Abstract
Electromechanical delay (EMD) is the time delay between the onset of muscle activity and the onset of force/joint torque. This delay appears to be linked to muscular contraction efficiency. However, to our knowledge, limited evidence is available regarding the magnitude of the EMD in stroke-impaired muscles. Accordingly, this study aims to quantify the EMD in both paretic and non-paretic triceps surae muscles of chronic hemispheric stroke survivors, and to investigate whether the EMD is related to voluntary force-generating capacity in this muscle group. Nine male chronic stroke survivors were asked to perform isometric plantarflexion contractions at different force levels and at different ankle joint angles ranging from maximum plantarflexion to maximum dorsiflexion. The surface electromyograms were recorded from triceps surae muscles. The longest EMD among triceps surae muscles was chosen as the EMD for each side. Our results revealed that the EMD in paretic muscles was significantly longer than in non-paretic muscles. Moreover, both paretic and non-paretic muscles showed a negative correlation between the EMD and maximum torque-generating capacity. In addition, there was a strong positive relationship between the EMD and shear wave speed in paretic muscles as well as a negative relationship between the EMD and passive ankle joint range of motion. These findings imply that the EMD may be a useful biomarker, in part, associated with contractile and material properties in stroke-impaired muscles.
| Original language | English (US) |
|---|---|
| Article number | 102475 |
| Journal | Journal of Electromyography and Kinesiology |
| Volume | 56 |
| DOIs | |
| State | Published - Feb 2021 |
Funding
We thank all participants in this study. We also thank Andres Cardona for technical preparation. This study was supported by grants from the National Institute on Disability, Independent Living, and Rehabilitation Research ( 90SFGE0005 ), the Davee Foundation Stroke Research Seed Grant Initiative and the Northwestern University Department of Neurology, Division of Stroke and Neurocritical Care , and the National Institutes of Health ( R01HD089952 ). William Zev Rymer, MD, PhD is Director of the Single Motor Unit Laboratory at the Shirley Ryan AbilityLab (formerly the Rehabilitation Institute of Chicago, or RIC). He served as the former Vice President for Research and the John G. Searle Chair of Rehabilitation Research at the RIC. Dr. Rymer has appointments as Professor of PM&R, Physiology, and Biomedical Engineering at Northwestern University. He received his medical training from the University of Melbourne, graduating with honors, and his PhD in Neuroscience from Monash University. His research concerns the neural control and biomechanics of movement in human and animal models, and the disturbances of voluntary movement and their origins in people with neurological disabilities, particularly those with stroke and spinal cord injury. He currently holds grants from the NIH, NIDILRR, and several foundations. He has published more than 300 papers, with more than 150 in the fields of biomechanics and control of movement. Dr. Rymer has conducted large and successful pre- and post-doctoral training programs in bioengineering and physiology for many years. He is currently Project Director of a NIDILRR-funded multi-center clinical trial to evaluate the effectiveness of intermittent hypoxia therapy in individuals with spinal cord injury.
Keywords
- Electromyogram
- Muscle material properties
- Muscle weakness
- Muscular contraction efficiency
- Stroke
ASJC Scopus subject areas
- Clinical Neurology
- Biophysics
- Neuroscience (miscellaneous)