Hemodynamic mechanisms of the attenuated blood pressure response to mental stress after a single bout of maximal dynamic exercise in healthy subjects

To determine the hemodynamic mechanisms responsible for the attenuated blood pressure response to mental stress after exercise, 26 healthy sedentary individuals (age 29 ± 8 years) underwent the Stroop color-word test before and 60 min after a bout of maximal dynamic exercise on a treadmill. A subgroup (N = 11) underwent a time-control experiment without exercise. Blood pressure was continuously and noninvasively recorded by infrared finger photoplethysmography. Stroke volume was derived from pressure signals, and cardiac output and peripheral vascular resistance were calculated. Perceived mental stress scores were comparable between mental stress tests both in the exercise (P = 0.96) and control (P = 0.24) experiments. After exercise, the systolic blood pressure response to mental stress was attenuated (pre: 10 ± 13 vs post: 6 ± 7 mmHg; P < 0.01) along with lower values of systolic blood pressure (pre: 129 ± 3 vs post: 125 ± 3 mmHg; P < 0.05), stroke volume (pre: 89.4 ± 3.5 vs post: 76.8 ± 3.8 mL; P < 0.05), and cardiac output (pre: 7.00 ± 0.30 vs post: 6.51 ± 0.36 L/min; P < 0.05). Except for heart rate, the hemodynamic responses and the mean values during the two mental stress tests in the control experiment were similar (P > 0.05). In conclusion, a single bout of maximal dynamic exercise attenuates the blood pressure response to mental stress in healthy subjects, along with lower stroke volume and cardiac output, denoting an acute modulatory action of exercise on the central hemodynamic response to mental stress.     

Sex differences in blood pressure responses to mental stress are abolished after a single bout of exercise: underlying hemodynamic mechanisms

We aimed to investigate whether the pressor responses to mental stress (MS) are exaggerated in men due to heightened cardiac responses, before and after a bout of exercise. Fifteen men and 19 women underwent a protocol consisting of blood pressure (BP), cardiac output (CO) and forearm vascular assessments at baseline and during MS, and these measurements were performed before and 60 min after a bout of exercise. Before exercise, BP response was significantly augmented in men (Δ16 ± 2 mmHg) compared to women (Δ11 ± 1 mmHg). This BP response was accompanied by greater increases in CO in men and similar vascular responses between sexes. After exercise, BP and CO responses to MS were attenuated in men and, consequently, no sex differences were observed. Vascular responses were not affected by exercise. The mechanism underlying the lack of sex differences in BP response to MS after exercise was found to be a marked attenuation in CO in men only.     

Relationship between blood pressure reactions on an ergometric and an emotional stress test

Summary The relationship between blood pressure reactions on an ergometric and an emotional stress test was studied in a population of 62 normotensive subjects. Significant correlations for systolic (r=0.34,p=0.004) and diastolic (r=0.30,p=0.01) blood pressure were found.It is concluded that 1) there is a individual-specific blood pressure reactivity, 2) Hypertension is closely related to the individualspecific systolic blood pressure reactivity for it is known that hypertensives exhibit stronger systolic blood pressure reactions on both stressors.     

Skin vascular response in the hand during sinusoidal exercise in physically trained subjects

The effect of physical training on the cutaneous vascular response during transient exercise load is unclear. We determined the phase response and amplitude response of cutaneous vascular conductance (CVC) in the hand during sinusoidal exercise in endurance exercise-trained and untrained subjects. Subjects exercised on a cycle ergometer with a sinusoidal load for 32 min. The load variation ranged from 10% [23 (1) W in the trained group, 19 (1) W in the untrained group] to 60% [137 (4) W, 114 (6) W] of peak O₂ uptake, and five different time periods (1, 2, 4, 8, and 16 min) were selected. Skin blood flow in the dorsal hand and palm were monitored by laser-Doppler flowmetry. CVC was evaluated from the ratio of blood flow to mean arterial pressure. During sinusoidal exercise, the amplitude of CVC was smaller in the dorsal hand than palm for shorter periods (1, 2, and 4 min) (P<0.05). The phase lag of CVC was smaller in the dorsal hand than palm for longer periods (8 and 16 min) (P<0.05). The amplitude response did not differ significantly between the two groups. The phase lag of CVC in the dorsal hand (P<0.05) and palm (P=0.06) was larger in the trained group than untrained group. These findings suggest that glabrous and nonglabrous skin vascular responses in the hand differ during transient exercise load, and physically trained subjects show a slower vascular response in the two skin areas to exercise stimulation than do untrained subjects.     

