Investigating the Neuromuscular Response to Sudden Wrist Perturbations

The purpose of this work was to evaluate changes in forearm muscle activity and co-contraction caused by sudden wrist perturbations during a dynamic wrist tracking task using a haptic wrist robot. Surface electromyography was recorded from eight muscles of the upper-limb. Participants were seated with their forearm placed on an armrest, grasping the handle of a haptic wrist robot. Participants performed trials consisting of 17 repetitions of ±40° of wrist flexion/extension. During trials, participants received 3 perturbations. Perturbations varied based on condition: radial or ulnar direction, during flexion or extension, and with known or unknown timing. Co-contraction ratios for all muscle pairs illustrated significantly greater extensor activity across all experimental conditions. Expected (known) perturbations produced greater anticipatory muscle activity as well as greater task performance. While improving performance, this increase in anticipatory muscle activity may leave muscles susceptible to early-onset fatigue and chronic overuse injuries in the workplace