Relaxation and subjective estimates of muscle tension: Implications for a central efferent theory of muscle control

The relationship of “awareness of muscle tension” to depth of relaxation was explored. In one experiment, accuracy of forearm flexor control was assessed using the psychophysical method of magnitude production, and depth of flexor relaxation was measured using the integrated EMG before and after EMG biofeedback training. No consistent relationship between motor-control accuracy and depth of relaxation was found. A second, similar experiment with frontalis showed increased accuracy of frontalis control with deeper relaxation. Accuracy of passive, verbal judgments of spontaneous frontalis tension fluctuation exhibited no clear relationship with depth of relaxation. It was concluded that forearm flexor and frontalis may be under the control of distinct mechanisms, and that afferent information probably contributes to the control of neither muscle. Three structural theories of the control mechanisms were considered, and one depending on the central monitoring of efferent outflow(rather than afferent inflow) seemed most compatible with the frontalis data. Both flexor and frontalis data could be accounted for by a two-phase scheme combining central outflow monitoring with the monitoring of mental contents for arousal value at very low muscle tension levels.     

The effects of EMG feedback training during problem solving: a case study.

The present case study investigated the effects of competing task demands on biofeedback training to reduce frontalis muscle tension. Baseline levels of frontalis muscle tension were recorded for relaxation and problem solving. The subject was trained to decrease muscle tension with biofeedback for the problem-solving task alone. The results indicated that EMG training during problem-solving was successfully accomplished. Frontalis muscle tension during relaxation baseline did not change as a result of reductions in muscle tension during problem-solving feedback training. This suggests that the decrease of muscle tension cannot be attributed to reductions in overall muscle tension levels. Instead, training was specific to the problem-solving feedback phases. Additionally, it was found that accuracy in problem-solving did not decline as a result of simultaneous feedback training. Thus EMG biofeedback training can be accomplished and exercised without disruption of ongoing mental activity.     

The effects of EMG feedback training during problem solving

The present case study investigated the effects of competing task demands on biofeedback training to reduce frontalis muscle tension. Baseline levels of frontalis muscle tension were recorded for relaxation and problem solving. The subject was trained to decrease muscle tension with biofeedback for the problem-solving task alone. The results indicated that EMG training during problem solving was successfully accomplished. Frontalis muscle tension during relaxation baseline did not change as a result of reductions in muscle tension during problem-solving feedback training. This suggests that the decrease of muscle tension cannot be attributed to reductions in overall muscle tension levels. Instead, training was specific to the problem-solving feedback phases. Additionally, it was found that accuracy in problem-solving did not decline as a result of simultaneous feedback training. Thus EMG biofeedback training can be accomplished and exercised without disruption of ongoing mental activity.     

Effect of therapist's active presence on EMG biofeedback training of headache patients

Sixteen patients suffering from tension or mixed headaches participated in a frontalis EMG treatment schedule of 15 sessions where the therapist was either actively present or almost completely absent. The aim of this study was to evaluate the impact of the therapist's active presence on the subject's ability to lower the EMG level. The active presence of the therapist consistently led to higher frontalis EMG level than that during the therapist's absence. Data also show that the EMG feedback administered was apparently effective in reducing subjective headache intensity along with EMG levels. The findings raise the question of an optimal dosage of presence and activity of the therapist during EMG feedback training.     

Effectiveness of EMG biofeedback training for controlling arousal in subsequent stressful situations

Thirty-five subjects participated in (1) a pretreatment session during which arousal was measured while subjects anticipated and then viewed a stressful film; (2) four 20-min treatment sessions during which subjects received either contingent EMG biofeedback (biofeedback treatment), instructions to attend to a variable pitch tone (attention-placebo control), instructions to relax as much as possible (instructions-only control), or instructions to sit quietly (no-treatment control); and (3) a posttreatment session that was identical to the pretreatment session. Results indicate that when compared to the subjects in the control conditions, subjects who received EMG biofeedback were not effective in reducing frontalis EMG levels during treatment or while viewing the stressful film, but they were effective in reducing frontalis EMG levels while anticipating the stressful film. There was no evidence that EMG biofeedback influenced either skin conductance or self-reports of arousal.This research was supported in part by Bio-Medical and General Research Fund grants from the University of Kansas to David S. Holmes. Appreciation is due to B. Kent Houston, Edward F. Morrow, and Charles A. Hallenbeck for their contributions to the project.     

