• Chih-Chung Chen and Mark I Johnson.
• Faculty of Health, Leeds Metropolitan University, Leeds, West Yorkshire, UK.
• Clin Physiol Funct Imaging. 2010 Jul 1;30(4):260-8.

AbstractElectrophysiological studies suggest that there are differential frequency effects during TENS. The aim of this experimental study was to assess the effects of strong non-painful TENS administered at 3 pulses per second (pps) and 80 pps on cold-pressor pain in healthy human participants. A repeated measure design was used with participants receiving TENS at 3 pps and 80 pps in the same experiment. There were six cold-pressor pain tests conducted on the hand with each type of TENS delivered via four electrodes on the ipsilateral forearm for 20 min. Outcomes were differences in pain threshold (s) and intensity (VAS) after 5 and 15 min of TENS. A 2 x 3 factorial repeated measure ANOVA was performed on data. Thirty-five participants completed the experiment. Statistically significant effects were detected for condition, time and interactions between time x condition for both threshold and intensity. There were statistically higher pain thresholds and lower pain intensities for 3 pps when compared to 80 pps after 5 and 15 min of TENS. The differences after 15 min of TENS were 1.70 s to 3.70 s (95% CI) for threshold and 6.63-15.5 mm (95% CI) for pain intensity. In conclusion, strong non-painful TENS at 3 pps was superior to 80 pps at reducing experimentally induced cold-pressor pain. The implications of these findings are discussed.

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