Heart rate discrimination and heart rate control: a test of Brener's theory

Three experiments were conducted to examine predictions from Brener's theory regarding the relationship between autonomic discrimination and autonomic control. Experiment 1 examined the possibility that training subjects to discriminate their heart rates would enhance their skill at controlling that response. Twenty subjects participated in two sessions during which one group of 10 subjects received training (knowledge of results) on the Ashton discrimination technique. The second group performed the discrimination task but received no training. All subjects then took part in a third session of heart rate (HR) control (both increase and decrease) where half of each of the aforementioned groups received feedback during the control task, while the other half performed the HR control task without feedback. Results indicated that for the control of both HR increases and decreases, there was no significant difference between those subjects trained to discriminate their HR, and those who had received no training to discriminate HR. The second experiment investigated the hypothesis that training subjects with feedback to control their HR would enhance their capacity to discriminate their heart activity. Ten subjects participated in two sessions of HR control during which half the subjects received feedback training to increase HR. During a third session, all subjects underwent a test of discrimination ability using the Ashton technique, and no knowledge of results regarding performance was provided. Results confirmed the hypothesis. The final experiment in the series investigated the discrimination/control relationship within a problem-solving framework and used 20 subjects. Results confirmed the hypothesis that subjects forewarned at the time of discrimination training that a heart rate control task was to follow would perform better than 10 subjects receiving no forewarning of the task objective. This effect took place independently of cardiac discrimination ability. A second finding from this experiment was that subjects trained to discriminate heart rate were better able to increase heart rate than untrained subjects. This result contradicts that of Experiment 1, and reasons for this anomaly are discussed in detail.     

Relation of Learned Heart Rate Control to Self-Report in Different Task Environments

A widely-expressed view based on early studies of the verbal report in biofeedback holds that response awareness is unnecessary for learned control of visceral responding. However, more recent evidence has questioned this view. This article reports two experiments that analyzed verbal reports with the methods of recent studies while examining procedural differences between early and recent research. Experiment 1 assessed the effects of bidirectional versus unidirectional training on heart rate control and self-report. Experiment 2 examined heart rate control and self-report in two task environments that differed with regard to whether somatomotor action was afforded or allowed. No instances of response learning without response awareness were observed in either experiment, even when task environments approximating those of the early biofeedback studies were used. The results support viewpoints of biofeedback that assign a role to response awareness in the development of instructed control.     

Heart Rate as a Discriminative Stimulus

Two experiments were performed to evaluate characteristics of heart activity as discriminative stimuli. In Study I two multiple baseline across subjects designs were utilized to assess the efficacy of trial and error and fading procedures in increasing the detection of heart rate activity above and below an average level. Both trial and error and fading procedures were effective in increasing discrimination accuracy. A 4.4 bpm interval around the subject's mean heart rate was employed as the discriminative stimulus in Study II. Significant stimulus control exerted by the criterion stimuli was found during both training and testing conditions. Experimental procedures were discussed for determining which sensory events in a complex stimulus dimension such as a physiological change are actually exerting stimulus control.     

Stimulus omission and recovery of the electrodermal and digital vasoconstrictive components of the orienting response.

Three experiments are reported which investigated Sokolov's (1968) hypothesis that, after a number of stimulus presentations, complete omission of a stimulus leads to increased responsiveness of the orienting response (OR). The skin conductance response (SCR) and finger pulse volume (FPV) response components of the OR were studied. In experiment 1 (N=60), the effect of number of pre-omission training trials on response recovery was investigated, while experiment 2 (N=120) investigated the effects of stimulus intensity (70 or 90 dB) and interstimulus interval (12 or 21 sec) on recovery to stimulus omission following a fixed number of training trials. In experiment 3 (N=40), an attempt was made to control for possible below-zero habituation effects by training each subject to a habituation criterion before stimulus omission. All experiments employed a 1000 Hz tone of 3 sec duration which was presented at a constant interstimulus interval. Although recovery of the SCR did occur under some conditions, the results were largely negative. Manipulation of the number of training trials, training stimulus intensity and interstimulus interval had little effect on response recovery. A consistent finding, however, was that subjects who displayed SCR recovery also displayed significantly more spontaneous fluctuations in skin conductance during the pre-stimulus period and required significantly more training trials to reach the criterion of habituation than did subjects displaying no recovery. Moreover, the SCRs displayed by 'labile' subjects on omission trials were significantly larger than those displayed on either the last training trial or during a control interval just prior to stimulus omission.     

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.     

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.     

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.     

