Changes in thoracic erector spinae regional activation during postural adjustments and functional reaching tasks after spinal cord injury

Abstract Background: A substantial proportion of individuals with incomplete spinal cord injury (SCI) exhibit reduced volitional control of trunk muscles due to damage of the corticospinal tract, resulting in impaired postural control and function. Studies using conventional bipolar electromyography (EMG) showed altered activity of the trunk muscles in people with SCI. However, the spatial distribution of trunk muscle activity remains unknown. Therefore, this study aimed to investigate the spatial distribution of the erector spinae (ES) below the level of injury in individuals with incomplete SCI during postural tasks and multidirectional reaching tasks using high-density EMG. Methods: Twenty-one individuals with incomplete SCI and 21 age-matched healthy controls performed two postural tasks (rapid shoulder flexion and external perturbation tasks) and multidirectional reaching tasks. EMG amplitude of the thoracic ES and displacement of the arm, trunk, and centre of pressure were recorded during the tasks. Results: Overall, the EMG amplitude of the ES was lower, and activation was distributed more in the caudal part of the ES in individuals with SCI compared with the controls during the postural and reaching tasks. EMG amplitude was greater during reaching forward than returning to the upright posture in the controls; however, this phase-dependent difference in the EMG amplitude was not present in individuals with SCI. Conclusions: Our findings demonstrate alterations in regional activation of the thoracic ES during postural and reaching tasks after SCI, suggesting a loss of selective control from the central nervous system to the trunk muscles.