscle for scapular motion, is associated with short-term improvements in shoulder clinical outcomes.

Publication Date: 

2021 Dec



Hegarty, KA., Hsu, M., Roy, J., Kardouni, RJ., Kutch, JJ., Michener, AL. (2021) 'Evidence for increased neuromuscular drive following spinal manipulation in individuals with subacromial pain syndrome', Clin Biomech (Bristol, Avon).2021 Dec;90:105485.

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