***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: BACKGROUND Recent studies have shown that a transcutaneous electrical nerve stimulation ( TENS ) and interferential current ( IFC ) application reduces pain in subjects with musculoskeletal disorders . However there are no clinical trials evaluating or comparing the muscle relaxation generated for these devices . PURPOSE To compare the muscle relaxation of the upper trapezius induced by the application of TENS and IFC in females with chronic nonspecific neck discomfort . METHODS Sixty-four females between 18 and 40 years of age and a history of nonspecific neck discomfort were r and omly assigned to a TENS or an IFC group . The women in the TENS ( N = 32 ; mean age 22 years ) and IFC ( N = 32 , mean age 23 years ) group were su bmi tted to current application during 3 consecutive days and were assessed by  electromyography ( EMG ) in different times aim ing to quantify the muscular tension of the upper trapezius . A visual analogue scale ( VAS ) was used as pain measure at baseline ( before TENS or IFC application ) and at the end of the study . RESULTS At baseline , demographic , pain , and EMG assessment data were similar between groups . Those in the IFC group had a significant trapezius relaxation after 3 IFC applications when compared to baseline and intermediate evaluations ( P < 0.05 ) . In contrast , the same analysis showed no significant difference between all assessment s in the TENS group ( P > 0.05 ) . In relation to pain relief , both groups showed an improvement at the end of the study when compared to baseline ( both , P < 0.05 ) . The between-group analysis showed no difference for the subjects who received such IFC as TENS application ( P < 0.05 ) . CONCLUSION IFC induced the upper trapezius relaxation after 3 sessions in females with neck discomfort , but the TENS application did not change the muscular tension . However , these results should be carefully interpreted due to the lack of differences between groups . A significant pain decrease was found in the subjects of both groups , however , only the IFC application presented a clinical ly important improvement OBJECTIVE To compare the effectiveness of transcutaneous electrical nerve stimulation ( TENS ) , interferential currents ( IFCs ) , and shortwave diathermy ( SWD ) against each other and sham intervention with exercise training and education as a multimodal package . DESIGN A double-blind , r and omized , controlled , multicenter trial . SETTING Departments of physical medicine and rehabilitation in 4 centers . PARTICIPANTS Patients ( N=203 ) with knee osteoarthritis ( OA ) . INTERVENTIONS The patients were r and omized by the principal center into the following 6 treatment groups : TENS sham , TENS , IFCs sham , IFCs , SWD sham , and SWD . All interventions were applied 5 times a week for 3 weeks . In addition , exercises and an education program were given . The exercises were carried out as part of a home-based training program after 3 weeks ' supervised group exercise . MAIN OUTCOME MEASURES Primary outcome was a visual analog scale ( 0 - 100 mm ) to assess knee pain . Other outcome measures were time to walk a distance of 15 m , range of motion , Western Ontario and McMaster Universities Osteoarthritis Index ( WOMAC ) , Nottingham Health Profile , and paracetamol intake ( in grams ) . RESULTS We found a significant decrease in all assessment parameters ( P<.05 ) , without a significant difference among the groups except WOMAC stiffness score and range of motion . However , the intake of paracetamol was significantly lower in each treatment group when compared with the sham groups at 3 months ( P<.05 ) . Also , the patients in the IFCs group used a lower amount of paracetamol  at 6 months ( P<.05 ) in comparison with the IFCs sham group . CONCLUSIONS Although all groups showed significant improvements , we can suggest that the use of physical therapy agents in knee OA provided additional benefits in improving pain because paracetamol intake was significantly higher in the patients who were treated with 3 sham interventions in addition to exercise and education Objectives . Newly developed bidirectional modulated sine waves ( BMW ) might provide some derived benefit to patients with low back pain . Pain relief by transcutaneous electric nerve stimulation ( TENS ) with BMWs was tested . Material s and Methods . Analgesic effects of BMWs and conventional bidirectional pulsed waves on chronic back pain in 28 patients were compared , and effects of repeated TENS using BMWs on chronic back pain were investigated in 21 patients by means of a r and omized double-blind , sham-controlled , parallel-group method . Pain intensity was assessed using numerical rating scale ( NRS ) . Results . There was significant immediate reduction in NRS in patients receiving BMWs , and 60 min after treatment compared to sham TENS . Weekly repeated treatments using massage and TENS with BMWs for 5 weeks result ed in a decrease of NRS , but there were no significant differences between the TENS plus massage and sham TENS plus massage groups . Conclusions . This study shows that TENS with BMWs significantly inhibits chronic back pain , and treatment effects are attained within a day . The results also suggest that there were no statistically significant long-term effects of TENS with BMW in the repeated treatment UNLABELLED Transcutaneous electrical nerve stimulation ( TENS ) is an electrophysical modality used for pain management . This study investigated the dose response of different TENS intensities on  experimentally induced pressure pain . One hundred and thirty TENS naïve healthy individuals ( 18 - 64 years old ; 65 males , 65 females ) were r and omly allocated to 5 groups ( n = 26 per group ) :  Strong Non Painful TENS ; Sensory Threshold TENS ; Below Sensory Threshold TENS ; No Current Placebo TENS ; and Transient Placebo TENS . Active TENS ( 80 Hz ) was applied to the forearm for 30 minutes . Transient Placebo TENS was applied for 42 seconds after which the current amplitude automatically reset to 0 mA. Pressure pain thresholds ( PPT ) were recorded from 2 points on the h and and forearm before and after TENS to measure hypoalgesia . There were significant differences between groups at both the h and and forearm ( ANOVA ; P = .005 and .002 ) . At 30 minutes , there was a significant hypoalgesic effect in the Strong Non Painful TENS group compared to : Below Sensory Threshold TENS , No Current Placebo TENS and Transient Placebo TENS groups ( P < .0001 ) at the forearm ; Transient Placebo TENS and No Current Placebo TENS groups at the h and ( P = .001 ) . There was no significant difference between Strong Non Painful TENS and Sensory Threshold TENS groups . The area under the curve for the changes in PPT significantly correlated with the current amplitude ( r(2 ) = .33 , P = .003 ) . These data therefore show that there is a dose-response effect of TENS with the largest effect occurring with the highest current amplitudes . PERSPECTIVE This study shows a dose response for the intensity of TENS for pain relief with the strongest intensities showing the greatest effect ; thus , we suggest that TENS intensity should be titrated to achieve the strongest possible intensity to achieve maximum pain relief CONTEXT AND OBJECTIVE Transcutaneous electrical nerve stimulation ( TENS ) and interferential current are the most used electrotherapy methods , although there is little scientific evidence to support their use . The aim of this study was to compare the effects of TENS and interferential current among patients with nonspecific chronic low back pain . DESIGN AND SETTING Single-blind r and omized controlled trial in the Department of Physiotherapy , Centro Universitário de Maringá . METHODS One hundred and fifty patients were r and omly divided into three groups : TENS ( group 1 ) , interferential current ( group 2 ) and controls ( group 3 ) . The patients design ated for electrotherapy received ten 30-minute sessions , while the control group remained untreated . All patients and controls were evaluated before and after treatment using a visual analog scale and the McGill Pain and Rol and Morris question naires , and regarding their use of additional medications . RESULTS There was a mean reduction on the visual analog scale of 39.18 mm with TENS , 44.86 mm with interferential current and 8.53 mm among the controls . In the Rol and Morris question naire , group 1 had a mean reduction of 6.59 ; group 2 , 7.20 ; and group 3 , 0.70 points . In group 1 , 84 % of the patients stopped using medications after the treatment ; in group 2 , 75 % ; and in group 3 , 34 % . There was no statistically significant difference between the TENS and interferential current groups ( P > 0.05 ) ; a difference was only found between these groups and the controls ( P < 0.0001 ) . CONCLUSION There was no difference between TENS and interferential current for chronic low back pain treatment . CLINICAL TRIAL REGISTRATION NCT01017913 Background In the currently available research publications on electrical therapy of low back pain , generally no control groups or detailed r and omization were used , and such studies were often conducted with relatively small groups of patients , based solely on subjective