Robotic assessment of manual asymmetries in unimanual and bimanual wrist joint position sense

Despite being so similar from a biomechanical perspective, the left and the right arms develop with different dexterity and important functional differences. This asymmetry in motor performance, most commonly known as handedness, has been extensively investigated in numerous research. However, whether such a dominance exists in the proprioceptive system remains unclear. To this end, manual asymmetries in proprioceptive sensitivity were examined in fourteen neurologically healthy right-handed individuals, with a unimanual and bimanual robot-Aided wrist joint position matching (JPM) task, whereby they are required to replicate a reference wrist angle in the absence of vision. The results did not provide any evidence of manual asymmetries in proprioceptive acuity but some indication of asymmetry was singled out in motor execution, with smoother movement trajectories when the task was performed by the non dominant hand. In contrast, experimental conditions (unimanual vs. bimanual) appeared to influence proprioceptive acuity as well as movement kinematics: in the unimanual condition proprioceptive acuity was higher and more consistent and, despite the fact that movements were found to be faster in the unimanual task, they resulted smoother if performed with two hands at the same time. In sum, our results indicated that while there was a decrement in performance during bimanual tasks, there was no evidence of proprioceptive hand dominance.