Voluntary Control of Systolic Blood Pressure During Postural Change

The effects of biofeedback and voluntary control procedures on systolic blood pressure and heart rate during postural change were investigated in 30 normotensive men. Systolic pressure was measured with a continuous blood pressure tracking cuff, and blood pressure feedback was provided on a beat-to-beat basis. Postural changes in pressure, and corresponding heart rate changes, were examined in three experimental groups (N = 10 each). In two groups, subjects were given feedback training to increase or to decrease systolic blood pressure. In the third group, subjects were simply asked to increase their pressure but were not given feedback about their performance. Voluntary control of systolic pressure was attempted while subjects were seated and during postural change—sitting to standing. Subjects were also instructed to maintain voluntary blood pressure control in subsequent no-feedback test trials. During postural change, voluntary control procedures caused significant alterations in tonic levels of systolic pressure, but phasic blood pressure reactivity was unaffected. With respect to postural changes in heart rate, both tonic and phasic treatment effects were observed. Implications of the findings for basic and clinical research are discussed.     

Instructed heart rate control in a high heart rate population

Forty college students were selected from a large number of introductory psychology students on the basis of high heart rate during an initial screening session. Subjects were then contacted and participated in two additional sessions during which heart rate, respiration rate, and skin conductance measures were obtained. Each session consisted of a baseline period followed by five trial periods during which subjects attempted to control their heart rate or performed a visual tracking task. Subjects were randomly assigned to one of four groups. One group served as a control and monitored a visual feedback display driven by their own heart rate but received no instructions to decrease their heart rate. In contrast, the three heart rate control groups were instructed to decrease heart rate during the trial periods by utilizing a relaxation procedure, proportional biofeedback, or proportional biofeedback plus criterion information. No group differences were present during the baseline periods. During feedback trials, however, all the training groups differed from the control in heart rate but did not differ from each other. It is suggested that feedback displays may not facilitate heart rate reduction beyond the level achieved by instructing subjects to use a general relaxation procedure.     

The effect of chronic anxiety level upon self control of heart rate

A sample of 90 subjects were rated on the IPAT anxiety scale and 5 subjects (3 male and 2 female) per group were selected from each of the high and low anxiety categories. All subjects were naive participants in heart rate biofeedback sessions utilising analogue visual feedback. Following a heart rate baseline (no feedback) session, all subjects were required to raise their heart rate and lower their heart rate in two separate trials, a visual ‘target’ criteria being provided. The data collected consisted of a resting baseline heart rate value, mean heart rate increase, and mean heart decrease values expressed as beats per minute. Results indicated a marked ability for highly anxious subjects to self-induce heart rate increases only and for low anxious subjects to decrease their heart rate only.     

The effect of voluntary control of heart rate deceleration on skin conductance level: An example of response fractionation

Twenty-four undergraduate male volunteers participated in an experiment designed to assess the effect of voluntary control of heart rate deceleration on skin conductance level. One group of subjects received heart rate feedback training and a second group performed a tracking task. Because heart-rate feedback was presented via a visual display, the tracking task group was included to control for display monitoring influences on heart rate. Results demonstrated feed-back mediated acquisition of learned control of heart rate slowing. More importantly, the heart-rate slowing performance was accompanied by increases in skin conductance level. This ‘fractionation’ of physiological responding suggests the presence of a physiological response pattern which may counter initial attempts to produce greater magnitude slowing effects.     

Systolic Blood Pressure and Heart Rate Changes During Three Sessions Involving Biofeedback or No Feedback

Two groups of normotensive human subjects of both sexes received contingent feedback for increases or decreases in systolic blood pressure, and two additional groups received random (non-contingent) feedback or no feedback. Subjects in all groups served fur three 1-hr sessions separated by intervals of 24 hrs. Reliable decreases in blood pressure, reaching a maximum of 9.5 mm Hg at the end of the third session, were observed in the decrease group. No systematic changes in blood pressure were observed in the increase, random, or no-feedback groups. Heart rate increased or decreased in the groups receiving contingent feedback for increasing or decreasing blood pressure, respectively. It is concluded that contingent feedback is effective in lowering blood pressure and that decreases are augmented by extended training. The covariance of heart rate and blood pressure is discussed with reference lo curlier experiments.     

