Predictors of success in the EMG biofeedback training of hyperactive male children

EMG biofeedback training is continuing to evolve as a promising treatment of hyperactivity. But while research on its application suggests that this technique induces significantly lower EMG levels in experimental samples as a whole, it also discloses that some children evidence but limited reductions. Most likely, this variability is introduced by differences in subject attributes. This study assessed that prospect by examining whether four common subject characteristics correlated with the extent of decrease in EMG level achieved by 59 hyperactive school-aged boys. Those variables were pretreatment EMG level, age degree of hyperactivity, and locus of control. Number of applications or training sessions was included as the fifth predictor. A multiple regression analysis determined that only locus of control was predictive of success in EMG training; however, it accounted for 72% of the variance. Implications of these findings are discussed.     

Biofeedback training in frontalis muscle relaxation and enhancement of belief in personal control

The hypothesis that biofeedback training in frontalis muscle relaxation increases beliefs in internal (personal) locus of control was tested. Subjects were divided into two groups (internals and externals) based on Mirels' (1970) factor analyzedpersonal control subscale of Rotter's (1966) I-E Scale. Internal and external subjects were assigned randomly to one of three conditions: biofeedback (BF), false feedback (FF), or no feedback (NF). All subjects were measured on frontalis electromyographic (EMG) activity. Training consisted of three sessions spaced 1 week apart. Each session was comprised of a 5-minute baseline (nonfeedback) trial followed by a 20-minute experimental session. After each experimental session, subjects completed a questionnaire which assessed the extent to which they attributed their EMG performance to personal and environmental sources. After three sessions, subjects were posttested on the I-E Scale. Results indicated that subjects receiving BF reduced their EMG activity more than did subjects in either the FF or NF conditions, and this effect was maintained across all three sessions. Subjects who received BF shifted toward internal personal locus of control from pre- to posttesting, whereas no such change was found for either FF or NF subjects. Also, the relationship between BF training and change in personal locus of control was mediated by subjects attributing their EMG reduction more to personal effort than to properties of the task. Results are discussed in terms of the importance of contingent feedback as a determinant of cognitions of control.     

The effects of EMG-assisted relaxation training on the academic performance, locus of control, and self-esteem of hyperactive boys

This study investigated effects of EMG-assisted relaxation training on the academic performance, locus of control, and self-esteem of hyperactive junior high school-age boys. Twenty-four subjects each were randomly assigned to the treatment and control condition. Treatment consisted of six 20 to 25-minute sessions conducted biweekly. Pretreatment frontalis EMG, math, reading, and language performance, locus of control, and self-esteem were assessed for both groups. Outcome measures were again obtained on these dependent variables 2 weeks after the last treatment session. Experimental subjects demonstrated significantly higher posttreatment reading and language performance. Math performance gain did not reach statistical significance. A significant internal shift in locus of control was observed; however, self-esteem did not improve to that level. These outcomes correlated with significantly lower posttreatment frontalis EMG in the experimental group. EMG level did not change during the course of this study for control subjects. Implications of these findings are discussed in terms of existent research.     

EMG and EEG biofeedback training in the treatment of a 10-year-old hyperactive boy with a developmental reading disorder

The serial application of electromyographic (EMG) and sensorimotor (SMR) biofeedback training was attempted with a 10-year-old boy presenting a triad of symptoms: an attention deficit disorder with hyperactivity, developmental reading disorder, and ocular instability. Symptom elimination was achieved, for all three aspects of the triad, following the procedure of first conditioning a decrease in EMG-monitored muscle tension and then conditioning increases in the amplitude of sensorimotor rhythm over the Rolandic cortex. The learned reduction of monitored EMG levels was accompanied by a reduction in the child's motoric activity level to below that which had been achieved by past administration of Ritalin. In addition, the attention deficit disorder with hyperactivity was no longer diagnosable following the EMG biofeedback training. The learned increase in the amplitude of monitored SMR was accompanied by remediation of the developmental reading disorder and the ocular instability. These results remained unchanged, as ascertained by follow-ups conducted over a 24-month period subsequent to the termination of biofeedback training.     

