Study of the effects of various transcutaneous electrical nerve stimulation (TENS) parameters upon the RIII nociceptive and H-reflexes in humans

Despite over two decades of clinical use, the neurophysiological and anti-n ociceptive effects of transcutaneous electrical nerve stimulation (TENS) ha ve yet to be definitively described. The current study was designed to exam ine the effect of TENS on the RIII nociceptive reflex elicited in healthy h uman subjects; the H-reflex was measured concomitantly to monitor changes i n alpha-motoneuron excitability. Following approval from the university's e thical committee, 50 healthy human volunteers (25 male and 25 female) parti cipated in the study. The subjects ranged in age from 18 to 30 years (mean 22, SD 3). Subjects were randomly allocated equally to a control group or o ne of four TENS groups. In the TENS groups, stimulation was applied for a t otal of 15 min over the sural nerve in the left leg. Ipsilateral RIII and H -reflexes were recorded five times during the 45 min experimental period. I n addition, subjects also rated pain associated with the RIII reflex using a computerized visual analogue scale (VAS). Statistical analysis using two- way repeated-measures ANOVA showed no differences between groups for H-refl ex, RIII reflex nor VAS data. These results suggest that TENS does not sign ificantly affect either of the two reflexes, at least using the parameters and application time in the current study.