An investigation into the effects of frequency-modulated transcutaneous electrical nerve stimulation (TENS) on experimentally-induced pressure pain in healthy human participants.
Frequency-modulated transcutaneous electrical nerve stimulation (TENS) delivers currents that fluctuate between preset boundaries over a fixed period of time. This study compared the effects of constant-frequency TENS and frequency-modulated TENS on blunt pressure pain in healthy human volunteers. Thirty-six participants received constant-frequency TENS (80 pps), frequency-modulated TENS (20 to 100 pps), and placebo (no current) TENS at a strong nonpainful intensity in a randomized cross-over manner. Pain threshold was taken from the forearm using pressure algometry. There were no statistical differences between constant-frequency TENS and frequency-modulated TENS after 20 minutes (OR = 1.54; CI, 0.29, 8.23, P = 1.0). Both constant-frequency TENS and frequency-modulated TENS were superior to placebo TENS (OR = 59.5, P < .001 and OR = 38.5, P < .001, respectively). Frequency-modulated TENS does not influence hypoalgesia to any greater extent than constant-frequency TENS when currents generate a strong nonpainful paraesthesia at the site of pain. The finding that frequency-modulated TENS and constant-frequency TENS were superior to placebo TENS provides further evidence that a strong yet nonpainful TENS intensity is a prerequisite for hypoalgesia.


CONCLUSIONS
This study provides evidence that TENS, delivered at a strong nonpainful intensity, increases pain threshold to pressure algometry in healthy participants over and above that seen with placebo (no current) TENS. Frequency-modulated TENS does not increase hypoalgesia to any appreciable extent to that seen with constant-frequency TENS.
Chen
Chih-Chung
CC
Faculty of Health, Leeds Metropolitan University, and Leeds Pallium Research Group, Leeds, United Kingdom.
Johnson
Mark I
MI
D000328:Adult; D018592:Cross-Over Studies; D005260:Female; D006801:Humans; D008297:Male; D009619:Nociceptors / Q000502:physiology; D010146:Pain / Q000209:etiology / Q000503:physiopathology; D059408:Pain Management; D010147:Pain Measurement / Q000379:methods; D017288:Pain Threshold / Q000502:physiology; D010292:Paresthesia / Q000209:etiology / Q000503:physiopathology; D010525:Peripheral Nerves / Q000502:physiology; D015990:Placebo Effect; D011312:Pressure / Q000009:adverse effects; D004561:Transcutaneous Electric Nerve Stimulation / Q000009:adverse effects / Q000379:methods* / Q000706:statistics & numerical data; D016896:Treatment Outcome