Plantar pressure trigger for reliable nerve stimulus application during dynamic H-reflex measurements

Area of Science:

• Neuroscience
• Biomechanics
• Human Movement Science

Background:

• Standardizing nerve stimulation during gait is essential for accurate H-reflex measurements.
• Altered pre-synaptic inhibition can lead to misinterpretations in dynamic H-reflex studies.
• A reliable method is needed to synchronize nerve stimulation with the gait cycle.

Purpose of the Study:

• To investigate the intersession reliability of the soleus muscle H-reflex during treadmill walking.
• To evaluate the efficacy of a plantar pressure sole for triggering tibialis nerve stimulation synchronized to the gait cycle.

Main Methods:

• Seven participants walked on a treadmill at 5 km/h.
• A plantar pressure sole detected heel strike to trigger tibialis nerve stimulation.
• Electromyography (EMG) recorded soleus muscle activity.
• H-reflex and M-wave amplitudes were measured to calculate the Hmax/Mmax ratio.

Main Results:

• The plantar pressure sole demonstrated excellent intersession reliability (ICC=0.89).
• Test-retest variability was 13.0% (±11.8), with a systematic error of 2.4% via Bland-Altman analysis.
• The method reliably triggered tibialis nerve stimulation synchronized to the gait cycle.

Conclusions:

• A plantar pressure sole provides a reliable method for synchronizing nerve stimulation to the gait cycle.
• This technique is suitable for evaluating reflex activity, specifically the soleus muscle H-reflex, during walking.
• The findings support the use of this simple technique to improve the accuracy of dynamic H-reflex measurements.