question naires and pain assessment scales ( lacking measurement methods to objectify the therapeutic progress ) . The available literature also lacks a comprehensive and large-scale clinical study . The purpose of this study was to assess the effects of treating low back pain using selected electrotherapy methods . The study assesses the influence of individual electrotherapeutic treatments on reduction of pain , improvement of the range of movement in lower section of the spine , and improvement of motor functions and mobility . Material / Methods The 127 patients qualified for the therapy ( ultimately , 123 patients completed the study ) and assigned to 6 comparison groups : A – conventional TENS , B – acupuncture-like TENS , C – high-voltage electrical stimulation , D – interferential current stimulation , E – diadynamic current , and F – control group . Results The research showed that using electrical stimulation with interferential current penetrating deeper into the tissues results in a significant and more efficient elimination of pain , and an improvement of functional ability of patients suffering from low back pain  on the basis of an analysis of both subjective and objective parameters . The TENS currents and high voltage were helpful , but not as effective . The use of diadynamic currents appears to be useless . Conclusions Selected electrical therapies ( interferential current , TENS , and high voltage ) appear to be effective in treating chronic low back pain Background Chronic pain is a public health problem although there is a paucity of prevalence data from countries in the Middle East and North Africa . The aim of this study was to estimate the prevalence of chronic pain and neuropathic pain in a sample of the general adult population in Libya . Methods A cross-sectional telephone survey was conducted before the onset of the Libyan Civil War ( February 2011 ) on a sample of self-declared Libyans who had a l and line telephone and were at least 18 years of age . R and om sampling of household telephone number dialling was undertaken in three major cities and interviews conducted using an Arabic version of the Structured Telephone Interviews Question naire on Chronic Pain previously used to collect data in Europe . In addition , an Arabic version of S-LANSS was used . 1212 individuals were interviewed ( response rate = 95.1 % , mean age = 37.8 ± 13.9 years , female = 54.6 % ) . Results The prevalence of chronic pain ≥ 3 months was 19.6 % ( 95 % CI 14.6 % to 24.6 % ) with a mean ± SD duration of pain of 6 · 5 ± 5 · 7 years and a higher prevalence for women . The prevalence of neuropathic pain in the respondents reporting chronic pain was 19 · 7 % ( 95 % CI 14 · 6 - 24 · 7 ) , equivalent to 3 · 9 % ( 95 % CI 2 · 8 to 5 · 0 % ) of the general adult population . Only , 71 ( 29 · 8 % ) of respondents reported that their pain was being adequately controlled . Conclusions The prevalence of chronic pain in the general adult population of Libya was approximately 20 % and comparable with Europe and North America . This suggests that chronic pain is a public health problem in Libya . Risk factors are being a woman , advanced age and unemployment . There is a need for improved health policies in Libya to ensure that patients with chronic pain receive effective management OBJECTIVE To compare the effectiveness of transcutaneous electrical nerve stimulation and interferential current in primary dysmenorrhea . DESIGN A prospect i ve , r and omized , and controlled study . SETTING Hacettepe University School of Physical Therapy and Rehabilitation . PATIENTS Thirty-four volunteer subjects with primary dysmenorrhea ( mean age : 21.35 + /- 1.70 years ) were included . Statistical analyses were performed in 32 subjects who completed all measures . INTERVENTIONS Fifteen subjects received interferential current application for 20 minutes and 17 subjects received transcutaneous electrical nerve stimulation for 20 minutes when they were experiencing dysmenorrhea . OUTCOME MEASURES Physical characteristics , years since menarche , length of menstrual cycle ( days ) , and duration of menstruation ( days ) were recorded . Visual analog scale ( VAS ) intensities of menstrual pain , referred lower limb pain , and low back pain were recorded before treatment , and immediately , 8 hours , and 24 hours after treatment . RESULTS Intensities of the evaluated parameters decreased beginning from just after the applications 
    Output:
    
In general , both transcutaneous electrical nerve stimulation and interferential current improved pain and functional outcomes without a statistical difference between them .