No description available.

There is clear evidence that the autonomic nervous system (ANS) is lateralized at both the peripheral as well as the central levels of the nervous system. Both the vagus and the sympathetic ganglia asymmetrically innervate the sino-atrial node and the myocardium of the heart. This lateralization has also been observed in afferent as well as efferent projections to nuclei in the brainstem, hypothalamus, and amygdala. Where laterality has not been as clear is in regions of the frontal lobe dedicated to the regulation of autonomic nervous system responses. This study addressed that issue via the implementation of lateralized autonomic response-evoking tasks. With the use of cardiovascular and electrodermal measures, the present study indexed autonomic responses to lateralized stimuli. This study also explored the role of lateralization within sex as well as in relation to reported gender identity. The findings lend support to the right hemisphere as serving a dominant role in regulating sympathetic nervous system activity, while lending less conclusive support for lateralization of parasympathetic nervous system regulation. Men demonstrated greater lateralization for sympathetic nervous system responses across several different metrics of autonomic indices. The exploration of gender variables in relation to lateralization of autonomic responses was generally not supported. / Master of Science

Excessive sympathetic cardiovascular reactivity to stressful tasks is a risk factor for the development of cardiovascular disease (CVD). Many populations with a greater risk for CVD instead demonstrate blunted cardiovascular reactivity to stressful tasks. The motivational intensity theory identifies how motivation and effort influence sympathetic reactivity. Blunted reactivity may be a potential index of motivational dysregulation, which leads to poor behavioral decisions such as excess smoking or alcohol use, in turn increasing the risk for CVD. The current study sought to demonstrate how inhibited effort due to poor ability feedback with a low-contingency reward could directly increase the risk for CVD through perseverative cognition and impaired recovery. Participants (N = 89) were given either poor or good feedback on a working memory task that was purported to be related to another related working memory task. Participants were then informed that they could secure a low- or high-contingency reward opportunity by meeting a performance standard. EKG, impedance cardiography, blood pressure, and pupillometry were recorded throughout. Pre-ejection period reactivity and self-reported effort were greatest in participants given good feedback with a high-contingency reward and poor feedback with a low-contingency reward. Greater effort and sympathetic reactivity support previous findings linking these two measures. The results also suggest evaluating both internal and external rewards is important when examining motivation.

The cardiovascular effects of whole body heat stress during exercise are well established. However the independent contribution of elevated skin temperature (Tsk) or core temperature (Tc) on these responses remains unclear. The purpose of this study was to determine how increases in Tsk and Tc alone and in combination, impact cardiovascular responses during moderate intensity exercise. To accomplish this goal, eight healthy, recreationally active males were immersed to the neck in a cold (14 - 17°C) or hot (40 - 42.5°C) water bath for 20 to 25 min to alter Tc immediately prior to exercise with either cool Tsk (i.e. fans) or warm Tsk (i.e. heaters). Conditions during exercise were cool skin and cool core (CC), warm skin and cool core (WC), cool skin and warm core (CW), and warm skin and warm core (WW), and were conducted in a randomized crossover design. When data was combined (n=16), warm core conditions (CW and WW) were associated with significantly higher average heart rate (HR) and lower stroke volume (SV) during exercise compared to cool core conditions (CC and WC); 168.1 ± 3.2 vs. 152.2 ± 4.0 beats/min and 139.2 ± 7.3 vs. 147.7 ± 9.4 mL/beat, respectively. The approximate 9 mL/beat decline in SV and 16 beat/min increase in HR in warm core conditions tended to increase cardiac output (Q), 23.2 ± 0.6 vs. 22.2 ± 0.7 L/min, P=0.078. Similarly, warm Tsk conditions (WC and WW) were associated with significantly higher average HR and lower SV during exercise compared to cool Tsk conditions (CC and CW); 165.2 ± 3.3 vs. 155.1 ± 3.4 beats/min and 140.8 ± 7.8 vs. 146.0 ± 8.7 mL/beat, respectively. Additionally, there was also a trend for Q to be elevated with warm skin (23.0 ± 0.6 vs. 22.4 ± 0.6, P=0.075). Although combined data indicated that warm Tsk conditions significantly lowered average SV by ~6 mL/beat, there was no reduction in SV during exercise by warm Tsk, when Tes was cool (i.e. <37.0°C), as evidenced by identical values for SV in CC and WC, 147.7 ± 9.8 vs. 147.7 ± 9.0 mL/beat, respectively. In contrast, SV was significantly lower in WW compared with CW, 133.9 ± 7.0 vs. 144.4 ± 7.8 mL/beat, respectively. Therefore, the major reduction in SV by warm Tsk occurred during WW, when Tes was elevated (i.e. >38.0°C). Analyzing data independently for precooling and preheating conditions revealed that warm Tsk was associated with greater HR drift from 5 to 20 min of exercise, compared to cool Tsk, when esophageal temperature (Tes) was both cool or warm (23.9 ± 2.2 vs. 17.5 ± 2.3 and 12.3 ± 1.3 vs. 4.6 ± 1.7 beats/min, respectively). These observations demonstrate that both Tes and Tsk can directly influence cardiovascular responses during exercise, as indicated by elevations in HR during exercise with warm Tsk, with both warm and cool Tes. However SV is not compromised by warm Tsk if Tes is below 37.5°C. Furthermore, when both Tes and Tsk are elevated simultaneously, cardiovascular strain (i.e. increased HR and reduced SV) is much greater than when either is elevated alone. This is demonstrated by the finding that average HR was 175.8 ± 3.2 beats/min in WW, compared to 149.8 ± 4.0, 154.7 ± 4.1, and 160.3 ± 3.5 beats/min, in CC, WC, and CW, respectively, and the fact that SV was lowest during exercise in WW. In conclusion, individuals exercising in the heat should take measures to keep skin cool, especially when Tes is 39°C or greater to attenuate the cardiovascular strain that occurs with warm Tsk, when Tes is elevated. / text

