Analgesic Effects of Transcutaneous Electrical Nerve Stimulation and Interferential Current on Experimental Ischemic Pain Models: Frequencies of 50?Hz and 100?Hz

[Purpose] This study compared the analgesic effects of transcutaneous electrical nerve stimulation (TENS) and interferential currents (IFC) on induced ischemic pain in healthy volunteers. [Subjects] The subjects were 36 volunteers (18 male, 18 female) without known pathology that could cause pain. Their mean age was 24.5±2.2 years. [Methods] A single-blind and parallel-group method was used. Subjects were randomly allocated to receive each 50 Hz TENS, 50 Hz IFC, 100 Hz TENS, and 100 Hz IFC. This study experimentally induced ischemic pain in otherwise pain-free subjects using a modified version of the submaximal effort tourniquet technique. Subjects completed twelve cycles of the ischemic-induced pain test. The primary outcome measure was the change in self-reported of pain intensity during one of four possible treatments. [Results] There were significant effects for Time, which were attributed to a significant reduction in pain intensity for all groups. There were no significant effects for groups or group-time interaction. The 50 Hz IFC treatment was more comfortable than the other treatments in the present study, and it is likely to be better accepted and tolerated by patients. [Conclusion] We conclude that there were no differences in the analgesic effects of the four treatments under the present experimental conditions. The 50 Hz IFC treatment is more comfortable than the other treatments.Key words: Transcutaneous electrical nerve stimulation, Interferential current, Ischemic pain model     

Effects of electric stimulation on C and A delta fiber-mediated thermal perception thresholds

OBJECTIVE: To determine if interferential current (IFC) or transcutaneous electric nerve stimulation (TENS) alters C and A delta fiber-mediated thermal perception thresholds. DESIGN: Single-blind, randomized controlled trial. SETTING: Laboratory. PARTICIPANTS: One hundred forty healthy women volunteers (mean age +/- standard deviation, 20.6+/-2.7 y). INTERVENTIONS: Subjects were randomly and exclusively assigned to 1 of 7 groups (n=20 in each): 0, 5, and 100 Hz of IFC; 5 and 100 Hz of TENS; placebo and control stimulation. Stimulation was applied through 2 electrodes placed over the median nerve. Warm sensation, cold sensation, hot pain, and cold pain perception thresholds were measured from the thenar eminence by using a quantitative sensory testing device and a method of limits algorithm. MAIN OUTCOME MEASURES: Warm sensation, cold sensation, hot pain, and cold pain thresholds (degrees C) before, during, and after stimulation. RESULTS: There was a statistically significant effect of time for all 4 thermal perception thresholds (separate 2-way analyses of variance with repeated measures, all P<.001). There were no statistically significant differences between experimental groups, nor any interaction effects (all P>.05). CONCLUSIONS: Neither IFC nor TENS altered C and A delta fiber-mediated thermal perception thresholds. The results suggest that any analgesic mechanisms with these modalities are likely to be complex.     

Effects of simultaneous dual-site TENS stimulation on experimental pain

Transcutaneous electrical nerve stimulation (TENS) is commonly used for pain relief. However, little robust research exists regarding the combination of parameters required to provide effective doses. This study investigated the hypoalgesic effects of different parameter combinations, applied simultaneously at two sites (segmental and extrasegmental), on pressure pain threshold (PPT) in pain-free humans. Two-hundred and eight volunteers (median age 22 years, range 20–26) were randomized to eight groups: six active TENS groups, placebo and control. Parameter combinations were such that frequency always differed at each site (110 Hz or 4 Hz), but intensity could be either the same or different levels: high (to tolerance without pain) or low (strong but comfortable). TENS was administered to the forearm over the radial nerve and the ipsilateral leg below the fibular head for 30 min with monitoring for 30 further minutes. PPT measurements were taken bilaterally from the mid-point of first dorsal interosseous muscle, by an independent blinded rater, at baseline and at six subsequent 10-min intervals. Log-transformed data were analysed using repeated-measures analysis of covariance (baseline values and gender as covariates). Those groups using high-intensity stimulation at the segmental stimulation sites showed significantly greater hypoalgesia than placebo (p < 0.025 in each case). The largest hypoalgesic effect was for simultaneous high-intensity stimulation at segmental and extrasegmental sites, using different frequencies. These results reaffirm that high-intensity stimulation (regardless of frequency) is of fundamental importance in effective dosage.     

