Effects of Intensity of Transcutaneous Electrical Nerve Stimulation (TENS) on Pressure Pain Threshold and Blood Pressure in Healthy Humans

Objectives: Transcutaneous electrical nerve stimulation (TENS) is primarily used for pain relief. However, evidence is beginning to emerge that TENS may also have a lowering effect on systemic blood pressure (BP). The purpose of this study was to investigate the comparative effects of 2 intensities on pressure pain threshold (PPT) and resting BP in healthy humans, using low-frequency stimulation applied segmentally to the pain site. Methods: In a double-blind design, 40 volunteers, stratified by sex, were randomly allocated to 4 groups: high-intensity ("to tolerance without pain"), low-intensity ("strong but comfortable"), placebo, and control. TENS (2 Hz, 250 mu) was applied over the distribution of the superficial radial nerve of the dominant hand for 30 Minutes. The outcome variables were measured at baseline and at 6 subsequent 10-minute intervals. For the PPTs, 2 measurements were taken bilaterally from the first dorsal interosseous muscle using a pressure algometer. The BP was measured in the brachial artery with an automatic monitor. Data difference scores were analyzed using repeated-measures and 1-way analyses of variance. Results: The high-intensity group showed a significant rise in PPT compared with the low-intensity, placebo, and control groups for both measurement sites, which sustained 30 minutes poststimulation. TENS produced no significant effect on BP, regardless of intensity. Discussion: These results affirm that high levels of intensity are of fundamental importance in effective TENS dosage. This also applies for low frequency, segmental stimulation. Resting BP seems not to be dependent on intensity.