Exercise training and orthostatic intolerance: a paradox?

Orthostatic Hypotension in Benign Prostatic Hyperplasia Patients and Its Association With Alpha-1 Antagonist Use: A Comprehensive Literature Review

Orthostatic hypotension (OH) is frequently observed in benign prostatic hyperplasia (BPH) patients undergoing alpha-1 adrenergic antagonist (A1AA) therapy. While previous studies have acknowledged the prevalence of OH in BPH patients on A1AAs, limited data exist on ranking the safety of different A1AAs. This comprehensive review explores the underlying mechanisms of OH, examines numerous factors influencing its development, and provides insights into effective treatment strategies such as hydration, gradual postural changes, leg exercises, compression stockings, and tilt-table training for BPH management. The review highlights the significance of individualized care, interdisciplinary collaboration, and further research to optimize A1AA treatment, improve patient outcomes, and enhance quality of life.

Upward resetting of the vascular sympathetic baroreflex in middle-aged male runners

This study focused on the influence of habitual endurance exercise training (i.e., committed runner or nonrunner) on the regulation of muscle sympathetic nerve activity (MSNA) and arterial pressure in middle-aged (50 to 63 yr, n = 23) and younger (19 to 30 yr; n = 23) normotensive men. Hemodynamic and neurophysiological assessments were performed at rest. Indices of vascular sympathetic baroreflex function were determined from the relationship between spontaneous changes in diastolic blood pressure (DBP) and MSNA. Large vessel arterial stiffness and left ventricular stroke volume also were measured. Paired comparisons were performed within each age category. Mean arterial pressure and basal MSNA bursts/min were not different between age-matched runners and nonrunners. However, MSNA bursts/100 heartbeats, an index of baroreflex regulation of MSNA (vascular sympathetic baroreflex operating point), was higher for middle-aged runners (P = 0.006), whereas this was not different between young runners and nonrunners. The slope of the DBP-MSNA relationship (vascular sympathetic baroreflex gain) was not different between groups in either age category. Aortic pulse wave velocity was lower for runners of both age categories (P < 0.03), although carotid β-stiffness was lower only for middle-aged runners (P = 0.04). For runners of both age categories, stroke volume was larger, whereas heart rate was lower (both P < 0.01). In conclusion, we suggest that neural remodeling and upward setting of the vascular sympathetic baroreflex compensates for cardiovascular adaptations after many years committed to endurance exercise training, presumably to maintain arterial blood pressure stability. NEW & NOTEWORTHY Exercise training reduces muscle sympathetic burst activity in disease; this is often extrapolated to infer a similar effect in health. We demonstrate that burst frequency of middle-aged and younger men committed to endurance training is not different compared with age-matched casual exercisers. Notably, well-trained, middle-aged runners display similar arterial pressure but higher sympathetic burst occurrence than untrained peers. We suggest that homeostatic plasticity and upward setting of the vascular sympathetic baroreflex maintains arterial pressure stability following years of training.

Exercise-Induced Modulation of Baroreflex Control of Sympathetic Nerve Activity

Exercise modulates arterial pressure (AP) regulation over various time spans. AP increases at the onset of exercise and this increase is then sustained during exercise. Once exercise is stopped, AP is suppressed for up to an hour afterwards. Prolonged endurance training is associated with dysfunction of the sympathetic regulation of AP in response to posture changes (orthostatic intolerance). Baroreflex control of sympathetic nerve activity (SNA) has been extensively studied to understand the mechanisms underlying exercise-induced changes in AP. We have previously presented entire baroreflex AP-SNA curves during and after exercise, and during central volume expansion, obtained using direct measurements of renal sympathetic nerve activity (RSNA) in conscious animals. In this review, we describe the modulatory effects of exercise on baroreflex control of AP based on these entire AP-RSNA baroreflex curves. We suggest that both acute and chronic exercise can have modulatory effects on the entire baroreflex curve for SNA, and that these effects differ among time periods.

Effects of physical activity on the symptoms of Tourette syndrome: A systematic review

There is irrefutable evidence that routine physical activity or exercise can offer considerable health benefits to individuals living with various mental disorders. However, it is not clear what effect physical activity has on the symptoms of Tourette syndrome. Despite a paucity of evidence, physical activity or exercise has already been recommended by various health organizations for the management of tics. We provide a systematic review of the effects of physical activity or exercise on tic symptomology in individuals with Tourette syndrome. Major electronic databases were searched for all available publications before August 2017. Keywords and MeSH terms included "physical activity" or "exercise" or "exercise therapy" or "physical exertion" or "sports" and "tics" or "tic disorders" or "Tourette." Eight studies were included, the majority of which were case reports. Despite a number of methodological limitations of the included studies, the review points to a trend that the effects of acute physical activity are intensity-dependent, where light intensity may alleviate and vigorous intensity may exacerbate tics. Chronic physical activity, however, appears to reduce the severity of tics even at higher intensity. Several physiological mechanisms may explain the differential effects of acute and chronic physical activity in Tourette syndrome. Future randomized controlled studies should better characterize the effects of different intensities and types of physical activity in Tourette syndrome.

