The current study was designed to examine the neurophysiological and hypoalgesic effects of three types of electrical stimulation. Following approval by the University's Research Ethical Committee, healthy volunteers (n = 40; 20 males and 20 females; age 20-40 years; mean age 26.18 years) were recruited and screened for contraindications. Subjects were randomly allocated in equal numbers to the following groups: control, transcutaneous electrical nerve stimulation (TENS; 150 Hz, 125 mus), interferential therapy (IFT; 150 Hz, 125 lts) or action potential stimulation therapy (APS; 153 Hz, 6.4 ms). All treatments were applied under double-blind conditions for 15 min over the course of the median nerve in the subject's right forearm. Antidromic median nerve compound action potentials (CAPs) were recorded pretreatment, immediately post-treatment (i.e. at 15 min) and then at 25, 35 and 45 min. Immediately following CAP recording, mechanical pain threshold (MPT) was recorded from two sites on the palmar surface of the right hand. Statistical analysis showed significant differences between groups for peak to peak amplitude (PPA) at 25, 35 and 45 min (Kruskal-Wallis: P = 0.01, 0.01 and 0.02). Mann-Whitney U-tests indicated a significant increase in PPA in the IF-F group compared with all other groups at 25 and 35 min and compared with the TENS and APS groups at 45 min. No significant differences were found for the MPT data. This study has therefore demonstrated that none of the aforementioned modalities produced a significant hypoalgesic effect; however, IFT produced a significant change in PPA compared with TENS and APS.
