Comparison of Discrete Cardiovascular Fitness Groups on Plasma Catecholamine and Selected Behavioral Responses to Psychological Stress

Discrete cardiovascular fitness groups consisting of high-fit (n=10) and low-fit (n=9) men performed a well-learned vigilance task and their self-report, performance, and plasma catecholamine responses were compared. No significant differences were observed between the fitness groups on self-report or psychomotor performance responses to the vigilance task. However, the low-fit group took significantly longer than high-fit subjects to complete the first of three sets of anagrams administered immediately after the vigilance task. Plasma norepinephrine but not epinephrine response was greater in the low-fit group compared to their high-fit counterparts. The findings indicate that enhanced cardiovascular fitness may be characterized by an attenuated plasma norepinephrine response to a vigilance task with sustained cognitive performance subsequent to the task.     

The effect of participation in an exercise training program on cardiovascular reactivity in sedentary middle-aged males.

Exaggerated cardiovascular reactivity to mental stressors may be a risk factor for cardiovascular disease. To determine if participation in a moderate intensity aerobic exercise training program reduces cardiovascular reactivity to laboratory stressors, 40 sedentary middle-aged males were randomly assigned: training group (n = 25) and control group (n = 15). Cardiovascular reactivity during and after three mental stressors (passive responding, push-button Stroop and verbal Stroop) and mild exercise (bicycle ergometer) was assessed before and after an 8-week intervention. VO2(peak) was determined using the Balke protocol. Among 19 subjects who completed the training, VO2(peak) increased 13.7%. Also, trained compared to untrained subjects showed significant reductions in baseline and absolute heart rate responses to all stressors. Baseline adjusted heart rates were significantly lower during push-button Stroop recovery and during verbal Stroop. Blood pressure, T-wave amplitude, finger pulse amplitude and pulse transit time responses were unaffected by exercise training. It was concluded that participation in a short-term, moderate intensity aerobic exercise training program may have a cardioprotective effect by significantly reducing absolute and baseline-adjusted heart rate responses to stressors.     

Aerobic Fitness Affects Cardiovascular and Catecholamine Responses to Stressors

Subjects of varying degrees of aerobic fitness were subjected to four laboratory stressors in a test of the hypothesis that aerobic fitness is associated with decreased responsiveness to stressors other than exercise. Blood pressure, heart rate, norepinephrine, epinephrine, and psychological responses to a film of industrial accidents (passive psychological stressor), the Stroop word color task (active psychological stressor), the cold pressor test (passive physical stressor), and running to exhaustion on a treadmill (active physical stressor) were measured. Baseline systolic blood pressure and relative diastolic responses to the film, Stroop task, and exercise were smaller in fit subjects over 40 than in less fit subjects of the same age group. Heart rates were lower in fit subjects at most times, except during and after maximal exercise. Norepinephrine was lower after 9 min of exercise in fit subjects, but was much higher at exhaustion, after these subjects had accomplished more work. Norepinephrine levels fell rapidly and were not different among groups 3 and 10 min after exercise. There was no preferential generalization of the “fitness effect” to the active psychological task.     

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.     

Influence of aerobic exercise training and relaxation training on physical and psychologic health following stressful life events

An experiment was conducted to determine whether aerobic exercise training or relaxation training would be effective for reducing the deleterious effects of life stress on physical and psychologic health. Over 1000 college students were surveyed, and 55 of those who reported experiencing a high number of negative life events over the preceding year were assigned to an aerobic exercise training condition, a relaxation training condition, or a no-treatment control condition. Physical and psychologic health were assessed with self-report measures before, halfway through, immediately following, and 8 weeks after the 11-week training (and control) period. Heart rate data collected during a treadmill test indicated that the aerobic exercise training was effective for improving cardiovascular fitness. Psychologic measures indicated that the exercise training condition was more effective than the other two conditions for reducing depression during the first 5 weeks of training. No differences were found among the conditions on self-report measures of physical health. These findings suggest that aerobic exercise training may be useful for reducing the severity and duration of depressive reactions following stressful life change.     

