Effect of Muscle Fatigue of the Thoracic Erector Spinae on Neuromuscular Control and Performance in People with Adolescent Idiopathic Scoliosis

Adolescent idiopathic scoliosis (AIS) distorts spinal alignment and increases the demand for active postural stabilization. Understanding the biomechanical impacts associated with muscle fatigue would inform the role and importance of paraspinal muscle endurance for efficacy of postural stability in AIS individuals.

This study investigated the effects of muscle fatigue over the thoracic erector spinae (TES) on muscle activity along the upper-limb kinetic chain and spinal kinematics in individuals with AIS.

Electromyography of spinal, axioscapular and scapulohumeral muscles, and spinal mobility measured by surface tomography were compared between 15 AIS participants and 15 healthy controls (HC) during unilateral shoulder elevations with and without weights, performed before and after the fatigue task (prone isometric chest raise).

No significant difference was found between the AIS and HC groups for endurance of trunk extensors. Significant time-and-group interactions were found in TES, lower trapezius (LTr), lateral deltoid (LD) and anterior deltoid between the convex side of the AIS (AISconvex) and HC groups. Significant decreases in both coronal translation and rotational mobility were found at AISconvex during the weighted-abduction tasks post-fatigue. Contrarily, a significant increase in rotational mobility was demonstrated at AISconvex during weighted-flexion tasks post-fatigue.

Our results reveal a comparable paraspinal muscle endurance between the AIS and HC groups. TES, LTr, LD activation at AISconvex were most affected by the fatigue of trunk extensors. The increase in muscle activation post-fatigue provides no additional active postural stability but may increase the risk of back pain and related shoulder pathologies over the convex side in AIS individuals.