Analysis of Agonist and Antagonist Muscles Coupling During Hand Grip in Post Stroke Participants

Abstract

After a stroke, the hand grip movement of the hemiparetic hand is impaired due to the loss of corticospinal input to the common drive. The analysis of the muscles coupling during movements can be made using the coherence method. This study proposed the analysis of the Magnitude Squared Coherence (MSC) between agonist-agonist (AG-AG) and agonist-antagonist (AG-AN) muscle pairs in a group of 9 post stroke participants compared to 32 healthy controls. Surface Electromyographic signals were acquired from the muscles Extensor Digitorum, Extensor Pollicis Brevis, Flexor Digitorum Superficialis, Flexor Digitorum Profundus and Flexor Pollicis Longus during hand grip movement and rest. The MSCs from the two participant groups were compared in the frequency bands delta, theta, alpha, beta and gamma, using a Wilcoxon test for independent samples. The results showed that the MSCs of AG-AG and AG-AN muscle pairs in post stroke participants are smaller (p < 0.01) than in healthy controls during hand grip movement. At rest, the behavior is repeated for the AG-AG muscles, but there is more coupling between AG-AN muscle pairs in post stroke participants in the lower frequencies. This can indicate that the coupling between AG-AG and AG-AN muscles is weakened in post Stroke participants and that there are anomalous motor unit activations at rest in AG-AN muscle pairs. This can happen due to the damaged corticospinal inputs to the common drive in post stroke participants.