No description available.

Cardiovascular and hormonal responses to +700 head-up tilt (HUT: orthostatic challenge) were compared between six endurance exercise trained (ET) and six untrained (UT) subjects prior to and immediately following 4 hours of -60 head-down rest (HDR). The ET subjects showed a significant (P < 0.05) decrease in orthostatic tolerance time (pre syncopal symptoms) during post-HDR HUT, while no difference was observed between ET and UT groups in pre-HDR HUT. The volume regulatory hormonal responses were similar between ET and UT groups whether during HUT or HDR. The pre-syncopal subjects had a greater increase in plasma arginine vasopressin and less increase in plasma renin activity and plasma aldosterone during HUT than was observed in non syncopal subjects. These data suggest that HDR deconditioning was more effective in the ET subjects.

In cerebral palsied adults, the cardiovascular responses to different types of exercise have not previously been ascertained. Therefore, the purpose of this study was to determine the blood pressure and heart rate responses of adults with cerebral palsy to static muscular contractions and to dynamic muscular contractions. Fifteen adults with cerebral palsy and 15 able-bodied adults (average age for each group = 30 years) performed a static exercise protocol and a dynamic resistance exercise protocol using each limb (or the limbs capable of meeting the requirements of the exercise protocol). Heart rate and blood pressure were assessed before, during, and after each exercise bout with each limb. During the static exercise protocol, each subject performed static contractions at 40% of maximal voluntary contraction to fatigue. The dynamic exercise protocol for each limb consisted of three 20-second bouts of hydraulic resistance exercise each of which was followed by 20 seconds of rest. No differences were found between the two groups of subjects in heart rate and blood pressure during static exercise. In dynamic exercise, however, the trend in heart rate from bout to bout differed between the groups. In addition, the cerebral palsied group's diastolic pressure was higher than that of the able-bodied group at the end of dynamic exercise. The findings of this study indicate that although the heart rate and blood pressure responses to dynamic resistance exercise in the cerebral palsied subjects differed from the responses of the able-bodied subjects, healthy adults with cerebral palsy may safely perform both static and dynamic resistance exercise. More research using this disabled population is needed so that guidelines for prescribing exercise for adults with cerebral palsy may be developed.

