The level of physical activity affects adrenal and cardiovascular reactivity to psychosocial stress

Physical activity plays a key role in the control of neuroendocrine, autonomic, and behavioral responses to physical and psychosocial stress. However, little is known about how the level of physical activity modulates stress responsiveness. Here, we test whether different levels of physical activity are associated with different adrenal, cardiovascular, and psychological responses to psychosocial stress. In addition, competitiveness is assessed as a personality trait that possibly modulates the relationship between physical activity and stress reactivity. Eighteen elite sportsmen, 50 amateur sportsmen, and 24 untrained men were exposed to a standardized psychosocial laboratory stressor (Trier Social Stress Test). Repeated measures of salivary free cortisol, heart rate, and psychological responses to psychosocial stress were compared among the 3 study groups. Elite sportsmen exhibited significantly lower cortisol, heart rate, and state anxiety responses compared with untrained subjects. Amateur sportsmen showed a dissociation between sympathetic and hypothalamic-pituitary-adrenal responsiveness to stress, with significantly reduced heart rate responses but no difference in cortisol responses compared with untrained men. Different levels of competitiveness among groups did not mediate stress reactivity. Our results are in line with previous studies indicating reduced reactivity of the autonomic nervous system to psychosocial stress in trained individuals. More importantly, these findings imply a differential effect of the level of physical activity on different stress-related neurophysiological systems in response to psychosocial stress.     

Trained men show lower cortisol, heart rate and psychological responses to psychosocial stress compared with untrained men

Physical activity has proven benefits for physical and psychological well-being and is associated with reduced responsiveness to physical stress. However, it is not clear to what extent physical activity also modulates the responsiveness to psychosocial stress. The purpose of this study was to evaluate whether the reduced responsiveness to physical stressors that has been observed in trained men can be generalized to the modulation of physiological and psychological responses to a psychosocial stressor. Twenty-two trained men (elite sportsmen) and 22 healthy untrained men were exposed to a standardized psychosocial laboratory stressor (Trier Social Stress Test). Adrenocortical (salivary free cortisol levels), autonomic (heart rate), and psychological responses (mood, calmness, anxiety) were repeatedly measured before and after stress exposure. In response to the stressor, cortisol levels and heart rate were significantly increased in both groups, without any baseline differences between groups. However, trained men exhibited significantly lower cortisol and heart rate responses to the stressor compared with untrained men. In addition, trained men showed significantly higher calmness and better mood, and a trend toward lower state anxiety during the stress protocol. On the whole, elite sportsmen showed reduced reactivity to the psychosocial stressor, characterized by lower adrenocortical, autonomic, and psychological stress responses. These results suggest that physical activity may provide a protective effect against stress-related disorders.     

Invited editorial

There is a world-wide trend for children to begin serious athletic training at progressively younger ages. Since there are no data concerning the cardiorespiratory function of Turkish children, the purpose of this study was to compare maximal oxygen uptake in well-trained and untrained children of similar ages. The trained subjects (20) were junior swimmers from a private college swimming team, and the untrained ones (20) were from the same school. Maximal oxygen uptake was directly measured during progressive treadmill exercise using open circuit spirometry. No significant differences in height, mass, and age were noted between the trained and untrained groups. Maximal aerobic power in absolute values and expressed per kilogram of body mass, was 19·57% and 20·06%, respectively: higher in the trained than in the untrained group (p < 0·05). These data suggest that physical training significantly increases maximal aerobic power in young subjects.     

Effect of a six-month aerobic exercise training program on cardiovascular responsivity in healthy middle-aged adults.

The purpose of this study was to determine the effects of a six month aerobic exercise training regimen on cardiovascular responsivity to mental arithmetic in healthy middle-aged men and women. Subjects were randomly assigned to a moderate intensity exercise intervention or to an assessment-only control group. Before and after the intervention subjects' heart rates and blood pressures were measured doing a mental arithmetic task (N = 83). Other physiological and psychosocial measures included the Type A structured interview and a maximal exercise treadmill test. Validated adherence to the exercise regimen exceeded 75% and there were significant increases in aerobic capacity in those subjects receiving exercise training. Exercise did not significantly reduce cardiovascular responsivity to the stress task. Type A behavior did not interact with reactivity across exercisers or controls nor was it significantly correlated with adherence. The results are discussed with respect to factors that have been previously reported to potentially influence the exercise/reactivity relationship.     

