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.     

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.     

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.     

Comparison of the Salivary Changes Associated With a Relaxing and With a Stressful Procedure

This study examined the hypothesis that salivary characteristics could constitute objective measures of anxiety in response to anxiety-reducing or provoking interventions. Salivary parameters (volume, turbidity, pH, proteins, amylase, calcium, and chloride) of 16 normal volunteers were recorded along with psychophysiological (EMG, skin conductance level and responses, skin temperature, and heart rate) and subjective (Mood Adjective Check List) measures, before and after two contrasting experimental interventions: a relaxation procedure and stressful intellectual tasks. Multivariate and univariate analyses of variance indicated that salivary characteristics did not vary differentially whether a relaxing or stressing procedure was executed, while these contrasting interventions induced clearly opposite psychophysiological and subjective responses. However, the saliva collected before and after the stressing session was different from the sample collected before and after the relaxation session, suggesting that salivary characteristics are more related to the general apprehension and demands of a given situation than to an immediate stressing or calming intervention. It is concluded that the psychological meaning of salivary responses differs from that of the more classical psychophysiological parameters.     

Psychophysiological response patterns to positive and negative film stimuli

The aim of the present study was to investigate differential emotional response patterns to film stimuli by multimodal assessment of mood ratings, perception of bodily sensations, salivary cortisol, autonomic variables and facial electromyogram (EMG). Film stimuli, chosen to elicit positive and negative emotional states, were presented to 12 subjects with general anxiety disorder and 12 controls. Changes in mood, bodily sensations, autonomic activity (heart rate, respiration rate and skin conductance), facial EMG activity (corrugator and zygomatic muscle region) and salivary cortisol were measured. Analyses revealed differential changes in all response systems except for respiration rate and salivary cortisol. Although high-anxious subjects did not differ from controls in their average responses to the negative film stimuli, there is a tendency of a greater coherence of emotional response components in generalized anxiety subjects. However, spontaneous facial expressions to positive and negative film stimuli were associated with augmented electrodermal activity within both groups. Results are interpreted in light of directional response fractionation, dimensional approaches of emotion, and the facial feedback literature.     

Autonomic and hypothalamic-pituitary-adrenal stress resilience: Impact of cardiac vagal tone

Resilience refers to the ability to cope with stressful events. Variation in the activity of the stress-responsive sympatho-adrenal-medullary and hypothalamic-pituitary-adrenal axes is particularly important for adaptive stress responses and thus may give rise to individual differences in resilience. Here, we investigated whether cardiac vagal tone and adult attachment style are related to psychophysiological stress resilience by exposing a sample of healthy young men and women (n = 68) to a laboratory stress test while monitoring autonomic (heart rate, salivary alpha-amylase), hypothalamic-pituitary-adrenal (salivary cortisol), and psychological stress levels. Our results demonstrate that adult attachment style did not influence autonomic, hypothalamic-pituitary-adrenal, or psychological stress responses. In contrast, higher resting cardiac vagal tone was associated with stress-induced increases in cortisol. This suggests a role for sympathetic influences on heart rate regulation in hypothalamic-pituitary-adrenal stress responses, and extends previous observations of a link between vagal tone and stress resilience.     

Effects of expectancy on physiological responsivity in novice meditators

Forty non-meditators were randomly assigned to 4 experimental cells devised to control for order and expectation effects. The subjects (all female) were continuously monitored on 7 physiological measures during both meditation and rest. Each subject was her own control in an 'abab' experimental paradigm comparing meditation to rest. The subjects, meditating for the first time, showed marginally lower psychophysiological arousal during the meditation than rest condition for systolic blood pressure, heart rate, skin conductance level and digital skin temperature. Deliberately fostering positive expectations of meditation was associated with lower physiological arousal in terms of diastolic and systolic blood pressure, heart rate and skin conductance level.     

Dissociation of physiology and behavior in PTSD.