Effects of thermotherapy and transcutaneous electrical nerve stimulation on patients with primary dysmenorrhea: A randomized,placebo-controlled,double-blind clinical trial

ObjectivesTo evaluate the effects of thermotherapy and transcutaneous electrical nerve stimulation (TENS) on pain intensity, pressure pain threshold (PPT) and conditioned pain modulation (CPM) in patients with primary dysmenorrhea (PD).DesignA randomized, placebo-controlled, double-blind clinical trial.SettingPhysiotherapy Department of the Universidade Cidade de São Paulo, São Paulo (Brazil).InterventionsEighty-eight dysmenorrheic women were randomly allocated into four groups: Thermotherapy + TENS(n = 22), Thermotherapy(n = 22), TENS(n = 22) and Placebo(n = 22). Thermotherapy was applied by microwave diathermy (20 min), and TENS (200 μs, 100 Hz, 30 min), into the lower abdomen both.Main outcome measuresPain intensity was measured using the numeric rating scale (NRS) and the McGill Pain Questionnaire (Br-MPQ). PPT and CPM were recorded from women’s abdominal and lumbar. The evaluation was done in 5 times: baseline, after 20, 50, 110 min and 24 h from intervention.ResultsThere was a significant decrease in the NRS for Thermotherapy + TENS vs. TENS, for Thermotherapy vs. TENS and for Placebo, after 20 min; for Thermotherapy vs. TENS and for Placebo, after 110 min and 24 h. Abdome PPT increased in the Thermotherapy + TENS vs. TENS and Placebo, after 50 min; for Thermotherapy + TENS vs. Placebo and for Thermotherapy vs. Placebo, after 110 min. No changes in lumbar PPT and CPM were observed.ConclusionsThe use of thermotherapy reduced NRS compared to the TENS and Placebo after 20, 110 min and 24 h. Thermotherapy demonstrated an increase in the PPT in the abdomen after 50 and 110 min and decreased the Br-MPQ scores after 110 min in patients with PD.     

Correlation between change in pain,disability, and surface electromyography topographic parameters after interferential current treatment in patients with chronic low back pain

[Purpose] Surface electromyography (SEMG) topography is used to objectively assess patients with low back pain (LBP). This study aimed to investigate the correlation between SEMG topographic variables, pain, and disability in patients with chronic LBP (CLBP) after interferential current (IFC) treatment, and to evaluate IFC treatment efficacy using SEMG topography. [Participants and Methods] Twenty nine patients with CLBP were recruited for a 6-week IFC treatment. Pain and disability scores, and the root-mean-square difference (RMSD) of SEMG topographic variables (relative areas [RAs] at flexion and extension) were compared before and after the intervention by repeated measures ANOVA; the correlation between variables was also explored and p-value was set at 0.001. [Results] Significant positive correlations between changes in pain score and the RMSD of RA at flexion (r(29)=0.593), and between changes in pain and disability scores (r(29)=0.426) were observed. All participants showed statistically significant improvements in the RMSD of RA at flexion, pain score, and disability score after IFC treatment. [Conclusion] SEMG topographic variables are closely associated with changes in pain score in patients with CLBP after IFC treatment. The RMSD of RA at flexion can be used as an objective marker in IFC treatment efficacy evaluation.     

