Conventional versus acupuncture-like transcutaneous electrical nerve stimulation on cold-induced pain in healthy human participants: effects during stimulation.

Objectives:  To compare the hypoalgesic effects of conventional transcutaneous electrical nerve stimulation (TENS) (high frequency, low intensity) and acupuncture-like TENS (AL-TENS, low frequency, high intensity) on cold-induced pain. Design:  Randomized controlled parallel group study comparing the effects of strong non-painful AL-TENS, conventional TENS and placebo (no current) TENS on cold-pressor pain threshold (CPT) and pain intensity. Two baseline (pre-intervention) measures and three during intervention measures of CPT and cold pain intensity (four point category scale) were recorded. Setting:  Physiology laboratory in Leeds Metropolitan University. Participants:  One hundred and twenty-one healthy participants. Interventions:  Each participant received one of three TENS interventions over their flexor digitorum profundus: (i) high pulse rate TENS with a strong non-painful paraesthesia (conventional), (ii) low-rate burst mode TENS that caused strong non-painful phasic muscle twitching (acupuncture like) or (iii) no current (placebo) TENS. Main outcome measure:  Difference between conventional TENS and AL-TENS in cold pain threshold relative to pre-TENS baseline after 25 min of stimulation. Results:  No differences were detected for CPT or cold pain intensity during conventional TENS compared with AL-TENS. When compared with placebo TENS, the confidence intervals for the ratio of intervention CPT to baseline CPT, for both AL-TENS (0·966, 1·424) and conventional TENS (0·948, 1·401), were close to the positive side of one, although neither reached statistical significance. Conclusions:  Unlike some previous studies, the present study detected no differences in hypoalgesia between AL-TENS, conventional TENS and placebo (no current) TENS during stimulation.

© 2011 The Authors. Clinical Physiology and Functional Imaging © 2011 Scandinavian Society of Clinical Physiology and Nuclear Medicine.

PMID: 21771255