Learning to Control Heart Rate: Effects of Varying Incentive and Criterion of Success on Task Performance

The effects of motivational variables on learned heart rate speeding and slowing were investigated. Undergraduate volunteers were randomly assigned to two groups which received feedback tasks differing in difficulty, i.e., a median target display (50% of all heart intervals would be successful based on no-feedback performance) and a quartile target (25% predicted success), Equal subgroups received either a monetary reward for successful performance or received no supplementary incentive. The results indicated that directional changes in heart rate could be achieved with simple instructions, and that heart rate control performance was generally superior under incentive conditions. Speeding showed overall improvement over feedback sessions, and over trials for the median target group. Slowing performance showed no general improvement over sessions and no effects of target. The effects of incentives on heart rate slowing were strongest on trial periods when subjects were under instructions to reduce heart rate, but no feedback display was presented. The results are interpreted within a skills learning conception of cardiac rate control training.     

Effects of Feedback on the Control of Skin Temperature Using the Tension-Relaxation Experiment

The effects of feedback on the control of peripheral skin temperature were examined using a tension-relaxation experiment. Sixteen male undergraduates were assigned to feedback or no-feedback groups and asked to increase the temperature of the right index finger immediately after decreasing with (in the feedback group) or without (in the no-feedback group) feedback during 10 training sessions. A no-feedback transfer session (post-test) followed these sessions. During the training sessions, skin temperature corresponded to instructions in the feedback group, whereas it did not in the no-feedback group. Feedback control did not transfer to the no-feedback condition. These results were discussed in terms of the ceiling-effect hypothesis in the baseline-relaxation type experiment and of the subjects' cognitive events, including strategies.     

Adaptation to visual feedback delays in manual tracking: evidence against the Smith Predictor model of human visually guided action

We report adaptation to delayed visual feedback during a manual tracking task, testing the nature of the adapted responses with frequency analysis. Two groups of seven subjects tracked unpredictable targets using a handheld joystick, alternating between pursuit and compensatory display trials. The test group then practised for 1 h per day with a visual feedback delay of 300 ms; the control group practice under normal undelayed conditions. Introduction of the visual feedback delay significantly disrupted tracking performance, with an increase in errors and a reduction in frequency of corrective movements. Subjects showed clear evidence of adaptation during the 5 day experiment, decreasing tracking error and decreasing the mean power of intermittent corrections. However, there was no evidence of a return towards the initial high frequency intermittent tracking. We suggest that the adaptation observed in this study reflects the modification of predictive feedforward actions, but that these data do not support control based on Smith Prediction.     

The Role of Instructions Versus Instructions Plus Feedback in Voluntary Heart Rate Slowing

Two independent groups of human subjects (both sexes) received continuous binary feedback plus instructions or instructions alone in a heart rate (HR) slowing task. The results indicated that subjects in both groups decreased HR over time, but there were no salient group differences. This suggests that, at least for HR slowing, feedback is not a powerful controller of the behavior; indeed, the stronger statement that feedback is superfluous in HR slowing tasks seems warranted, but must be qualified since there was not a feedback-only group. It was suggested that inclusion of a no-feedback, instructions alone group, is a necessary condition from which to compare the effects of feedback.     