Locus of control and frontal electromyographic response training

Forty-eight normal subjects from a college population, representing extreme internal and external orientations on a locus of control scale, were provided an auditory signal in a laboratory relaxation setting. For one group (feedback) the pitch of the signal varied as a function of frontal electromyographic (EMG) levels, while for another group (control) the pitch was constant. The feedback subjects acquired lower EMG potentials than did the control subjects, and the internal subjects in the feedback condition acquired lower levels than did the external subjects. In the control condition, no consistent differences in EMG levels between internal and external subjects were obtained. These results were stable across two replications, three ethnically distinct groups, and both sexes. Additional measures designed to reflect the effects of the frontal EMG training as a generalized relaxation technique for this population, including finger temperatures and a variety of postexperiment questionnaire ratings of relaxation, yielded negative results. Tests of other predictions from the locus of control construct are also discussed.This research was supported by NIMH Special Postdoctoral Fellowship No. MH58202-01.     

Change Mechanisms Associated with Combined Relaxation/EMG Biofeedback Training for Chronic Tension Headache

Therapeutic mechanisms hypothesized to underlie improvements in tension headache activity achieved with combined relaxation and eleclromyographic (EMG) biofeedback therapy were examined. These therapeutic mechanisms included (1) changes in EMG activity in frontal and trapezii muscles, (2) changes in central pain modulation as indexed by the duration of the second exteroceptive silent period (ES2), and (3) changes in headache locus of control and self-efficacy. Forty-four young adults with chronic tension-type headaches were assigned either to six sessions of relaxation and EMG biofeedback training (N = 30) or to an assessment only control group (N = 14) that required three assessment sessions. Measures of self-efficacy and locus of control were collected at pre- and posttreatment, and ES2 was evaluated at the beginning and end of the first, third, and lost session. EMG was monitored before, during, and following training trials. Relaxation/EMG biofeedback training effectively reduced headache activity: 51.7% of subjects who received relaxation/biofeedback therapy recorded at least a 50% reduction in headache activity following treatment, while controls failed to improve on any measure. Improvements in headache activity in treated subjects were correlated with increases in self-efficacy induced by biofeedback training but not with changes in EMG activity or in ES2 durations. These results provide additional support for the hypothesis that cognitive changes underlie the effectiveness of relaxation and biofeedback therapies, at least in young adult tension-type headache sufferers.     

Effects of alternative control procedures for electromyographic biofeedback relaxation training

Twenty-four college students participated in a single session of electromyographic (EMG) biofeedback in a comparison of three experimental control procedures commonly employed in biofeedback relaxation training research. One group received contingent EMG biofeedback from the forehead area, and each subject in this group served as his or her own control. Subjects in a second group received noncontingent EMG feedback from a tape recorder but were instructed to use the feedback signal to relax their forehead muscles (single blind). Subjects in a third group received the same auditory feedback as those in the second group but were not told the purpose or source of the feedback stimulus (yoked control). The contingent feedback group showed significantly less EMG activity when compared to the other two groups. However, this group did not exhibit significant EMG level decrements from the beginning to end of the session. This seemingly contradictory finding may have been due to statistically capitalizing on the artifactually high EMG level of the experimental and control groups, although the single-blind and yoked-control groups showed nonsignificant increases across the session. The single-blind group's data had a variance several times larger than the other two groups' variance. Findings are discussed with respect to a probing hypothesis as opposed to the previously offered frustration hypothesis. Of the three control procedures, the data suggest the yoked control as the procedure of choice for EMG biofeedback relaxation research.The authors would like to thank David Kazar and Claudia Coleman for their technical assistance with this article.     

