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


METHODS
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).


RESULTS
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.


CONCLUSIONS
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.
Barrella
M
M
Endocrine and Diabetes Unit, Ospedale L. Sacco, University of Milan, Milan, Italy.
Toscano
R
R
Goldoni
M
M
Bevilacqua
M
M
D000200:Action Potentials / Q000502:physiology; D000328:Adult; D000704:Analysis of Variance; D004576:Electromyography / Q000295:instrumentation / Q000379:methods; D006801:Humans; D009046:Motor Neurons / Q000502:physiology; D018482:Muscle, Skeletal / Q000294:innervation*; D012021:Reflex, Abnormal / Q000502:physiology*; D013127:Spinal Nerves / Q000502:physiology; D009435:Synaptic Transmission / Q000502:physiology; D013979:Tibial Nerve / Q000502:physiology; D004561:Transcutaneous Electric Nerve Stimulation / Q000295:instrumentation / Q000379:methods*