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 oxidative stress in response to routine incremental cycling exercise in healthy sedentary subjects

The kinetics of blood markers of the oxidative stress during and after an incremental exercise until the maximal performances is not documented in healthy sedentary subjects. We studied subjects of both sexes cycling on an ergometer until or near the V(O)(2)(max) measurement, and we measured during exercise and a 30-min recovery period the plasma concentration of thiobarbituric acid reactive substances (TBARS) which explored the production of reactive oxygen species (ROS) and two antioxidants (plasma reduced ascorbic acid (RAA) and erythrocyte reduced glutathione (GSH)). Despite we noted inter-individual differences in the instants of maximal variations of TBARS, GSH, and RAA, they were all measured within the first 20 min of the post-exercise recovery period, and at the 30th min of recovery, the three ROS blood markers tended to recover their pre-exercise levels. The maximal TBARS increase was positively correlated with V(O)(2)(max) and negatively correlated with the magnitude of RAA consumption. Our results indicate the existence of an early post-exercise oxidative stress in healthy sedentary volunteers. They also show that the ROS production is proportional to the maximal aerobic power and inversely related to the consumption of plasma antioxidants.     

Postural stability of hemodynamic responses during mental challenge

Laboratory stress testing is typically conducted while subjects are seated, whereas real-life stressors may often be encountered while standing. The present study of 20 healthy young men evaluated blood pressure and underlying hemodynamic adjustments to a standardized mental arithmetic task performed twice while seated and twice while standing. Blood pressure increased during mental arithmetic in both postures, but the underlying hemodynamic determinants of the pressor responses were different for the two postures. Augmented cardiac output was responsible for increasing blood pressure during seated task performance, whereas increased vascular resistance was the mechanism for the pressor response to the task performed while standing. Blood pressure and hemodynamic responses were reproducible subject characteristics for a given posture; test-retest correlations were significant for all cardiovascular measures. However, seated blood pressure responses were not significantly correlated with standing blood pressure responses. In contrast, significant between-posture correlations were found for cardiac output and vascular resistance responses. This preliminary evidence of postural stability of the hemodynamic determinants of blood pressure responses during stress is consistent with growing evidence that hemodynamic response tendencies are robust characteristics of reactivity. Ambulatory monitoring of hemodynamic response patterns during real-life stress may reveal more idiosyncratic profiles of stress reactivity than are displayed by blood pressure responses alone.     

Time course and mechanisms of hemoconcentration in response to mental stress

Hemoconcentration with mental stress exposure may be involved in the triggering of acute cardiovascular events. In the present study, hematocrit was measured repeatedly at baseline, during a 4 min mental stress task and during 20 min of recovery. Blood was sampled every 1-2 min throughout. Blood pressure, heart rate and R-wave to pulse interval, a measure of cardiac contractility, were measured with the same periodicity. The stress task elicited a 1.3% increase in hematocrit, which was sustained with full return to baseline level occurring only after 16 min of recovery. Between-subject correlations between hematocrit and hemodynamic activity were low. Aggregate within-subject coefficients were more impressive; the temporal profile of hematocrit correlated significantly with all hemodynamic variables. Similar within-subject analyses indicated that whereas cardiac contractility was correlated with hematocrit both during stress-related increase and subsequent recovery, blood pressure was related to hematocrit only during the increase. This suggests that stress-induced hemoconcentration may driven by different mechanisms than those which underlie its recovery.     