Individual responses to aerobic exercise: the role of the autonomic nervous system

It is well established that regular aerobic exercise training reduces all-cause mortality and improves a number of health outcomes. However, a marked heterogeneity in the training-induced changes, e.g. in terms of aerobic fitness, has been observed in healthy human subjects, even with highly standardized training programs. Mean improvements in aerobic fitness, expressed as maximal oxygen consumption, have been about 10-15% of the baseline values, but the training-induced changes have ranged from almost none to a 40% increase. The exact nature of the mechanisms responsible for this heterogeneity in response to regular aerobic exercise is not well known. In this review, we consider evidence of the association between the autonomic nervous system (ANS), aerobic fitness and aerobic training-induced changes in fitness. Results of recent studies support the hypothesis that assessment of ANS functioning includes important information concerning acute and chronic physiological processes before, during and after aerobic exercise training stimulus. Moreover, we show that daily assessment of ANS activity could serve as an indicator of appropriate physiological condition for aerobic training.     

The effects of aerobic and anaerobic training on fitness, blood pressure, and psychological stress and well-being

To determine whether fitness alters psychological and physiological indices of well-being, male police officers were assigned to either an aerobic or anaerobic training condition or to a no treatment control group. The training groups met three times per week in 45 min sessions aimed at improving either cardiovascular endurance or muscle strength. Aerobic fitness level, heart rate, blood pressure and self-report of stress and well-being were measured prior to and following 10 weeks of training. Post-training fitness measures confirmed the effectiveness of training and between group differences for physiological and self-report measures were found. Subjects undergoing aerobic training evinced larger changes on the self-report measures of well-being and stress than the anaerobic trainers and both groups showed significant improvement when compared to controls. This experiment provides support for the hypothesis that exercise, and in particular aerobic exercise, has positive effects of well-being. It is suggested that future research might usefully explore the particular contribution of different aspects of the training situation to these effects.     

Altered cardiovascular adaptability in depressed patients without heart disease

Abstract

Objectives. Despite its clinical importance and relevance for health care policy, the pathways between depression and stress regulation remain poorly understood. The objective of our study was to compare cardiovascular and autonomic responses to brief psychosocial stress in a group of severely depressed subjects without heart disease and a non-depressed control-group. Methods. We recorded cardiovascular and autonomic reactions to two different stress tasks including anger recall and mental arithmetic in a sample of 25 severely depressed and 25 non-depressed subjects. Aggregated data were compared with repeated-measures MANOVA. We used contrasts to evaluate different response patterns concerning cardiovascular and autonomic reactivity vs. recovery. Results. Depressed subjects showed overall reduced high-frequency heart rate variability and an altered cardiovascular adaptability concerning heart rate, blood pressure, cardiac output, and, on a trend level, peripheral resistance. With few exceptions, we found no differences between reactivity vs. recovery response patterns. Conclusions. Our results provide further evidence for altered cardiovascular reactivity and impaired cardiac autonomic functioning in depression. Further research is needed on psychophysiological response to either more disease-oriented or more personality-oriented stressors.     

