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

BACKGROUND: Research in animal models suggests 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 two groups: (1) CPM plus active TENS; (2) CPM plus placebo TENS. Pain threshold for heat (HPT) and pressure (PPT) were 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 2 min. TENS (100 µs, 100 Hz) was applied to the forearm for 20 min 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 (r(2) = 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 the effects of TENS on PPT.

Release of GABA and activation of GABA(A) in the spinal cord mediates the effects of TENS in rats.

Transcutaneous electrical nerve stimulation (TENS) is a commonly utilized non-pharmacological, non-invasive treatment for pain. GABA is a neurotransmitter in the dorsal horn of the spinal cord that mediates analgesia locally, and also through activation of supraspinal sites. TENS reduces hyperalgesia through activation of receptor-mediated pathways at the level of the spinal cord, and supraspinally. The current study tested the hypothesis that either high or low frequency TENS applied to the inflamed knee joint increases GABA in the spinal cord dorsal horn and activates GABA receptors spinally. We utilized microdialysis to sample the extracellular fluid before, during and after TENS and analyzed GABA in dialysates with high performance liquid chromatography. We analyzed the extracellular GABA concentrations in animals with and without knee joint inflammation induced by intra-articular injection of kaolin and carrageenan. We further tested if spinal blockade of GABA receptors prevents the antihyperalgesia produced by TENS in rats with joint inflammation. We show that high frequency TENS increases extracellular GABA concentrations in the spinal cord in animals with and without joint inflammation. The increases in GABA do not occur in response to low frequency TENS, and there are no increases in glycine in response to low or high frequency TENS. However, the reduction in primary hyperalgesia by both high and low frequency TENS is prevented by spinal blockade of GABA(A) receptors with bicuculline. Thus, high frequency TENS increases release of GABA in the deep dorsal horn of the spinal cord, and both high and low frequency TENS reduce primary hyperalgesia by activation of GABA(A) receptors spinally.

High-frequency, but not low-frequency, transcutaneous electrical nerve stimulation reduces aspartate and glutamate release in the spinal cord dorsal horn.

Transcutaneous electrical nerve stimulation (TENS) is a commonly utilized non-pharmacological treatment for pain. Studies show that low- and high-frequency TENS utilize opioid, serotonin and/or muscarinic receptors in the spinal cord to reduce hyperalgesia induced by joint inflammation in rats. As there is an increase in glutamate and aspartate levels in the spinal cord after joint inflammation, and opioids reduce glutamate and aspartate release, we hypothesized that TENS reduces release of glutamate and aspartate in animals with joint inflammation by activation of opioid receptors. Using microdialysis and HPLC with fluorescence detection, we examined the release pattern of glutamate and aspartate in the dorsal horn in response to either low-frequency (4 Hz) or high-frequency (100 Hz) TENS. We examined the effects of TENS on glutamate and aspartate release in animals with and without joint inflammation. High-frequency, but not low-frequency, TENS significantly reduced spinal glutamate and aspartate in animals with joint inflammation compared with levels in those without joint inflammation. The reduced release of glutamate and aspartate by high-frequency TENS was prevented by spinal blockade of delta-opioid receptors with naltrindole. Thus, we conclude that high-frequency TENS activates delta-opioid receptors consequently reducing the increased release of glutamate and aspartate in the spinal cord.

Wrestlers' minimal weight: anthropometry, bioimpedance, and hydrostatic weighing compared.

The need for accurate assessment of minimal wrestling weight among interscholastic wrestlers has been well documented. Previous research has demonstrated the validity of anthropometric methods for this purpose, but little research has examined the validity of bioelectrical impedance (BIA) measurements. Comparisons between BIA systems has received limited attention. With these two objectives, we compared the prediction of minimal weight (MW) among 57 interscholastic wrestlers using three anthropometric methods (skinfolds (SF) and two skeletal dimensions equations) and three BIA systems (Berkeley Medical Research (BMR), RJL, and Valhalla (VAL]. All methods showed high correlations (r values greater than 0.92) with hydrostatic weighting (HW) and between methods (r values greater than 0.90). The standard errors of estimate (SEE) were relatively small for all methods, especially for SF and the three BIA systems (SEE less than 0.70 kg). The total errors of prediction (E) for RJL and VAL (E = 4.4 and 3.9 kg) were significantly larger than observed nonsignificant BMR and SF values (E = 2.3 and 1.8 kg, respectively). Significant mean differences were observed between HW, RJL, VAL, and the two skeletal dimensions equations, but nonsignificant differences were observed between HW, BMR, and SF. BMR differed significantly from the RJL and VAL systems. The results suggest that RJL and VAL have potential application for this subpopulation. Prediction equation refinement with the addition of selected anthropometric measurement or moderating variables may enhance their utility. However, within the scope of our study, SF and BMR BIA appear to be the most valid methods for determining MW in interscholastic wrestlers.