Sheng Li1, Jie Liu2, Minal Bhadane3, Ping Zhou4, W Zev Rymer2. 1. Department 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. Electronic address: sheng.li@uth.tmc.edu. 2. Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, IL, United States. 3. Department 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. 4. Department of Physical Medicine and Rehabilitation, University of Texas Health Science Center - Houston, Houston, TX 77030, United States; Biomedical Engineering Program, University of Science and Technology of China, Hefei, China.
Abstract
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.
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.
Authors: Tessa R Hill; Tor Ivar Gjellesvik; Per Marius R Moen; Tom Tørhaug; Marius S Fimland; Jan Helgerud; Jan Hoff Journal: Am J Phys Med Rehabil Date: 2012-05 Impact factor: 2.159
Authors: Trent J Herda; Jorge M Zuniga; Eric D Ryan; Clayton L Camic; Haley C Bergstrom; Doug B Smith; Joseph P Weir; Joel T Cramer; Terry J Housh Journal: Physiol Meas Date: 2013-02-12 Impact factor: 2.833