Establishing the validity of a novel passive stress task

Laboratory tasks used to elicit a cardiovascular stress response in the laboratory can involve either active or passive coping. However, in previous work, passive stress tasks often incorporate a distinct physical stress element, such as the handgrip or cold pressor task, meaning observed changes in cardiovascular parameters may be the result of the physical element of the stressor rather than truly reflecting psychological stress. The present study aimed to establish the validity of a psychological passive stressor; one more analogous to active tasks than those previously employed in laboratory studies. Twenty-six young, healthy adults completed a speech task in the laboratory following a resting baseline period. Twelve months later, they were invited back to the laboratory and watched the video recording of their speech. Analyses confirmed that while both tasks elicited significant SBP and DBP change (all ps < .001), only the active task was associated with HR and CO reactivity (both ps < .001), while only the passive task was associated with TPR reactivity (p = .028). Furthermore, the passive stressor was associated with a mixed hemodynamic profile, whereas the active stressor was associated with a clear myocardial profile. This study confirms that watching a video recording of oneself complete a speech task is associated with a more vascular response profile, a response associated with passive coping contexts.     

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.     

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.     

The ability of active versus passive coping tasks to predict future blood pressure levels in normotensive men and women

Casual blood pressure (BP) after a 2-year follow-up interval was determined in 40 normotensive men and women (20 Blacks and 20 Whites), who had been initially tested for cardiovascular responses to a variety of active and passive coping tasks, including active speech, passive speech, reaction time, and forehead cold pressor tasks. Stepwise multiple regression analyses were used to identify the best model for predicting follow-up BP. Average systolic blood pressure (SBP) level during cold pressor stress was the single most powerful predictor of casual SBP over 2 years even after controlling for initial resting SBP. Other predictors of follow-up SBP were initial SBP, parental history of hypertension, and heart rate and SBP during passive speech (final model R(2) = .78). For follow-up diastolic blood pressure (DBP), the only significant predictors were initial DBP and male gender. These results contribute to a growing body of literature that suggests that cardiovascular measures observed during stressors have predictive validity above and beyond that of traditional predictor variables.     

Airflow and autonomic responses to stress and relaxation in asthma: the impact of stressor type.

The impact of stress on respiratory airflow in asthmatics is unclear. Part of the uncertainty may spring from the different physiological effects of different stressors. Given their potential to elicit increases in parasympathetic vagal activity, stressful situations that present few opportunities for coping (passive coping stressors) may be particularly problematic for people with asthma. Thirty-one adult asthmatics participated in a protocol including a widely used passive coping stressor (the cold pressor test), an active coping stressor (mental arithmetic), an interview about an upsetting asthma-related incident (viewed as a potential passive coping stressor given the exposure to unpleasant memories), and progressive muscle relaxation. Repeated measurements of airflow (via peak expiratory flow), vagal tone (via heart rate variability), and other variables were obtained. The cold pressor test, asthma interview and progressive muscle relaxation produced significant decreases in airflow compared to the baseline period. The cold pressor test and progressive muscle relaxation produced significant, complementary increases in vagal tone. These results suggest that passive coping stressors and other stimuli (e.g., certain forms of relaxation) that elicit increased vagal tone may be associated with poorer asthma control, a view consistent with a significant negative correlation between the participant's mean vagal tone response to the tasks and score on a measure of asthma self-efficacy.     

Familial influences on heart rate, blood pressure, and self-report anxiety responses to stress: Results from 100 twin pairs

Two hundred healthy adolescent to middle-aged individuals (12–44 years, M= 20 years) were tested in a standardized stress protocol. These individuals comprised 20 monozygotic female, 20 monozygotic male, 20 samesex dizygotic female, 20 same-sex dizygotic male, and 20 opposite-sex dizygotic twin pairs. Familial influences on heart rate, blood pressure, and self-report anxiety responses to four different kinds of stressors (Visual-Verbal Test for Conceptual Thought, mental arithmetic, isometric handgrip, cold pressor) were assessed using biometrical genetic model fitting. Evidence of significant genetic effects on resting heart rate and blood pressure was obtained, providing heritability estimates of .65, .63, and .58 for resting heart rate and systolic and diastolic blood pressure, respectively. Cardiovascular reactivity to the Visual-Verbal Test, mental arithmetic, and the cold pressor test appeared to be primarily influenced by genetic and idiosyncratic (nonfamilial) environmental factors, whereas reactivity to handgrip was more related to effects of the family environment. The results of multivariate model fitting suggested that the genetic effects on reactivity were relatively independent of those affecting resting heart rate and blood pressure and that there was significant overlap of genetic influences on heart rate and blood pressure responses to the two active coping tasks.     

