Influence of visual feedback gain and contraction intensity on the discharge properties of motor units recruited in a force-matching task

Decomposition of intramuscular electromyogram (iEMG) into its constituent motor unit spike trains is a useful tool for understanding the neurophysiological control of muscle force. Some experimental results have shown that the performance in a force-matching motor task is influenced by the gain of the visual feedback provided to the subject. In this project, the propose was to decompose iEMG signals from the Soleus muscle recorded in a force-matching task (plantarflexion contractions with different intensities). The motor unit spike trains were analyzed in six different conditions of visual feedback. From the results found, the visual feedback gain seems not to influence the discharge properties of MUs recruited in a force-matching task. Force intensity only influenced the number of recruited MUs and the MU FR, which is expected from the recruitment and rate coding mechanisms of force control.