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Updated: Feb 24, 2026
Isokinetic Robotic Device to Improve Test-Retest and Inter-Rater Reliability for Stretch Reflex Measurements in Stroke Patients with Spasticity
Published on: June 12, 2019
Stretch-reflex threshold modulation during active elbow movements in post-stroke survivors with spasticity
Nicolas A Turpin1, Anatol G Feldman1, Mindy F Levin2
1Department of Neuroscience, Montreal, QC, Canada; Institute of Biomedical Engineering, University of Montreal, Montreal, QC, Canada; Center for Interdisciplinary Research in Rehabilitation of Greater Montreal (CRIR), Montreal, QC, Canada.
Post-stroke spasticity involves exaggerated stretch reflexes (SRs). This study found that stroke survivors can modulate SR thresholds during active movement, and this ability is linked to motor impairment.
Area of Science:
- Neuroscience
- Rehabilitation Medicine
- Biomechanics
Background:
- Voluntary movements after stroke are often impaired by abnormal muscle activation stemming from exaggerated stretch reflexes (SRs).
- Understanding the regulation of SRs in spastic muscles is crucial for addressing movement disorders post-stroke.
Purpose of the Study:
- To investigate the capacity of individuals with post-stroke spasticity to regulate their stretch reflexes (SRs) in spastic muscles.
- To determine if the modulation of SR thresholds during active movement differs from passive stretching.
Main Methods:
- Recorded elbow flexor and extensor electromyography (EMG) and joint angles in 13 subjects with chronic post-stroke spasticity.
- Muscles were stretched passively (relaxed arm) and actively (antagonist contraction) at various velocities.
- Defined velocity-dependent SR thresholds and calculated the sensitivity of SRs to stretch velocity (µ), interpolating to find the tonic SR threshold (TSRT) angle.
Main Results:
- Tonic SR thresholds (TSRTs) during active motion occurred at different muscle lengths compared to passive stretches (10-40° increase in flexors, decrease in extensors).
- The sensitivity of SRs to stretch velocity (µ) increased significantly (1.5-4.0).
- Changes in flexor TSRTs during active versus passive stretches correlated with clinical spasticity (r=-0.68) and arm motor impairment (r=0.81).
Conclusions:
- Stretch reflex thresholds, typically measured at rest, are modulated during active movement in post-stroke individuals.
- Arm motor impairment is associated with the ability to modulate SR thresholds between active and passive states, rather than solely with passive-state values.
- Deficits in the range and modifiability of SR threshold regulation may explain the relationship between spasticity and movement disorders, serving as a measure of sensorimotor deficits post-stroke.
