Transfer of Heart Rate Feedback Training to Reduce Heart Rate Response to Laboratory Tasks

To examine whether transfer of heart rate (HR) feedback training to tasks not used during training could be improved by using multiple tasks during training, a modified multiple baseline across tasks, single subject design study was conducted using six high HR-reactive young adults. Participants received HR feedback training during the presentation of a videogame, and transfer of training was assessed to a mental arithmetic challenge and handgrip task. Transfer of training was next assessed following training with the mental arithmetic challenge and handgrip task. HR responses to each training task with no HR feedback were assessed during a pre-treatment session, an immediate post-training period following training on each task, a short delay (1–2 days) post-training session, and a long delay (1–2 weeks) post-training session. HR response to a novel speech task was assessed at pre-treatment and during short delay and long delay post-training sessions. Results revealed that participants reduced HR during training and generally maintained this reduction in HR during the immediate post-training assessment when HR feedback was not present. Participants were not able to reduce HR responses to tasks during short delay and long delay post-training sessions, and they were unable to transfer HR reduction skills to the speech task. Transfer of HR feedback training to new tasks was limited in nature and efforts to train across multiple stressors did not appear to improve transfer of training.     

Differential shaping of EEG theta rhythms

Heart rate, EEG, frontal EMG, and forearm EMG were recorded in 20 subjects for 3 baseline, 8 feedback, and 2 postbaseline sessions in order to compare two biofeedback methods of teaching subjects to increase theta EEG activity. Subjects were divided into high- and low-EMG groups. Five high-EMG subjects, and 5 low-EMG subjects then received 8 sessions of strictly theta feedback. The remaining 10 subjects, 5 from the high-EMG group, and 5 from the low-EMG group, received a “graduated” training which involved shaping the target response. This procedure consisted of 4 initial sessions of EMG feedback, followed by a second phase consisting of 4 sessions of theta feedback. Results showed a clear relationship between subjects' baseline frontal EMG levels and the effect of the training methods. Although subjects with high-EMG baseline increased their theta output only with the two-phase training, subjects with low-EMG baseline levels performed better when given theta feedback only. This result shows not only that amounts of theta can be reliably increased, but that training techniques should be adapted to the physiological characteristics of the individual—in this case, baseline levels of frontal EMG levels.     

Acute effects of verbal feedback on upper-body performance in elite athletes

Argus, CK, Gill, ND, Keogh, JWL, and Hopkins, WG. Acute effects of verbal feedback on upper-body performance in elite athletes. J Strength Cond Res 25(12): 3282-3287, 2011-Improved training quality has the potential to enhance training adaptations. Previous research suggests that receiving feedback improves single-effort maximal strength and power tasks, but whether quality of a training session with repeated efforts can be improved remains unclear. The purpose of this investigation was to determine the effects of verbal feedback on upper-body performance in a resistance training session consisting of multiple sets and repetitions in well-trained athletes. Nine elite rugby union athletes were assessed using the bench throw exercise on 4 separate occasions each separated by 7 days. Each athlete completed 2 sessions consisting of 3 sets of 4 repetitions of the bench throw with feedback provided after each repetition and 2 identical sessions where no feedback was provided after each repetition. When feedback was received, there was a small increase of 1.8% (90% confidence limits, ±2.7%) and 1.3% (±0.7%) in mean peak power and velocity when averaged over the 3 sets. When individual sets were compared, there was a tendency toward the improvements in mean peak power being greater in the second and third sets. These results indicate that providing verbal feedback produced acute improvements in upper-body power output of well-trained athletes. The benefits of feedback may be greatest in the latter sets of training and could improve training quality and result in greater long-term adaptation.     

The production and generalization of large-magnitude heart rate deceleration by contingently faded biofeedback

Eight subjects were taught to decrease their heart rates via biofeedback training. Four of these received contingently faded, beat-by-beat analogue feedback and contingent reinforcement each time their performance met a specified and adjusting criterion. The other four received continuous, beat-by-beat analogue feedback, but not the contingent reinforcement. Subjects in the two groups were yoked to ensure equal densities of reinforcement. Subjects in the first group were asked to decrease heart rates 15% from baseline and were then trained using only 75%, 50% and 25% of beat-by-beat feedback. It was hypothesized that the immediate reinforcement of appropriate behavior and the contingent fading(following mastery) of feedback would aid in the generalization of the response. Following completion of all criterion steps or 10 training sessions, whichever came first, all subjects were tested with no feedback and no contingent reinforcement. The group receiving contingently faded feedback training showed a significantly greater heart rate decrease in the training sessions and also the test session. These results were interpreted as indicating that biofeedback can be conceptualized as an operant conditioning paradigm, and that the use of operant techniques may help subjects produce clinically significant changes.This research was supported in part by a grant to Robert J. Gatchel from the National Heart, Lung, and Blood Institute (Grant No. NIH HL 21426-01).     