Slowed respiration training

A method of slowed respiration rate (RR) training is described that uses visual feedback of the respiratory cycle. Subjects assigned to the slowed RR training procedure were compared with subjects assigned to either a traditional frontal electromyographic (EMG) biofeedback condition or a control condition where no feedback was presented. RR, frontal EMG, heart rate, digital temperature, and skin conductance level were monitored simultaneously. The results indicated that RR training was effective in reducing RR, that RR training had little systematic effect on the other physiological variables, and the frontal EMG procedure did not in itself reduce RR. The advantages of the current methodological approach and the importance of respiration training were discussed along with a literature review. The relationship between RR training and the complexities of respiratory phenomena was discussed, as well as ways that future research using this method may help clarify current issues within respiration training.This research was supported by grant No. 2-S06RR08038-19 from the National Institutes of Health. The able work of Nora Barker and Robert Longoria is acknowledged, who served as biofeedback technicians.     

Identification of isometric contractions based on High Density EMG maps

Identification of motion intention and muscle activation strategy is necessary to control human–machine interfaces like prostheses or orthoses, as well as other rehabilitation devices, games and computer-based training programs. Pattern recognition from sEMG signals has been extensively investigated in the last decades, however, most of the studies did not take into account different strengths and EMG distributions associated to the intended task. The identification of such quantities could be beneficial for the training of the subject or the control of assistive devices. Recent studies have shown the need to improve pattern-recognition classification by reducing sensitivity to changes in the exerted strength, muscle-electrode shifts and bad contacts. Surface High Density EMG (HD-EMG) obtained from 2-dimensional arrays can provide much more information than electrode pairs for inferring not only motion intention but also the strategy adopted to distribute the load between muscles as well as changes in the spatial distribution of motor unit action potentials within a single muscle because of it.The objectives of this study were: (a) the automatic identification of four isometric motor tasks associated with the degrees of freedom of the forearm: flexion–extension and supination–pronation and (b) the differentiation among levels of voluntary contraction at low-medium efforts. For this purpose, monopolar HD-EMG maps were obtained from five muscles of the upper-limb in healthy subjects. An original classifier is proposed, based on: (1) Two steps linear discriminant analysis of the EMG information for each type of contraction, and (2) features extracted from HD-EMG maps and related to its intensity and distribution in the 2D space. The classifier was trained and tested with different effort levels. Spatial distribution-based features by themselves are not sufficient to classify the type of task or the effort level with an acceptable accuracy; however, when calculated with the “isolated masses” method proposed in this study and combined with intensity-base features, the performance of the classifier is improved. The classifier is capable of identifying the tasks even at 10% of Maximum Voluntary Contraction, in the range of effort level developed by patients with neuromuscular disorders, showing that intention end effort of motion can be estimated from HD-EMG maps and applied in rehabilitation.     

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.     

Neuromuscular adaptations to training

The purpose of this experiment was to determine whether there is a central adaptation to resistance overload. The right adductor pollicis muscle of each subject was trained with either voluntary (n = 9) or electrically stimulated contractions (n = 7), the contralateral muscle acted as an internal control, and seven other subjects acted as a control group. Training was the same in both groups: 15 contractions at 80% maximal voluntary contraction (MVC), 3 days/wk for 5 wk. Trained muscles in both groups increased MVC by approximately 15% (voluntary, P less than 0.01; stimulated, P less than 0.05). There was a small (9.5%) but significant (P less than 0.05) increase in MVC of the untrained muscles in the voluntary group. MVC did not change in the control group. Maximal electromyogram (EMG) was highly reproducible pre-to posttraining in the control group (r = 0.92, slope = 0.995) and did not change pre- to posttraining in the trained groups. Sensory adaptation to training caused a reduction in force sensation in the stimulated group (P less than 0.05) but not in the voluntary group. Because there was a small increase in MVC of the untrained muscle of the voluntary group (9.5%, P less than 0.05) but not in the stimulated group, it is possible that there is a central motor adaptation, but it is not manifested in increased neural drive (EMG). Moreover, this central adaptation may be responsible for the decrease in force sensation that follows training.     

