Effects of Transcutaneous Electrical Nerve Stimulation on Experimental Blunt Pressure Pain in Healthy Participants in Randomized Controlled Trial: Pulse Frequency and Pad Size

Abstract

Transcutaneous electrical nerve stimulation (TENS) is extensively utilized for antalgic effects in clinical practice but the optimal parameters and techniques for TENS treatment effect remain unknown. This study uses a randomized controlled design to examine the effects of the summation of temporal and spatial stimulations of TENS on a peripheral stimulation site. The aim was to investigate the hypoalgesia of pulse frequency (temporal stimulation) and pad size (spatial stimulation) using TENS on the forearm area for meaningful treatment effect. A hundred and eighty qualified healthy participants (equal numbers of males and females) were randomly divided into six groups (n = 30 per group): (1) control/standard pad (5 cm × 5 cm) group, (2) sham/standard pad group, (3) high frequency [80 pulses per second (pps)]/large pad (5 cm × 10 cm) group, (4) low frequency (3 pps)/large pad group, (5) high frequency/small pad (5 cm × 2.5 cm) group, and (6) low frequency/small pad group. Subjective intensity at a comfortable level was standardized on a regular pad for current density. The determined TENS intensity with consistent current density on large or small pads was then applied to the same participant. Each participant experienced a 30-min TENS and a 30-min post-TENS follow-up. The blunt pressure pain threshold was measured twice every 10 min during the 60-min experimental period. The TENS intervention with a high frequency and a large pad was found to significantly reduce pain starting from the 10th minute of TENS application and provided the best effects for reducing the blunt pressure pain during TENS. Pulse frequency is more crucial than pad size on the differentiated effects of TENS outcome. The meaningful treatment effect was statistically judged using a cut-off score of 40 N of force for the experimental pain threshold. These suggested the hypoalgesic effects of pulse frequencies and pad sizes of TENS while its temporal and spatial characteristics were considered.