The effect of frontal EMG biofeedback training on the behavior of children with activity-level problems

N=1 withdrawal designs were employed with three children evidencing activity-level problems. Tutoring sessions occurred daily over a 2 1/2-month period. Each child was reinforced for decreasing frontalis muscle tension during auditory feedback while working arithmetic problems. Feedback was faded while tension reduction reinforcement was maintained. These procedures were repeated with reinforcement for increasing, rather than decreasing, muscle tension. Frontal EMG level, percent time on task, and motoric activity rate were obtained during sessions. Parent ratings of problem behavior in the home were recorded daily. Biofeedback with reinforcement was effective in both raising and lowering muscle tension. Effects were maintained by reinforcement. Results suggest a direct relationship between tension and activity levels. Academic performance and problem behavior improved significantly with reductions in EMG activity, although individual exceptions to these findings were present. Results lend support to the efficacy of frontal EMG biofeedback training in reducing activity, increasing attention to an academic task, and reducing problem behaviors.     

Finger pulse amplitude and frontalis EMG biofeedback effects of single- and two-system training.

The relationship between finger pulse amplitude (PA) and frontalis EMG was studied first by looking at general physiological changes accompanying successful bidirectional PA control. Seven successful subjects were then asked to produce two patterns of PA and EMG (PAincEMGdec and PAdecEMGdec) while receiving both PA and frontalis EMG biofeedback. Results indicate subjects can easily produce the differentiation pattern of PAdecEMGdec but cannot produce the integration pattern of PAincEMGdec. These rather paradoxical results may indicate subjects were using an "attentional" rather than "arousal" strategy for controlling PA and have implications for the use of peripheral vasomotor training as a general relaxation technique.     

Effectiveness of multiple-site EMG biofeedback in the reduction of arousal

During the training phase, 36 subjects received (a) EMG biofeedback from multiple muscle sites, (b) EMG biofeedback from the frontal site, or (c) no biofeedback. Results indicated that neither biofeedback procedure reduced self-reports of anxiety, but that multiple-site biofeedback was effective in reducing several indices of autonomic arousal (pulse rate, finger pulse volume, and skin temperature) while frontal biofeedback was not. During the generalization/stress phase, all subjects were threatened with and received electric shocks and were told to apply the relaxation techniques they learned during the training phase even though no additional biofeedback would be provided. Results indicated that multiple-site biofeedback was effective in reducing self-reports of anxiety and autonomic arousal but that frontal biofeedback was not. These results confirm previous data indicating that frontal biofeedback is not an effective procedure for controlling stress, but suggest that EMG biofeedback can be effective in reducing self-reported anxiety and autonomic arousal if a multiple muscle-site feedback procedure is employed.     

Effects of an EMG biofeedback relaxation program on the control of diabetes

It was hypothesized that EMG biofeedback relaxation training, applied to a diabetic patient, would result in a decreased level of insulin with fewer episodes of ketoacidosis. A 20-year-old female, diabetic since age nine, kept daily records of insulin doses and rated herself on an emotionality and a diabetic scale. A full-semester baseline was taken. This was followed by a semester-long training program during which the patient practiced relaxing her frontalis muscle with a portable EMG feedback unit which produced a geiger-counter-like click feedback. A cassette-tape series was used along with the portable EMG. The patient was encouraged to practice twice each day and to attempt to maintain a relaxed state even when not in the practice situation. The daily use of the portable unit was terminated at the end of the semester. In addition, the patient ceased practicing twice daily with the cassette tape. Daily insulin averaged 85 units for the six-week baseline and 59 for the final six weeks of the training period. Moreover, at the end of the training period the average dose had reached 43 units. During the training period the patient rated herself as decreasing in emotionality and in diabetic fluctuations.Supported by the National Institute of Mental Health Grant MH-15596.     

