Heterogeneity of psychophysiological stress responses in fibromyalgia syndrome patients

Dysregulated psychophysiological responses have been observed in patients with fibromyalgia syndrome (FMS), although the results are inconsistent. Surface electromyographic (EMG), systolic and diastolic blood pressure, heart rate (HR), and skin conductance levels (SCLs) were continuously recorded at baseline, and during a series of stress and relaxation tasks in 90 FMS patients and 30 age and sex matched healthy controls (HCs). The patient sample demonstrated lower baseline EMG levels compared to the HCs on all tasks. In contrast, the patients displayed elevated HR and SCL (sympathetic vasomotor and sudomotor indices, respectively) during both stress tasks. A cluster analysis identified four psychophysiological response patterns: 63.3% of HCs showed increased muscle tension and stable cardiovascular responses; 34.8% of FMS patients showed a pattern of increased sympathetic vasomotor reactivity with stable sudomotor and reduced muscular response; 12.2% of FMS patients showed a pattern of increased sympathetic sudomotor reactivity connected with increased sympathetic vasomotor response and reduced muscular response; and, in contrast, 46.7% of FMS patients showed a pattern of parasympathetic vasomotor reactivity and reduced sudomotor as well as muscular response. The identification of low baseline muscle tension in FMS is discrepant with other chronic pain syndromes and suggests that unique psychophysiological features may be associated with FMS. The different psychophysiological response patterns within the patient sample support the heterogeneity of FMS.     

Stress and psychophysiological dysregulation in patients with fibromyalgia syndrome

Fibromyalgia syndrome (FMS) is a prevalent musculoskeletal pain disorder characterized by diffuse pain and associated psychophysiological symptoms. Despite extensive research in the past 3 decades, the etiology and pathophysiology of FMS and effective treatment approaches are yet to be delineated. Recently, it has been suggested that FMS may be related to hypofunctional stress systems, particularly in the autonomic nervous system (ANS) and the hypothalamic-pituitary-adrenal (HPA) axis. Studies have demonstrated that patients with FMS exhibit lowered sympathoadrenal reactivity to stress. These findings seem to be consistent with the large volume of research indicating the inverse relationship between pain sensitivity and sympathetic reactivity. In this paper, we discuss the role of stress in the pain experience in general, stress in patients with FMS, and review the studies evaluating the ANS and HPA functions in response to various stressors.     

Regulation of mental states and biofeedback techniques: Effects on breathing pattern

The purpose of the present study was to examine whether breathing pattern may be used as a reliable index for the effectiveness of techniques applied for the regulation of mental states. Heart rate (HR), breathing pattern, galvanic skin response (GSR), and electromyogram (EMG) of the frontalis muscle were measured in 39 male and female subjects aged 18–25 years during 10-minute treatment with relaxation technique (autogenic training and/or music) followed by 10 minutes of imagery training. In the first 7 sessions biofeedback (BFB) was not included, while during the last 6 sessions BFB was introduced and utilized by the subjects. Relaxation (music or autogenic training) led to a decrease in breathing frequency, attributed to lengthening of expiration time, as well as reduced HR, GSR, and frontalis EMG response. In most instances imagery training was related to an increase in these indices. Specifically, significant tachypnea was observed during imagery of sprint running. In most cases BFB substantially augmented the physiological responses. In conclusion, our data suggest that, compared with HR, GSR, and EMG responses, the breathing pattern is at least as sensitive to the mental techniques employed, and may be useful as a psychophysiological index for diagnosis and testing, especially in sport practice.     

Cephalic vasomotor feedback in the modification of migraine headache

The effect of cephalic vasomotor response (CVMR) and frontalis electromyographic (EMG) feedback on control of temporal arterial vasoconstriction and frontalis muscle activity in migraine and muscle contraction headache patients was investigated. A single subject multiple baseline design (across subjects and responses) was introduced to evaluate (1) patterning in the two physiological systems and (2) the effects of CVMR and EMG feedback on headache activity. The data indicated that (a) all four patients demonstrated an ability to control CVMR activity during CVMR feedback and EMG during EMG feedback, (b) idiosyncratic patterns of physiological activity emerge during feedback training, and (c) learned control of the pain mechanism for muscle contraction and migraine headaches was related to reduced frequency and duration of these headaches.Portions of this paper were presented at the Ninth Annual Convention of the Association for Advancement of Behavior Therapy, San Francisco, 1975.     