Electromyograph Biofeedback: Generalization and the Relative Effects of Feedback, Instructions, and Adaptation

The present research describes two experiments. The first experiment examined training conditions designed to enhance generalization during electromyograph (EMG) biofeedback. Twelve female and 12 male subjects were randomly assigned to one of four conditions: frontalis EMG biofeedback; frontalis, forearm extensor and masseter biofeedback; frontalis, forearm extensor and semispinalis/splenius biofeedback; and a no-feedback (instructions only) condition. EMG and heart rate were monitored during 3 training sessions. Although reliable decreases in EMG and heart rate were obtained, no differential effect of single- versus multiple-muscle biofeedback was observed; nor, indeed, were differences between biofeedback and no-feedback apparent. A second experiment was conducted to determine whether EMG and heart rate reductions reflected a general relaxation response or were simply due to the effects of adaptation. Twenty-four female subjects were randomly assigned to either a frontalis EMG biofeedback, a no-feedback or an adaptation control condition. Results indicated that decreases in frontalis EMG levels were due to the instructions to relax whereas heart rate decreases were attributable to adaptation. Equivalence between biofeedback and no-feedback conditions was again apparent. It was concluded that this finding raises serious questions about the presumed critical role of the feedback signal in EMG biofeedback.     

Effects of Binary and Proportional Feedback on Bidirectional Control of Heart Rate

Six male and 6 female volunteers formed three groups of 4 subjects in a study on the efficacy of different forms of visual feedback on control of heart rate (HR). One group received proportional feedback from a meter plus a binary success signal, one group received only proportional feedback, and one group received only the binary signal. Subjects received 6 acquisition sessions and 4 extinction sessions. For HR increase, groups receiving proportional feedback showed mean control over the last 2 acquisition sessions of +10 bpm, whereas the group receiving only binary feedback showed control of +4 bpm. For HR decrease, both groups receiving proportional feedback showed mean control over the last 2 acquisition sessions of -4 bpm, whereas the group receiving only binary feedback showed negligible control. During extinction there was no immediate reduction hi control of either HR increase or HR decrease but both declined over extinction sessions. Results indicate that proportional feedback is clearly superior to binary feedback, and that the addition of a binary signal to proportional feedback does not reliably enhance control. Results are consistent with an operant conditioning interpretation of feedback control.     

Cardiopulmonary Adjustments During Operant Heart Rate Control

Twenty-three healthy men and women participated in a 5-session experiment in which they attempted to increase and decrease their heart rate with the assistance of visual analogue biofeedback. As a group subjects did successfully raise and lower heart rate from resting baseline. These changes in heart rate were closely paralleled by changes in V, a measure of cardiac vagal tone. Heart rate slowing was associated with increases in V, and heart rate speeding was associated with decreases in V. Respiration rate and amplitude did not differ significantly between heart rate slowing and speeding trials, and covariance analysis indicated that respiratory changes did not account for the heart rate or V effects. The weighted coherence between respiration and heart rate showed that cardiopulmonary coupling increased during heart rate slowing and decreased during heart rate speeding. Individual differences in cardiac vagal tone and cardiopulmonary coupling were unrelated to heart rate speeding and slowing performance.     

Biofeedback Training of Blood Pressure: A Comparison of Three Feedback Techniques

Three biofeedback procedures were compared for their effectiveness in training subjects to modify systolic blood pressure (BP). Three groups of 6 normotensives received three training sessions using one of three types of systolic BP feedback: 1) proportional feedback at 75-sec intervals, 2) relatively continuous proportional feedback, or 3) a form of continuous binary feedback. Three subjects also completed a fourth, no-feedback, session. Each session consisted of 5 training cycles, during which the subject was first instructed to “lower” BP and then “don't lower” BP. This design permitted demonstration of subjects' ability to control BP, rather than just lowering it. Systolic and diastolic BPs were recorded, as were heart rate, respiration rate and respiration volume. The continuous binary feedback technique was most successful in producing systolic BP control, apparently due to the short feedback latency and maximal information available to subjects. Diastolic BP often increased within sessions even when systolic BP decreased. No consistent covariation between BP and other physiological responses was observed, although at times these responses varied systematically with instruction. Continued systolic BP control at diminished levels was demonstrated by subjects who completed a fourth, no-feedback, session.     