An investigation of the development of analgesic tolerance to TENS in humans

Transcutaneous electrical nerve stimulation (TENS) is a noninvasive modality used to control pain. Animal models show that repeated TENS application produces analgesic tolerance and cross-tolerance at spinal opioid receptors. The aim of the present investigation was to examine whether repeated application of TENS produces analgesic tolerance in humans. One hundred healthy subjects were randomly assigned to 1 of 4 groups: control, placebo, low-frequency (4 Hz) or high-frequency (100 Hz) TENS. TENS was applied daily for 5 days to the nondominant upper limb; pressure-pain threshold (PPT) measurements were recorded before and after TENS. Temporal summation to mechanical stimulation was recorded on days 1 and 5, before and after TENS. Diffuse noxious inhibitory control (DNIC) was tested on day 5 using the cold pressor test and PPT measurements. There was an initial increase in PPTs in both low- and high-frequency TENS groups when compared with placebo or control groups. However, by day 5 this TENS-induced increase in PPT did not occur, and there was no difference between active TENS and placebo or control groups. High-frequency TENS decreased temporal summation on day 1 when compared with day 5. DNIC increased the PPT similarly in all groups. These data suggest that repeated daily application of TENS results in a decrease in its hypoalgesic effect by the fifth day and that the tolerance-like effect to repeated TENS results from tolerance at centrally located opioid receptors. The lack of change in DNIC response suggests that TENS and DNIC utilize separate pathways to produce analgesia.     

Transcutaneous Electrical Nerve Stimulation and Interferential Current Combined with Exercise for the Treatment of Knee Osteoarthritis: A Randomised Controlled Trial

Interferential current (IFC) and transcutaneous electrical nerve stimulation (TENS) are forms of electrical stimulation frequently used to treat knee osteoarthritis (OA). The relative effectiveness of these two modalities is currently unknown. The purpose of this study was to evaluate the effects of IFC and TENS, when used in conjunction with exercise, on pain and function in patients with knee OA. Forty-six subjects with radiographically confirmed OA were randomly assigned to one of three groups: TENS and standardised exercises, IFC and exercises or exercises alone. An electrical stimulator was used to apply IFC or TENS at 80 Hz for 20 minutes. All groups had a standardised exercise programme. Treatment was applied twice per week for 4 weeks. Outcomes included a 10-point pain rating scale for pain intensity and the Western Ontario and McMaster University Osteoarthritis Index (WOMAC). A two-way repeated measures ANOVA performed on the pain assessment score showed a statistically significant effect of time (p < 0.001), but not of experimental group (p = 0.813) or interaction (p = 0.067). A similar result was obtained for WOMAC score (p < 0.001, p = 0.241 and p = 0.130 for time, group and interaction effects, respectively). All treatment protocols led to significant improvements in pain and function over time. Neither IFC nor TENS displayed significant additional effects over exercise alone.     

Investigating the effects of myofascial induction therapy techniques on pain,function and quality of life in patients with chronic low back pain

IntroductionLow back pain (LBP) is well documented as a common health problem; it is the leading cause of activity limitation and work absence throughout much of the world, and it causes an enormous economic burden on individuals, families, communities, industry, and governments. The aim of this study was to comparatively investigate the effects of myofascial induction therapy (MIT) against pain neuroscience education (PNE) on pain and function in patients with chronic low back pain (CLBP).MethodForty patients with CLBP were included and randomly divided into two groups according to the treatment program (40 min/session, 2 sessions/week during 8-week), as follows: the MIT and the PNE groups. The outcome measures were the fear-avoidance beliefs questionnaire (FABQ), Roland Morris disability questionnaire, McGill pain questionnaire, finger floor test, SF-36 quality-of-life questionnaire, and thoracolumbar fascia ultrasound imaging results. Patients were evaluated before and after treatment.ResultsWithin both groups, all outcome scores showed a significant improvement (p < 0.05). After 8-week, SF-36 physical function, physical role and mental health scores significantly improved in MIT group compared with PNE group, finger floor test score significantly decreased in MIT group compared with PNE group, and FABQ score significantly decreased in PNE group compared with MIT group (p < 0.05).ConclusionsAlthough both MIT and PNE were found to be effective on pain and function in patients with CLBP, MIT techniques were substantially better in improving the mobility of trunk flexion and quality of life in these patients.     