Sympathetic activation is associated with increases in EMG during fatiguing exercise

The purpose of this study was to test the hypothesis that efferent sympathetic neural discharge is coupled with the development of muscle fatigue during voluntary exercise in humans. In 12 healthy subjects (aged 20-34 yr) we measured heart rate (HR), arterial blood pressure (AP), and noncontracting, skeletal muscle sympathetic nerve activity (MSNA) in the leg (peroneal nerve) before (control) and during each of three trials of submaximal (30% of maximum) isometric handgrip exercise performed to exhaustion. In six of the subjects of eletromyographic (EMG) activity of the exercising forearm was also measured. HR and AP increased significantly (P less than 0.05) in the 1st min of exercise in all trials. In contrast, neither MSNA nor EMG activity increased significantly above control during the 1st min of exercise, but both parameters subsequently increased in a progressive and parallel manner (P less than 0.05). The overall correlation coefficient between MSNA and EMG activity (144 observations) was 0.85 (P less than 0.001). With successive trials the magnitudes of the increases in HR, AP, MSNA, and EMG activity were greater at any absolute point in time during exercise. These results indicate that sympathetic activation to noncontracting skeletal muscle is directly related to the development of muscle fatigue (as assessed by the change in EMG) during prolonged isometric exercise in humans. Furthermore, our findings demonstrate that previous fatiguing contractions alter the time course of the sympathetic neural adjustments to exercise.     

Cardiopulmonary responses to static exercise

Ventilatory and cardiovascular responses to isometric exercise, with special reference to hand-grip exercise, were reviewed. Blood flow through the forearm (FBF) during muscular contraction is dependent on relative strength to MVC (maximum voluntary contraction), duration of exercise, and hand temperature. FBF could attain steady state during exercise with intensities less than 15% MVC. Heart rate (HR) starts to increase with a latency as short as 0.4 to 0.6 sec in conscious animals and men in response to voluntary as well as electrically induced isometric exercise. This response is vagally transmitted. The sympathetic nerves mediated HR response with a longer delay is also found. Cardiac contractility is augmented via sympathetic beta-receptors during isometric exercise. With aging, HR response tends to be intensified, whereas, stroke volume response tends to be depressed. Thus increased cardiac output is resulted in elevated arterial blood pressure. Total vascular resistance is reported to be unaltered, or to increase, despite of consistent increase in muscle sympathetic activities during the isometric exercise. Ventilation is augmented during exercise, but the pattern of its response is not in full agreement among investigators. The underlying mechanisms to elicit those responses are discussed.     

EMG Reactivity and Oral Habits Among Young Adult Headache Sufferers and Painfree Controls in a Scheduled-Waiting Task

Previous research has shown that patients with facial pain exhibit a pattern of physiological and behavioral reactivity to scheduled-waiting tasks that may help account for the development of facial pain. The present study extended this line of research by examining the psychophysiological reactivity of headache sufferers in a similar task. A total of 34 frequent headache sufferers screened by International Headache Society (IHS) criteria and 13 painfree controls completed a psychophysiological assessment consisting of 4 phases (adaptation, free-play, scheduled-play, and recovery) that included a scheduled-waiting condition (scheduled-play) designed to produce adjunctive behavior. Masseter and frontalis EMG were measured continuously during each phase and self-reported oral habits and pain ratings were collected following each phase. A significant interaction and group effect was found on frontalis EMG, with the headache group exhibiting elevated EMG levels across the phases, whereas the control group exhibited increasing EMG levels that peaked during the scheduled-play phase. Only a significant phase effect was found on masseter EMG, with the highest EMG levels recorded during the scheduled-play phase for both groups. In addition, a significant phase effect was found on self-reported oral habits data. Overall, these results provide general support for the adjunctive behavior effect, but the predicted difference in magnitude between the groups was not found.     

Upper trapezius muscle activity patterns during repetitive manual material handling and work with with a computer mouse.

