Related Experiment Video
Updated: May 1, 2026
Electroencephalography Network Indices as Biomarkers of Upper Limb Impairment in Chronic Stroke
Published on: July 14, 2023
Activation deficit correlates with weakness in chronic stroke: evidence from evoked and voluntary EMG recordings
Sheng Li1, Jie Liu2, Minal Bhadane1
1Department of Physical Medicine and Rehabilitation, University of Texas Health Science Center - Houston, Houston, TX 77030, United States; Neurorehabilitation Research Laboratory, TIRR Memorial Hermann Hospital, Houston, TX 77030, United States.
Objective:
To use evoked (M-wave) and voluntary (during maximal voluntary contraction (MVC)) EMG recordings to estimate the voluntary activation level in chronic stroke.
Methods:
Nine chronic hemiparetic stroke subjects participated in the experiment. M-wave (EMGM-wave) and MVC (EMGMVC) EMG values of the biceps brachii muscles were recorded.
Results:
Peak torque was significantly smaller on the impaired than non-impaired side. EMGM-wave was also significantly smaller on the impaired than non-impaired side. However, the normalized EMGM-wave/TorqueMVC ratio was not significantly different between two sides. In contrast, both absolute EMGMVC and normalized EMGMVC/TorqueMVC were smaller on the impaired than non-impaired side. The voluntary activation level, EMGMVC/M-wave, was also smaller on the impaired than non-impaired side. The voluntary activation level on the impaired side was highly correlated with weakness (R=0.72), but very low (R=0.32) on the non-impaired side.
Conclusion:
Collectively, our findings suggest that both peripheral and central factors contribute to post-stroke weakness, but activation deficit correlates most closely with weakness as estimated from maximum voluntary torque generation.
Significance:
These findings serve to highlight the potential benefit from high-intensity exercises to enhance central activation for facilitation of motor recovery.