Training reduces autonomic cardiovascular responses to both exercise-dependent and -independent stimuli in humans

Training attenuates the sympathetic pressor response to dynamic exercise. However, it is uncertain how training alters other patterns of cardiovascular autonomic activation. Therefore, we have quantified circulatory responses to a series of standard autonomic tests in highly fit and unfit subjects and examined the effects of a short-term training programme on these responses. Subjects were defined as either unfit (n = 8) or fit (n = 8) on the basis of training history and a maximal fitness test (VO2peak 54 +/- 2.3 cf. 68 +/- 2.8 (ml min(-1)) kg(-1), means + S.E.M., P < 0.05). On a separate day, the blood pressure, heart rate and forearm vascular conductance responses to a sustained handgrip to fatigue, 2 min mental arithmetic and 2 min of cold exposure were measured. All stimuli were associated with elevated blood pressures and heart rates, but these responses were significantly attenuated in the trained group. In the untrained subjects, forearm vascular conductance increased during exercise (from 0.032 +/- 0.004 to 0.05 +/- 0.007 (ml min(-1)) 100 ml(-1) mm Hg(-1), P < 0.05) and during mental arithmetic (from 0.028 +/- 0.003 to 0.04 +/- 0.006 (ml min(-1)) 100 ml(-1) mm Hg(-1) , p < 0.05), but trained subjects showed no rise in conductance during either test. All untrained subjects undertook a moderate intensity 5-week training programme, which significantly increased VO2peak (54 +/- 2.3 to 57 +/- 2 (ml min(-1)) kg(-1), p < 0.05). Qualitatively similar blunting of pressor, tachycardic and vasodilator responses were seen in this group post-training. These results demonstrate that the blunting of sympathetic vasomotor activation that follows training is not restricted to reflexes associated with exercise, and does not depend on training being prolonged or intense.     

Effects of aerobic exercise training and relaxation training on cardiovascular activity during psychological stress

Students who reported experiencing a high number of stressful life events were randomly assigned to: (a) an aerobic training condition, (b) a relaxation training condition, or (c) a no treatment control condition. Immediately before and after the 11 week training/control period, subjects' aerobic fitness and cardiovascular responses to acute psychological stress were assessed. Results indicated that: (1) subjects in the aerobic training condition showed significantly greater improvements in aerobic fitness than subjects in the other conditions, and (2) the subjects in the aerobic training condition showed significantly greater reductions in heart rate during all phases of the stress than subjects in the other conditions. Post-training differences between aerobic and control conditions during the moderate psychological stress were as great as 17 b.p.m. These results provide evidence for the utility of aerobic training for reducing cardiovascular activity during psychological stress, and they are consistent with earlier findings linking fitness to less illness following stress, reductions in depression and enhanced recovery in cardiac patients.     

Effects of imipramine on the autonomic responses of obsessive-compulsives to auditory tones

It has been argued that a mechanism of clomipramine's efficacy for obsessive-compulsive disorder is its reduction of excessive autonomic reactivity. The present study evaluated this proposed mechanism of action by assessing the effect on autonomic responding of imipramine, which is structurally similar to clomipramine, but lacks therapeutic efficacy for obsessive-compulsives. Twenty-three obsessive-compulsive patients received three sessions of 20 unsignalled 1000-Hz, 100-dB tones of 1-sec duration and 100-msec rise-time. Skin conductance level, response frequency and magnitude, and heart rate were scored for an adaptation period and for each tone onset. Six weeks after the first tone session, during which half of the subjects received imipramine while the remainder received placebo, the second tone assessment was performed. A third tone assessment was performed after an additional 4 weeks of medication. Percentage of nonresponders was also evaluated for each group. Imipramine reduced electrodermal activity and increased heart rate. Skin conductance level and both number and amplitude of responses decreased significantly after 6 weeks of imipramine, compared with placebo, with further attenuation of electrodermal activity after 10 weeks of the drug. Electrodermal nonresponding increased dramatically for the imipramine group as compared to the nondrug group. These results reveal effects of imipramine on autonomic responding, and cast doubt on the hypothesis that a mechanism for successful drug treatment of obsessive-compulsive disorder is decreased autonomic reactivity.     

Interocular transfer in parallel visual pathways in pigeons

Pigeons were trained to perform intensity, color and pattern tasks monocularly. After their training was completed, a unilateral electrolytic lesion was made either in the nucleus rotundus or in the nucleus opticus principalis thalami (OPT). The lesion was made in the trained hemisphere (contralateral to the trained eye) in half of the subjects and in the untrained hemisphere in the other half. After a 7-day recovery period the birds were retrained on the same tasks with the previously untrained eye. A rotundal lesion, on either side, resulted in the loss of interocular transfer of discrimination, whereas neither contralateral nor ipsilateral OPT lesions affected discrimination. These results suggest that the tectofugal visual pathway plays a crucial role in the interhemispheric transfer of visual information in pigeons.     

