ABSENCE OF CONSISTENT EFFECTS OF REPETITIVE TRANSCUTANEOUS ELECTRICAL-STIMULATION ON SOLEUS H-REFLEX IN NORMAL SUBJECTS

Our purpose was to determine the effects of transcutaneous electrical nerve stimulation (TENS) on the soleus H-reflex amplitude in normal su bjects. Eleven subjects were tested in five experimental sessions, the purpose of which was to compare the effects of 30 minutes of TENS del ivered at either 50 or 99Hz (250mus pulses) on a mixed (common peronea l nerve or CPN) versus a sensory (sural) nerve. The soleus H-reflex wa s elicited according to the classic protocol of Hugon (1973). Control values (H(ctrl)) were measured for 5 minutes prior to and for 10 minut es after the TENS was administered at twice the sensory threshold. No statistically significant session (treatment) effects (two-way ANOVAs for repeated measures; alpha = 0.05) resulted from the stimulation of the CPN or the sural nerve at 50 or 99Hz. However, although no specifi c trends were shown across all subjects, there was a definite tendency towards inhibition greater-than-or-equal-to 10% H(crtl)) of the H-ref lex in 63% of the subjects after 30 minutes of TENS at 99Hz over the C PN, and in 50% of the subjects when TENS was applied over the sural ne rve at 99Hz. The inherent variability of the H-reflex amplitude in nor mal subjects as well as the use of different stimulation paradigms and TENS parameters could explain the controversial findings present in t he literature. (C) 1994 by the American Congress of Rehabilitation Med icine and the American Academy of Physical Medicine and Rehabilitation