The effects of electromyographic feedback training on suppression of the oral-lingual movements associated with tardive dyskinesia.

The efficacy of electromyographic feedback training in reducing the magnitude and frequency of the oral-lingual movements associated with tardive dyskinesia (TD) was investigated in a groups design. Twenty adult male inpatients diagnosed as having TD using the Abnormal Involuntary Movements Scale (AIMS) were randomly assigned to one of two treatment conditions. Following identification, all participants were initially reduced to the lowest effective dosage of neuroleptics, and then discontinued from anticholinergics. Following one month on this regimen, they were given a course of feedback training consisting of ten 14-minute sessions. Group one participants were provided with a tone contingent upon oral-lingual movements above a yoked threshold. Group two participants were given noncontingent feedback tones generated randomly. Weekly AIMS were administered as well as an initial baseline during each session to determine current level of oral-lingual activity. An analysis of session effects indicated significantly more suppression of oral-lingual activity in the contingent group versus the noncontingent feedback group. Jaw and forehead activity also measured showed reductions of similar magnitudes for both groups.     

Repeated training with augmentative vibrotactile feedback increases object manipulation performance

Most users of prosthetic hands must rely on visual feedback alone, which requires visual attention and cognitive resources. Providing haptic feedback of variables relevant to manipulation, such as contact force, may thus improve the usability of prosthetic hands for tasks of daily living. Vibrotactile stimulation was explored as a feedback modality in ten unimpaired participants across eight sessions in a two-week period. Participants used their right index finger to perform a virtual object manipulation task with both visual and augmentative vibrotactile feedback related to force. Through repeated training, participants were able to learn to use the vibrotactile feedback to significantly improve object manipulation. Removal of vibrotactile feedback in session 8 significantly reduced task performance. These results suggest that vibrotactile feedback paired with training may enhance the manipulation ability of prosthetic hand users without the need for more invasive strategies.     

A comparison of direct blood pressure feedback and electromyographic feedback on the blood pressure of normotensives

Groups of 20 normotensive subjects were assigned to one of three conditions to help them lower their blood pressure: (1) intermittent visual feedback of blood pressure; (2) continuous analogue auditory feedback of frontal EMG; (3) an instructed, no-feedback condition. Both groups receiving feedback showed greater within-session lowering of systolic blood pressure than the no-feedback control group. Although the group receiving intermittent visual feedback of blood pressure lowered blood pressure more than the EMG feedback group at the first session, in three subsequent sessions, the two feedback groups did not differ.     

Voluntary heart rate deceleration: A critical evaluation

This experiment was designed as a test of the view that the human heart rate (HR) deceleration response can be brought under voluntary control, when some form of exteroceptive feedback is available. Sixteen female volunteers were randomly assigned to two groups. The first group received instructions to decrease their HR plus a continuous negative (failure) binary feedback, while the second group received only the instructions. Each subject was given four sessions of HR deceleration training. Two identical tests were presented, one before and the other after the series of training sessions. These tests were divided into two parts. In the first part, subjects attempted to decrease their HR while undergoing an ischemic arm pain stress. In the second part, subjects performed a 40-trial HR discrimination task. The results indicate that all subjects decrease HR during both rest and voluntary control periods within each training session, but there are no significant group differences, no improvement in HR deceleration control over the four training sessions, and no difference in performance between rest and voluntary control periods. Similarly HR, blood pressure (BP), and the HR×BP product levels during the ischemic stress condition and the HR discrimination performance do not show group differences. It is suggested that the HR deceleration response may not meet the criteria generally applied to the definition of a voluntary response.     

Validity and reliability of peak tibial accelerations as real-time measure of impact loading during over-ground rearfoot running at different speeds

Studies seeking to determine the effects of gait retraining through biofeedback on peak tibial acceleration (PTA) assume that this biometric trait is a valid measure of impact loading that is reliable both within and between sessions. However, reliability and validity data were lacking for axial and resultant PTAs along the speed range of over-ground endurance running. A wearable system was developed to continuously measure 3D tibial acceleration and to detect PTAs in real-time. Thirteen rearfoot runners ran at 2.55, 3.20 and 5.10 m·s⁻¹ over an instrumented runway in two sessions with re-attachment of the system. Intraclass correlation coefficients (ICCs) were used to determine within-session reliability. Repeatability was evaluated by paired T-tests and ICCs. Concerning validity, axial and resultant PTAs were correlated to the peak vertical impact loading rate (LR) of the ground reaction force. Additionally, speed should affect impact loading magnitude. Hence, magnitudes were compared across speeds by RM-ANOVA. Within a session, ICCs were over 0.90 and reasonable for clinical measurements. Between sessions, the magnitudes remained statistically similar with ICCs ranging from 0.50 to 0.59 for axial PTA and from 0.53 to 0.81 for resultant PTA. Peak accelerations of the lower leg segment correlated to LR with larger coefficients for axial PTA (r range: 0.64–0.84) than for the resultant PTA per speed condition. The magnitude of each impact measure increased with speed. These data suggest that PTAs registered per stand-alone system can be useful during level, over-ground, rearfoot running to evaluate impact loading in the time domain when force platforms are unavailable in studies with repeated measurements.     