Aerobic Exercise Training Improves Orthostatic Tolerance in Aging Humans

PURPOSE

This study was designed to test the hypothesis that aerobic exercise training of the elderly will increase aerobic fitness without compromising orthostatic tolerance (OT).

METHODS

Eight healthy sedentary volunteers (67.0 ± 1.7 yr old, four women) participated in 1 yr of endurance exercise training (stationary bicycle and/or treadmill) program at the individuals' 65%-75% of HRpeak. Peak O2 uptake (V˙O2peak) and HRpeak were determined by a maximal exercise stress test using a bicycle ergometer. Carotid baroreceptor reflex (CBR) control of HR and mean arterial pressure (MAP) were assessed by a neck pressure-neck suction protocol. Each subject's maximal gain (Gmax), or sensitivity, of the CBR function curves were derived from fitting their reflex HR and MAP responses to the corresponding neck pressure-neck suction stimuli using a logistic function curve. The subjects' OT was assessed using lower-body negative pressure (LBNP) graded to -50 mm Hg; the sum of the product of LBNP intensity and time (mm Hg·min) was calculated as the cumulative stress index.

RESULTS

Training increased V˙O2peak (before vs after: 22.8 ± 0.92 vs 27.9 ± 1.33 mL·min·kg, P < 0.01) and HRpeak (154 ± 4 vs 159 ± 3 bpm, P < 0.02) and decreased resting HR (65 ± 5 vs 59 ± 5 bpm, P < 0.02) and MAP (99 ± 2 vs 87 ± 2 mm Hg, P < 0.05). CBR stimulus-response curves identified a leftward shift with an increase in CBR-HR Gmax (from -0.13 ± 0.02 to -0.27 ± 0.04 bpm·mm Hg, P = 0.01). Cumulative stress index was increased from 767 ± 68 mm Hg·min pretraining to 946 ± 44 mm Hg·min posttraining (P < 0.05).

CONCLUSION

Aerobic exercise training improved the aerobic fitness and OT in elderly subjects. An improved OT is likely associated with an enhanced CBR function that has been reset to better maintain cerebral perfusion and cerebral tissue oxygenation during LBNP.

A definition of normovolaemia and consequences for cardiovascular control during orthostatic and environmental stress

The Frank–Starling mechanism describes the relationship between stroke volume and preload to the heart, or the volume of blood that is available to the heart—the central blood volume. Understanding the role of the central blood volume for cardiovascular control has been complicated by the fact that a given central blood volume may be associated with markedly different central vascular pressures. The central blood volume varies with posture and, consequently, stroke volume and cardiac output (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \dot{Q} $$\end{document}) are affected, but with the increased central blood volume during head-down tilt, stroke volume and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \dot{Q} $$\end{document} do not increase further indicating that in the supine resting position the heart operates on the plateau of the Frank–Starling curve which, therefore, may be taken as a functional definition of normovolaemia. Since the capacity of the vascular system surpasses the blood volume, orthostatic and environmental stress including bed rest/microgravity, exercise and training, thermal loading, illness, and trauma/haemorrhage is likely to restrict venous return and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \dot{Q} $$\end{document}. Consequently the cardiovascular responses are determined primarily by their effect on the central blood volume. Thus during environmental stress, flow redistribution becomes dependent on sympathetic activation affecting not only skin and splanchnic blood flow, but also flow to skeletal muscles and the brain. This review addresses the hypothesis that deviations from normovolaemia significantly influence these cardiovascular responses.

Normovolaemia defined by central blood volume and venous oxygen saturation

1. The intravenous administration of fluid and blood has to balance the danger of unexpected death in response to a reduction of central blood volume (CBV) against that of developing pulmonary and/or peripheral oedema. 2. The initial cardiovascular response to haemorrhage is similar to that developed in response to standing. In the upright position, adults are subjected to a reduction of CBV of approximately 0.5 L and can therefore tolerate a blood loss of approximately 1 L when supine. 3. However, volume administration directed by cardiovascular variables is seldom precise, even with integration of the bradycardia and hypotension developed when CBV decreases by approximately 30%. Immediate intervention is needed because such a reduction in CBV raises the lower limit of cerebral autoregulation to approximately 80 mmHg compared with the commonly considered value of approximately 60 mmHg with an associated risk of developing brain ischaemia and irreversible shock. 4. Alternatively, the volume load can be monitored both directly and accurately by means of thoracic electrical admittance. A functional definition of normovolaemia may be the filling of the heart that ensures cardiac output and oxygen delivery. From that perspective, supine humans are normovolaemic in that a maximal venous oxygen saturation (Svo2) is established. 5. Conversely, Svo2 decreases in the upright position and, with a blood loss of approximately 100 mL, Svo2 is reduced by 1%. It is suggested that, in supine humans and guided by Svo2, normovolaemia may be established to an accuracy of approximately 100 mL and that its adequacy is controlled by recording cerebral oxygenation.