Psychophysiological reactivity and the prediction of cardiovascular disorders

Two aspects of psychophysiological reactivity that might be relevant to subsequent cardiovascular morbidity were explored in this study. Thirty-six volunteers participated in a single experimental session, during which three taxing cognitive tasks were performed. Interbeat interval, pulse transit time, and respiratory and electrodermal variables were monitored throughout. Large differences between individuals in psychophysiological reactions to the tasks were recorded, and two forms of analysis were therefore performed. Firstly, there is evidence that people exhibiting Type A coronary-prone behaviour pattern show heightened cardiovascular reactions to challenging tasks, and this was tested by administering a student version of the Jenkins Activity Survey. However, high scores on the questionnaire were not associated with interbeat interval or transit time hyper-reactivity. Amongst male subjects the reverse trend was found, since those with scores at the Type B end of the scale produced greater cardiovascular reactions. The second analysis examined the relationship between cardiovascular and other psychophysiological reactions. Cardiovascular responses tended to be coordinated, so that subjects displaying large tachycardias also produced substantial modifications in transit time. Furthermore, haemodynamic hyper-reactivity was not reflected in generalised autonomic lability, since reactive individuals did not show exaggerated responses in electrodermal or respiratory variables. Thus people exhibiting large transit time and heart rate modifications may have specific disturbances in cardiovascular stability, putting them at risk for later haemodynamic disorder.     

Deficits in operant behavior and alteration of CA1, CA3 hippocampal dendritic arborization due to subicular lesions

The deficits in operant behavior and the alterations in dendritic arborizations of Cornu Ammonis 1 and Cornu Ammonis 3 (CA1 and CA3) hippocampal areas were investigated in subicular lesioned rats. The subjects were female Wistar rats aged 120 days, and were divided into four groups: one serving as age-matched untrained control, a second group received training and sham lesioning, a third group were only trained, and the fourth group were first trained and then subjected to subicular lesions. The rats were food-deprived 24 hours prior to operant behavior training sessions. Two training sessions for operant behavior with continuous reinforcement of 10 minutes duration per day were done during the shaping session, following which rats were allowed 10 minutes of operant food reward for 10 days. On the eleventh day, only the operant behavior and sham-operated rats were used for subicular lesion and sham surgery, respectively. After 72 hours of surgical recovery, operant behavioral testing was performed daily as before for a further period of 10 days. Later, all groups of rats were killed and the hippocampus was processed for rapid Golgi staining. Our results suggest that subicular lesions produce a significant reduction in operant learning. Further, the Golgi studies revealed a reduction in dendritic branching points and intersections of apical and basal CA1, CA3 neurons in lesioned rats.     

Exaggerated psychophysiological reactivity: issues in quantification and reliability

Marked physiological reactivity to challenging mental tasks has been associated with elevated risk for, as well as the presence of, coronary heart disease. However, little systematic enquiry into the reliability and quantification of such exaggerated reactivity has emerged. Subjects were 32 male, managerial employees, ranging in age from 22 to 56 yr, who satisfied the following criteria: no history or current signs of heart disease, presence of Type A behavior pattern as revealed by the Structured Interview, and an increase during an initial psychosocial stress testing of at least 25% over baseline in at least three out of five psychophysiological indices. Heart rate, systolic blood pressure, diastolic blood pressure, plasma epinephrine and plasma norepinephrine levels were monitored while challenging mental tasks were performed in three sessions (screening, pretraining and posttraining) spaced several weeks apart. Psychophysiological reactivity during the tasks emerged as a consistent trait. For all five measures, change scores from baseline during the screening session were significantly correlated with change scores during the pretraining session. Moreover, the magnitude of the change scores were similar in the screening and pretraining sessions. Analysis of cross correlations within and between indices provided little support for the use of data transformations such as residual scores or analysis of covariance. Finally, on four out of five measures, the challenging tasks were found to be comparable in the degree of reactivity elicited. These findings suggest that, for selected Type A men, exaggerated psychophysiological reactivity occurs reliably when monitored with multiple indices, appears insensitive to mere passage of time, and can be uniformly elicited by a variety of tasks.     