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.     

EMG-biofeedback reduction of tension headache

The biofeedback literature affirms the therapeutic efficacy of EMG-biofeedback-assisted relaxation for the treatment of tension headache. However, this form of therapy has failed to focus on the role of cognitive variables in the control and perception of tension headache. The present case study provides a prototype treatment combining cognitive behavior-modification procedures with EMG-biofeedback training to treat a subject with chronic tension headache. Phase I, baseline, involved collecting mean EMG and daily headache activity, emphasizing specification of environmental stressors. Phase II, cognitive skills-training, focused on:(1) identifying negative self-statements(cognitions) related to stressors, and(2) training the subject to replace negative self-statements with coping self-instructions. This treatment resulted in a 33% headache reduction over baseline, with no concomitant changes in frontalis EMG. Phase III, EMG-biofeedback training, resulted in a 38% reduction in mean EMG level and a 66% reduction in mean headache activity when compared to baseline. The results suggest the importance of attending to cognitive factors in the treatment of tension headache.This paper was presented at the 6th annual meeting of the Biofeedback Research Society, Monterey, California, 1975.     

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.     

EMG stability as a biofeedback control

Factors that may confound comparisons between electromyographic (EMG) biofeedback training and its control conditions include feedback quality and experience of success. We investigated the usefulness of a control procedure designed to overcome these potential sources of confounding. The procedure consisted of training muscle tension stability. We used it as a control for frontal EMG relaxation training in children with asthma. To equate the groups for feedback quality and experience of success, we gave each child in the control condition audio feedback decreasing in pitch when muscle tension was at or near baseline levels, and feedback increasing in pitch when muscle tension was either substantially above or below baseline levels. Children in both groups were instructed to decrease the pitch of the tone. In comparison to children in the relaxation condition, the children in the control condition exhibited stable levels of muscle tension throughout eight training sessions. We concluded that feedback for stable muscle tension may be a useful control procedure for EMG biofeedback training whenever experimental and control procedures differ in either feedback quality of degree to which they permit subjects to experience success.This research was supported by NIH-Grant HL 27402. We are grateful to Paul Schnitter who constructed the EMG stability feedback device.     

Biofeedback-induced relaxation training as an alternative for the elementary school learning-disabled child

This study examined the effects of biofeedback-induced relaxation training on attention to task, impulsivity, and locus of control among 32 learning-disabled children between the ages of 8 and 11 years. Attention to task and impulsivity were measured by the Matching Familiar Figures Test and locus of control was measured by the Nowicki-Strickland Scale. Participants were randomly assigned to experimental (N = 16) and control (N = 16) groups. The study spanned a total of 8 weeks, with the experimental treatment consisting of three sessions spaced approximately 2 weeks apart. The treatment included EMG biofeedback training used with relaxation tapes. Univariate F values and discriminant analysis procedures revealed that the attention to task and impulsivity measures proved to be valid discriminators, respectively beyond the .01 and .05 levels of significance. Experimental group subjects had significantly fewer number of errors on the attention to task measure and significantly lower impulsivity scores. It was concluded that the biofeedback-induced relaxation training affords promise in assisting learning-disabled children in reaching their education potentials. It was recommended that future research examine the long-term efficacy and the transfer to school-related tasks of this intervention.     

