Augmented muscle activation in reaching movements after stroke

Abstract

Purpose. Post-stroke hemiparesis can cause motor deficits that affect the completion of functional activities, such as reaching. The study aim was to quantitatively compare the changes in muscle activation between hemiparetic individuals during the subacute and chronic phases of recovery and healthy individuals in a reaching task. Methods. The electromyographic activity was recorded of the upper trapezius (UT), biceps brachii (BB), triceps brachii (TB), flexor carpi ulnaris (FCU), and extensor carpi radialis (ECR ) muscles in 10 subacute individuals (group 1), 10 chronic individuals (group 2), and 10 healthy individuals (group 3). The normalized root mean square (nRMS) was calculated, followed by a qualitative index based on maximum activation, and the occurrence of co-contraction was analysed. Results. In the nRMS analysis, group 1 presented significantly higher activation than group 3 for BB, TB, and ECR ; group 2 showed significantly higher activation than group 3 for BB and FCU. In the qualitative analysis, group 1 exhibited greater activity for UT, group 2 for ECR , and group 3 for UT. There was no statistically significant difference in the co-contraction analysis between the antagonist muscle pairs of BB/TB and FCU/ECR. Conclusions. Muscle activation was greater in the post-stroke groups in comparison with healthy individuals.