Decrease in the excitability of spinal nerve function corresponding to the soleus muscle during terminal phase of heel-raise imagery.
Hirokazu Takasaki, Hitoshi Asai, Kenji Suehiro and 2 others
PMID 39624344WHAT IT FOUND
Imagining a heel raise increased spinal nerve excitability for 600 ms after the cue, but this effect disappeared by 800 ms.
The study tested healthy adults lying down, so it does not show this timing applies to patients or functional movement.
Key findings
01Spinal nerve excitability, measured by the H/M max ratio, was significantly higher than rest at 0, 200, 400, and 600 ms after the start of the imagery cue.
02Excitability was not significantly different from rest at 800 ms, and was significantly lower than the peak observed at 400 ms.
03The vividness of the mental imagery, as rated by participants, did not correlate with the change in spinal nerve excitability.
STILL TO COME
How it was doneWhat they foundWhat it means for PTsWhat it means for OTsWhat it means for SLPs
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What it does not show
The study was conducted on healthy young adults (mean age 27.1 years), so the findings may not apply to stroke patients or older adults with different neural excitability baselines. Participants were lying supine (on their backs), not standing. This removes the postural and gravitational demands of the actual movement, which could alter how the nervous system responds to imagery. The study only measured excitability at five specific time points (0, 200, 400, 600, 800 ms). Changes between these points, or after 800 ms, were not captured. The imagery was silent (no actual movement occurred). The results describe the neural response to imagining the movement, not the response during actual execution.
Declared interests
The authors declared no specific funding from public, commercial, or not-for-profit sectors.
The easy way to misread this
Do not assume that motor imagery provides a sustained increase in spinal excitability throughout a movement task. The effect was short-lived, peaking at 400 ms and disappearing by 800 ms. Also, do not expect that making the imagery 'more vivid' will change the spinal response, as no correlation was found.