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.     

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.     

Influence of a brief aerobic training program on heart rate and subjective response to a psychologic stressor

An experiment was conducted to determine whether a brief program of aerobic exercise would reduce the heart rate and subjective responses of high- and low-fit subjects to a psychologic stressor. Thirty-four high-fit and 34 low-fit subjects were exposed to a moderate stressor (recall of digits backwards test) while their heart rates and subjective responses were monitored. Approximately half of the high- and low-fit subjects then participated in a 13-week aerobic exercise training program, whereas the other subjects did not. After the 13-week period, the subjects were again exposed to the stressor. Results indicated that a) in the pretest the low-fit subjects showed a greater heart rate response to the stressor than the high-fit subjects, b) the training program was effective for increasing subjects' levels of aerobic fitness, and c) the training program was effective for reducing the heart rate response to the stressor of low-fit subjects. These findings provide support for the relationship between fitness and the response to psychologic stressors and they suggest that aerobic training may be an effective way of helping low-fit persons deal with psychologic stressors.     

Differential effects of active and passive laboratory stressors on immune function in healthy men

The immunomodulatory effects of acute laboratory stressors were examined by comparing active and passive stressors in a between-subjecls design. Healthy male volunteers (N = 67) were recruited and randomly assigned to an active. passive, or no stressor condition. Subjects were exposed to either the Stroop and mental arithmetic tasks (active), two surgery films (passive), or two nature films (no stress). Cardiovascular reactivity, plasma catecholamines and Cortisol. and self-reported distress were measured pretask and posttask. Lymphocyte proliferation to concanavalin A (Con A), pokeweed mitogen (PWM), and phytohemagglutinin was assessed at baseline, after the first task, after the second task, and 30 min later. Lymphocyte proliferation to Con A and PWM was significantly reduced in response to the stressors. Different response patterns emerged, depending on the type of stressor and the mitogen used. Changes in lymphocyte proliferation were significantly associated with cardiovascular reactivity during the tasks. Results are discussed in terms of potency of the stressors and mechanisms underlying passive versus active laboratory tasks. Implications for future research are addressed. This study was supported by Uniformed Services University of the Health Sciences Grant R0726S     

Parental History of Essential Hypertension, Active Coping, and Cardiovascular Reactivity

Differences in cardiovascular reactivity to stress between individuals with and without a family history of essential hypertension (EH) may be affected by stimulus characteristics and/or individual differences in behavioral response. Twenty-four male students with a parental history of EH and 24 without a parental history of EH participated in two laboratory sessions during which two “active’ (mental arithmetic and the Stroop word-color interference test) stressors and one “non-active’ (isometric hand-grip) stressor were presented. Family history subjects exhibited greater systolic blood pressure responses than non-family history subjects only to the two active stressors in Session 2, despite the fact that, overall, isometric hand-grip elicited the largest responses. High-performing Stroop subjects with a parental history of EH displayed greater heart rate responses to the task than high-performing subjects without a parental history of EH in both sessions. No group differences appeared among poor performers. The degree to which a stressor encourages active coping behavior appears to be one determinant of differences in cardiovascular response between individuals with and without a family history of EH.     

The Effects of Stress on Natural Killer Cell Activity in Healthy Men1

Several studies have shown that exposure to acute laboratory stressors produces an immediate change in immune function. We examined the effects of a mild laboratory stressor on natural killer (NK) cell cytotoxicity and on psychological and cardiovascular measures in 24 adult males. Subjects in the experimental condition worked on the Stroop task without interference for 30 min with blood samples drawn at baseline, 10, 20, and 30 min into the task, and 40 min after completing the task. The 30-min stressor produced increases in self-reported stress and tension, and in SBP, DBP, and HR. It was also associated with a decrease in NK cell cytotoxicity 40 min after the stressor. Results are discussed in relation to the effects of mild and intense stressors and future research implications.     

Psychophysiological responses to the Stroop Task after a maximal cycle ergometry in elite sportsmen and physically active subjects.