Influence of fitness and gender on blood pressure responses during active or passive stress

We examined hemodynamic and autonomic components of blood pressure responses during active and passive stressor tasks in a sample of young, normotensive men and women who were physically active but differed on fitness (i.e., VO2peak). During the hand cold pressor, increases in systolic blood pressure were inversely related to fitness among women but not men. Regardless of gender, fitter participants had a greater increase in cardiac pace during mental arithmetic, coherent with a decreased cardiac-vagal component of heart rate variability, and a greater compensatory reduction in stroke volume. Fitness was otherwise unrelated to changes in cardiac output and vascular resistance during the stressor tasks. Our findings suggest that cardiorespiratory fitness augments the cardiac-vagal withdrawal that is characteristic of mental arithmetic. The blunted systolic blood pressure response to the hand cold pressor among fitter women suggests that cardiorespiratory fitness should be considered as a covariate in studies that examine the hand cold pressor as a predictor of future hypertension among women.     

Heart rate recovery normality data recorded in response to a maximal exercise test in physically active men

Background

Despite a growing clinical interest in determining the heart rate recovery (HRR) response to exercise, the limits of a normal HRR have not yet been well established.

Purpose

This study was designed to examine HRR following a controlled maximal exercise test in healthy, physically active adult men.

Methods

The subjects recruited (n = 789) performed a maximal stress test on a treadmill. HRR indices were calculated by subtracting the first and third minute heart rates (HRs) during recovery from the maximal HR obtained during stress testing and designated these as HRR-1 and HRR-3, respectively. The relative change in HRR was determined as the decrease in HR produced at the time points 1 and 3 min after exercise as a percentage of the peak HR (%HRR-1/HR_peak and %HRR-3/HR_peak, respectively). Percentile values of HRR-1 and HRR-3 were generated for the study population.

Results

Mean HHR-1 and HHR-3 were 15.24 ± 8.36 and 64.58 ± 12.17 bpm, respectively, and %HRR-1/HR_peak and %HRR-3/HR_peak were 8.60 ± 4.70 and 36.35 ± 6.79 %, respectively. Significant correlation was detected between Peak VO₂ and HRR-3 (r = 0.36; p < 0.001) or %HRR-3/HR_peak (r = 0.23; p < 0.001).

Conclusions

Our study provides normality data for HRR following a maximal Ergometry test obtained in a large population of physically active men.     

Consistency of heart rate and sympathovagal reactivity across different autonomic contexts

Theories that psychophysiological reactivity constitutes a risk factor for coronary artery disease assume that reactivity is a consistent individual characteristic. We tested this assumption by measuring reactivity to three psychologically challenging tasks performed by 22 healthy subjects across different autonomic contexts produced by positional change. Dependent variables included heart rate (HR), low-frequency (LF; 0.04–0.15 Hz) and high-frequency (HF; 0.15–0.50Hz) heart period variability, and the LF/HF ratio. HR (r= .44, p < .05) and LF/HF ratio (r= .48, p= .03) reactivity were modestly correlated across the different autonomic contexts, but HF and LF power reactivity were not. These findings suggest that HR reactivity to psychological challenge is a modestly consistent characteristic of individuals, despite differences in autonomic context. Although the same is true of cardiac sympathovagal balance, reactivity of HF and LF power were less consistent.     

Regulation of cardiac function during a cold pressor test in athletes and untrained subjects

By using (dP/dt)/P of carotid artery pulse, a non-invasive index of cardiac contractility, we examined the regulatory mechanism of cardiac function during a cold pressor test in athletes and untrained subjects. Twenty-four healthy subjects (9 athletes, 8 untrained subjects, and 7 hyperreactors of 4 athletes and 3 untrained subjects with a rise of 15 mmHg or greater in systolic and/or diastolic blood pressure) underwent the cold pressor test according to Hines and Brown (Am Heart J 11:1–9, 1936): immersion of the right hand in 4°C water for 1 min. Although mean blood pressure increased during the cold stress in all the groups, cardiac function differed. In athletes, heart rate and cardiac contractility caused cardiac output to increase while total peripheral resistance (TPR) did not change. In untrained subjects, however, heart rate and cardiac contractility tended to decrease cardiac output and thus TPR increased. In hyperreactors, heart rate and cardiac contractility increased during cold stress, and also TPR increased. After the end of the test, heart rate and cardiac contractility decreased only in untrained group. The findings that during a cold pressor test heart rate and cardiac contractility are enhanced in athletes but depressed in untrained subjects indicate that the state of physical training influences cardiac sympathetic neural reactivity to cold stress, except for hyperreactors.     

