Individuals with hemiparetic stroke abnormally perceive their elbow torques when abducting their paretic shoulder

Objective: Individuals with hemiparetic stroke exhibit an abnormal coupling between shoulder abduction and elbow flexion, or flexion synergy, due to an increased reliance on cortico-bulbospinal pathways. While this motor impairment is well documented, its impact on how movements are perceived remains unexplored. This study investigates whether individuals with hemiparetic stroke accurately perceive torques at their paretic elbow while abducting at their shoulder. Methods: Ten individuals with hemiparetic stroke participated. We recorded the extent of their abnormal joint coupling as the torque at their elbow, with respect to the maximum voluntary torque in elbow flexion, when abducting at their shoulder. Next, we estimated the perception of their elbow torque by reporting their errors on our torque-matching task. Results: When abducting at the shoulder, the participants with stroke generated a greater non-volitional torque at their paretic elbow (13.2 ± 8.7%) than their non-paretic elbow (1.2 ± 11.2%) (p = 0.003). Regarding the perception of our torque-matching task, participants overestimated their torques to a lesser extent at their paretic elbow (1.8 ± 6.6%) than at their non-paretic elbow (6.2 ± 5.4%) (p = 0.004). Conclusions: Torque perception at the paretic elbow differed from the non-paretic elbow when abducting at the shoulder. Significance: This work advances our understanding of the i) somatosensory deficits occurring post hemiparetic stroke and ii) neural basis of torque perception.