Acute Emotional and Cardiovascular Effects of Stressful Mental Work During Aerobic Exercise

The acute effects of engaging in challenging mental work during a single session of aerobic exercise were examined on measures of subjective mood and cardiovascular function. Fifty-seven female subjects were randomly assigned to participate in either a 10-min aerobic exercise condition or a no-exercise control condition. Half of the subjects in each group performed digits backward problems during this time period, and no mental stressors were presented to the other subjects. The results indicated that the exercise and mental stress conditions had additive effects on subjective anxiety levels and on cardiovascular responses during exercise. Both exercise and mental stress increased heart rate. In addition, exercise had anti-anxiety and vasodilative effects, but both of these influences were attenuated by opposing main effects for mental stress exposure. No effects were found for exercise on measures of cardiovascular reactivity to a later digits backward stressor. The results are consistent with previous research in suggesting that exposure to mental stressors during aerobic exercise provides no acute psychological benefits but attenuates some of the mood improvements and vasodilative effects of the exercise activity.     

Effects of a 12-week endurance training program on the physiological response to psychosocial stress in men: a randomized controlled trial

The present study experimentally tested the cross-stressor adaptation hypothesis by examining whether endurance exercise training leads to reductions in the physiological stress response to a psychosocial stressor. We randomly assigned 149 healthy men to a 12-week exercise training, relaxation training, or a wait list control group. Before and after intervention we assessed the groups’ physical fitness (lactate testing) and compared their physiological stress responses to the Trier Social Stress Test for Groups in terms of salivary free cortisol, heart rate (HR) and heart rate variability (HRV); the final sample consisted of 96 subjects. As hypothesized, the exercise training significantly improved fitness and reduced stress reactivity in all three parameters; however, it only improved stress recovery in terms of HR. The relaxation program reduced only cortisol, but not HR or HRV reactivity; no changes emerged for the control group. The findings suggest that the cross-stressor adaptation hypothesis is valid for cardiovascular as well as endocrine stress reactivity.     

Aerobic Fitness, Physical Activity, and Psychophysiological Reactions to Mental Tasks

The association between aerobic fitness, exercise, and psychophysiological reactivity was assessed in cross-sectional and prospective analyses. Seventy-five healthy but sedentary adults carried out a sub-maximal exercise test and easy and difficult problem solving tasks. Blood pressure, heart rate, skin conductance level, respiration rate, tidal volume, and oxygen consumption were monitored and additional heart rate was also computed. Differences between relatively fit and unfit individuals were found in respiration rate during tasks and in skin conductance level during post-task recovery periods, with a tendency toward diminished heart rate reactivity in fitter people. Subjects were subsequently allocated to four conditions: high intensity aerobic training, moderate intensity aerobic training, an undemanding strength and flexibility program (designed as an attention-placebo condition), and waiting list control. Training programs were conducted over a 10-week period, and were followed by a second laboratory session. Appropriate changes in aerobic performance over the training period were observed in the 12-min run/walk test. There were no important modifications in psychophysiological stress reactions associated with the different experimental conditions. These results are discussed in relation to the literature concerning the effects of fitness and physical activity on physiological response patterns.     

Plasma catecholamine and cardiovascular reactivity during an acute high ropes course event.

The primary purpose of this study was to describe physiological responses to an acute high ropes course stress. The selected dependent variables were epinephrine (E), norepinephrine (NE), heart rate (HR), systolic/diastolic blood pressure (BPs and BPd) and self-reported anxiety. A secondary purpose was to explore possible relationships between the observed physiological responses and physical fitness. College-age males were recruited for preliminary V(O(2)) max testing to identify a high-fit and low-fit subject pool. Eleven were identified as eligible participants and gave informed consent. Six participants were in the high-fit category (V(O(2)) max>60 ml/kg) and five in the low-fit category (V(O(2)) max<42 ml/kg). The Power Pole, a common high ropes course event, was selected as the acute field-based challenge activity. During participation in the challenge, a series of five (T1-T5) 10-ml blood samples were taken (via intravenous catheter) to be analyzed for E and NE. Subjective anxiety, HR, BPs and BPd were also measured at T1-T5. When the data were analyzed in a 2 (fitness group) x 5 (time) factorial ANOVA, there was a significant main effect for time with each dependent variable. However, the only difference between fitness levels was found with HR. These results indicate that the Power Pole is an acute field-based stressor for individuals of both high and low fitness levels. Due to the lack of difference between fitness groups for all variables other than HR, we conclude that participating in the Power Pole event elicits more stress of a psychosocial nature than stress of physical exertion.     