Training effects of cross-country skiing and running on maximal aerobic cycle performance and on blood lipids

Summary Two experiments were carried out to compare the cardiorespiratory and metabolic effects of cross-country skiing and running training during two successive winters. Forty-year-old men were randomly assigned into skiing (n = 15 in study 1,n = 16 in study 2), running (n = 16 in study 1 andn = 16 in study 2) and control (n = 17 in study 1 andn = 16 in study 2) groups. Three subjects dropped out of the programme. The training lasted 9–10 weeks with 40-min exercise sessions three times each week. The training intensity was controlled at 75%–85% of the maximal oxygen consumption (VO_2max) using portable heart rate metres and the mean heart rate was 156–157 beats·min^–1 in the training groups. In the pooled data of the two studies the mean increase in theVO_2max (in ml·min^–1·kg^–1) on a cycle ergometer was 17% for the skiing group, 13% for the running group and 2% for the control group. The increase inVO_2max was highly significant in the combined exercise group compared to the control group but did not differ significantly between the skiing and running groups. The fasting serum concentrations of lipoproteins and insulin did not change significantly in any of the groups. These results suggested that training by cross-country skiing and running of the same duration and intensity at each session for 9–10 weeks improved equally the cardiorespiratory fitness of untrained middle-aged men.     

腹式呼吸和自生训练对心率及指温影响的初步探讨

放松训练能缓解应激引起的紧张状态。自生训练和腹式呼吸是常见的两种简便易行的放松方法。自生训练是 19世纪末由德国柏林脑生理研究所的奥思卡 .沃特 (Ｏｓｋａｒｖｏｇｔ)从催眠研究中发展来的 ,其目的就是使人的生理、心理和情绪过程正常化 ,恢复肌体的平衡。腹式呼吸是气功中常用的呼吸训练方法 ,慢的、深的、有规律的腹式呼吸可降低应激水平[1] 。本研究试图初步了解腹式呼吸和自生训练对心率和指温的影响。1　实验方法1.1　被试的选择实验对象为河北师范大学一年级女生 ,共 4 5人 ,年龄 18- 2 1岁。身体健康 ,均为右利手 ,未进行过放…     

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.     

Failure to alter sympathoadrenal response to psychosocial stress following aerobic training

This experiment assessed the impact of aerobic training on sympathoadrenal, heart rate and subjective responses to psychosocial stress. Subjects were six previously sedentary males who demonstrated marked improvement in fitness level following 10 weeks of training. Plasma samples, heart rate and subjective arousal ratings were obtained prior to, during, and following exposure to stressful mental tasks within a laboratory session. With the exception of training-related bradycardia which was manifest throughout the session, no changes in plasma epinephrine and norepinephrine concentrations, heart rate or subjective reactivity or recovery were seen. These findings are inconsistent with the hypothesized beneficial effects of aerobic training on stress-response. Methodological factors such as self-selection inherent in previous correlation work or the duration of the training program should be considered in this context. The potential contribution of training-related bradycardia to enhanced coping with challenging situations is explored.     

Experimental manipulation of aerobic fitness and the response to psychosocial stress: heart rate and self-report measures

To determine whether aerobic fitness training alters response to psychosocial stress, 38 males were randomly assigned to either aerobic, anaerobic (weight-lifting), or waiting-list control groups. Experimental groups met three to four times per week in 1-hr sessions aimed at improving either cardiovascular endurance or muscular strength. Aerobic fitness level, heart rate and subjective response to laboratory psychosocial stress, and self-reports of daily stress, coping resources and psychologic symptoms were assessed prior to and following 10 weeks of training. Although posttraining fitness measures confirmed the effectiveness of aerobic training, no group differences were seen on laboratory or self-report measures. However, for aerobic trainers alone, fitness improvement tended to correlate with faster heart rate recovery following psychosocial stress. Fitness improvement was not correlated with any other psychologic changes. This experiment provides only modest support for the hypothesis that aerobic training alters response to psychosocial stress. It is suggested that future work on the psychologic effects of aerobic fitness explore the contribution of training parameters as well as subject characteristics.     

Involvement of the autonomic nervous system in motor adaptation: acceleration or error reduction?