We have previously reported that subjects with posttraumatic stress disorder (PTSD) differ from trauma controls in their ability to produce and withhold responses in the Stop-Signal Task depending on the motivational context as determined by financial reward. This experiment measured skin conductance and heart rate to assess autonomic changes accompanying these different patterns of behavior. Fowles hypothesized that heart rate would increase with behavioral activation and that increases in skin conductance would accompany behavioral inhibition. Both PTSD and comparison groups showed the expected behavioral changes in response to rewards, but they differed in their physiological responses. The subjects in the traumatized comparison group showed changes in skin conductance and heart rate consistent with Fowles' hypothesis and the observed changes in behavioral inhibition and activation. However, PTSD subjects showed no significant change in either physiological measure. These results demonstrate a dissociation between autonomic reactivity and motivated behavior in PTSD that may represent one aspect of emotional numbing.     

Anxiety impairs decision-making: psychophysiological evidence from an Iowa Gambling Task

Using the Iowa Gambling Task (IGT) and psychophysiological correlates of emotional responses (i.e., heart rate and skin conductance), we investigate the effects of trait anxiety (TA) on decision-making. We find that high TA is associated with both impaired decision-making and increased anticipatory physiological (somatic) responses prior to advantageous trials. For both high and low TA, skin conductance responses preceding advantageous trials predict decisions. At the same time, somatic responses to choice outcomes reflect differences between high and low TA sensitivities to punishments and rewards. The pattern of impaired decision-making and increased somatic markers that we find in high TA may have important implications for neuropsychological decision theory. In particular, it offers an example of defective modulation of somatic signals, coupled with disrupted discrimination of advantageous and disadvantageous choices.     

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.     

Reproducibility of skeletal muscle vasodilatation responses to Stroop mental challenge over repeated sessions

Skeletal muscle blood flow responses to stress have implications for psychobiological disease pathways. An important assumption underlying psychophysiological studies relating stress reactivity with disease risk is that individuals are characterized by stable response profiles that can be reliably assessed using acute psychophysiological stress testing. We examined the reproducibility of forearm vasodilatation, blood pressure, and cardiac responses to a 2 min Stroop mental challenge over two repeated stress sessions that were on average 3.6 months apart. Participants were 21 healthy men and women (aged 21.8+/-3.7 years). Vasodilatation, blood pressure and heart rate responses displayed no habituation between sessions, although there was significantly greater cardiac parasympathetic involvement during the second testing session. Significant test-retest correlations between the sessions were observed for both forearm blood flow and heart rate reactivity. These findings demonstrate skeletal muscle vasodilatation responses to repeated stress are robust, so may be a useful psychophysiological indicator in studies of stress reactivity and disease risk.     

The pupil response as an indicator of user experience in a digital exercise game

To study whether psychophysiological indicators are suitable measures of user experience in a digital exercise game (exergame), a laboratory study employing both psychophysiological and self‐report measures was conducted. Sixty‐six participants cycled for 10 min on an ergometer while pupil diameter, skin conductance, and heart rate were measured; afterward, they completed a user experience questionnaire. The participants performed under three experimental conditions varying between subjects: active gaming (participants controlled the altitude of a digital bird by varying their pedal rate in order to catch letters flying across the screen), observing a game (they observed a replay of another participant’s game), and no‐game (blank screen). Only the gaming condition showed evidence for statistically significant pupil dilations—indicating emotional arousal—in response to game events (catching a letter) or corresponding points in time. The observational condition did not differ statistically from the no‐game control condition. Self‐reports also indicated that the gaming condition was rated most fun and least demanding. Other psychophysiological indicators (heart rate, skin conductance) showed no systematic effects in response to game events, rather they steadily increased during training. Thus, pupil responses were shown to be suitable indicators of positive emotional reactions to game events and user experience in a (training) game.     