Regional brain activation as a biological marker of affective responsivity to acute exercise: influence of fitness

Previous research has shown that regional brain activation, assessed via frontal electroencephalographic (EEG) asymmetry, predicts affective responsivity to aerobic exercise. To replicate and extend this work, in the present study we examined whether resting brain activation was associated with affective responses to an acute bout of aerobic exercise and the extent to which aerobic fitness mediated this relationship. Participants (high-fit, n = 22; low/moderate-fit, n = 45) ran on a treadmill for 30 min at 75% VO2max. EEG and affect were assessed pre- and 0-, 10-, 20-, and 30-min postexercise. Resting EEG asymmetry predicted positive affect (as measured by the energetic arousal subscale of the Activation Deactivation Adjective Check List) postexercise. Furthermore, resting frontal EEG asymmetry predicted affect only in the high-fit group, suggesting the effect might be mediated by some factor related to fitness. It was also shown that subjects with relatively greater left frontal activation had significantly more energy (i.e., activated pleasant affect) following exercise than subjects with relatively greater right frontal activation. In conclusion, aerobic fitness influenced the relationship between resting frontal asymmetry and exercise-related affective responsivity.     

The effects of nonconcurrent and concurrent relaxation training on cardiovascular reactivity to a psychological stressor

Eight patients in a cardiac rehabilitation program, after exposure to two psychological stressors approximately equivalent with respect to cardiovascular reactivity, were given nonconcurrent progressive muscle relaxation training and retested for reactivity. They were then provided with relaxation training concurrently with one of the stressors and exposed again to the two stressors. No significant effects for nonconcurrent progressive muscle relaxation training were detected. Concurrent training, in contrast, produced reductions in both systolic and diastolic blood pressure. Reductions resulting from training on the target stressor showed little tendency to generalize to the nontarget stressor; the discrimination was particularly well defined for systolic blood pressure. We conclude that muscle relaxation techniques are maximally effective in reducing reactivity to psychological stressors when relaxation training is provided concurrently with the stressor. Our findings further suggest that to inculcate the relaxation response reliably across different situations, specific training to enhance generalization may be needed.     

Efficiency of Coping with a Real-Life Stressor: A Multimodal Comparison of Aerobic Fitness

The mediating effects of aerobic fitness on the psychological and physiological responses to a real-life psychological stressor (rappelling) were examined. Subjective anxiety, heart rate, nor epinephrine, epinephrine, and cortisol were monitored in IS male novice rappellers at various intervals before and following the rappel task. Results showed that high fit compared to low fit subjects maintained overall lower heart rate levels. Aerobic power was associated with faster recovery from subjective anxiety and a more efficient recovery for relative plasma epinephrine measures. Norepinephrine, heart rate, and cortisol did not parallel this recovery pattern. These results provide some support for the research which indicates that high levels of aerobic power are associated with greater coping efficiency.     

