Electromyographic patterns of the rat hindlimb in response to muscle stretch after spinal cord injury

Spinal Cord, 2018 · DOI: 10.1038/s41393-018-0069-z · Published: June 1, 2018

Simple Explanation

Stretching is a common therapy for muscle contractures and spasticity after spinal cord injury (SCI). This study aims to characterize the electromyographic (EMG) patterns in rat hindlimbs in response to muscle stretch after SCI, measuring applied forces during stretching. The study identified three main EMG patterns in response to stretch: clonic-like, air-stepping, and spasms. These patterns are similar to those reported in humans. The torques applied during stretching were comparable to those applied by physical therapists when stretching patients, based on the ratio of torque to body weight.

Study Duration

8 weeks

Participants

4 female Sprague Dawley rats

Evidence Level

Not specified

Key Findings

1
Three main EMG patterns in response to stretch were identified: clonic-like, air-stepping, and spasms.
2
The torques applied during stretching ranged from 0.8–6 N*cm and did not change significantly over the weeks of stretching, except for quadriceps stretches, which gradually increased.
3
Stretching evokes EMG patterns in rats similar to those reported in humans including clonus and spasms.

Research Summary

This study characterized hindlimb EMG patterns in rats with SCI in response to muscle stretch, identifying clonic-like, air-stepping, and spasm responses, which are similar to those seen in humans. The study also measured the torques applied during stretching and found them to be comparable, when scaled for body weight, to those used by physical therapists in human patients. The findings suggest that stretching may have similar effects on the nervous system in rats and humans, warranting further investigation of its impact on motor function in human subjects.

Practical Implications

Translational Relevance

The similarity in EMG patterns between rats and humans suggests that rat models can be useful for studying the effects of stretching on motor circuitry after SCI.

Clinical Considerations

The study highlights the importance of considering the applied torques during stretching interventions for SCI patients, as they are comparable to those used in animal models.

Further Research

The study calls for further investigation into the effects of stretching on motor function in human subjects with SCI, given the potential for similar nervous system effects as observed in rats.

Study Limitations

1
Small sample size may limit the statistical significance of some findings.
2
Accuracy of force sensor measurements is dependent on precise localization.
3
Comparison of torques between rats and humans is limited by unknown sensitivity to applied torques in rats.

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