Evaluation of Myocardial and Peripheral Vascular Responses During Reaction Time, Mental Arithmetic, and Cold Pressor Tasks

The primary purpose of this study was to examine the covariation of cardiac output and forearm blood flow during reaction time, mental arithmetic, and cold pressor tasks. Cardiac output was indexed using impedance cardiography, whereas impedance venous occlusion plethysmography was used lo index forearm blood flow. Cardiac output increased significantly over resting values in all three tasks, hut the pattern of these increases differed. Large heart rate increases during mental arithmetic and cold pressor tasks more than offset stroke volume decreases; the increases in the reaction time task were due to relatively smaller heart rate increases with stroke volume augmentation. For forearm blood flow, all task levels were higher than resting levels, but only mental arithmetic levels were statistically higher. The correlation between cardiac output and forearm blood flow change was significant for the reaction time task, but not for the mental arithmetic or cold pressor tasks.     

Parental Hypertension and Cardiovascular Response to Stress in Healthy Young Adults

One indicator of elevated risk for subsequent development of essential hypertension is the presence of the disorder in either or both parents. Exaggerated cardiovascular responsivity to stress has also been suggested as a possible precursor to hypertension. This study examined the relationship between parental hypertension and the heart rate (HR), systolic (SBP), and diastolic blood pressure (DBP) levels of 103 healthy college-age men, during two resting conditions and stressful cold pressor and reaction time tasks. Sons of hypertensive parents (N = 25) showed higher HR and SBP than sons of normotensive parents (N = 78) during both rest and stress, but these differences were greatest during the stressful reaction time (RT) task. No reliable differences in DBP were seen. A subsample of 45 subjects, including 14 with hypertensive parents, were also monitored during a second stress, the cold pressor test; only trends toward HR or BP differences related to parental hypertension were seen for this stress, although HR and SBP differences during the RT task were still significant (p<.05) even in this smaller group. Since the incidence of high blood pressure is known to be greater among the offspring of hypertensive parents, these findings suggest that cardiovascular responses to certain types of stress (e.g., active coping tasks) may help predict future risk of hypertension.     

Chronic pain and cardiovascular stress responses in a general population: the Tromsø Study

We tested whether cardiovascular stress responsiveness is elevated in individuals experiencing chronic pain in a large general population sample. Blood pressure (BP) and heart rate (HR) were assessed at rest, during the cold pressor test, and during subsequent recovery in 554 individuals reporting daily chronic pain and 3,082 individuals free of chronic pain. After correcting for potential confounds, differences as a function of chronic pain status were noted for only 5 of 23 cardiovascular outcomes despite very high statistical power. Compared to the pain-free group, the chronic pain group displayed higher baseline HR/mean arterial pressure (MAP) ratio (p = .03), greater systolic BP (SBP) reactivity during the cold pressor test (p = .04), and higher HR/MAP ratio (p = .047) and significantly less SBP (p = .017) and MAP (p = .041) return to baseline during recovery. Findings suggest that changes in cardiovascular stress responsiveness associated with chronic pain are of limited clinical significance and unlikely to contribute to increased cardiovascular risk in the chronic pain population.     

