Effects of acupoints TENS on heat pain threshold in normal subjects

Objective. To delineate the influence of transcutaneous electrical nerve stimulation (TENS) on heat pain threshold and vibration threshold in human. Methods. Twenty healthy, young subjects, aged from 20 to 39, participated in the study. They were randomly allocated into either TENS or placebo group. Thirty minutes of conventional TENS (200 μs pulses at 100 Hz and 2 - 3 times sensory threshold) or placebo stimulation was applied to the acupuncture points (LI4) on each subject's left hand. Heat pain and vibration thresholds were measured using Medoc TSA-2001 and VSA-3000 respectively on the thenar eminence of each subject's left hand. These assessments were done at 30, 20 and 10 minutes before and 0, 10, 20, 30, 40 and 50 minutes after 30 minutes of TENS or placebo treatment. Results. This study showed a significant increase in heat pain threshold by 0.81 °C and 1.54 °C respectively at 0 (P=0.002) and 20 minutes (P=0.004) after 30 minutes of TENS application to the LI4 acupoint of young healthy subjects, compared with placebo stimulation. Interestingly, no significant difference in vibration threshold was found between the TENS and placebo groups. Conclusion. The effect of TENS on the acupoint is to reduce pain but not tactile (specifically vibration) sensibility.Department of Rehabilitation Science