***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: Objective The aim of this exploratory study was to investigate changes in pain , disability , and muscle activation patterns in patients with chronic whiplash-associated disorder ( WAD ) after 4 weeks of myofeedback training . Methods Eleven WAD patients received ambulatory myofeedback training  , during which upper trapezius muscle activation and relaxation were continuously recorded and processed for 4 weeks . Feedback was provided when muscle relaxation was insufficient . Pain in neck , shoulders , and upper back ( Visual Analogue Scale ) , disability ( Neck Disability Index ) , and muscle activation patterns during rest , typing , and stress tasks ( surface electromyography ) were assessed before and after the 4 weeks of training . Results Pain intensity decreased after 4 weeks of training . Clinical ly relevant changes were found with regard to pain in the neck and upper back region ( 55 % of the patients ) , right shoulder ( 64 % ) , and left shoulder ( 18 % ) . A trend for decreased disability was found which was clinical ly relevant in 36 % of the patients . A remarkable reduction was found in the Neck Disability Index items concerning headache and lifting weights . Overall , muscle activation was lower and muscle relaxation was higher after the training period with the largest differences during rest . Clinical ly relevant changes in surface electromyography parameters were found in a minority of patients . Conclusion Four weeks of ambulant training may be beneficial in reducing pain and disability levels and normalizing muscle activation patterns in chronic WAD patients . A r and omized-controlled study is recommended to further explore the effects of myofeedback training PURPOSE Although daytime clenching is believed to be one of the oral parafunctions leading to dental problems , a treatment strategy has not yet been devised . Electromyogram ( EMG ) biofeedback training was performed to ascertain its effect on the regulation of daytime clenching behavior . MATERIAL S AND METHODS Twenty subjects ( mean age , 30.9±5.6 years ) who had mild to moderate masticatory muscle pain with daytime clenching behavior were r and omly divided into either a biofeedback group ( BF ) or control group ( CO ) . Subjects were fitted with a hearing-aid-shaped EMG recording and biofeedback apparatus which was used to record EMG data under natural conditions from the temporal muscle , continuously for five hours on four consecutive days . EMG data on Days 1 and 4 were recorded without biofeedback as pre-test and post-test , respectively , and on Days 2 and 3 , subjects in the BF group noticed their clenching behaviors via an alert sound from the EMG biofeedback apparatus . No alert sound was given for the CO group throughout the recording sessions . RESULTS There was no significant difference in the number of clenching events for five hours between the BF group ( 4.6±2.5 ) and CO group ( 4.6±0.9 ) on Day 1 , however a significant decrease was found in the BF group between Day 1 ( 4.6±2.5 ) and Day 4 ( 2.4±1.7 ; P<0.05 ) . CONCLUSION Daytime clenching was reduced in the short-term with the help of an EMG biofeedback system under natural circumstances . Further research is needed to confirm a long-lasting effect There is emerging evidence that feedback techniques based on contingent electrical stimulation ( CES ) have an inhibitory effect on the electromyogram ( EMG ) activity of jaw-closing muscles and therefore could be useful in the management of sleep bruxism . This polysomnographic ( PSG ) study was design ed to investigate the effect of CES on PSG parameters in subjects with self-reported bruxism . Fourteen subjects underwent a full PSG investigation in the laboratory for three consecutive nights - one night of adaptation , one night without CES  , and one night with CES - in a r and omized order . During all sessions the EMG activity was recorded by a portable feedback device from the temporalis muscle . An electrical pulse , which was adjusted to a moderate , but non-painful , intensity , was applied to subjects during the session with CES , if jaw-muscle activity was detected . The total sleep time , the number of micro-arousals per hour of sleep , the time spent in sleep stages 3 and 4 and in rapid eye movement ( REM ) sleep , and the number of periodic limb movements , were not influenced by CES . The number of EMG episodes per hour of sleep during the nights with and without CES was not significantly different . The present study suggests that CES at non-painful intensities does not cause major arousal responses in any of the sleep parameters assessed in this study & NA ; Temporom and ibular disorders ( TMD ) represent a group of chronic painful conditions involving the muscles of mastication and the temporom and ibular joint . Several studies have reported