The effects of electromyographic feedback training on suppression of the oral-lingual movements associated with tardive dyskinesia

The efficacy of electromyographic feedback training in reducing the magnitude and frequency of the oral-lingual movements associated with tardive dyskinesia (TD) was investigated in a groups design. Twenty adult male inpatients diagnosed as having TD using the Abnormal Involuntary Movements Scale (AIMS) were randomly assigned to one of two treatment conditions. Following identification, all participants were initially reduced to the lowest effective dosage of neuroleptics, and then discontinued from anticholinergics. Following one month on this regimen, they were given a course of feedback training consisting of ten 14-minute sessions. Group one participants were provided with a tone contingent upon oral-lingual movements above a yoked threshold. Group two participants were given noncontingent feedback tones generated randomly. Weekly AIMS were administered as well as an initial baseline during each session to determine current level of oral-lingual activity. An analysis of session effects indicated significantly more suppression of oral-lingual activity in the contingent group versus the noncontingent feedback group. Jaw and forehead activity also measured showed reductions of similar magnitudes for both groups.This work was sponsored in part by a Research Advisory Grant from the Department of Veterans Affairs awarded to Joanne Intrator. We gratefully acknowledge the valuable contributions of K. Duvvi, S. Kemble, and L. Kolman.     

The use and utility of EMG biofeedback with chronic schizophrenic patients

This study examined the efficacy of muscle relaxation training via electromyographic (EMG) biofeedback from the frontalis and forearm extensor muscles of schizophrenic inpatients. Thirty chronically hospitalized patients were randomly assigned to one of three conditions: EMG biofeedback from the forearm extensor and frontalis muscles, progressive relaxation, and a control group. Treatment consisted of one session of orientation and baseline, and six sessions of training. The results indicated that the schizophrenic patients receiving EMG training had significantly lower EMG recordings than the progressive relaxation group, which, in turn, was significantly lower than the control group. Analyses of covariance on the Tension-Anxiety scale from the Profile of Mood States revealed no significant effects, while finger-tapping rates were significantly improved only for the arm receiving feedback training in the EMG group. On the Nurses Observation Scale for Inpatient Evaluation the biofeedback group significantly improved on the Social Competence and Social Interest factors.     

The effects of the distribution of training on learning feedback-assisted cardiac acceleration

In order to test a hypothesis derived from a motor skills learning model of cardiac acceleration control, groups of subjects were given biofeedback training for four sessions to learn cardiac acceleration under four different training schedules: (1) all sessions in one day, (2) daily sessions, (3) sessions every other day, and (4) weekly sessions. Ability to accelerate heart rate both with and without feedback was determined at each session. Also ability to accelerate heart rate without feedback was determined 1 week after the last training session as a measure of retention. Although there was highly significant (p less than.0001) evidence of heart rate control both with and without feedback, there were no differences in degree of control attributable to distribution of training sessions. There was, however, a trend (p less than .10) for subjects trained under the most distributed training schedule (weekly) to show more retention than subjects trained under a less distributed schedule (daily).     

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.     

Specificity of finger pulse volume feedback during relaxation

The effect of biofeedback during brief periods of relaxation was examined. Two groups (10 subjects in each group) were asked to relax as completely as possible during a series of six 3-minute relaxation periods in each of two 1-hr sessions. One group received biofeedback based on finger pulse volume (FPV) during the relaxation trials, while the other group received no biofeedback. Measures of heart rate, respiration rate, skin conductance level, and FPV were recorded during the sessions, and subjective ratings concerning relaxation were obtained after each session. The results showed that FPV scores for the groups differed during the relaxation trials of the second session, but other measures failed to distinguish between the groups. The group that received FPV feedback revealed a significantly higher level of FPV (relative to baseline) than the group that received no feedback.     