Sex differences in the hemodynamic responses to mental stress: Effect of caffeine consumption

The effect of caffeine on stress responses was compared in 25 men and 22 women in a 2-week placebo-controlled, double-blind, randomized crossover trial. On each week, participants abstained from all dietary sources of caffeine before undergoing a 6-h laboratory protocol under placebo or caffeine exposure followed by a 30-min mental stressor with blood pressure (BP) and cardiovascular hemodynamic assessments. On the placebo session, men and women showed a significant BP increase to stress, although women had significant cardiac responses whereas men had vascular responses. Caffeine ingestion before stress caused both men and women to have enhanced hemodynamic responses to the stressor associated with an increase in cardiac index and a drop in the peripheral resistance index. Caffeine enhances the cardiovascular fight-or-flight response pattern to stress in men and women.     

Symptoms of depression and cardiovascular reactions to acute psychological stress: evidence from a population study

Depression and exaggerated cardiovascular reactivity are considered risk factors for cardiovascular disease, possibly as a result of common antecedents, such as altered autonomic nervous system function. We examined the association between depressive symptomatology and cardiovascular reactions to psychological stress in 1608 adults (875 women) comprising 3 distinct age cohorts: 24-, 44-, and 63-year olds. Depression was assessed using the Hospital Anxiety and Depression Scale. Blood pressure and heart rate were measured at baseline and during the paced auditory serial arithmetic test. Depression scores were negatively associated with systolic blood pressure and heart rate reactions, after adjustment for likely confounders such as sex, cohort, occupational status, body mass index, stress task performance score, baseline cardiovascular activity, antidepressant, and antihypertensive medication. The direction of association was opposite to that which would be expected if excessive reactivity were to mediate the association between depression and cardiovascular disease outcomes or if they shared common antecedents.     

The effect of acute aerobic exercise on stress related blood pressure responses: a systematic review and meta-analysis

The beneficial impact of regular exercise on cardiovascular health is partly mediated by psychobiological mechanisms. However, the effect of acute exercise on psychobiological responses is unclear. Thus, we performed a systematic review of randomised controlled trials (RCTs) that examined the effect of acute aerobic exercise on blood pressure (BP) responses (the change from baseline to stress) to psychosocial laboratory tasks. Fifteen RCTs met inclusion criteria of which ten demonstrated significant reductions in post-exercise stress related BP responses compared with control (mean effect sizes for systolic and diastolic BP, 0.38 and 0.40). Studies involving greater exercise doses tended to show larger effects, with the minimum dose to show a significant effect being 30 min at 50% VO2max. No other moderators emerged from the examination of participant characteristics, research designs and stressor characteristics. In conclusion, an acute bout of aerobic exercise appears to have a significant impact on the BP response to a psychosocial stressor.     

Optimism moderates psychophysiological responses to stress in older people with Type 2 diabetes

Optimism is thought to be beneficial for health, and these effects may be mediated through modifications in psychophysiological stress reactivity. Type 2 diabetes (T2D) is associated with reduced cardiovascular responses to stress and heightened cortisol over the day. This study assessed the relationships between optimism, stress responsivity, and daily cortisol output in people with T2D. A total of 140 participants with T2D were exposed to laboratory stress. Heart rate (HR), systolic (SBP), diastolic blood pressure (DBP), and cortisol were measured throughout the session. Cortisol output over the day was also assessed. Optimism and self‐reported health were measured using the revised Life Orientation Test and the Short Form Health Survey. Optimism was associated with heightened SBP and DBP stress reactivity (ps < .047) and lower daily cortisol output (p = .04). Optimism was not related to HR, cortisol stress responses, or the cortisol awakening response (ps > .180). Low optimism was related to poorer self‐reported physical and mental health (ps < .01). Optimism could have a protective role in modulating stress‐related autonomic and neuroendocrine dysregulation in people with T2D.     