Firstly, upper trapezius EMG activity patterns were recorded on the dominant side of 6 industrial production workers and on the side operating a computer mouse of 14 computer-aided design (CAD) operators to study differences in acute muscular response related to the repetitiveness of the exposure. The work tasks were performed with median arm movement frequencies ranging from 5 min(-1) to 13 min(-1) and were characterized by work cycle times ranging from less than 30 sec to several days. However, the static and median EMG levels and EMG gap frequencies were similar for all work tasks indicating that shoulder muscle loads may be unaffected by large variations in arm movement frequencies and work cycle times. An exposure variation analyses (EVA) showed that the EMG activity patterns recorded during production work were more repetitive than during CAD work, whereas CAD work was associated with more static muscle activity patterns, both may be associated with a risk of developing musculoskeletal symptoms. Secondly, upper trapezius EMG activity patterns recorded on the mouse side of the CAD operators were compared with those recorded on the non-mouse side to study differences in muscular responses potentially related to the risk of developing shoulder symptoms which were more prevalent on the mouse side. The number of EMG gaps on the mouse side were significantly lower than the values for the upper trapezius on the non-mouse side indicating that more continuous activity was present in the upper trapezius muscle on the mouse side and EVA analyses showed a more repetitive muscle activity pattern on the mouse side. These findings may be of importance to explain differences in the prevalence of shoulder symptoms.     

Sex differences in the modulation of vasomotor sympathetic outflow during static handgrip exercise in healthy young humans

Sex differences in sympathetic neural control during static exercise in humans are few and the findings are inconsistent. We hypothesized women would have an attenuated vasomotor sympathetic response to static exercise, which would be further reduced during the high sex hormone [midluteal (ML)] vs. the low hormone phase [early follicular (EF)]. We measured heart rate (HR), blood pressure (BP), and muscle sympathetic nerve activity (MSNA) in 11 women and 10 men during a cold pressor test (CPT) and static handgrip to fatigue with 2 min of postexercise circulatory arrest (PECA). HR increased during handgrip, reached its peak at fatigue, and was comparable between sexes. BP increased during handgrip and PECA where men had larger increases from baseline. Mean ± SD MSNA burst frequency (BF) during handgrip and PECA was lower in women (EF, P < 0.05), as was ΔMSNA-BF smaller (main effect, both P < 0.01). ΔTotal activity was higher in men at fatigue (EF: 632 ± 418 vs. ML: 598 ± 342 vs. men: 1,025 ± 416 a.u./min, P < 0.001 for EF and ML vs. men) and during PECA (EF: 354 ± 321 vs. ML: 341 ± 199 vs. men: 599 ± 327 a.u./min, P < 0.05 for EF and ML vs. men). During CPT, HR and MSNA responses were similar between sexes and hormone phases, confirming that central integration and the sympathetic efferent pathway was comparable between the sexes and across hormone phases. Women demonstrated a blunted metaboreflex, unaffected by sex hormones, which may be due to differences in muscle mass or fiber type and, therefore, metabolic stimulation of group IV afferents.     

The effect of mental loads on muscle tension, blood pressure and blink rate

Surface electromyogram (EMG), blood pressure (BP), blink rate (BR) and heart rate (HR) were recorded before and during 4 types of mental task. The mental task involved 3 tasks that encompassed the memory (M), visual search (VS) and color-word (CW) tasks besides the control task (CT) of maintaining a similar posture while focusing on a single spot on the computer screen. Except for CW, any voluntary movement for response to visual stimuli given were not demanded. Slightly but significant increases in integrated EMG (iEMG) were shown in terapezius, biceps and gastrocnemius muscles during tasks except for CT. Especially in the trapezius muscle during M, the most remarkable enhancements of iEMG and BP were shown. In VS and CW tasks, significant decreases in BR were observed, although in M and CT tasks there were no significant changes in it. There were no significant changes in HR in any type of tasks. The present study demonstrated the increase in muscle tension due to mental needs of cognitive tasks per se accompanying changes in BP and BR. And, enhancement of these physiological responses by memory loads and eyeball movement was discussed as a possible mechanism.     