An Investigation of the Hypoalgesic Effects of TENS Delivered by a Glove Electrode

This randomized, placebo-controlled, blinded study investigated the hypoalgesic effects of high-frequency transcutaneous electrical nerve stimulation (TENS) delivered via a glove electrode compared with standard self-adhesive electrodes. Fifty-six TENS-naïve, healthy individuals (18 to 50 years old; 28 men, 28 women) were randomly allocated to 1 of 4 groups (n = 14 per group): glove electrode; placebo TENS using a glove electrode; standard electrode; and no treatment control. Active TENS (continuous stimulus, 100 Hz, strong but comfortable intensity) was applied to the dominant forearm/hand for 30 minutes. Placebo TENS was applied using a burst stimulus, 100-Hz frequency, 5-second cycle time for 42 seconds, after which the current amplitude was automatically reset to 0 mA. Pressure pain thresholds (PPTs) were recorded from 3 points on the dominant and nondominant upper limbs before and after TENS. Statistical analyses of dominant PPT data using between-within groups ANOVA showed significant differences between groups at all 3 recording points (P = .01). Post hoc Scheffe tests indicated no significant difference between the standard electrode and glove electrode groups. There was a significant hypoalgesic effect in the standard electrode group compared with the control group and between the glove electrode group and both the control and placebo TENS groups. There was no significant interactive effect between time and group at any of the recording points (P > .05).PerspectiveThis study presents a comparison of the hypoalgesic effects of 2 different types of TENS electrode, a novel glove electrode and standard self-adhesive rectangular electrodes. The glove electrode provides a larger contact area with the skin, thereby stimulating a greater number of nerve fibers. The results show that both electrodes have similar hypoalgesic effects and therefore give the clinician another choice in electrode.     

Transcutaneous electrical nerve stimulation (TENS) as compared to placebo TENS for the relief of acute oro-facial pain

The present paper describes the effect of high frequency, low frequency and placebo TENS on acute oro-facial pain in 62 patients, attending to an emergency clinic for dental surgery; they had all suffered pain for 1-4 days. The patients were randomly assigned to one of three groups receiving either high frequency (100 Hz), low frequency (2 Hz) or placebo TENS. In the two groups receiving TENS (42 patients) 16 patients reported a reduction in pain intensity exceeding 50%; out of these 16 patients, 4 patients reported complete relief of pain. In the placebo group (20 patients) 2 patients reported a pain reduction of more than 50%; out of these 2 patients, none reported a complete pain relief. Mechanical vibratory stimulation augmented the pain reduction obtained by TENS in 5 out of 10 patients.     

Effect of Interferential Current Stimulation in Management of Hemiplegic Shoulder Pain

Objective

To study the immediate effects of interferential current stimulation (IFC) on shoulder pain and pain-free passive range of motion (PROM) of the shoulder in people with hemiplegic shoulder pain (HSP).

Design

Double-blind, placebo-controlled clinical trial.

Setting

Institutional physical therapy clinic, neurologic rehabilitation center.

Participants

A population-based sample of people with HSP (N=30) was recruited.

Intervention

Participants were divided into 2 groups—an IFC group and a placebo group—by using a match-paired method (age, sex, and Brunnstrom motor recovery stage). In the IFC group, participants received IFC for 20 minutes with an amplitude-modulated frequency at 100Hz in vector mode. The current intensity was increased until the participants felt a strong tingling sensation.

Main Outcome Measures

Pain intensity and pain-free PROM of the shoulder until the onset of pain were measured at baseline and immediately after treatment.