Shifting hemodynamics of blood pressure control during prolonged mental stress

The present study examined the hemodynamics underlying blood pressure elevations for evidence of a shift in the control of blood pressure during prolonged mental stress. Mean arterial pressure (MAP), cardiac output (CO), and total peripheral resistance (TPR) were measured at rest, during a 28-min mental arithmetic stress task, and during recovery, in 30 young healthy men and women. The stress task elicited a sustained increase in MAP: CO rose during the first half of the task but returned to baseline levels during the last quarter of the task, whereas TPR increased as the task progressed. When participants' hemodynamic reactions were classified as cardiac, vascular, or neither, there were more cardiac reactors early relative to late in the task, whereas there were more vascular reactors late relative to early. Thus, the sustained pressor response was initially supported mainly by cardiac mechanisms but subsequently by predominantly vascular mechanisms.     

Prolonged platelet activation in individuals with elevated blood pressure in response to a moderate exercise challenge

We examined the magnitude of 20-min moderate exercise-induced platelet activation in 50 volunteers with normal ( n =31) or elevated blood pressure (EBP; n =19). Blood was drawn before, immediately after, and 25 min after exercise. Antibody-staining for platelet activation markers, P-selectin, and fibrinogen receptors was done with and without adenosine diphosphate (ADP) stimulation in whole blood for flow cytometric analyses. Exercise led to increases in percent aggregated platelets and percent platelets expressing P-selectin or PAC-1 binding ( p s≤.001). This increase in percent platelets expressing P-selectin continued even after a 25-min rest only in the EBP group ( p ≤.01) accompanied by an increase in percent of aggregated platelets ( p ≤.05). Although ADP stimulation led to increased platelet activation at rest, it was attenuated following exercise, even among EBP individuals. A moderate exercise challenge induced prolonged platelet activation in individuals with EBP but attenuation in activation to further stimulation by an agonist. Findings suggest that a recovery period after physical stress appears critical in individuals with high BP regarding platelet activation and aggregation, which can lead to an acute coronary syndrome in vulnerable individuals.     

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.     

Differences in muscle sympathetic nerve response to isometric exercise in different muscle groups

The aim of this study was to examine the effects of muscle fibre composition on muscle sympathetic nerve activity (MSNA) in response to isometric exercise. The MSNA, recorded from the tibial nerve by a microneurographic technique during contraction and following arterial occlusion, was compared in three different muscle groups: the forearm (handgrip), anterior tibialis (foot dorsal contraction), and soleus muscles (foot plantar contraction) contracted separately at intensities of 20%, 33% and 50% of the maximal voluntary force. The increases in MSNA relative to control levels during contraction and occlusion were significant at all contracting forces for handgrip and at 33% and 50% of maximal for dorsal contraction, but there were no significant changes, except during exercise at 50%, for plantar contraction. The size of the MSNA response correlated with the contraction force in all muscle groups. Pooling data for all contraction forces, there were different MSNA responses among muscle groups in contraction forces (P = 0.0001, two-way analysis of variance), and occlusion periods (P = 0.0001). The MSNA increases were in the following order of magnitude: handgrip, dorsal, and plantar contractions. The order of the fibre type composition in these three muscles is from equal numbers of types I and II fibres in the forearm to increasing number of type I fibres in the leg muscles. The different MSNA responses to the contraction of different muscle groups observed may have been due in part to muscle metaboreflex intensity influenced by their metabolic capacity which is related to by their metabolic capacity which is related to the fibre type.     

Reduction in extracellular muscle volume increases heart rate and blood pressure response to isometric exercise