Diastolic Blood Pressure and Heart Rate Biofeedback Training During Orthostatic Stress

Forty male college student volunteers were asked either to increase their diastolic pressure or their heart rate while sitting and during orthostatic stress (going from a sitting to a standing position), and half of them were also given second- to-second visual feedback for the target variable. Systolic blood pressure was also continuously recorded. Comparisons were made between baseline and voluntary control conditions, and test trials were included to examine immediate carry-over effects. With voluntary control instructions, substantial increases in tonic levels were obtained for the three cardiovascular variables in both sitting and postural change conditions. In general, the increases were significantly greater for feedback than for no-feedback conditions. Phasic effects of feedback were also observed during postural change conditions: the blood pressure troughs and the heart rate peak occurred earlier with feedback than for instructions only. Immediate transfer effects were obtained in feedback conditions only. The results were discussed in terms of concomitant effects of somatic and cognitive activities. The distinctive feedback effects on the time course of the responses suggest that a precise analysis of response patterns is needed in selecting appropriate feedback methods in the management of orthostatic hypotension.     

The Regulation of Blood Pressure Reactions to Taxing Conditions using Pulse Transit Time Feedback and Relaxation

Two experiments are described in which 40 normotensive subjects were trained to reduce blood pressure (BP) both in undistracting conditions and while performing taxing tasks. Biofeedback was compared with relaxation in each case, and BP was continously monitored by the pulse wave velocity method. In Study 1, feedback and relaxation groups produced similar BP reductions when control was attempted in isolation. However, the relaxation group was significantly disturbed during performance of an auditory choice reaction time (RT) task. In contrast, feedback subjects showed identical BP modifications in the two conditions. In Study 2, the differences during the RT task proved to be short lived. However, the feedback group overcame pressor reactions to a mental arithmetic test more rapidly than could relaxation subjects, and the difference between groups persisted during no-feedback trials. In both studies, modifications were more specific in the feedback condition, since alterations in heart rate, respiration and general activity were less prominent. It is suggested that it may be fruitful to use feedback for training people to overcome BP reactions to taxing conditions, rather than trying to modify tonic level alone.     

Blood Pressure Control: A Comparison of Feedback and Instructions Using Pulse Wave Velocity Measurements

A comparison was made between blood pressure changes with exteroceptive feedback and simple instructions. Twenty subjects were instructed either to raise or lower pressure for four sessions, while a further 20 were allowed to view an analogue visual display of mean arterial pressure. Pressure changes were continuously monitored with the pulse wave velocity method. When changes were analyzed from the initial baseline, both groups showed divergence between Increase and Decrease over trials, but feedback enhanced control in Increase only. On assessment from the running baseline, feedback control was superior in both direction conditions. This difference may In due to interaction between running baseline changes and experimental conditions. Control by feedback groups deteriorated when feedback was withdrawn. Modifications were accompanied by alterations in heart rate, respiratory activity and movement, although the association was of a gross nature only, being more prominent in increase conditions.     

Cardiac-Respiratory-Somatic Relationships and Feedback Effects in a Multiple Session Heart Rate Control Experiment

An experiment addressing several unresolved issues in operant conditioning of heart rate (HR) in human subjects was performed. Cardiac-respiratory relationships, cardiac-somatic relationships, effects of biofeedback, and individual differences were examined in terms of their stability across multiple training sessions. Thirty subjects participated in 3 training sessions. Each session began with 4 trials of attempted HR change without feedback followed by 8 trials with “proportional” feedback of HR. On half the trials HR decrease was attempted while HR increase was attempted on the other half. Subjects were instructed to keep their respiration rate (RR) constant and not to engage in undue movement or muscle activity. Results indicated that subjects were able to produce significant HR increases and decreases from baseline levels, but these changes were accompanied by parallel changes in respiratory and somatic variables which persisted across sessions. Analysis of data from individual subjects was performed to explore the nature of individual differences in cardiac-respiratory-somatic patterns. The effects of biofeedback were unimpressive, suggesting at best a minor improvement in cardiac control with increased respiratory concomitance. Cardiac control, feedback effects, and cardiac-somatic patterns were stable over sessions. There was evidence of some reduction in cardiac-respiratory parallelism across sessions.     

