Upper-limb coordination deficits in paraplegia during symmetrical movement tasks: Evidence from surface EMG and...

Neural pathways controlling the upper limb (UL) are spared in individuals with paraplegia, but the effect of lower-body sensorimotor pathways disruption on bilateral UL coordination remains unknown. This study aims to investigate the UL coordination in paraplegia during symmetrical movements.

Fifteen paraplegic individuals and nine healthy controls underwent surface electromyography and motion capture during two types of symmetrical movements to record activity of five bilateral shoulder muscles and bilateral shoulder joint angles. A modified Procrustes analysis aligned bilateral sEMG and angle curves. Maximum correlation coefficients (r_max) and normalized symmetry index (NSI) quantified bilateral similarity and symmetry. Canonical variates analysis (CVA) further assessed group differences.

The paraplegia group showed reduced bilateral symmetry and similarity compared to the controls. Main effects of group and movement were found for both r_max of all five muscles (group, p < 0.05; movement, p < 0.01) and NSI of shoulder joint angle in the sagittal plane (group, p = 0.049; movement, p = 0.006). Group effects (p < 0.05) were observed for NSI of the middle deltoid (MD), upper trapezius, and latissimus dorsi (LD). Significant movement effects were found in r_max of shoulder joint angle in the sagittal and coronal planes (p < 0.001). CVA achieved 93.8 % and 84.2 % group classification accuracy for the two movements, with MD, triceps brachii, and LD parameters contributing most.

Individuals with paraplegia exhibit impaired UL coordination, with neuromuscular measurements being more sensitive than kinematics in detecting deficits, highlighting the need for UL coordination restoration in rehabilitation.