Reduction of stuttering by young male stutterers using EMG feedback

A clinical program was designed in which male stutterers (age 10–14 years) were trained to reduce speech muscle tension by application of electromyograph (EMG) feedback. The program was designed (a) to reduce nonspeech EMG activity of facial muscles involved in speech, (b) to use this skill for control of muscle EMG activity while speaking, (c) to maintain the physiological EMG activity reduction with behavioral self-control techniques. Three subjects were treated on a single-subject ABCD baseline design, with an ABABAB reversal design within the treatment (B) phase. EMG feedback was shown to reduce stuttering in the clinic. After maintenance techniques were taught, stuttering was shown to have reduced 60–80% in the home environment while speech rate remained constant or increased. A 9-month follow-up showed that the improvement produced in treatment was continuing.     

Muscular response to the therapist and symptomatic improvement during biofeedback for tension headache.

The relationship between muscular response to the therapist's presence and symptomatic improvement was studied during biofeedback. Thirty-two patients suffering from tension headaches received muscular biofeedback training of six sessions plus a follow-up session two months later. Patients' electro-myographic frontal response was measured prior to treatment both with and without the therapist present. A relationship was found between symptomatic improvement at follow-up and muscular response to the therapist's presence before treatment: patients showing a decrease of at least 10% in muscular tension response to the presence of their future therapist improved more regarding headache intensity than the patients showing increase or smaller variation of their EMG. A significant correlation of .59 was found between the frontal EMG response to therapist presence during the evaluation session and headache improvement at follow-up. The results suggest that the decrease of muscular tension during the first contact with the therapist could be an indicator of good prognosis, possibly because of an immediate positive therapeutic relationship and/or favorable expectancies concerning future benefit of treatment.     

Adaptations to isolated shoulder fatigue during simulated repetitive work. Part II: Recovery

The shoulder allows kinematic and muscular changes to facilitate continued task performance during prolonged repetitive work. The purpose of this work was to examine changes during simulated repetitive work in response to a fatigue protocol. Participants performed 20 one-minute work cycles comprised of 4 shoulder centric tasks, a fatigue protocol, followed by 60 additional cycles. The fatigue protocol targeted the anterior deltoid and cycled between static and dynamic actions. EMG was collected from 14 upper extremity and back muscles and three-dimensional motion was captured during each work cycle. Participants completed post-fatigue work despite EMG manifestations of muscle fatigue, reduced flexion strength (by 28%), and increased perceived exertion (∼3 times). Throughout the post-fatigue work cycles, participants maintained performance via kinematic and muscular adaptations, such as reduced glenohumeral flexion and scapular rotation which were task specific and varied throughout the hour of simulated work. By the end of 60 post-fatigue work cycles, signs of fatigue persisted in the anterior deltoid and developed in the middle deltoid, yet perceived exertion and strength returned to pre-fatigue levels. Recovery from fatigue elicits changes in muscle activity and movement patterns that may not be perceived by the worker which has important implications for injury risk.     

Cholecystokinin selectively affects presympathetic vasomotor neurons and sympathetic vasomotor outflow

Cholecystokinin (CCK) is a potential mediator of gastrointestinal vasodilatation during digestion. To determine whether CCK influences sympathetic vasomotor function, we examined the effect of systemic CCK administration on mean arterial blood pressure (MAP), heart rate (HR), lumbar sympathetic nerve discharge (LSND), splanchnic sympathetic nerve discharge (SSND), and the discharge of presympathetic neurons of the rostral ventrolateral medulla (RVLM) in alpha-chloralose-anesthetized rats. CCK (1-8 microg/kg iv) reduced MAP, HR, and SSND and transiently increased LSND. Vagotomy abolished the effects of CCK on MAP and SSND as did the CCK-A receptor antagonist devazepide (0.5 mg/kg iv). The bradycardic effect of CCK was unaltered by vagotomy but abolished by devazepide. CCK increased superior mesenteric arterial conductance but did not alter iliac conductance. CCK inhibited a subpopulation (approximately 49%) of RVLM presympathetic neurons whereas approximately 28% of neurons tested were activated by CCK. The effects of CCK on RVLM neuronal discharge were blocked by devazepide. RVLM neurons inhibited by exogenous CCK acting via CCK-A receptors on vagal afferents may control sympathetic vasomotor outflow to the gastrointestinal tract vasculature.     