In the last few decades motor adaptation was extensively studied observing the invariant features of reaching movements. In a parallel neurobehavioral line of research emotional learning was studied under the umbrella of the ‘two-factor theory of learning’. In this study we explore the relation between motor learning and the autonomic response (heart rate, HR) of subjects performing point to point reaching movements holding a computer mouse. We consider two alternative outcomes: one is that autonomic response correlates with the learning rate and the second is that the autonomic response correlates with the residual error at the steady state. Eighteen subjects performed reaching movements under perturbed visual feedback demonstrating learning and after effects of learning. The hand movement as well as an Electrocardiogram signal were recorded throughout the training and carefully analyzed offline to extract the trial by trial error as well as the heart period. The results show clear correlation between the change in HR and the residual error but no correlation between the change in HR and the learning rate supporting the second alternative that the sensitivity to errors but not the learning rate correlates with the autonomic response. A control group of another seven subjects underwent the same experiment without the perturbed visual feedback. This control group showed no change in the HR. Further studies are required to validate this hypothesis and unravel the mechanism by which the autonomic response correlates with the residual motor error.     

Self-perception of the ability to work in the cold

Accumulating evidence of beneficial effects from physical exertion must be balanced against increased risk of cardiac arrest during performance. There is evidence that, by using such cues as heart rate, individuals can monitor their level of exertion perceptually. We undertook experiments to discover whether temperature and heart rate interact to affect self-perception when the effective temperature is moved downard from the comfort zone. In the first pilot study, 36 males practiced a new game, SwedeBall, for a period of 20 minutes. Twelve were randomly assigned to play at a temperature of 22 degrees C, another 12 to play at 0 degrees C, and the remaining 12 to play at -7 degrees C. The players showed tendencies toward an overall improvement in self-evaluations after brief practice, with more favorable responses when the temperatures were lower. In a second experiment on different days, 8 men pedaled a standard bicycle mounted as a wind trainer in a controlled environment chamber where the effective temperature was set at 26 degrees C, 8 degrees C, or -10 degrees C. The first 5-minute ride at each temperature was at a heart rate of 120 beats per minute (bpm), the second at 140 bpm, and a third at 160 bpm. We measured ratings of perceived effort (RPE), thermal impression, discomfort, perceived rate of speed, and projected endurance. The result confirmed that RPE was lowered by temperature when heart rate was constant. The data also showed that the lowered temperatures uniformly produced more favorable self-perceptions on the other four scales. The outcome is related to physiological problems that might arise when temperature depresses heart rate and reduces the experience of effort.     

High intensity deep water training can improve aerobic power in elderly women

Deep water running with wet vest is a safe form of exercise for elderly with mobility limitations. However, it is not known to what extent their aerobic power may be improved. Therefore, the aim was to assess the effects of high intensity deep water interval training with vest in elderly women. Twenty-nine healthy women 69 ± 4 years old participated. They performed a graded maximal exercise test on the cycle ergometer. They were randomly assigned to a control or to a training group. A submaximal exercise test on the cycle ergometer was executed only by the training group. They trained in deep water running/walking wearing a vest two times a week for 8 weeks. The target heart rate was 75% of maximal heart rate and the training consisted of several short working periods and resting intervals. After the intervention the heart rate at rest was 8% lower for the training group (P<0.01). Their heart rate at submaximal exercise was 3% less (P<0.01), their maximal oxygen uptake was raised by 10% (P<0.01), and their maximal ventilation was increased 14% (P<0.01). The values for the control group were unaltered after the period of intervention. In conclusion, high intensity deep water running with vest improves submaximal work capacity, maximal aerobic power, and maximal ventilation with the effects transferable to land-based activities in elderly women.     

The effects of raising alveolar PCO2 and ventilation separately and together on the sensitivity and setting of the baroreceptor cardiodepressor reflex in man

1. The effects of changes in ventilation and/or alveolar P(CO2) on the baroreflex control of heart rate have been studied in seven experiments on six young men and women who had been trained to control tidal volume and respiratory frequency at various levels independent of alveolar P(CO2), during hyperoxia.2. Intravenous phenylephrine provoked transient rises of directly measured arterial pressure during which individual systolic pressures (P) were linearly related to the following pulse interval (I). Baroreflex sensitivity was expressed as the slope of the regression of I on P, and reflex setting (I(ref)) as I at a single reference arterial pressure (= mean P for the experiment).3. Voluntary control of breathing had little effect on heart rate and arterial pressure (baroreflex setting), but diminished reflex sensitivity.4. Hypercapnia regularly caused tachycardia at the reference pressure (i.e. baroreflex setting lowered). The response was completely or partly reproduced by change of P(A, CO2) at constant ventilation in four subjects but not in two others; in them change of ventilation at constant P(A, CO2) completely mimicked the effect of free-breathing hypercapnia.5. Values of baroreflex sensitivity were relatively scattered. Hypercapnia caused a fall in baroreflex sensitivity in three subjects whether ventilation was fixed or free to rise. After separating the effect of voluntarily controlling ventilation, ventilation per se was without effect on reflex sensitivity.6. It is concluded that hypercapnia and hyperpnoea have separate effects on the baroreflex, the relative magnitudes of which differ from one subject to another. Baroreflex setting and sensitivity vary independently in response to change of ventilation and of P(A, CO2).     