Physical fitness moderates the psychophysiological responses to stress. This study attempts to determine whether the degree of fitness could affect the response to physical and psychological stress after comparing two groups of men with good physical fitness. Saliva samples from 18 elite sportsmen, and 11 physically active subjects were collected to determine hormonal levels after carrying out a maximal cycle ergometry. Heart rate and skin conductance level were continuously recorded before, during, and after a modified version of the Stroop Color-Word Task. With similar scores in trait anxiety and mood, elite sportsmen had lower basal salivary testosterone, testosterone/cortisol ratio, and HR before an ergometric session than physically active subjects, but no differences were found in salivary cortisol and blood pressure. Salivary testosterone and cortisol responses were lower and testosterone/cortisol ratio responses higher in elite sportsmen. During the Stroop Task, elite subjects showed lower heart rate and skin conductance level over the entire measurement period, and greater heart rate recovery with respect to the baseline values than physically active subjects. The effects of two standardised laboratory stressors on a set of psychophysiological variables were different when elite sportsmen and physically active subjects were compared.     

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.     

The effect of noise interference, type of cognitive stressor, and order of task on cardiovascular activity

In the search for reliable, easily applicable mental stressors many researchers have investigated the propensity of mental arithmetic and Stroop color discrimination tasks to elicit a physiological stress response; some researchers have added noise interference with the expectation of larger response magnitudes. The present study investigates a number of previously untested questions by directly comparing cardiovascular responses to mental arithmetic or the Stroop task with and without noise interference in a sample of 66 young adults. Half of all subjects were exposed to the additional noise interference, all subjects responded to both types of mental stressors. Blood pressure responses did not discriminate among the stressors but noise interference consistently augmented heart rate responses during mental arithmetic. Response to the second, repeated stressor was associated with highly significant response habituation effects for blood pressure. Furthermore, when mental arithmetic was presented first, both tasks elicited comparable and large responses; when the Stroop test was presented first both tasks triggered smaller responses but of comparable magnitude. Subjective evaluations of the stressors were not predictive of overall physiological response.     

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.     

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.     

The limit to exercise tolerance in humans: mind over muscle?

In exercise physiology, it has been traditionally assumed that high-intensity aerobic exercise stops at the point commonly called exhaustion because fatigued subjects are no longer able to generate the power output required by the task despite their maximal voluntary effort. We tested the validity of this assumption by measuring maximal voluntary cycling power before (mean ± SD, 1,075 ± 214 W) and immediately after (731 ± 206 W) (P < 0.001) exhaustive cycling exercise at 242 ± 24 W (80% of peak aerobic power measured during a preliminary incremental exercise test) in ten fit male human subjects. Perceived exertion during exhaustive cycling exercise was strongly correlated (r = −0.82, P = 0.003) with time to exhaustion (10.5 ± 2.1 min). These results challenge the long-standing assumption that muscle fatigue causes exhaustion during high-intensity aerobic exercise, and suggest that exercise tolerance in highly motivated subjects is ultimately limited by perception of effort.     

Infertility: Altered responses to stress in women undergoing in-vitro fertilization and recipients of oocyte donation

