Electromyography–Force Relation and Muscle Fiber Conduction Velocity Affected by Spinal Cord Injury

Bioengineering, 2023 · DOI: 10.3390/bioengineering10020217 · Published: February 6, 2023

Simple Explanation

This study uses electromyography (EMG) to understand how spinal cord injury (SCI) affects muscles. Specifically, it looks at the biceps brachii (BB) muscle and how its electrical activity relates to the force it produces. The study found that in people with SCI, the speed at which electrical signals travel through muscle fibers (muscle fiber conduction velocity or MFCV) is slower compared to healthy individuals. This suggests that SCI affects the properties of the muscles themselves. Also, the relationship between the EMG signal and the force produced by the muscle is different in some SCI patients. This could mean that the way the brain controls the muscle is impaired after an SCI.

Study Duration

Not specified

Participants

15 SCI subjects and 14 healthy control subjects

Evidence Level

Not specified

Key Findings

1
Muscle fiber conduction velocity (MFCV) was significantly slower in the SCI group than the control group at all force levels.
2
The EMG–force relation in eight SCI subjects was best fit with negative quadratic coefficients, suggesting impaired EMG modulation at high forces.
3
All healthy control EMG–force relations were best fit with positive quadratic coefficients.

Research Summary

This study examined central neural and peripheral muscle changes after a spinal cord injury (SCI) using surface electromyography (EMG). MFCV was found to be significantly slower in the SCI group than the control group, evident at all force levels. The alterations in MFCV and EMG–force relation after SCI suggest complex neuromuscular changes after SCI, including alterations in central neural drive and muscle properties.

Practical Implications

Rehabilitation Strategies

Understanding the specific neuromuscular changes after SCI (altered MFCV and EMG-force relationship) can inform targeted rehabilitation strategies to improve muscle function and motor control.

Diagnostic Tool

EMG analysis, particularly using linear electrode arrays, can serve as a valuable diagnostic tool to assess the extent of neuromuscular impairment following SCI.

Therapeutic Interventions

The findings can guide the development of therapeutic interventions, such as electrical stimulation or exercise programs, aimed at restoring muscle fiber conduction velocity and improving the efficiency of muscle activation.

Study Limitations

1
The study solely applied global surface EMG parameters, making it difficult to differentiate or quantify various motor unit properties.
2
Surface electrode only records superficial regions of a muscle, and intramuscular recording may be necessary to capture activity of deeper motor units.
3
The study is limited by a relatively small subject number for performing meaningful sub-group analysis.

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