Transcutaneous electrical nerve stimulation and conditioned pain modulation influence the perception of pain in humans

Abstract

Background Research in animal models suggest that transcutaneous electrical nerve stimulation (TENS) and conditioned pain modulation (CPM) produce analgesia via two different supraspinal pathways. No known studies have examined whether TENS and CPM applied simultaneously in human subjects will enhance the analgesic effect of either treatment alone. The purpose of the current study was to investigate whether the simultaneous application of TENS and CPM will enhance the analgesic effect of that produced by either treatment alone. Methods Sixty healthy adults were randomly allocated into 2 groups: 1) CPM plus Active TENS; 2) CPM plus Placebo TENS. Pain threshold for heat (HPT) and pressure (PPT) was recorded from subject’s left forearm at baseline, during CPM, during Active or Placebo TENS, and during CPM plus Active or Placebo TENS. CPM was induced by placing the subjects’ contralateral arm in a hot water bath (46.5°C) for two minutes. TENS (100µs, 100Hz) was applied to the forearm for 20 minutes at a strong but comfortable intensity. Results Active TENS alone increased PPT (but not HPT) more than Placebo TENS alone (p=0.011). Combining CPM and Active TENS did not significantly increase PPT (p=0.232) or HPT (p=0.423) beyond CPM plus Placebo TENS. There was a significant positive association between PPT during CPM and during Active TENS (r2=0.46, p=0.003). Conclusions TENS application increases PPT, however combining CPM and TENS does not increase the CPM’s hypoalgesic response. CPM effect on PPT is associated with effects of TENS on PPT.

Transcutaneous electrical nerve stimulation for the control of pain during rehabilitation after total knee arthroplasty: A randomized, blinded, placebo-controlled trial

“…These studies suggest that TENS is more effective for mechanical deep tissue pain than thermal cutaneous pain. In healthy controls we and others routinely show that TENS reduces PPTs [45,48,51]. …”

“…It is possible that the reduced effect over time is due to the development of tolerance to the TENS stimulation. Studies that have evaluated the effect of repeated TENS use have demonstrated tolerance to TENS after five days of repeated application when given at the same dose (frequency and intensity) in healthy human subjects and in animal studies [10,45]. Factors that prolong this tolerance include alternating between low and high frequency [23] and increasing the amplitude over time [62].…”

Central sensitization and changes in conditioned pain modulation in people with chronic nonspecific low back pain: a case–control study

“…The magnitude of pain inhibition during a CPM test was obtained from previous data on CPM and PPT in healthy controls by our research team (Correa et al 2013; Liebano et al 2013). At a significance level of 0.05 and power of 95 %, it was calculated that a minimum of 21 participants was required in each group (Minitab, v. 15, State College, PA).…”

Constructing and deconstructing the gate theory of pain

“…Some cells in the VPL in thalamus are known to respond selectively to pinch stimuli [20, 32], at least under anesthesia, implying that labeled lines might account for some behavioral responses to nociceptive input. However, there are other cells in the spinal dorsal horn, the wide dynamic range cells [46],that receive excitatory input from both nociceptive and non-nociceptive sensory inputs.…”