The effect of electrode placement on frontalis EMG measurement in headache patients

Comparisons were made between frontalis EMG surface recordings concurrently taken from horizontal, right vertical, and left vertical electrode placement configurations. Six migraine and seven tension headache patients were used as subjects. Results showed that, in general, a positive correlation existed between recordings from the three placements for both migraine and tension subjects as a group. However, marked individual differences were noted. It was concluded that electrode placement can be quite important in measuring changes in frontalis muscle tension for headache patients.     

Simultaneous biofeedback of heart rate and frontal EMG as a pretraining for the control of EEG theta activity

Following one base-line session, 20 normal subjects received four half hour sessions consisting of simultaneous feedback of heart rate and frontalis muscle (pretraining). Ten subjects received contingent (CF), the other ten noncontingent feedback (NCF). Subjects were asked to lower heart rate and frontal muscle tension (EMG). Heart rate within sessions decreased up to 19 bpm, with a mean of 4 bpm for the CF group. There was only a weak decrease over sessions, however, because of the strong habituation effect. The following events accompanied the heart rate decrease: (1) an increase of the variability of the heart rate, (2) a decrease of the variance of the EMG, (3) an increased correlation between heart rate slowing and EMG decrease, and (4) an increasing subjective experience of control of heart rate and EMG. After pretraining, subjects received eight sessions of auditory feedback of their frontal EEG theta activity (four sessions with CF and four sessions with NCF in balanced order). There was a weak increase of theta for the CF condition over sessions, but a decrease within the sessions. Pretraining on heart rate and frontal EMG control had no influence on the performance during theta training. It was hypothesized that control of heart rate slowing and theta control involve different mechanisms.     

The relative effectiveness of three techniques to induce the trophotropic response.

The purpose of this study was to examine the relative effectiveness of electromyographic biofeedback training (EMG BFT), meditation, and progressive muscle relaxation (PMR) in eliciting a relaxation or trophotropic response as measured by frontalis muscle tension, heart rate, electrodermal response, respiration rate, and skin temperature. Fifty-four college students were randomly assigned to one of five groups: (1) control, (2) placebo control, (3) EMG BFT, (4) meditation, (5) PMR. After baseline measures were obtained subjects were trained in 10 30-minute training sessions and posttested. Comparisons by ANOVAs indicated there was a significant decrease in muscle tension in the EMG BFT and meditation groups and significant decreases in respiration rate in the meditation and PMR groups. No other changes were attributed to treatment.     

Influence of motor unit firing statistics on the median frequency of the EMG power spectrum

Changes in the EMG power spectrum during static fatiguing contractions are often attributed to changes in muscle fibre action potential conduction velocity. Mathematical models of the EMG power spectrum, which have been empirically confirmed, predict that under certain conditions a distinct maximum occurs in the low-frequency part of the spectrum, indicating the dominant firing rate of the motor units. The present study investigated the influence of this firing rate peak on the spectral changes during a static fatiguing contraction at 50% of maximum EMG amplitude in the frontalis and corrugator supercilii muscles. An exponential decrease of the median frequency (MF) of the EMG power spectrum was observed when the firing rate peak was absent. When the firing rate peak was present, an exaggerated decrease of MF in the beginning of the contraction was found, which was associated with an increase in firing rate peak magnitude. In later stages of the contraction, a partial recovery of MF occurred, concomitant with a decrease in firing rate peak magnitude. The influence of the firing rate peak on MF was also investigated during nonfatiguing contractions of the frontalis muscle at 20, 40, 60, and 80% of maximum EMG amplitude. A curvilinear relationship between MF and contraction strength was found, whether firing rate peaks were present or absent. The presence of firing rate peaks, however, was associated with a decrease in MF which was inversely related to contraction strength, due to the inverse relationship between firing rate peak magnitude and contraction strength.     

