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.