that TMD is associated with enhanced sensitivity to experimental pain . Twenty‐three TMD subjects and 24 pain‐free matched control subjects participated in a set of studies which were design ed to evaluate whether the temporal integrative aspects of thermal pain perception are altered in TMD patients compared with control subjects . Specifically , we have examined in both TMD patients and in age‐ and gender‐matched control subjects : ( 1 ) the time‐course and magnitude of perceived pain evoked by the application of sustained 7‐s noxious thermal stimuli ( 45–48 ° C ) to the face and forearm , ( 2 ) the central summation of C‐fiber‐mediated pain produced by applying brief trains of noxious heat pulses to the skin overlying the ventral aspect of the right palm and ( 3 ) the ability to discriminate small increments in noxious heat applied to facial and volar forearm skin . Data collected from these studies indicate that TMD patients show enhanced temporal integration of thermal pain compared with control subjects . TMD patients show greater thermal C‐fiber‐mediated temporal summation than pain‐free subjects and they report a greater magnitude of sustained noxious heat pulses applied to either the face or the forearm than control subjects . In contrast to these findings , TMD and pain‐free subjects are equally able to discriminate and detect small increments of heat applied to noxious adapting temperatures . These findings suggest that the augmented temporal integration of noxious stimuli may result from alterations in central nervous system processes which contribute to the enhanced pain sensitivity observed in TMD patients & NA ; The pathophysiological mechanisms of myofascial temporom and ibular disorders ( TMD ) are still under investigation . The hypothesis that TMD pain is caused by a generalized sensitization of higher order neurons in the nociceptive pathways combined with a decreased efficacy of endogenous inhibitory systems has recently gained support in the literature . This study was design ed to further investigate the somatosensory sensibility within and outside the craniofacial region . Twenty‐two patients fulfilled the research diagnostic criteria for TMD for myofascial pain ( Dworkin and LeResche , J Craniom and ib Disord Facial Oral Pain 6 ( 1992 ) 301 ) and 21 age‐ and sex‐matched subjects served as a control group . The somatosensory sensibility to a deep tonic input was tested by st and ardized infusions of hypertonic saline into the masseter and anterior tibialis muscle . Furthermore , pressure pain thresholds ( PPTs ) and heat pain thresholds ( HPTs ) were assessed with phasic stimuli at the same sites before and following the infusions . Myofascial TMD patients reported infusion of hypertonic saline to be more painful on 10 cm visual analogue scales ( peak pain 8.8±0.4 cm ) than control subjects ( 6.8±0.5 cm , t‐test : P=0.003 ) in the masseter but not in the anterior tibialis ( 7.4±0.5 vs. 6.6±0.5 cm , P=0.181 ) . The perceived area of experimental masseter pain measured on drawings was marginally larger in TMD patients ( 2.6±0.5 arbitrary units ( a.u . ) ) than in control subjects ( 1.4±0.2 a.u . , Mann – Whitney : P=0.048 ) but no differences were observed for the anterior tibialis ( P=0.771 ) . The PPTs were lower in the myofascial TMD patients compared to the control group , both in the masseter ( analysis of variance ( ANOVA ) : P=0.002 ) and in the anterior tibialis ( P=0.005 ) , whereas there were no significant differences in HPT ( ANOVAs : P=0.357 , P=0.101 ) . There were no significant correlations between measures of somatosensory sensibility and measures of clinical pain intensity , pain duration , grade d chronic pain scores or somatization or depression scores ( Pearson : R<0.304 , P>0.172 ) . The present study in a well‐defined group of myofascial TMD patients found that the responsiveness to both tonic and phasic deep stimuli , but not to phasic superficial inputs at the pain threshold level , in the craniofacial region was higher compared with a control group . These findings suggest that myofascial TMD pain is associated with a facilitation of stimulus‐evoked pain primarily , but not exclusively related to the painful region AIMS To determine whether an intervention reduces oromotor activity and masticatory muscle pain in myofascial temporom and ibular disorder ( M/TMD ) patients with high levels of masticatory muscle activity associated with sleep bruxism . METHODS Fourteen women with M/TMD and prior polysomnographic evidence consistent with sleep bruxism participated in a 10-week single-group pre-test/ post-test mechanistic clinical trial . A 2-week period of baseline monitoring of individually biocalibrated electromyographic ( EMG ) events associated with sleep bruxism was followed by 6 weeks of EMG-event-contingent treatment via an innocuous electrical pulse to the