É hipótese que (treinamento) T iniciado na fase pré-hipertensiva possa reduzir a atividade simpática e aumentar a vagal ao coração, melhorando a regulação autonômica nos SHR. Investigamos em SHR e WKY jovens (29 dias) os efeitos do T sobre parâmetros hemodinâmicos, funcionamento dos barorreceptores arteriais, tônus simpático e vagal ao coração e variabilidades, e expressão de neurônios pré-ganglionares vagais (Colina Acetil Transferase, ChAT) nos núcleos dorsal motor do vago (DMV) e ambíguo (NA). Ratos T ou sedentários (S) foram canulados nas semanas 0, 1, 2, 4 e 8, para registros funcionais e remoção dos encéfalos para a quantificação (peroxidade e estereologia). A participação dos aferentes periféricos na modulação dos efeitos do T foi avaliada com a desnervação sinoaórtica (SAD). Os efeitos do T são modulados por baro- e quimiorreceptores. O T precoce corrige a disfunção baroreflexa, reduz a hipertonia simpática, mantém parcialmente a tonicidade de neurônios colinérgicos, aumentando a modulação vagal ao coração e melhorando controle autonômico da circulação. / We hypothesized that aerobic training (T) starting at the pre-hypertensive phase reduces not only the sympathetic activity, but increases vagal outflow to the heart, thus improving autonomic cardiovascular control. We investigated in young SHR and WKY the T-induced effects on hemodynamic parameters, activation of arterial baroreceptor, sympathetic and vagal tone to the heart, and the expression of pre-ganglionic parasympathetic neurons (Choline acetyl transferase, ChAT) in the dorsal motor nucleus of the vagus (DMV) and nucleus ambiguous (NA). Rats (29 days) were T or sedentary (S) and cannulated at weeks 0, 1, 2, 4 and 8. After functional recordings, brains were harvested for quantification of neurons (peroxidase and stereology). The peripheral afferents was evaluated in sinoaortic denervation (SAD). SAD abrogated the improvement of baroreflex control and resting bradycardia in intact SHR-T. T-induced effects were modulated by arterial baro- and chemoreceptors. When started at the pre-hypertensive phase, T corrects baroreflex dysfunction, reduces sympathetic hyperactivity, maintain the tonicity of pre-ganglionic cholinergic neurons thus increasing vagal outflow to the heart and allowing a better autonomic control of the circulation.

De nouvelles modalités de réentrainement sont nécessaires pour les patients présentant une sévère limitation à l’exercice tels que les patients souffrant de broncho-pneumopathie chronique obstructive (BPCO). Le pédalage « excentrique », caractérisé par une meilleure efficience, pourrait permettre à ces patients de se réentrainer plus efficacement. Toutefois, les modalités de prescription et les effets du pédalage excentrique méritent d’être étudiés.Chez le sujet sain, nos résultats ont montré un retard de réactivation parasympathique au décours du pédalage excentrique par rapport au concentrique réalisés à même puissance mécanique, avec une influence de la fréquence de pédalage sur les réponses cardio-respiratoires et autonomes. À même puissance métabolique, le pédalage excentrique se caractérise par un stress cardio-vasculaire et respiratoire plus important que lors du pédalage concentrique, et des réponses neuro-végétatives en faveur d’une activité sympathique plus élevée. La fonction vasculaire est altérée à l’issue du pédalage excentrique. Chez le patient atteint de BPCO, comme chez le sujet sain, le pédalage excentrique a un effet tachypnéisant.Nous pensons que la tension musculaire accrue nécessaire en pédalage excentrique à l’atteinte d’une puissance métabolique équivalente à l’exercice concentrique serait à l’origine d’une plus grande activité sympathique et d’une contrainte hémodynamique périphérique, expliquant l’augmentation de la contrainte cardio-vasculaire en pédalage excentrique. / New exercise modalities are required for patients severely limited during exercise such as chronic obstructive pulmonary disease patients (COPD). Eccentric “cycling”, characterized by better efficiency, could allow COPD patients to train more effectively. Nonetheless, prescription modalities and effects of eccentric cycling deserve to be more studied.In healthy subjects, our results showed a delayed parasympathetic reactivation after eccentric compared to concentric cycling matched for mechanical power, together with an influence of pedalling frequency on autonomic and cardiorespiratory responses. At similar metabolic power, eccentric cycling is characterized by a greater cardiovascular and respiratory stress than during concentric cycling, and altered autonomic nervous systems responses in favour to greater sympathetic activity. Vascular function is altered after eccentric cycling. In COPD patients, as in healthy subjects, eccentric cycling impose tachypneic breathing pattern.We believe that the higher muscle tension during eccentric cycling necessary to reach metabolic power similar to concentric leads to greater sympathetic activity and peripheral hemodynamic constraint, likely explaining the increased constraints on cardiovascular system during eccentric cycling.