Biofeedback-induced relaxation training as an alternative for the elementary school learning-disabled child

This study examined the effects of biofeedback-induced relaxation training on attention to task, impulsivity, and locus of control among 32 learning-disabled children between the ages of 8 and 11 years. Attention to task and impulsivity were measured by the Matching Familiar Figures Test and locus of control was measured by the Nowicki-Strickland Scale. Participants were randomly assigned to experimental (N=16) and control (N=16) groups. The study spanned a total of 8 weeks, with the experimental treatment consisting of three sessions spaced approximately 2 weeks apart. The treatment included EMG biofeedback training used with relaxation tapes. Univariate F values and discriminant analysis procedures revealed that the attention to task and impulsivity measures proved to be valid discriminators, respectively beyond the .01 and .05 levels of significance. Experimental group subjects had significantly fewer number of errors on the attention to task measure and significantly lower impulsivity scores. It was concluded that the biofeedback-induced relaxation training affords promise in assisting learning-disabled children in reaching their education potentials. It was recommended that future research examine the long-term efficacy and the transfer to school-related tasks of this intervention.     

Is group progressive relaxation training as effective with hyperactive children as individual EMG biofeedback treatment?

This study examined whether group progressive relaxation training was as effective as individual EMG biofeedback training in facilitating the academic achievement and self-control of 45 hyperactive elementary school children. Academic achievement was assessed with the Gates-MacGinities Reading Tests, and self-control was measured with the Nowicki-Strickland and the Teacher Rating scales. Eight sessions were scheduled at weekly intervals. Progressive relaxation was conducted in groups of seven or eight and was induced with a commercial audiocassette program. EMG training augmented frontalis biofeedback with those taped exercises. A placebo group listened to taped children's stories. Multivariate analysis of variance indicated no significant differences among the three contrast groups when all dependent variables were considered together. However, univariate F values and discriminant analysis disclosed locus of control to be significantly more internal for the progressive relaxation condition. Also, differences between the two relaxation and the placebo groups, though not statistically significant, were all in the expected direction. While the relative efficacy of group progressive relaxation could not be established conclusively, the data appeared sufficiently positive to warrant further investigation of this cost-effective prospective intervention.The opinions expressed by the authors are not necessarily those of their respective institutions.     

The role of EMG awareness in EMG biofeedback learning

Underlying most research on biofeedback learning is a theoretical model of the processes involved. The current study tested a prediction from the Awareness Model: High initial EMG awareness should facilitate response control during EMG biofeedback training. Seventy-two undergraduates were assessed for forehead EMG awareness by asking them to produce target responses from 1.0 to 5.0 µV every 15 s for 16 trials. Based on this assessment, two groups (high and low awareness) were trained for 64 trials to produce these target levels with either EMG biofeedback, practice (no feedback), or noncontingent EMG feedback. A transfer task was identical to the initial assessment. During training, the biofeedback group deviated less from target than the practice and noncontingent groups. The biofeedback group was the only group to improve from initial EMG awareness activity. During transfer, only the low awareness biofeedback group remained below initial EMG awareness level. These findings can be interpreted in terms of the Two-Process Model.     

Differential control during maximal concentric and eccentric loading revealed by characteristics of the electromyogram

Maximal eccentric loading has been associated with higher levels of spindle afferent activity but lower levels of integrated EMG as compared to maximal concentric loading. Elbow flexor EMG was recorded from 17 subjects during concentric (CONC) and eccentric (ECC) elbow flexion at 70° s⁻¹ using a Kin-Com dynamometer. We hypothesized that peak EMG amplitude would be more sensitive to fluctuations in facilitation by the spindle primary afferents via the segmental stretch reflex pathway, and that the mean EMG would be more reflective of the ongoing level of muscle activation. A ratio of peak to mean EMG (P/M EMG ratio) was predicted to be larger during maximal eccentric loading than maximal concentric loading. The peak EMG (P<0.013) and the P/M EMG ratio (P<0.001) were significantly greater during the ECC condition than the CONC condition. In a subgroup of three subjects who underwent 3 weeks of eccentrically biased weight training, EMG, peak torque and torque variability were assessed before and after training. P/M EMG ratio decreased, while peak torque and torque variability increased following the training. Differences in the P/M EMG ratio appear to reflect differences in the way eccentric and concentric muscle actions are controlled and do not simply represent less control during the eccentric task.