Results

Participants reported a greater reduction in pain during the most painful movement after treatment with IFC than with placebo (P<.05). The IFC group showed a greater improvement in posttreatment pain-free PROM than the placebo group in shoulder flexion (P<.01), abduction (P<.01), internal rotation (P<.01), and external rotation (P<.01).

Conclusions

This study provides evidence that IFC is effective for the relief of pain during movement and also increases the pain-free PROM of the shoulder in people with HSP.     

Get Your Head in the Game: A Replicated Single-Case Experimental Design Evaluating the Effect of a Novel Virtual Reality Intervention in People With Chronic Low Back Pain

Chronic low back pain (CLBP) is a leading cause of disability worldwide. Contemporary treatment of CLBP is suboptimal, with small-moderate effect sizes and high relapse rates. Virtual reality (VR) is an increasingly accessible technology that can improve adherence to exercise programs through gamification. Using VR to facilitate exercise adherence and enjoyment may improve the clinical outcomes. This study aimed to evaluate the effects of a gamified VR graded activity intervention in people with CLBP, using commercially available and bespoke VR programs. A sequentially replicated, multiple-baseline, randomized AB single-case experimental design was undertaken in 10 people with CLBP. Outcomes were assessed daily and included pain intensity (primary) and pain catastrophizing, pain-related fear, and anxiety/worry (secondary). The effect of the intervention on the primary outcome was evaluated using a multilevel-model, nonparametric randomization test. The VR graded activity intervention resulted in a significant reduction in pain intensity (effect estimate = −1.0, standard error = .27, P < .0011) with 4 participants achieving ≥30% pain reduction (minimum important change). There was a significant effect of the intervention on pain catastrophizing but not pain-related fear or anxiety/worry measures. These findings provide preliminary support for a VR graded activity program to reduce pain in people with CLBP.PerspectiveThis novel, VR graded activity intervention reduced pain intensity and catastrophizing in people with CLBP. The intervention also had high adherence and enjoyment. Given that this intervention involved 2 freely available VR programs, it can be easily translated into clinical practice.     

Efficacy of Videoconference Group Acceptance and Commitment Therapy (ACT) and Behavioral Activation Therapy for Depression (BATD) for Chronic Low Back Pain (CLBP) Plus Comorbid Depressive Symptoms: A Randomized Controlled Trial (IMPACT Study)

This study examined the efficacy of adding a remote, synchronous, group, videoconference-based form of acceptance and commitment therapy (ACT) or behavioral activation therapy for depression (BATD) to treatment-as-usual (TAU) in 234 patients with chronic low back pain (CLBP) plus comorbid depressive symptoms. Participants were randomly assigned to ACT, BATD, or TAU. Compared to TAU, ACT produced a significant reduction in pain interference at posttreatment (d = .64) and at follow-up (d = .73). BATD was only superior to TAU at follow-up (d = .66). A significant reduction in pain catastrophizing was reported by patients assigned to ACT and BATD at posttreatment (d = .45 and d = .59, respectively) and at follow-up (d = .59, in both) compared to TAU. Stress was significantly reduced at posttreatment by ACT in comparison to TAU (d = .69). No significant between-group differences were found in depressive or anxiety symptoms. Clinically relevant number needed to treat (NNT) values for reduction in pain interference were obtained at posttreatment (ACT vs TAU = 4) and at follow-up (ACT vs TAU = 3; BATD vs TAU = 5). In both active therapies, improvements in pain interference at follow-up were significantly related to improvements at posttreatment in psychological flexibility. These findings suggest that new forms of cognitive-behavioral therapy are clinically useful in improving pain interference and pain catastrophizing. Further research on evidence-based change processes is required to understand the therapeutic needs of patients with chronic pain and comorbid conditions.Trial numberNCT04140838.PerspectiveGroup videoconference-based ACT and BATD showed greater efficacy than TAU for reducing pain interference and pain catastrophizing in patients with CLBP plus clinically relevant depression. Psychological flexibility appeared to be the main contributor to treatment effects for both ACT and BATD.     