Clinical impressions suggest the presence of considerable anxietyand depression in infertile couples. We utilized a psychologicalstress test to assess adaptations to provoked stress to improvethe psychological profile of infertile women. A psychologicalstress test was administered to four groups: normal menstruatingfemales (controls, n = 13); oocyte donors (n = 13); recipientsof oocyte donation (n = 7); and women undergoing standard in-vitrofertilization (IVF; mean age 38.0 years; n = 8). The psychologicalstress test consisted of three active coping tasks: (i) serialsubtraction, (ii) Stroop colour test, (iii) speech task and(iv) one passive coping task, the cold-pressor test. Haemo-dynamicresponses (HD) were monitored before, during and after the psychologicalstress test, and serum samples were drawn for catecholaminesand cortisol. Baseline blood pressures were similar among groups.The psychological stress test elicited different biophysicalresponses in controls compared with the other groups (P <0.001). Oocyte donors had different speech task responses frombaseline, although these and the other parameters of the psychologicalstress test were not different from either the recipient orIVF groups. Blood pressure responses from baseline were bluntedin both recipients and standard IVF patients following provokedstress. Baseline cortisol and norepi-nephrine were similar amongall groups, yet provoked stress elicited a significant increasein controls (142.0 ± 25.2%, P < 0.001) compared withoocyte donors (17.1 ± 19.7%), recipients and standardIVF patients (mean –15.5 ± 17.3% respectively).Norepinephrine responses were apparently greater in controls(60.1 ± 13.1%) compared with oocyte donors (41.8 ±27%) and recipient and IVF groups combined (21.7 ± 12.4%)but this result was not significant. These data suggest thatinfertile women have blunted biophysical and biochemical reactionsto provoked behavioural stressors. Oocyte donors demonstrateblunted passive coping responses similar to those of infertilewomen, yet still respond to active coping stressors in a mannersimilar to that of normal controls. Our data suggest that infertilitytherapy combined with the anticipation of success or failureresults in blunted patterns of response to passive coping stressors.However, blunted active coping responses are unique to infertilewomen.     

Protective effect of interval exercise on psychophysiological stress reactivity in children

Two studies determined whether interval exercise reduces children's stress reactivity. For Experiment 1 children completed interval exercise ( n =14) or watched TV ( n =14) for 25 min. After 20 min rest children completed a speech task. Speech-induced diastolic blood pressure (DBP) reactivity was dampened in the exercise group ( p <.05). For Experiment 2 children ( n =22) completed interval exercise-speech and TV-speech conditions on separate days. Physical activity was assessed by accelerometry and aerobic fitness estimated by submaximal exercise. DBP, systolic BP, and heart rate (HR) reactivity to the speech stressor were dampened ( p <.05) after exercise compared to TV watching. Fitness was positively associated with HR reactivity. Interval exercise that mimics usual patterns of physically active play dampens cardiovascular reactivity to interpersonal stress.     

The effect of laboratory stressors on glycemic control and gastrointestinal transit time

This study compared effects of an active coping task (computerized stressors involving arithmetic, anagrams, and Atari games) and a passive coping task (cold pressor) on gastrointestinal transit time and glycemic response to an oral glucose load. Eleven normal weight males were studied; subjects participated in three counterbalanced sessions, each including a 45-minute baseline, 20-minute experimental period (active coping, passive coping, or nonstress control) and 2.5-hour recovery period. The stressors produced different cardiovascular and catecholamine responses; systolic and diastolic blood pressure were highest during cold pressor (p less than 0.001), heart rate was highest during computer stressor (p less than 0.001), and norepinephrine excretion was greatest during cold pressor (p less than 0.002). However, both stressors delayed gastrointestinal transit time compared with the control condition (p less than 0.009 and p less than 0.026 for cold pressor and computerized stressor, respectively) and both delayed the time of peak glucose response (p less than 0.002 and p less than 0.05, respectively). Implications of these findings for patients with diabetes and for effects of stress on eating behavior are discussed.     

Association of Aerobic Fitness with Pulse Rate and Subjective Responses to Psychological Stress

Ten high fit and 10 low fit subjects first sat quietly during a baseline period and then participated in a mildly stressful task (recall of digits backwards). Pulse rates and levels of subjective arousal were assessed during the baseline period and during the task performance period. Initial analyses indicated that task performance resulted in general increases in pulse rates, subjective cognitive arousal, and subjective somatic arousal. More importantly, it was found that high fit subjects evinced a smaller pulse rate increase in response to stress than did low fit subjects, but the high and low fit subjects did not differ in their subjective responses to stress. These results are consistent with a growing body of research which indicates that a high level of aerobic fitness is associated with reduced physiological reactivity to psychological stress.     