Effects of moderate exercise training on plasma volume, baroreceptor sensitivity and orthostatic tolerance in healthy subjects

The effect of physical training on an individual's ability to withstand an orthostatic stress is unclear. This study was undertaken to determine the effects on orthostatic tolerance in healthy volunteers of training at a level appropriate for unfit subjects and cardiorespiratory patients. In 11 asymptomatic, untrained subjects the following assessments were made: plasma volume by Evans Blue dye dilution and blood volume derived from haematocrit; carotid baroreceptor sensitivity from the slope of the regression of change in cardiac interval against pressure applied to a neck chamber; orthostatic tolerance as time to presyncope in a test of head-up tilting combined with lower body suction; exercise test relating heart rate to oxygen consumption. Subjects were then given a training schedule (5BX/XBX, Royal Canadian Air Force) involving 11-12 min of mixed exercises per day until an age/sex related 'target' was reached. Following training all subjects showed evidence of improved fitness, seen as decreases in heart rate at an oxygen uptake (Vo2) of 1.5 1 min-1 and in the elevation of the regression line between heart rate and Vo2. All also had increases in plasma and blood volumes and decreases in baroreceptor sensitivity. Seven of the subjects showed increases in orthostatic tolerance. Improvement in orthostatic tolerance was related to a low initial tolerance, and was associated with increases in plasma volume and decreases in baroreceptor sensitivity. These results show that moderate exercise training increases orthostatic tolerance in subjects who do not already have a high initial tolerance and suggest that training may be of value in the management of untrained patients with attacks of syncope due to orthostatic intolerance.     

Feedback Effects and Respiratory Involvement in Voluntary Control of Heart Rate

One within-subject single session experiment involving 30 subjects and one between-subject single session experiment involving 42 subjects were performed to evaluate the effects of augmented sensory feedback and to specify the nature of cardiac-respiratory relationships during attempted bi-directional control of heart rate (HR). Subjects were instructed to attempt to control HR while maintaining a constant respiration rate (RR), and were provided with either no feedback, HR feedback, or HR and RR feedback of the “digital” proportional type. In addition to measures of heart and respiratory period, a measure of respiratory volume was included in the second experiment. Results of both experiments indicate that (1) subjects can significantly increase and decrease HR; (2) feedback does not affect the magnitude or consistency of HR control; (3) significant parallel changes in RR accompany changes in HR regardless of the amount of feedback provided; (4) significant increases in respiratory volume accompany HR increases; and (5) large magnitude HR changes arc produced by some subjects within the single session. Implications of these findings for the concomitance model of autonomic and central nervous system interactions; for single vs multiple training sessions; for the use of paced respiration; and for a learning model of HR control are discussed.     

EFFECTS OF DEPTH AND RATE OF BREATHING ON HEART RATE AND HEART RATE VARIABILITY

Effects of depth and rate of breathing on heart rate (HR) and HR variability were observed in two experiments. Respiration rate (RR) affected only cardiac stability, faster breathing producing more stable cardiac rate. Respiration depth (RD) affected both HR level and variability. Deep breathing produced faster, more variable HR, while shallow breathing had the opposite effects. A third experiment, in which Ss were trained to control HR using respiration, further illustrated the dramatic effects of respiration on cardiac rate. Implications of these results for experiments utilizing HR as a dependent variable and studies of autonomic control were discussed.     

Chronotropic and inotropic effects on the dog heart of stimulating the efferent cardiac sympathetic nerves

1. The chronotropic and inotropic responses of the dog heart to stimulation of the ansae subclaviae were studied.2. The maximum rate of rise of pressure in the left ventricle (dP/dt max) was used as an index of the inotropic changes.3. In experiments in which the secondary inotropic effects of changes in heart rate and blood pressure were prevented it was shown that, using stimuli which produced the same chronotropic response, stimulation of the left ansa subclavia resulted in an inotropic change which was about eight times greater than that which resulted from stimulation of the right ansa subclavia.4. In experiments in which heart rate and blood pressure were allowed to change freely it was shown that the secondary inotropic effects of changes in blood pressure and heart rate amounted to about 70% of the total inotropic change when the right ansa subclavia was stimulated and about 20% of the total change when the left ansa subclavia was stimulated.