Does amplitude-modulated frequency have a role in the hypoalgesic response of interferential current on pressure pain sensitivity in healthy subjects? A randomised crossover study

Objective

To investigate the hypoalgesic effect of amplitude-modulated frequency during interferential current therapy using an experimentally induced mechanical pain model in normal subjects. This study examined pain pressure sensitivities achieved when the amplitude-modulated frequency parameter was present (100 Hz) and absent (0 Hz).

Design

Randomised controlled crossover trial with repeated measures.

Setting

University research laboratory.

Participants

Forty-six healthy volunteers (23 males, 23 females).

Interventions

Two interferential therapy protocols (with and without amplitude-modulated frequencies) were applied to the lumbar area on two different days.

Main outcome measures

Pressure pain thresholds over the lumbar area were measured before, during and after application of the interferential therapy protocols.

Results

A three-way analysis of variance with repeated measures failed to show any statistically significant difference between the two protocols in modifying pressure pain threshold values (mean difference 0.017 kg/cm², 95% confidence interval −0.384 to 0.350, P = 0.93). Statistically significant differences were identified (P < 0.001) between measurements, indicating a comparable decrease in pain sensitivity in both groups. However, the increase in pressure pain thresholds (0.76 kg/cm²) failed to reach a level of clinical importance.

Conclusions

The addition of an amplitude-modulated frequency parameter to interferential therapy did not influence mechanical pain sensitivity in healthy subjects. Amplitude-modulated frequency is therefore unlikely to have a physiological hypoalgesic effect.     

Baroreflex sensitivity associated hypoalgesia in healthy states is altered by chronic pain

While experimental baroreceptor stimulation is known to elicit hypoalgesia in healthy individuals, the impact of spontaneous baroreflex sensitivity (BRS) on acute pain responses is not known. We tested for associations between BRS and pain responses in healthy individuals, whether these associations are altered in chronic low back pain (CLBP), and the role of alpha-2 adrenergic (ADRA2) mechanisms in these effects. Twenty-five healthy controls and 21 CLBP subjects completed three acute pain tasks after receiving placebo or an intravenous ADRA2 antagonist (yohimbine hydrochloride, 0.4 mg/kg) across two sessions in counterbalanced order. Resting pre-drug spontaneous BRS was assessed using the sequence method. CLBP subjects displayed lower resting BRS^Down than controls (p < .05). Drug × BRS^Down interactions indicated that significant BRS-related hypoalgesia on thermal pain threshold and tolerance was eliminated with yohimbine (p’s < .05). Subject Type × BRS^Up interactions on finger pressure (MPQ-Sensory) and ischemic tasks (MPQ-Sensory, pain threshold, intra-task numeric intensity ratings) indicated that inverse BRS/pain associations in controls (p’s < .05) were absent in CLBP subjects. Subject Type × Drug × BRS^Down interactions on finger pressure MPQ-Sensory and intra-task numeric intensity ratings (p’s < .05) indicated that for controls, yohimbine attenuated the significant inverse BRS/pain sensitivity associations noted under placebo. In contrast, CLBP subjects displayed a nonsignificant positive BRS/pain association under placebo, with yohimbine producing an inverse association similar to controls (significant for MPQ-Sensory). Results suggest presence of spontaneous BRS-related hypoalgesia in healthy individuals that is partially mediated by ADRA2 mechanisms, and that CLBP blunts BRS-related hypoalgesia. As a group, the CLBP subjects do not manifest baroreceptor-induced antinociception.     