Existing and Training Induced Differences in Aerobic Fitness: Their Relationship to Physiological Response Patterns During Different Types of Stress

Aerobic fitness has been associated with various desirable psychological and physiological characteristies. Recently, attenuation of physiological reactivity during stressful situations was added to this list, although comparison of the stress responses of sportsmen and sedentary subjects has yielded equivocal results. The present study examined cardiovascular patterns rather than single variables, and tried to clarify these matters. Tasks were used that were known to increase blood pressure through different combinations of changes in cardiac output and vascular resistance. Autonomic nervous system dynamics underlying these response patterns were studied using preejection period as an index of β-adrenergic activity, and respiratory sinus arrhythmia as an index of vagal activity. Pre-existing differences in aerobic fitness in a sample of sedentary subjects were related to their responses during the stressful tasks and the recovery periods afterwards. This approach prevented confounding of the relationship between fitness and stress-reactivity with the psychological effects of regular exercise. Furthermore, it excluded the bias in psychological makeup that is introduced when subjects spontaneously engaged in sports are compared to non-exercising persons. To rule out a third (hereditary?) factor underlying both stress-reactivity and fitness, physiological responses before and after a seven-week training program were compared to those of subjects in a waiting list control group. Substantial individual differences in aerobic fitness were found in spite of the fact that all subjects reported low levels of habitual activity. During two active coping tasks, diastolic blood pressure reactivity and vagal withdrawal were negatively related to these pre-existing differences in fitness. No such relation was seen during a cold pressor test or during recovery from the tasks. Neither β-adrenergic cardiac reactivity nor heart rate responses were related to fitness, but the absolute heart rate during the tasks was lower in the more fit subjects. Seven weeks of training were not effective in changing either reactivity or recovery of any of the variables. The discrepancy between cross-sectional and longitudinal results in the present study suggests that training of longer duration is necessary to induce the psychological or physiological changes underlying reduced reactivity. The latter may include changes in cardiac vagal/sympathetic balance or in adrenoceptor sensitivity. Alternatively, both psychological and physiological determinants of stress-reactivity may be related to aerobic fitness at a dispositional level.     

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.     

Cardiopulmonary Adjustments During Exercise and an Aversive Reaction Time Task: Effects of Beta-Adrenoceptor Blockade

The purpose of this study was to compare the cardiopulmonary and hemodynamic adjustments to a physical (bicycle exercise) and behavioral (aversive reaction time) stressor. A related aim was to assess the role of beta-adrenergic mechanisms in mediating these physiological responses. Thirty-four subjects were exposed to both stressors while oxygen consumption, carbon dioxide production, pulmonary ventilation, end-tidal oxygen and carbon dioxide, as well as heart rate were calculated breath-by-breath. Fourteen of these subjects were pretreated with 4 mg (iv) of propranolol hydrochloride. The remaining 20 subjects (intact) were subdivided post-hoc into the 10 most and 10 least reactive on the basis of their heart rate response to the reaction time task. The results indicate that for the intact group both exercise and the reaction time task produced significant increases in heart rate although the magnitude of the heart rate change was reliably greater during exercise. Beta-adrenergic blockade partially diminished the tachycardia to exercise but entirely abolished the tachycardia to behavioral stress. Interestingly, the most and least reactive subjects did not exhibit differential heart rate acceleration during exercise despite a reliable difference during the reaction time task. Oxygen consumption significantly increased to predictable levels during exercise but failed to change during the reaction time task for both the most and least reactive groups. These results suggest that the tachycardia elicited by the reaction time task in reactive subjects was not associated with an appropriate increase in oxygen consumption, relative to exercise, and may therefore be indicative of systemic overperfusion.     

Psychologic and physiologic reactivity to stressors in eating disordered individuals

The present study explored a potential mechanism for the relationship between stressors and binge eating: specifically, whether subjects with behaviors and attitudes reflecting disordered eating show distinctive psychologic or physiologic reactivity to stressors. Female undergraduates participated in a laboratory study involving four psychologically stressful tasks. Blood pressure and pulse rate were monitored, and several psychologic questionnaires were administered. Analyses revealed that the tasks provoked significant cardiovascular and affective responses in both high- and low-disordered eaters. There were no differences between groups in cardiovascular responsivity or mood state in response to diverse stressors. However, those with more disordered eating reported an increased desire to binge in response to the stressors, along with more global stress, lower self-esteem, and lower mastery than the comparison group. The results suggest that the increased desire to binge in response to stressors reported by subjects higher in disordered eating cannot be accounted for by differences in cardiovascular reactivity or negative hedonic state, relative to what subjects low in disordered eating showed in response to the same stressors.     

