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Eura Medicophys. 2007 Mar;43(1):37-47. Epub 2006 Dec 12.

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

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Endocrine and Diabetes Unit, Ospedale L. Sacco, University of Milan, Milan, Italy.



Changes in the amplitude of Hoffmann reflex (H-reflex) may reflect variations in the characteristics of the largely monosynaptic circuitry that is explored and are a possible target for diagnostic and physical therapeutic intervention. However, previous attempts to induce predictable changes in the H-reflex amplitude by transcutaneous electrical nervous stimulation (TENS) have generally failed. Previous workers applied fixed frequency in the low- (2-5 Hz) or in the high- (100 Hz) field, but they did not attempt to vary frequency and/or impulse duration in time.


We evaluated the effect of a new type of painless electric stimulation, i.e. frequency rhythmic electrical modulation system (FREMS). FREMS is characterized by the use of transcutaneous electric pulses with sequentially modulated frequency (f: 1-39 Hz) and width (w: 10-40 micro s) at constant, perceptive threshold voltage (approximately 150 V). FREMS was applied at the abductor hallucis muscle (AHM), as conditioning stimulus of the H-reflex which was recorded ipsilaterally at the soleus muscle, according to the classic method, in 10 normal volunteers (age range 21-40 years).


H-reflex amplitude was substantially decreased (-50%) during FREMS and H-reflex amplitude variations were influenced by w/f variation in time during FREMS subphase C in a predictable way (r(2)=0.43; P<0.001). Our results suggest an effective ability of FREMS to modulate H reflex amplitude.


The ability to achieve large and predictable changes of the H-reflex amplitude simply by modulating both frequency and duration of a conditioning painless electrical stimulation offers new possibilities for the treatment of diseases characterized by motoneuron excitability abnormalities.

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