Summary To investigate the effect of local dehydration on heart rate and blood pressure during static exercise, six healthy male subjects performed exercise of the calf muscles with different extracellular volumes of the working muscles. Exercise consisted of 5 min of static calf muscle contractions at about 10% of maximal voluntary contraction. The body position during exercise was identical in all tests, i.e. supine with the knee joint 90° flexed. During a 25-min pre-exercise period three different protocols were employed to manipulate the calf volume. In test A the subjects rested in the exercise position; in test B the body position was the same as in A but calf volumes were increased by venous congestion [cuffs inflated to 10.67 kPa (80 mmHg)]; in test C the calf volumes were decreased by lifting the calves about 40 cm above heart level with the subjects supine. To clamp the changed calf volumes in tests B and C, cuffs were inflated to 300 mmHg 5 min before the onset of exercise. This occlusion was maintained for 1 min after the termination of exercise. Compared to tests A and B, the reduced volume of test C led to significant increases in heart rate and blood pressure during exercise. Oxygen uptake did not exceed resting levels in tests B and C until the cuffs were deflated, indicating that only calf muscles contributed to the neurogenic peripheral drive. It is concluded that extracellular muscle volume plays a significant role in adjusting heart rate and blood pressure during static exercise.     

D919G polymorphism of methionine synthase gene is associated with blood pressure response to benazepril in Chinese hypertensive patients

Individual variation in drug response is considered to have multiple origins arising from interactions among susceptible genes and environmental factors. A total of 726 hypertensive patients who took benazepril 10 mg once a day for 15 days and their families from Huoqiu county of Anhui Province, China, were used to study the association between D919G polymorphism of methionine synthase (MTR) gene and the antihypertensive effect of this angiotensin-converting enzyme inhibitor. Compared to the 919D allele, both population-based (P=0.010) and family-based association tests (additive model P=0.018, dominant model P=0.025) demonstrated that the 919G allele was associated with a significantly less diastolic blood pressure reduction. No significant association was found between the extent of systolic blood pressure reduction and benazepril therapy. Our finding suggests that the D919G polymorphism of the MTR gene may be a useful genetic marker to predict the antihypertensive effect of short-term benazepril therapy in hypertensive patients of Anhui Province, China.     

Temperature-induced changes in metabolic and hormonal responses to intensive dynamic exercise

Seven male subjects performed intensive cycle exercise to exhaustion at subnormal muscle temperature (T_m, 29 ± 2.8 °C). Exercise at exactly the same rate of exercise and duration (370 ± 34 W, 1.5 ± 0.15 min) was then repeated with normal T_m (35 ± 0.9 °C). During exercise both the arterial (a) and femoral venous (fv) contents of oxygen were significantly higher at subnormal than at normal T_m, because of the higher haemoglobin concentration, but the a-fv oxygen difference was the same in the two situations. The rate of increase in lactate concentration in both arterial and venous blood during exercise was the same in the two situations. During exercise the plasma concentrations of adrenaline and noradrealine in arterial and venous blood were significantly higher at subnormal than at normal T_m. At rest and after exercise the calf blood flow was significantly reduced at subnormal T_m At the end of exercise the concentrations of glucose-6-phosphate and lactate in the muscle were significantly higher at subnormal T_m than in the muscle of normal temperature. These findings suggest that there was a greater increase in glycolysis in the muscle of subnormal temperature during exercise, possibly as a result of impaired work efficiency and/or reduced blood flow in the cold muscle.     

Contribution of adrenomedullin to homeostatic response to cold stress in rat model

Acute stress known to stimulate sympathetic activity as well as the hypothalamo-pituitary–adrenal (HPA) axis, produces a significant increase in adrenomedullin (ADM) levels in the pituitary gland, plasma and adrenal glands, all of which are key components of HPA axis, suggesting a regulatory or protective role for ADM in countering HPA activation following a variety of physiological and psychological stressors. This study was conducted to assess a rat model for in depth investigation of biochemical mechanisms and consequences of cold stress. Four groups of Sprague–Dawley rats were observed for their serum total protein, glucose, trigliceride and cholesterol levels as well as their blood pressures after housing at room temperature, administration of ADM (1.0 nm/kg), exposing to cold stress (8 °C for 48 h) and exposing to ADM injection in addition to cold stress. The results suggest that application of ADM in addition to cold stress may act via receptors on different end-organs and causes altered metabolic regulation taking partial or total occupation of ADM receptors, stimulated in response to cold application induced physiologic ADM release before pharmacological ADM administration.