Assessment of cardiac contractility during a cold pressor test by using (d<Emphasis Type="Italic">P</Emphasis>/d<Emphasis Type="Italic">t</Emphasis>)/<Emphasis Type="Italic">P</Emphasis> of carotid artery pulses

The ratio of the first derivative (dP/dt) of a carotid artery pulse to the developed pressure (P), (dP/dt)/P, is an easily measurable, noninvasive index of cardiac contractility even in moderate exercise. We examined the effects of transient cold exposure on cardiac contractility in normal reactors (n = 12) and hyperreactors (an increase in systolic or diastolic pressure >15 mm Hg; n = 6) by using this index. Eighteen healthy participants were subjected to the cold pressor test, which required them to immerse the right hand in chilly water (4°C) for 2 min. Although cold stress maximally increased mean blood pressure during the second minute, it maximally increased heart rate and cardiac contractility after 60 s of immersion in both groups of subjects. Comparing normal reactors and hyperreactors by two-way ANOVA revealed a group × time interaction for heart rate but not for cardiac contractility. These findings suggest that the increase in cardiac contractility during cold-water immersion dose not reflect the levels of heart rate and muscle sympathetic nerve activity, and that the specific responses of cardiac function to a cold pressor test in hyperreactors depends on heart rate rather than cardiac contractility.     

Influence of cold water face immersion on post-exercise parasympathetic reactivation

The aim of the present study was to investigate the effect of cold water face immersion on post-exercise parasympathetic reactivation, inferred from heart rate (HR) recovery (HRR) and HR variability (HRV) indices. Thirteen men performed, on two different occasions, an intermittent exercise (i.e., an all-out 30-s Wingate test followed by a 5-min run at 45% of the speed reached at the end of the 30–15 Intermittent Fitness test, interspersed with 5 min of seated recovery), randomly followed by 5 min of passive (seated) recovery with either cold water face immersion (CWFI) or control (CON). HR was recorded beat-to-beat and vagal-related HRV indices (i.e., natural logarithm of the high-frequency band, LnHF, and natural logarithm of the square root of the mean sum of squared differences between adjacent normal R–R intervals, Ln rMSSD) and HRR (e.g., heart beats recovered in the first minute after exercise cessation) were calculated for both recovery conditions. Parasympathetic reactivation was faster for the CWFI condition, as indicated by higher LnHF (P = 0.004), Ln rMSSD (P = 0.026) and HRR (P = 0.002) values for the CWFI compared with the CON condition. Cold water face immersion appears to be a simple and efficient means of immediately accelerating post-exercise parasympathetic reactivation.     

Cardiovascular stress reactivity tasks successfully predict the hypotensive response of isometric handgrip training in hypertensives

This study aimed to determine whether: (a) isometric handgrip (IHG) training lowers resting blood pressure (BP), (b) cardiovascular reactivity to a serial subtraction (SST), IHG (IHGT), and cold pressor (CPT) task predicts this hypotensive response, and (c) cardiovascular reactivity is attenuated posttraining. Resting BP and cardiovascular reactivity to a SST, IHGT, and CPT were measured in 24 hypertensives (51–74 years) before and after 10 weeks of IHG training (n = 12) or control (n = 12). IHG training lowered resting BP (Δ8/5 mmHg), whereby the decrease in systolic BP was correlated to pretraining systolic BP reactivity to the SST (r = ?.85) and IHGT (r = ?.79; all ps < .01), but not the CPT (r = .34; p > .01). Furthermore, following IHG training, systolic BP reactivity to the SST (Δ7 mmHg) and IHGT (Δ8 mmHg) was reduced (all ps < .01). The results offer promising implications for hypertensives and may provide a tool to identify IHG training responders.     

The relationship between the pressor response to involuntary isometric exercise and the contractile protein profile of the active muscle in man

The present investigation examined the relationship between the pressor response during electrically evoked isometric ankle plantar flexion and the contractile protein profile of the active muscle in seven young men [mean (SD) age, 26 (6) years] and five older men [70 (4) years]. Muscle biopsy samples were taken from lateral gastrocnemius (LG) and soleus (SOL) of each subject. These were analysed for isomyosin composition using non-denaturing pyrophosphate polyacrylamide gel electrophoresis. The degree of association was examined between the cardiovascular changes and the fast isomyosin content of LG and SOL individually and in combination (SOL/LG). In the total subject group there was no association between the heart rate response or the change in systolic blood pressure (BP) and the fast isomyosin composition. However, the change in diastolic BP was significantly associated with the fast isomyosin composition of SOL/LG (diastol-licBP=0.31+0.045%FM SOL/LG,r=0.65,P=0.029). These findings suggest that the magnitude of the peripheral reflex mediated pressor response to isometric exercise and the fast isomyosin content of the active muscle are related.     