Aerobic exercise intensity and time of stressor administration influence cardiovascular responses to psychological stress

This study examined cardiovascular responses as a function of time following exercise in which participants were exposed to a laboratory stressor. Ninety (42 women) young (18-35 years old) nonsmoking normotensive participants engaged in 30 min of high and low intensity (75-80% and 50-55% VO(2) max) aerobic exercise and a sedentary control condition. Participants were randomly assigned to a laboratory stressor 5, 30, or 60 min following the exercise bout. Results indicate that low and high intensity exercise significantly reduce heart rate (HR) and systolic and diastolic blood pressure reactivity and HR recovery values. An inverse relationship between intensity of exercise and subsequent cardiovascular reactivity was found. These findings suggest attenuated stress responses following acute exercise depend both on exercise intensity and the time of exposure to psychological stress following exercise.     

The Relationship Between Cardiovascular Responses in the Laboratory and in the Field

The psychophysiological responses to laboratory stressors are often examined because it is believed that such responses relate to responsiveness in real life situations. This belief has seldom been tested. The changes in heart rate, pulse transit time, and respiration rate produced by a variety of laboratory tasks (active and passive coping and physical exercise) were related to ambulatory measures of heart rate in 32 young men. The field measures were the difference in heart rate between the waking day and when asleep, and estimates of the variability of heart rate during the day, derived from time series analyses. Average changes in heart rate and pulse transit time during specific tasks did not relate consistently to heart rate in the field. However, an active coping index, derived from the ratio of the peak heart rate during an active coping task to the peak during physical exercise related to all the field measures of heart rate responsiveness. This index, which may relate to measures of additional heart rate and heightened sympathetic response to stress, also correlated positively with Trait Anxiety and elevated basal sympathetic arousal, as measured by skin conductance level. Measures of the cardiovascular response to a passive coping task, the cold pressor, and exercise did not relate to heart rate responses in the field. The findings suggest that heightened cardiac responsiveness in real life is exhibited by subjects who show elevated peak responses to active coping stressors specifically.     

Intraocular pressure changes: the influence of psychological stress and the Valsalva maneuver

The effects of psychological stress and the Valsalva maneuver on short-term variations of intraocular pressure (IOP) were studied in 49 healthy adults. Psychological stress consisted of mental arithmetic tasks presented in counterbalanced order by computer and by the experimenter. Additionally, a standardized Valsalva maneuver was performed (in counterbalanced order with the psychological stressors). IOP was measured with a Goldmann tonometer before and after performance of each stressor. All three stressors transiently and highly significantly increased IOP, although the Valsalva maneuver produced changes of a greater magnitude (10.2 mmHg) than the psychological stressors (1.3 mmHg). Subjective stress ratings and heart rate increased in response to all stressors. There were no effects of task sequence, eye muscle tension, sex, smoking status (some smokers misreported their smoking status), or regular marijuana use, but regular physical exercise was associated with less IOP increase during psychological stress.     

Aerobic exercise improves hippocampal function and increases BDNF in the serum of young adult males

Physical activity has been reported to improve cognitive function in humans and rodents, possibly via a brain-derived neurotrophic factor (BDNF)-regulated mechanism. In this study of human subjects, we have assessed the effects of acute and chronic exercise on performance of a face-name matching task, which recruits the hippocampus and associated structures of the medial temporal lobe, and the Stroop word-colour task, which does not, and have assessed circulating concentrations of BDNF and IGF-1 in parallel. The results show that a short period of high-intensity cycling results in enhancements in performance of the face-name matching, but not the Stroop, task. These changes in cognitive function were paralleled by increased concentration of BDNF, but not IGF-1, in the serum of exercising subjects. 3 weeks of cycling training had no effect on cardiovascular fitness, as assessed by VO₂ scores, cognitive function, or serum BDNF concentration. Increases in fitness, cognitive function and serum BDNF response to acute exercise were observed following 5 weeks of aerobic training. These data indicate that both acute and chronic exercise improve medial temporal lobe function concomitant with increased concentrations of BDNF in the serum, suggesting a possible functional role for this neurotrophic factor in exercise-induced cognitive enhancement in humans.