Effect of muscle fatigue of the thoracic erector spinae on neuromuscular control and performance in people with adolescent idiopathic scoliosis

Background and purpose:
Adolescent idiopathic scoliosis (AIS) is a condition characterized by spinal mal-alignment, which may impair the stability and biomechanics of the spine. It has been hypothesized that long-term unbalanced compensatory neuromuscular control between the convex- and concave-side of the paraspinal muscles may further contribute to their asymmetrical activation and histological composition. To understand the role and the effects associated with muscle fatigue of paraspinal muscles in postural stability, this study investigated spinal alignment and neuromuscular control during shoulder elevations and the effects of paraspinal muscles fatigue on these factors.
Methods:
Electromyography of paraspinal muscles and spinal mobility (measured by surface tomography) during unilateral shoulder elevations with and without weights, before and after the fatigue task of the trunk extensors were compared between 15 AIS participants and 15 healthy controls (HC)
Results:
No between-group difference was found in endurance of trunk extensors. Significant time-and-group interaction was found in thoracic erector spinae (TES) between convex side of AIS (AISconvex) and HC groups. Significant decreases in both coronal translation and rotational mobility were found at AISconvex during the weighted-abduction at post-fatigue comparisons. Contrarily, a significant increase in rotational mobility was demonstrated at AISconvex during weighted-flexion tasks post-fatigue.
Conclusion:
Our results reveal a comparable paraspinal muscle endurance between the AIS and HC groups. TES activation at AISconvex was most affected by the fatigue of trunk extensors. The increase in muscle activation post-fatigue provides no additional active postural stability, however, its long-term effects on the curvature progression and spine health in AIS is yet to be investigated.