Frequency rhythmic electrical modulation system (FREMS) on H-reflex amplitudes in healthy subjects.

Area of Science:

• Neuroscience
• Biomedical Engineering
• Rehabilitation Science

Background:

• The Hoffmann reflex (H-reflex) amplitude reflects monosynaptic circuitry excitability, a potential target for diagnostics and therapy.
• Previous attempts using transcutaneous electrical nervous stimulation (TENS) with fixed frequencies failed to predictably alter H-reflex amplitude.
• Novel electrical stimulation parameters are needed to effectively modulate H-reflex.

Purpose of the Study:

• To evaluate the efficacy of a new painless electrical stimulation, the frequency rhythmic electrical modulation system (FREMS), in modulating H-reflex amplitude.
• To investigate the predictability of H-reflex amplitude changes induced by FREMS.

Main Methods:

• FREMS utilizes transcutaneous electrical pulses with sequentially modulated frequency (1-39 Hz) and width (10-40 μs) at a constant perceptive threshold voltage.
• FREMS was applied to the abductor hallucis muscle as a conditioning stimulus for ipsilateral H-reflex recording at the soleus muscle in 10 healthy volunteers.
• H-reflex was recorded using the classic method in normal volunteers aged 21-40 years.

Main Results:

• FREMS application resulted in a significant decrease in H-reflex amplitude (approximately -50%).
• H-reflex amplitude variations were predictably influenced by the modulation of pulse width and frequency during FREMS subphase C (r²=0.43; P<0.001).
• FREMS demonstrated an effective ability to modulate H-reflex amplitude.

Conclusions:

• Modulating both frequency and duration of painless electrical stimulation with FREMS allows for large and predictable changes in H-reflex amplitude.
• This finding opens new therapeutic avenues for diseases characterized by abnormal motoneuron excitability.
• FREMS represents a promising tool for neuromodulation and rehabilitation.