Using Psychophysiological Measures to Examine the Temporal Profile of Verbal Humor Elicitation

Despite its pervasiveness in popular culture, there remains much to be learned about the psychological and physiological processes that underlie our experience of humor. In the present study, we examined the temporal profile of verbal humor elicitation using psychophysiological measures of heart rate (HR) and facial electromyography (EMG). Consistent with recent prior research on cardiovascular changes to perceived humor, we found that HR acceleration was greater for jokes relative to non-jokes, and was positively related to the level of perceived humor elicited by these jokes. In addition, activity recorded from the zygomaticus major muscle that controls smiling was found to be greater for jokes relative to non-jokes. To link these physiological changes to the psychological processes that govern humor comprehension, we took the initial inflection point of the zygomatic EMG response as a marker for the onset of humor comprehension, and used this marker to probe the pattern of cardiovascular activity at this time-point. We estimated the onset of the humor response to occur during the initial HR deceleration phase, and found that jokes relative to non-jokes elicited a decreased HR response at this time-point. This result questions the previously forwarded notion that the psychological “moment of insight” that signals the start of the humor response is always associated with heightened cardiovascular activity. This discrepancy is discussed in relation to possible differences in the cognitive processes required to comprehend different forms of humor. At a broader level, our results also demonstrate the advantages of combining different psychophysiological measures to examine psychological phenomena, and illustrate how one such measure can constrain the interpretation of others.     

The application of generalizability theory to surface electromyographic measurements during psychophysiological stress testing: how many measurements are needed?

Generalizability theory is an extension of classical reliability theory that allows multiple sources of measurement error in an experimental design to be investigated simultaneously. In the present study, generalizability theory was used to evaluate measurement error in psychophysiological test procedures used to differentiate tension headache patients from normal controls based upon measures of electromyographic (EMG) responding. Thirty-three subjects who met diagnostic criteria for tension-type headache and 40 normal control subjects who rarely or never experienced headache participated in two laboratory sessions. EMG activity of head and neck muscles was recorded while subjects performed baseline, relaxation, choice reaction time, psychomotor tracking, and cold pressor tasks. Variance components were computed for an experimental design having subjects nested within experimenters and crossed with sessions and replications. Generalizability coefficients were computed for combinations of various numbers of sessions and replications. The generalizability of EMG measures was highly variable, depending on the experimental conditions in force. The largest sources of measurement error were attributed to the unique responsiveness of individual subjects under a particular set of treatment conditions. For some stress tests currently in use, data from several testing sessions may need to be averaged in order to achieve acceptable levels of generalizability. Generalizability greater than 0.80 can be expected only rarely when data are collected during a single session. In the research setting, low generalizability may account for the failure of EMG-based stress tests to differentiate tension headache patients from controls during stressful task performance. In the clinical setting, the generalizability of information derived from "stress profiling" or muscle "scanning" techniques, which depend on results obtained during a single testing session, is doubtful.     

Responses in muscle sympathetic nerve activity to sustained hand-grips of different tensions in humans

To clarify whether sympathetic nerve activity increases in relation to the tension of a sustained muscle contraction, muscle sympathetic nerve activity (MSA) was recorded directly from the peroneal nerve fascicle at the popliteal fossa by means of tungsten microelectrodes in five healthy male subjects. A sustained muscle contraction was performed by handgrip for two minutes in a supine position at tensions of 10, 30 and 45% of maximal grip strength (MGS). MSA, electrocardiogram (ECG) using bipolar electrodes from the chest and surface electromyogram (EMG) from the extensor pollicis longus were recorded simultaneously before and during the sustained handgrip. Arterial blood pressure was measured at the resting upper arm by auscultation. During handgrip with tensions of 10, 30 and 45% MGS, average MSA burst rate (bursts X min-1) increased to 122, 152 and 230% of the resting value, respectively. During the same experimental procedures with tensions of 10, 30 and 45% MGS, average heart rate increased to 105, 110 and 111% of the resting value. These results confirm that sympathetic outflow to a resting muscle is increased with elevation of tension in an active muscle. This process would promote perfusion pressure in the active muscle.     