Psychophysiological Correlates of Electrodermal Lability

This study of 75 college student subjects investigated the psychophysiological correlates of electrodermal lability. Resting-stabile and resting-labile subjects were defined as those who were respectively below and above the median of all same-sex subjects in frequency of nonspecific skin conductance responses during rest, whereas stimulus-stabile and stimulus-labile subjects were those respectively below and above the median in trials to habituation of the skin conductance orienting response. These two classification systems were found to be highly correlated with one another, but not entirely equivalent. With both lability measures, labiles had higher resting skin conductance levels than stabiles and also exhibited larger skin conductance orienting responses to both signal and nonsignal tones. Labiles produced orienting responses with shorter latencies, rise times, and half recovery-times. Resting-labiles also differed from resting-stabiles in the components of the triphasic heart rate response to the tones, having larger decelerative responses. The data are consistent with the view that labiles are better able than stabiles to allocate attentional capacity to environmental events and to respond to changing demands in an attentional situation.     

Human salivary alpha-amylase reactivity in a psychosocial stress paradigm.

Biological indicators for stress reactions are valuable markers in psychophysiological research and clinical practice. Since the release of salivary enzyme alpha-amylase was reported to react to physiological and psychological stressors, we set out to investigate human salivary alpha-amylase changes employing a reliable laboratory stress protocol to investigate the reactivity of salivary alpha-amylase to a brief period of psychosocial stress. In a within-subject repeated-measures design, 24 healthy adults were exposed to the TSST and a control condition on separate days with randomized sequence. Salivary alpha-amylase, salivary cortisol and heart rate were repeatedly measured before, during and after both conditions. Significant differences between psychosocial stress and the rest condition in alpha-amylase activity [F(3.74,86.06)=4.52; P=0.003], cortisol levels [F(4.21,88.32)=12.48; P<0.001] and heart rate [F(1,22)=81.15; P<0.001] were observed, with marked increases before and after stress. The data corroborate findings from other studies that showed increased levels of alpha-amylase before and after psychological stress. We discuss the role of salivary alpha-amylase as a promising candidate for a reliable, noninvasive marker of psychosocial stress.     

Attentional, emotional and hormonal data in subjects of different ages

The differences in attentional style among subjects of different ages and the influence of emotionality on the attentional components were studied for a limited experimental period. Variation in the hormonal data and its relation to behavioural parameters were also evaluated. The subjects enrolled in the study were divided into four age groups (A 18–29, B 30–45, C 46–59, D 60–77 years). The attentional tests involved different types of attention: alert, go/no-go, divided attention and working memory. Emotionality was assessed on the basis of skin conductance, heart rate and frontalis muscle tone. Testosterone (T), free testosterone (fT), non-specifically bound testosterone (NST), sex hormone binding globulin (sHBG), oestradiol, cortisol and adrenocorticotrophic hormone were determined in the plasma. The data were analysed to identify endocrine and behavioural differences related to sex and age. The results showed an influence of age on reaction time (RT) and RT variability. This was particularly evident for groups C and D with respect to A in the simple (alert) and complex RT tests (go/no-go and working memory). Divided attention, with the highest RT, showed a clear distinction between group A and the other groups. The difference in frontalis electromyography (EMG) (test vs control) increased with age, while the autonomic responses (skin conductance and heart rate) did not vary. In most attentional tests, the age-related reduction of RT was associated with increased T, fT and NST and decreased cortisol.     