Reliability of ultrasound measurement of the lateral abdominal and lumbar multifidus muscles in individuals with chronic low back pain: A cross-sectional test-retest study

ObjectivesUltrasound (US) imaging has been suggested to evaluate the morphology and function of trunk muscles; however, little is known about the reliability of the US measures in patients with chronic low back pain (CLBP). This study aimed to evaluate intrarater reliability of US imaging of the lateral abdominal and lumbar multifidus muscles in individuals with nonspecific CLBP.MethodsIn this cross-sectional study, intrarater within-day and between-day reliability of US measurements of the transversus abdominis, internal oblique, external oblique and lumbar multifidus (at the L3-L4, L4-L5, and L5-S1 levels) muscles were obtained on both sides. The resting and contracted thickness and contraction ratio of each muscle were measured in 21 individuals with nonspecific CLBP.ResultsAll US measurements of the lateral abdominal and lumbar multifidus muscles demonstrated good to excellent within-day (Intraclass correlation coefficients (ICCs: 0.80–0.98) and between-day (ICCs: 0.80–0.97) reliability. The standard error of the measurement (SEMs) and minimal detectable change (MDCs) of the lateral abdominal muscles on both sides ranged 0.5–1.6 mm and 0.4–4.4 mm, respectively. The SEMs and MDCs of the LM muscles on both sides ranged 1.1–2.7 mm and 2.86–7.49 mm, respectively.ConclusionThe findings indicate that US imaging has good to high intrarater within- and between-day reliability for assessing absolute thickness and contraction ratio of the trunk muscles on both right and left sides in patients with nonspecific CLBP. The vertical alignment of the US transducer is a reliable method for assessing the lateral abdominal muscles.     

Spatial distribution of lumbar erector spinae muscle activity in individuals with and without chronic low back pain during a dynamic isokinetic fatiguing task

BackgroundIndividuals with chronic low back pain (CLBP) commonly present with increased trunk muscle fatigability; typically assessed as reduced time to task failure during non-functional isometric contractions. Less is known about the specific neuromuscular responses of individuals with CLBP during dynamic fatiguing tasks. We investigate the regional alteration in muscle activation and peak torque exertion during a dynamic isokinetic fatiguing task in individuals with and without CLBP.MethodsElectromyography (EMG) was acquired from the lumbar erector spinae unilaterally of 11 asymptomatic controls and 12 individuals with CLBP, using high-density EMG (13 × 5 grid of electrodes). Seated in an isokinetic dynamometer, participants performed continuous cyclic trunk flexion-extension at 60^o/s until volitional exhaustion.FindingsSimilar levels of muscle activation and number of repetitions were observed for both groups (p > 0.05). However, the CLBP group exerted lower levels of peak torque for both flexion and extension moments (p < 0.05). The centre of lumbar erector spinae activity was shifted cranially in the CLBP group throughout the task (p < 0.05), while the control participants showed a more homogenous distribution of muscle activity.InterpretationPeople with CLBP displayed altered and potentially less efficient activation of their lumbar erector spinae during a dynamic fatiguing task. Future studies should consider using high-density EMG biofeedback to optimise the spatial activation of the paraspinal musculature in people with low back pain (LBP).     

Is mechanical pain threshold after transcutaneous electrical nerve stimulation (TENS) increased locally and unilaterally? A randomized placebo‐controlled trial in healthy subjects