skin overlying the temporalis muscle . Treatment was discontinued during 2-week follow-up monitoring . Each night before sleep , subjects recorded their average daily pain . RESULTS Mixed-model analysis of variance showed a reliable reduction of EMG events during contingent stimulation treatment periods , but frequency of EMG events returned to baseline levels during follow-up ( linear term , P = .002 ; quadratic term , P = .001 ) . In contrast , nightly pain reports failed to show any systematic changes during treatment ( linear and quadratic trends , both P > .10 ) . CONCLUSION Spontaneous pain severity and nighttime oromotor activity vary independently over nights , even in M/TMD patients selected for relatively high levels of both characteristics UNLABELLED Several case-control studies have been conducted that examine the association between autonomic variables and persistent pain conditions ; however , there is a surprising dearth of published studies in this area that have focused on temporom and ibular disorders ( TMD ) . The current study presents autonomic findings from the baseline case-control study of the OPPERA ( Orofacial Pain : Prospect i ve Evaluation and Risk Assessment ) cooperative agreement . Measures of arterial blood pressure , heart rate , heart rate variability , and indirect measures of baroreflex sensitivity were assessed at rest and in response to a physical ( orthostatic ) and psychological ( Stroop ) stressors in 1,633 TMD-free controls and 185 TMD cases . In bivariate and demographically adjusted analyses , greater odds of TMD case status were associated with elevated heart rates , reduced heart rate variability , and reduced surrogate measures of baroreflex sensitivity across all experimental procedures . Principal component analysis was undertaken to identify latent constructs revealing 5 components . These findings provide evidence of associations between autonomic factors and TMD . Future prospect i ve analyses in the OPPERA cohort will determine if the presence of these autonomic factors predicts increased risk for developing new onset TMD . PERSPECTIVE This article reports autonomic findings from the OPPERA Study , a large prospect i ve cohort study design ed to discover causal determinants of TMD pain . Findings indicate statistically significant differences between TMD cases and controls across multiple autonomic constructs at rest and during both physical and psychologically challenging conditions . Future analyses will determine whether these autonomic factors increase risk for new onset TMD This study investigated effects of electromyographic ( EMG ) biofeedback ( BFB ) and transcutaneous electrical neuromuscular stimulation ( TENS ) on the EMG activity of the masticatory muscles and skin conductance level ( SCL ) of patients , suffering from myofacial pain syndrome . In the course of the investigation , EMG activity as well as the SCL was measured after a 20 min BFB or , respectively , after a myomonitor session in 20 patients and pre- and post-treatment values were compared . Results showed tendencies of decreased mean-EMG levels for both groups after the treatment sessions , with higher EMG values for the myomonitor group . There was no indication of a significant decrease in mean EMG levels over the sessions . Furthermore , an increase of the SCL during the period of treatment was observed for both groups in session I and II , while session III produced nearly stable values . No existing correlations for changes in SCL and EMG-activity could be established Bruxism contributes to the development of temporom and ibular disorders as well as causes dental problems . Although it is an important issue in clinical dentistry , no treatment approaches have been proven effective . This study aim ed to use electromyogram ( EMG ) biofeedback ( BF ) training to improve awake bruxism ( AB ) and examine its effect on sleep bruxism ( SB ) .  Twelve male participants ( mean age , 26·8 ± 2·5 years ) with subjective symptoms of AB or a diagnosis of SB were r and omly divided into BF ( n = 7 ) and control ( CO , n = 5 ) groups to undergo 5-h daytime and night-time EMG measurements for three consecutive weeks . EMG electrodes were placed over the temporalis muscle on the habitual masticatory side . Those in the BF group underwent BF training to remind them of the occurrence of undesirable clenching activity when excessive EMG activity of certain burst duration was generated in week 2 . Then , EMGs were recorded at week 3 as the post-BF test . Those in the CO group underwent EMG measurement without any EM 
    Output:
    
Most of the selected studies showed a significant correlation between biofeedback usage and reduction of masticatory muscle activity .
By analyzing qualified studies , it can be concluded that biofeedback can be an effective tool in masticatory muscle activity management