Learning complex arithmetic--an fMRI study

Aim of the present functional magnet resonance imaging (fMRI) study was to detect modifications of cerebral activation patterns related to learning arithmetic. Thirteen right-handed subjects were extensively trained on a set of 18 complex multiplication problems. In the following fMRI session, trained and untrained problems (closely matched for difficulty) were presented in blocked order alternating with a number matching task and a fact retrieval task. Importantly, left hemispheric activations were dominant in the two contrasts between untrained and trained condition, suggesting that learning processes in arithmetic are predominantly supported by the left hemisphere. Contrasting untrained versus trained condition, the left intraparietal sulcus showed significant activations, as well as the inferior parietal lobule. A further significant activation was found in the left inferior frontal gyrus. This activation may be accounted for by higher working memory demands in the untrained as compared to the trained condition. Contrasting trained versus untrained condition a significant focus of activation was found in the left angular gyrus. Following the triple-code model [Science 284 (1999) 970], the shift of activation within the parietal lobe from the intraparietal sulcus to the left angular gyrus suggests a modification from quantity-based processing to more automatic retrieval. The present study shows that the left angular gyrus is not only involved in arithmetic tasks requiring simple fact retrieval, but may show significant activations as a result of relatively short training of complex calculation.     

Anxiogenic effects of repeated administrations of 20% CO2-enriched air: stability within sessions and habituation across time

Increasingly carbon dioxide-enriched air is being used as an aversive unconditioned stimulus in laboratory examinations of anxiety. Yet, little is known about the stability of the autonomic and subjective effects of this stimulus across repeated inhalations and sessions. We examined whether repeated administrations of high concentrations of CO2-enriched air produced either habituation, stability, or sensitization across several autonomic and self-report indices within one session (Experiment 1) and then several sessions (Experiment 2) of exposure. Results suggest that non-clinical participants do not habituate to CO2 within sessions, but do show habituation on cardiac and subjective report of anxiety across sessions. Individual difference factors such as anxiety sensitivity and suffocation fear seem to moderate some of these effects, including self-reported distress and anxiety in response to the challenge. These results support the use of CO2 as a panicogenic aversive stimulus in laboratory models of fear onset and in clinical settings for interoceptive exposure treatments of panic.     

Effect of changes in cardiac autonomic balance on blood pressure regulation in man

The role of cardiac autonomic balance in fitness-related differences in blood pressure regulation was evaluated by comparing the cardiovascular responses to lower body negative pressure (LBNP) in 10 trained and 10 untrained men. Cardiac autonomic balance was quantified as the ratio of resting heart rate to intrinsic heart rate, and was significantly lower in the trained subjects (0.68 +/- 0.03) than the untrained subjects (0.81 +/- 0.03) indicating a greater parasympathetic dominance at rest in the trained subjects. Arterial pressure decreased significantly more during LBNP in the trained subjects and was due to lower chronotropic and vasoconstrictor responses in these trained subjects. 'Cardiac autonomic balance' was equilibrated between the groups by partial parasympathetic blockade with atropine sulfate in the trained subjects and partial sympathetic blockade with metoprolol tartrate in the untrained subjects. Equilibration of cardiac autonomic balance eliminated the group differences in blood pressure maintenance, and chronotropic and vasoconstrictor responsiveness during LBNP. It was hypothesized that the elevated tone of parasympathetic control of the heart rate of the trained subjects resulted in an attenuation of blood pressure regulation.     