Effect of low-dose endurance training on heart rate variability at rest and during an incremental maximal exercise test

We evaluated the effects of low-dose endurance training on autonomic HR control. We assessed the heart rate variability (HRV) of 11 untrained male subjects (36.8 +/- 7.2 years) at rest and during an incremental maximal aerobic exercise test prior to a 7-week preparatory period and prior to and following a 14-week endurance training period, including a low to high intensity exercise session twice a week. Total (0.04-1.2 Hz), low (0.04-0.15 Hz) and high (0.15-1.2 Hz) frequency power of HRV were computed by short-time Fourier transform. The preparatory period induced no change in aerobic power or HRV. The endurance training period increased peak aerobic power by 12% (P < 0.001), decreased the HR (P < 0.01) and increased all HRV indices (P < 0.05-0.01) at absolute submaximal exercise intensities, but not at rest. In conclusion, low-dose endurance training enhanced vagal control during exercise, but did not alter resting vagal HR control.     

Interactive effects of type A personality and psychological and physical stressors on human cardiovascular functions

The first part of this study examined the relationship(s) between Type A behavior scores and heart rate, blood pressure and impedance derived cardiovascular measures in response to discrete stressors during a standardized psychophysiological assessment. Expts. 2A and 2B considered cardiovascular responses to dynamic exercise stress alone and in combination with psychological and cold pressor tests. Gender and stroke volume changes during the psychological stress correlated 0.45 (P less than 0.02) with Type A score. Subscale scores of Job Involvement correlated 0.78 (P less than 0.02) with stroke volume, total systemic resistance and heart rate during the psychological stressor, and systolic blood pressure during the cold pressor task. The combined effects of psychological stress and dynamic exercise on systolic and diastolic blood pressure were significantly greater than the individual effects of these stressors. The use of impedance cardiography in measuring cardiovascular variables that correlate with Type A behavior, during psychophysiological assessments, may further elucidate our understanding of Type A behavior in addition to providing information about how stress interacts with aerobic exercise.     

Psychologic effects of cardiovascular conditioning: a controlled experiment

Although there have been numerous studies documenting a relationship between physical fitness and psychologic functioning, few have employed the type of experimental design that would allow conclusions to be drawn regarding cause and effect. In the present study, college students were randomly assigned to a cardiovascular conditioning program or to a control program designed to give the appearance of physical training while minimizing cardiovascular benefits. Both groups were tested for cardiovascular fitness as well as on a number of self-rating scales before and after the 6-week program. The cardiovascular group demonstrated a significantly greater improvement in cardiovascular fitness than the control group and also tended to show a greater reduction in anxiety and greater increase in measures of general psychologic well-being.     

Influence of age and moderate-intensity exercise training on heart rate variability in young and mature adults.

The purpose of this study was to examine the influence of age and moderate-intensity exercise training on heart rate variability (HRV), and to elucidate further the mechanism of training-induced bradycardia and cardioprotection. Electrocardiograms were recorded from 12 young (18-24 yrs) and 12 mature (29-43 yrs) individuals during supine rest and submaximal moderate exercise. Recordings were obtained prior to, midway, and following 16 weeks of aerobic exercise training designed to improve cardiorespiratory fitness and health. Training resulted in augmented estimated VO2max and bradycardia during rest and submaximal exercise. Total and low frequency components of HRV during exercise were significantly increased for the mature subjects following training whereas other measures of HRV were not significantly changed for either group. It was concluded that training of moderate intensity was insufficient to induce changes in the autonomic control of heart rate for young to mature subjects. The lack of significant HRV changes may suggest the existence of a vagal critical point, below which training-induced increases in vagal modulation may be forthcoming, and above which changes in vagal modulation may be negligible. Training-induced bradycardia and the cardioprotective effect of regular aerobic exercise may result from factors other than an increased vagal modulation.