Psychophysiological Responses of Female Headache Sufferers and Controls Using a Picture-Viewing Paradigm

Despite the advancement of the biopsychosocial model, the interrelationship between behavioral, emotional, and physiological factors in tension-type headache (TTH) remains unclear. Using a picture-viewing paradigm, the present study investigated differences between females with TTH and controls on physiological reactivity, affective valence and arousal, and oral motor habits. In addition, the concordance between EMG activity and self-reported oral habits (i.e., proprioceptive awareness) and EMG activity and self-reported affect (i.e., affective coherence) were measured using within-subject correlations per individual and then compared between groups. Data were analyzed for 27 TTH sufferers and 27 controls who completed a questionnaire packet followed by a psychophysiological assessment consisting of 3 phases (adaptation, scheduled-viewing, recovery) with EMG activity recorded continuously at 3 sites (frontalis, corrugator, zygomatic). During the scheduled-viewing phase, participants were presented with 24 pictures designed to elicit positive, neutral, and negative affect. Compared to controls, the headache group reported elevations in pain, oral habits, and stress across the 3 phases of the assessment, along with elevations in arousal while viewing the pictures. There were no significant differences between the groups in EMG activity while viewing the pictures. Analyses on concordance revealed partial evidence for poor proprioceptive awareness and affective coherence among the headache group, although the correlations were not significantly different than the control group. These findings suggest that arousal, stress perception, and oral habits may play a role in the pathophysiology of TTH and that within-subject designs should be tested further against group designs when measuring psychophysiological concordance.     

The Effect of Facial and Trapezius Muscle Tension on Respiratory Impedance in Asthma

This study tested two theories about the relationship between voluntary changes in muscle tension and pulmonary function in asthma. Kotses has theorized that decreased facial muscle tension decreases respiratory impedance via a hypothesized vagaltrigeminal reflex, but that muscle tension in other muscle groups has no such effect. Others have suggested that decreased thoracic muscle tension improves pulmonary function. Subjects were 19 volunteer asthmatic adults. They performed 3-minute cycles of deliberate muscle contraction, alternating two each for the shoulder and forehead muscles, followed by dominant forearm contraction. Surface EMG was measured from the frontalis and right trapezius areas. Airway impedance was measured by forced oscillation pneumography. Cardiac interbeat interval and respiratory sinus arrhythmia were measured to assess vagal tone. Frequency dependence of respiratory impedance increased during shoulder tension, giving some support to the theory relating thoracic tension to impairment in pulmonary function. Correlational analyses suggested a negative relationship between changes in cardiac interbeat interval and both frontalis muscle tension and decreased compliance of tissues in the airways. These findings are the opposite of those predicted by the vagal-trigeminal reflex theory.     

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.     

The relative effectiveness of three techniques to induce the trophotropic response

The purpose of this study was to examine the relative effectiveness of electromyographic biofeedback training(EMG BFT), remeditation, and progressive muscle relaxation(PMR) in eliciting a relaxation or trophotropic response as measured by frontalis muscle tension, heart rate, electrodermal response, respiration rate, and skin temperature. Fifty-four college students were randomly assigned to one of five groups:(1) control,(2) placebo control,(3) EMG BFT,(4) meditation,(5) PMR. After baseline measures were obtained subjects were trained in 10 30-minute training sessions and posttested. Comparisons by ANOVAs indicated there was a significant decrease in muscle tension in the EMG BFT and meditation groups and significant decreases in respiration rate in the meditation and PMR groups. No other changes were attributed to treatment.     

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.