Electrodermal Nonresponding Among College Undergraduates: Temporal Stability, Situational Specificity, and Relationship To Heart Rate Change

Based on a large screening project, 24 electrodermal nonresponders to nonsignal tones were chosen from an undergraduate population and compared on multiple electrodermal, heart rate, and personality measures to an equal number of randomly selected control subjects. Questions addressed in this study included the reliability of the nonresponder category with repeated testing, its stability across situations, its concurrent relationship with other psychophysiological measures, and its ability to predict scores on more standardized measures of individual differences. It was determined that nonresponders continued to produce smaller specific skin conductance responses (SCRs) during a second testing session two weeks after the initial screening, and these differences remained when subjects were tested under signal conditions. However, 50% of the initial nonresponders did produce SCRs by the completion of all testing. Nonresponders and controls differed on other electrodermal measures as well, with nonresponders producing fewer spontaneous fluctuations under all conditions and lower skin conductance levels during initial screening and under signal conditions. Nonresponders and control subjects also differed in heart rate response during the signal procedure. Control subjects produced the anticipated cardiac deceleration, whereas nonresponders produced a pronounced heart rate increase. The two groups did not differ on measured personality characteristics, but when nonresponders were divided into subgroups based on consistency of response pattern, several differences did emerge.     

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.     

Characterizing the psychophysiological signature of boredom

Research on the experience and expression of boredom is underdeveloped. The purpose of the present study was to explore the psychophysiological signature of the subjective experience of boredom. Healthy undergraduates (n = 72) viewed previously validated and standardized video clips to induce boredom, sadness, and a neutral affective state, while their heart rate (HR), skin conductance levels (SCL), and cortisol levels were measured. Boredom yielded dynamic psychophysiological responses that differed from the other emotional states. Of particular interest, the physiological signature of boredom relative to sadness was characterized by rising HR, decreased SCL, and increased cortisol levels. This pattern of results suggests that boredom may be associated with both increased arousal and difficulties with sustained attention. These findings may help to resolve divergent conceptualizations of boredom in the extant literature and, ultimately, to enhance our understanding and treatment of clinical syndromes in which self-reported boredom is a prominent symptom.     

Psychological Correlates of Nonspecific Skin Conductance Responses

Previous research has indicated that the frequency of skin conductance responses without external stimulation or motor activity is a reliable indicator of psychophysiological states and traits. Some authors have suggested that cognitions elicit nonspecific skin conductance responses. These cognitions may resemble the stimuli that evoke a specific skin conductance response. In a within subjects design (n = 31 graduate students) the onset of nonspecific skin conductance responses triggered a signal for the subject to rate cognitions on several indices. These ratings ("absent" to "fully present") were compared with samples in the absence of phasic electrodermal activity. The subjects' current concerns, negative emotion, subjective arousal, and inner speech were rated to be significantly more intense at the time of nonspecific skin conductance responses compared to electrodermal nonresponding periods. Cognitive processes seem to be concomitants of nonspecific skin conductance responses.     

Simulation of the geomagnetic field experienced by the International Space Station in its revolution around the Earth: effects on psychophysiological responses to affective picture viewing

There is evidence suggesting that exposure to an abnormal magnetic environment may produce psychophysiological effects related to abnormalities in responses to stress. This may be of relevance for space medicine where astronauts are exposed to a magnetic field different from that exerted by the Earth. Aim of this study was to assess how the exposure of the head to a magnetic field simulating the one encountered by the International Space Station (ISS) during a single orbit (90 min) around the Earth affects the cardiovascular and psychophysiological parameters. Twenty-four human volunteers were studied double blindly in random order under sham and magnetic exposure. During exposure, the persons were shown a set of pictures of different emotional content while subjective self-rating, skin conductance (SC), blood pressure (BP), and heart rate (HR) were measured. In addition, BP, HR, and tooth pain threshold were assessed before and after exposure. While subjects were under magnetic exposure, skin conductance was strongly differentiated (F_2,36 = 22.927; p = 0.0001), being high during emotionally involving (positive and negative) pictures and low during neutral pictures. Conversely, when subjects were under sham exposure, no significant differences were observed. There was, however, a trend for higher heart rate during picture viewing under magnetic exposure as compared to sham exposure. No effects were found for the other variables. These results suggest that an abnormal magnetic field that simulates the one encountered by ISS orbiting around the Earth may enhance autonomic response to emotional stimuli.