Rectus femoris hyperreflexia contributes to Stiff-Knee gait after stroke.
Tunc Akbas, Kyoungsoon Kim, Kathleen Doyle and 5 others
PMID 32843057WHAT IT FOUND
After stroke stiff-knee gait, people whose knee bent less during swing had a stronger thigh-muscle stretch reflex at toe-off.
This reflex was larger than when healthy people deliberately tightened the same muscle, so voluntary overactivity alone may not explain it.
Key findings
01In people with post-stroke stiff-knee gait, larger rectus femoris H-reflex responses were strongly related to less peak knee flexion during swing.
02During walking, rectus femoris H-reflex responses were higher in the post-stroke group than in healthy controls walking normally or deliberately increasing rectus femoris activity.
03Healthy controls showed lower rectus femoris H-reflex during walking than standing, but the post-stroke group did not show this standing-to-walking reduction.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
The sample was small, with ten post-stroke participants and ten healthy controls studied; one post-stroke participant could not complete the study and one healthy H-reflex value was excluded as an outlier. The study reports a correlation between reflex excitability and knee flexion; it did not alter reflex excitability or test a treatment, so it cannot show that hyperreflexia causes stiff-knee gait. Healthy controls voluntarily increased rectus femoris activity, which does not fully imitate the altered reflex, muscle properties, or coordination seen after stroke. The post-stroke group varied in time since stroke, medications, ankle-foot orthosis or cane use, walking speed, and peak knee flexion, so these factors could not be separated. The post-stroke group was 19.2 years older than the healthy control group, although the authors note that age generally reduces reflex excitability rather than increases it. H-reflex amplitude had to be estimated after subtracting an exponential fit to reduce overlap between the M-wave and H-reflex, which can add variability. Some data were excluded: kinematic data were unavailable for one post-stroke participant, one healthy participant's RF EMG biofeedback data were rejected, and one healthy H-reflex value was removed as an outlier.
The easy way to misread this
Do not conclude that rectus femoris hyperreflexia causes stiff-knee gait or that reducing it will improve walking. The study was an observational comparison of ten post-stroke participants and healthy controls and reported a correlation, not a treatment effect.