Electromyographic response is altered during robotic surgical training with augmented feedback

There is a growing prevalence of robotic systems for surgical laparoscopy. We previously developed quantitative measures to assess robotic surgical proficiency, and used augmented feedback to enhance training to reduce applied grip force and increase speed. However, there is also a need to understand the physiological demands of the surgeon during robotic surgery, and if training can reduce these demands. Therefore, the goal of this study was to use clinical biomechanical techniques via electromyography (EMG) to investigate the effects of real-time augmented visual feedback during short-term training on muscular activation and fatigue. Twenty novices were trained in three inanimate surgical tasks with the da Vinci Surgical System. Subjects were divided into five feedback groups (speed, relative phase, grip force, video, and control). Time- and frequency-domain EMG measures were obtained before and after training. Surgical training decreased muscle work as found from mean EMG and EMG envelopes. Grip force feedback further reduced average and total muscle work, while speed feedback increased average muscle work and decreased total muscle work. Training also increased the median frequency response as a result of increased speed and/or reduced fatigue during each task. More diverse motor units were recruited as revealed by increases in the frequency bandwidth post-training. We demonstrated that clinical biomechanics using EMG analysis can help to better understand the effects of training for robotic surgery. Real-time augmented feedback during training can further reduce physiological demands. Future studies will investigate other means of feedback such as biofeedback of EMG during robotic surgery training.     

Muscular response to the therapist and symptomatic improvement during biofeedback for tension headache

The relationship between muscular response to the therapist's presence and symptomatic improvement was studied during biofeedback. Thirty-two patients suffering from tension headaches received muscular biofeedback training of six sessions plus a follow-up session two months later. Patients' electro-myographic frontal response was measured prior to treatment both with and without the therapist present. A relationship was found between symptomatic improvement at follow-up and muscular response to the therapist's presence before treatment: patients showing a decrease of at least 10% in muscular tension response to the presence of their future therapist improved more regarding headache intensity than the patients showing increase or smaller variation of their EMG. A significant correlation of .59 was found between the frontal EMG response to therapist presence during the evaluation session and headache improvement at follow-up. The results suggest that the decrease of muscular tension during the first contact with the therapist could be an indicator of good prognosis, possibly because of an immediate positive therapeutic relationship and/or favorable expectancies concerning future benefit of treatment.The authors thank Mrs. G. Parisé for her assistance during the experimentation, Ms. M. Newman for her editorial corrections, and Ms. A. Khan for her secretarial work.     

Viscerosomatic interaction induced by myocardial ischemia in conscious dogs.

Studies tested the hypothesis that myocardial ischemia induces increased paraspinal muscular tone localized to the T(2)-T(5) region that can be detected by palpatory means. This is consistent with theories of manual medicine suggesting that disturbances in visceral organ physiology can cause increases in skeletal muscle tone in specific muscle groups. Clinical studies in manual and traditional medicine suggest this phenomenon occurs during episodes of myocardial ischemia and may have diagnostic potential. However, there is little direct evidence of a cardiac-somatic mechanism to explain these findings. Chronically instrumented dogs [12 neurally intact and 3 following selective left ventricular (LV) sympathectomy] were examined before, during, and after myocardial ischemia. Circumflex blood flow (CBF), left ventricular contractile function, electromyographic (EMG) analysis, and blinded manual palpatory assessments (MPA) of tissue over the transverse spinal processes at segments T(2)-T(5) and T(11)-T(12) (control) were performed. Myocardial ischemia was associated with a decrease in myocardial contractile function and an increase in heart rate. MPA revealed increases in muscle tension and texture/firmness during ischemia in the T(2)-T(5) segments on the left, but not on the right or in control segments. EMG demonstrated increased amplitude for the T(4)-T(5) segments. After LV sympathectomy, MPA and EMG evidence of increased muscle tone were absent. In conclusion, myocardial ischemia is associated with significant increased paraspinal muscle tone localized to the left side T(4)-T(5) myotomes in neurally intact dogs. LV sympathectomy eliminates the somatic response, suggesting that sympathetic neural traffic between the heart and somatic musculature may function as the mechanism for the interaction.