Submovement changes characterize generalization of motor recovery after stroke

Submovements are hypothesized to be discrete building blocks of human movement. Changes in their parameters appear to account for features observed in processes of motor learning and motor recovery from stroke. Our previous studies analyzed submovement changes in subjects recovering from stroke. Subjects were trained on point-to-point movements with the assistance of a rehabilitation robot as part of a stroke treatment protocol. Results suggested that recovery starts first by regaining the ability to generate submovements and then, over a longer time period, by reacquiring the means to combine submovements. Over recovery submovements became fewer, longer, and faster and such changes contributed to changes in movement smoothness. Taken together these results lent support to the theory that movement is produced via centrally generated submovements and that changes in submovements characterize recovery. More recently, we investigated generalization of training. We found that stroke subjects trained on point-to-point movements became progressively better able to draw circles, a task on which they had received no training. The goal of this paper was to further investigate the changes that occur in untrained movements during motor recovery from stroke. Specifically we wanted to test whether changes in smoothness and submovements also characterize untrained movements. We analyzed circle drawing movements performed by 47 chronic stroke subjects who underwent training on point-to-point movements over an 18-session robot-assisted therapy program. We found that during recovery the shapes drawn by subjects became not only closer to circles (a task not trained during therapy) but also smoother. Concurrently, submovements grew fewer, longer, and faster. These results are consistent with the theory that movement is produced via submovements and suggest that changes in smoothness and submovements might characterize and describe the process of motor recovery from stroke. Also, they are consistent with the idea that motor recovery after a stroke shares similar traits with motor learning.     

Fact learning in complex arithmetic—the role of the angular gyrus revisited

In recent theoretical considerations as well as in neuroimaging findings the left angular gyrus (AG) has been associated with the retrieval of arithmetic facts. This interpretation was corroborated by higher AG activity when processing trained as compared with untrained multiplication problems. However, so far neural correlates of processing trained versus untrained problems were only compared after training. We employed an established learning paradigm (i.e., extensive training of multiplication problems) but measured brain activation before and afte training to evaluate neural correlates of arithmetic fact acquisition more specifically. When comparing activation patterns for trained and untrained problems of the post‐training session, higher AG activation for trained problems was replicated. However, when activation for trained problems was compared to activation for the same problems in the pre‐training session, no signal change in the AG was observed. Instead, our results point toward a central role of hippocampal, para‐hippocampal, and retrosplenial structures in arithmetic fact retrieval. We suggest that the AG might not be associated with the actual retrieval of arithmetic facts, and outline an attentional account of the role of the AG in arithmetic fact retrieval that is compatible with recent attention to memory hypotheses. Hum Brain Mapp 37:3061–3079, 2016. © 2016 Wiley Periodicals, Inc.     

Rehabilitative training following unilateral pyramidotomy in adult rats improves forelimb function in a non-task-specific way

Spontaneous functional recovery following injury to the adult central nervous system can be enhanced with increased and focused activity, either through altered behaviour (skill learning, exercise or training) or by artificial stimulation (magnetic or electrical). In terms of training, the choice of paradigm plays a key role in the recovered behaviour. Here we show that task-specific training leads to improved forelimb function that can be translated to a novel forelimb task. Adult Long–Evans rats received a unilateral pyramidotomy and we studied the effects of different post-lesion training paradigms for their ability to recover function in the impaired limb. We trained rats on either the single pellet grasping or the horizontal ladder task. Rats were tested on both tasks regardless of the training paradigm and also on a related, but novel forelimb task, the Staircase. Horizontal ladder training led to full recovery of this task, and also limited recovery on the familiar but untrained single pellet grasping task. In comparison, single pellet grasping training led to a smaller improvement on the horizontal ladder, but interestingly the same degree of recovery on the single pellet grasping task as horizontal ladder trained animals. Both training groups performed equally well on a novel, untrained forelimb grasping task. These results show that task-specific forelimb training can lead to functional recovery also in non-trained, complex, forelimb movements. Anatomically, only single pellet grasping training was associated with enhanced sprouting of the intact corticospinal tract across the cervical spinal cord midline to innervate the denervated side of the spinal cord.