EEG signature and phenomenology of alpha/theta neurofeedback training versus mock feedback

Alpha/theta (a/t) neurofeedback training has in the past successfully been used as a complementary therapeutic relaxation technique in the treatment of alcoholism. In spite of positive clinical outcomes, doubts have been cast on the protocol's specificity when compared to alternative relaxation regimes. This study investigated the basic tenet underlying the a/t training rationale, that accurate a/t feedback representation facilitates the generation of these frequency components. Two groups of healthy volunteers were randomly assigned to either (a) real contingent a/t feedback training or (b) a noncontingent mock feedback control condition. The groups were compared on measures of theta/alpha (t/a) ratios within and across training sessions, as well as activational self-report scales after each session. The contingent a/t feedback group displayed significant within-session t/a ratio increments not evident in the mock control group, as well as higher overall t/a ratios in some but not all of the training sessions. No differences were found between the groups in terms of subjective activational phenomenology, in that both groups reported significantly lower levels of activation after training sessions. The data demonstrate that irrespective of considerations of clinical relevance, accurate a/t neurofeedback effectively facilitates production of higher within-session t/a ratios than do noncontingent feedback relaxation.     

Influence of ground reaction force perturbations on anterior cruciate ligament loading during sidestep cutting

Anterior cruciate ligament (ACL) injury risk is likely increased under unexpected loading conditions. Such situations may arise from mid-air contact with another athlete, or misjudgments in landing height, stride length or surface compliance resulting in an unbalanced landing and unexpected changes in the ground reaction forces (GRFs). The purpose this study was to identify how GRF perturbations influence ACL loading during sidestep cutting. Muscle-actuated simulations of sidestep cutting were generated and analyzed for 20 subjects. Perturbations of 20, 40 and 60% of the nominal value were applied to the posterior, vertical, and medial GRF. Open-loop, forward dynamics simulations were run with no feedback or correction mechanism which allowed deviations from the experimentally measured kinematics as a result of the GRF perturbations. Posterior and vertical GRF perturbations significantly increased ACL loading, although the change was more pronounced with posterior perturbations. These changes were primarily due to the sagittal plane component of ACL loading regardless of perturbation direction. Peak ACL loading occurred almost immediately after initial ground contact, and was thus predicated on initial joint configuration. The results of this study give merit to including knee flexion angle at initial ground contact in the evolving neuromuscular training modalities aimed at preventing non-contact ACL injury.     

The effects of practice and visual feedback on mandibular border movements

Twenty healthy subjects were studied on the effects of training on mandibular border movements. Maximum left (LL) and right (RL) lateral excursions, maximum protrusive movement (PT), maximum mouth opening (MO), the difference between left and right excursions (R-L), midline deflection (DF) during opening and closing and midline deviation of the jaw (MOD) at maximum opening position of mandibular border tracing with or without practicing and visual feedback were compared among various sessions. No significant difference has been found on the amount of border extension under the influence of training. However, 70 to 85% of the subjects had some improvement after verbal instruction practicing, while only 50 to 65% of the same subjects showed improvement through visual feedback. It is suggested that doing research related to the jaw border movement on healthy subjects does not have to train them to obtain comparable data. On the other hand, since repeated border tracing in healthy subjects did not worsen the results, practicing or visual feedback training might ascertain a repeatable border tracing.     

Variations in digital temperature during frontal EMG biofeedback training in normal subjects

During frontal EMG biofeedback training, the relationship between frontal EMG and digital skin temperature was investigated in two experiments, which varied the number of baseline and feedback sessions. The results of Experiment 1 suggested a "general relaxation effect," where digital temperature increased as frontal EMG decreased, especially for subjects with initially low hand temperature. Experiment 2 extended the number of baseline and feedback sessions and qualified the results of Experiment 1. EMG and digital temperature did not simultaneously converge toward general relaxation over the extended baseline or feedback sessions in Experiment 2. Furthermore, when the feedback signal was introduced, digital temperature dropped quickly but recovered to baseline levels within three feedback sessions; this drop in digital temperature was interpreted within the context of attentional demands of the biofeedback task. The results appeared consistent with the view that frontal biofeedback training teaches a discriminative skill of lower frontal EMG, and that this skill does not readily generalize to digital skin temperature.     

Peripheral Visual Performance Enhancement by Neurofeedback Training

Peripheral visual performance is an important ability for everyone, and a positive inter-individual correlation is found between the peripheral visual performance and the alpha amplitude during the performance test. This study investigated the effect of alpha neurofeedback training on the peripheral visual performance. A neurofeedback group of 13 subjects finished 20 sessions of alpha enhancement feedback within 20 days. The peripheral visual performance was assessed by a new dynamic peripheral visual test on the first and last training day. The results revealed that the neurofeedback group showed significant enhancement of the peripheral visual performance as well as the relative alpha amplitude during the peripheral visual test. It was not the case in the non-neurofeedback control group, which performed the tests within the same time frame as the neurofeedback group but without any training sessions. These findings suggest that alpha neurofeedback training was effective in improving peripheral visual performance. To the best of our knowledge, this is the first study to show evidence for performance improvement in peripheral vision via alpha neurofeedback training.