Background and Purpose . It is not fully understood how transcutaneous electrical nerve stimulation (TENS) intensity affects mechanical pain threshold. Method . Sixty‐six healthy volunteers (13 male, 53 female; 132 hands) without prior experience of TENS participated in the study, which comprised a randomized single‐blind controlled trial. TENS was administered for 20 minutes through electrodes (25 × 25 mm) placed on the hands and forearms with a fixed frequency of 100 Hz and pulse duration of 150 µs. TENS intensity was randomized and allocated in a concealed manner so that one arm received TENS with stimulation intensity set at participants' subjective sensory threshold and the other received TENS with stimulation intensity continuously adjusted by physiotherapists to a strong but comfortable non‐painful stimulation. Observers were blinded to stimulation intensity levels. Results . Mechanical pain threshold increased significantly, by a mean total of 0.79 kg/cm² (95% confidence interval [95% CI]: 0.54–1.04) (p < 0.001) on the strong but comfortable non‐painful stimulation side. The mean change in mechanical pain threshold on the sensory threshold side was 0.19 kg/cm² and did not reach statistical significance (95% CI–0.15 to 0.51). The mean stimulation intensity level for sensory threshold was 6.7 mA (95% CI: 5.65 to 7.83) which was significantly lower (p < 0.001) than the mean stimulation intensity for the strong stimulation, which was 20.5 mA (95% CI 16.6 to 24.4), respectively. The strong stimulation levels were, on average, 3.05 times higher than sensory threshold, but individual variations were large (range 1.2–6.1). Conclusions . TENS administered at a strong but comfortable non‐painful stimulation intensity increases mechanical pain threshold ipsi‐laterally in healthy subjects, whereas TENS administered at sensory threshold intensity does not. TENS may be ineffective if electrodes are placed contralaterally or distant to the pain site and if stimulation intensity levels are not titrated to subjective strong levels. Further clinical trials are needed to clarify if these findings may also be generalized to populations of chronic pain sufferers. Copyright © 2007 John Wiley & Sons, Ltd.     

A single-blind investigation into the hypoalgesic effects of different swing patterns of interferential currents on cold-induced pain in healthy volunteers

OBJECTIVE: To compare the analgesic effects of differing swing patterns of interferential current (IFC) on cold-induced pain. DESIGN: Single-blind intervention study in which subjects completed 6 cycles of the cold-induced pain test-2 pretreatment, 2 during treatment, and 2 posttreatment. SETTING: Laboratory. PARTICIPANTS: Forty healthy volunteers. INTERVENTIONS: Subjects were randomly allocated to receive 1 of 4 IFC treatment interventions: 1 integral 1, 6 integral 6, 6 wedge 6, or burst. IFC was administered for 20 minutes via 4 electrodes attached to the forearm (quadripolar application) at a strong but comfortable intensity using amplitude-modulated frequencies of 1 to 100 Hz. MAIN OUTCOME MEASURES: Change in pain threshold and self-report of pain intensity and unpleasantness from pretreatment baseline. RESULTS: Two-way repeated-measure analysis of variance found significant effects for time and group by time interaction (P<.01), but effects for groups failed to reach statistical significance (P=0.1). This suggests that when all groups are considered together, subjects experience a rise in pain threshold when IFC devices are switched on but not when they are switched off. However, the rise in pain threshold was not dependent on the swing pattern employed. Analysis of pain intensity and unpleasantness ratings found no effects for group or group by time interaction. CONCLUSIONS: There were no differences in the hypoalgesic effects of different swing patterns.     

A controlled study on the effects of transcutaneous electrical nerve stimulation and interferential therapy upon the RIII nociceptive and H-reflexes in humans

OBJECTIVE: To study the effect of transcutaneous electrical nerve stimulation (TENS) and interferential therapy (IFT) upon the RIII nociceptive reflex and H-reflex. DESIGN: Double-blind conditions. PARTICIPANTS: Seventy healthy subjects were randomly allocated to one of seven groups (n = 10 per group): Control, TENS 1 (5 Hz), TENS 2 (100 Hz), TENS 3 (200 Hz), IFT 1 (5 Hz), IFT 2 (100 Hz), IFT 3 (200 Hz). INTERVENTION: In the treatment groups, stimulation was applied over the right sural nerve for 15 minutes. MAIN OUTCOME MEASURES: Ipsilateral RIII and H-reflexes were recorded before treatment, immediately after treatment, and subsequently at 25, 35, and 45 minutes. Subjects rated the pain associated with the RIII reflex using a computerized visual analogue scale (VAS). RESULTS: Statistical analysis using ANOVA showed no significant differences between baseline and posttreatment measurement for RIII reflex, H-reflex, or VAS data. CONCLUSION: These results suggest that neither type of electrical stimulation (TENS or IFT) affects the RIII or H-reflexes, at least using the parameters and application time in this study.