Myoelectric and Force Feedback in the Facilitation of Isometric Strength Training: A Controlled Comparison

Three groups of 10 normal subjects were trained with 13 maximal isometric contractions on each of 8 days. During 8 of the 13 trials, subject groups received either myoelectric feedback (MFB), or force feedback (FFB), or no feedback. Over the 8 training days all groups increased EMG activity, but no significant group differences in rate of acquisition were obtained. All groups made gains in force over the 8 days. Force feedback produced better acquisition than either MFB or control conditions. However, both MFB and FFB produced comparable and significant differences between feedback and no-feedback trials within a session, highlighting the importance of control group designs in the assessment of biofeedback effects. Dissociation between surface EMG and force was shown not only in the training effects, but also in the difference between feedback and no-feedback performance within a session. An analysis of covariance revealed that during feedback trials MFB produced some EMG facilitation which could not be attributed to increased force production. This effect may have been due to selective reinforcement by MFB of co-contraction in the extraneous musculature, or of changes in motor unit firing patterns. These phenomena may also account for the relative failure of MFB to facilitate force acquisition. A one-month follow-up showed significant retention following similar losses of force in all groups.     

Evidence of a Role for Response Plans and Self-Monitoring in Biofeedback

Subjects in a control group were given feedback training for two unidentified visceral responses (increases and decreases in heart rate) and were then asked to provide a verbal report describing what they had done to control the feedback displays. Judges were given these reports and asked to determine training condition (increase heart rate on A trials and decrease heart rate on B trials, or the reverse) from them. Subjects in an experimental group received the same procedure but were also asked for a verbal report prior to receiving their first feedback display and thenceforth after each of the first 10 trials of feedback training. The results showed that: a) success at biofeedback learning is accompanied by verbal awareness of activities contributing to response production, and b) learning can be predicted (r= .80) by probing the subject's problem space before he has seen his first feedback trial. Extensive verbal probing of experimental subjects did not eventuate in superior learning in this group. The nature and role of problem-solving activity in biofeedback are discussed.     

Learning an environment–actor coordination skill: visuomotor transformation and coherency of perceptual structure

The coordination dynamics of learning were examined in a visuomotor tracking task. Participants produced rhythmic elbow flexion–extension motions to learn a visually defined 90° relative phase tracking pattern with an external sinusoidal signal. There were two visuomotor transformation groups, a correct feedback group and a mirrored feedback group with feedback representing the elbow’s motion transformed by 180°. In Experiment 1, the to-be-tracked signal and the participant’s motion signal were superimposed within a single window display. In Experiment 2, the to-be-tracked signal and participant’s signal were presented in separate windows. Before day 1 practice and 24 h after day 2 practice, participants attempted visually defined 0°, 45°, 90°, 135°, and 180° relative phase tracking patterns either with or without visual feedback of the arm’s motion. Before practice, only the 0° and 180° tracking patterns were stable. Practice led to a decrease in phase error toward the required 90° relative phase pattern with a corresponding increase in stability in both the experiments. No effect of visual transformation on performance emerged during practice in the single window task, but did emerge in the two window task. The one window training facilitated transfer to the four unpracticed relative phase patterns, whereas the two window training display only facilitated transfer performance to a single unpracticed relative phase pattern. These findings suggest that the perceptual structure determined the degree of learning and transfer and interacted with the visuomotor transformation. The present findings are discussed with reference to how the visual display constrains the coherency of independent signals with regard to learning and transfer and the role of perceptual discrimination processes linked to transfer.