Automated physical activity monitoring: Validation and comparison with physiological and self-report measures

Physical activity can be assessed via self-report, via physiological measures such as heart rate and oxygen uptake, or via automated monitor. An electronic accelerometer-based physical activity device (Actigraph) has been reported as an improvement over other activity measurement techniques in terms of utility and accuracy. Four studies provide systematic validation and reliability testing for this device and comparisons with other techniques for assessing daily activities. In the first study, the sensitivity of the Actigraph was determined for differentiating physical activities (walking, running, stair climbing, knee bends) versus sedentary activities (reading, typing, playing video games, and performing a mental arithmetic task). Fifteen healthy adults wore the Actigraph on their wrist during activities; oxygen uptake and heart rate were simultaneously recorded. Results revealed that the Actigraph significantly differentiated between the physical activities (p < .0001) and the sedentary activities (p < .0001). Actigraph counts also correlated significantly with oxygen uptake (r= .73) and heart rate (r= .71) during physical activities (r= .46) and sedentary activities (r= .35), respectively. Test-retest reliability was very high for 12 activities (r= .98). The high level of activity differentiation and strong relationship to oxygen uptake and heart rate suggest the usefulness of this device for behavioral and biomedical studies. However, these studies also indicate that the wrist may not always be the most adequate placement for indexing rate and intensity of daily activities and that further studies are needed to determine the optimal site of monitor attachment. Advantages and disadvantages of self-report, physiological, and automated measures of activity are discussed.     

Evaluation of autonomic neuropathy in diabetes mellitus

Summary Quantitative assessment of signs or symptoms of neuropathy, and the beat-to-beat variation, valsalva, orthostasis, handgrip and cold pressor tests, and measurements of plasma renin and catecholamine excretion rate were performed in 23 diabetic patients and 10 age-matched normal subjects.Significant inverse correlations were found between the clinical score and the beat-to-beat variation (a test of efferent vagus function) (r=-0.72,P<0.0005) or the pressor response to handgrip (possible test of efferent sympathetic integrity (r=-0.55,P<0.005) or the values of both tests combined (r=-0.79,P«0.0005); but not with the other measured parameters. Beat-to-beat variation was abnormal in all 9 diabetics with increased and in 9 of 14 with normal clinical score, whereas only seven and one patient from these subgroups, respectively, had an abnormal Valsalva ratio. The pressor response to handgrip was only slightly reduced in the diabetic patients, with greater tendency in those with abnormal clincal score. Additional possible indices of adrenergic dysfunction such as the pressor response to cold stimulus, plasma renin levels and noradrenaline or adrenaline excretion rates did not differ significantly between normal subjects and diabetics.These findings demonstrate a greater prevalence of parasympathetic as compared to sympathetic impairment in diabetic autonomic neuropathy; the beat-to-beat variation was the most sensitive among the tests used. An assessment of clinical evidence combined with non-invasive functional procedures such as the beat-to-beat variation and handgrip tests provide a valuable and easy to perform tool in the evaluation of diabetic neuropathy.     

The Standardized Mental Stress Test Protocol: Test-Retest Reliability and Comparison with Ambulatory Blood Pressure Monitoring

The mental stress test protocol is used extensively in research, but different laboratories often employ different stress tasks, utilize different dependent variables to index the stress response, and perform different transformations on the gathered data. The present study determined the test-retest reliability of 11 cardiovascular dependent variables during a resting baseline and three common stress tasks: playing a video game, performing a choice reaction-time test, and performing a cold-pressor test. Sixty healthy, middle-aged males underwent testing twice, approximately three months apart. Instructions were delivered via videotape and data were gathered on-line by computer to ensure a standard laboratory environment. Each task elicited significant increases in blood pressure, vascular rigidity, LVET, heart rate, and stroke volume. In addition, the cold-pressor test led to increases in total systemic resistance and mean systolic ejection rate. The absolute levels of the 11 dependent variables were correlated across tasks (partial r, baseline removed, = .06 to .69, 32 of 33 comparisons significant at p<.05), indicating that reactivity to stress generalizes across alternate test forms. The absolute levels also showed significant test-retest reliability (r= .32 to .82; 40 of 44 comparisons significant at p<.05). In addition, for 19 of 33 comparisons, absolute levels showed greater test-retest reliability than change scores derived by subtracting the initial resting baseline value from the stress-task value. Finally, blood pressures taken during the stress tests were more highly correlated with the average blood pressures measured via ambulatory monitoring than casual office pressures, suggesting that such stress values may more accurately reflect average blood pressure.