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This dissertation examined the effect of skeletal muscle stretching on central and peripheral cardiovascular responses in humans. Healthy males performed controlled passive stretching at three different stretching intensities of the plantar flexors on an isokinetic dynamometer. To determine how stretching effects peripheral cardiovascular parameters of muscle blood flow and perfusion of the popliteal artery, Doppler ultrasound velocimetry and imaging techniques were used to determine mean blood flow (MBF), antegrade blood flow and retrograde blood flow responses while near infrared spectroscopy (NIRS) was used to measure changes in muscle tissue oxygen extraction (deoxygenated hemoglobin; [HHb]) and blood volume (total hemoglobin+myoglobin; (Hbtot). To determine how stretching effects central cardiovascular parameters, heart rate (HR) was measured using electrocardiography and finger photoplethysmography was used to measure mean arterial pressure (MAP) simultaneous to peripheral cardiovascular responses. During each stretching session a significant elevation in antegrade and retrograde blood flow were observed, whereas MBF responses were not significantly altered suggesting that skeletal muscle stretching in humans does not alter blood flow but can cause a dramatic change in the biphasic nature of the blood flow responses. NIRS-derived estimates of [HHb] and [Hbtot] were significantly increased, suggesting that skeletal muscle stretching in humans increases muscle metabolism. Heart rate significantly rose in a stretch intensity- and time-dependent manner, whereas blood pressure was not significantly altered, suggesting a role for mechanoreceptive afferent feedback arising from the musculature to initiate rapid adjustments in blood flow control. After each stretching session a significant elevation in [Hbtot], MBF and antegrade blood flow responses were observed in each stretching condition, suggesting that stretching creates a post-stretch hyperemic response in humans. The retrograde blood flow responses were significantly decreased following each stretching session and these responses remained depressed at every time interval measured, suggesting that stretching in humans creates a lower level of resting myogenic tone and reduced downstream vascular resistance. These changes were also marked by significant decreases in MAP in a muscle stretching-extent dependent manner suggesting that: 1) skeletal muscle stretching in humans (afterward) mediates a baroreflex that serves to adjust central (HR and BP) parameters back to normal and 2) the magnitude of the stretch (i.e. higher intensity stretches) appear to dictate this response. Collectively, the data acquired from this investigation has examined and verified a critical role for skeletal muscle stretching and cardiovascular responses. Moreover, the reductions in BP and retrograde blood flow seen after stretching suggests that skeletal muscle stretching in humans reduces myogenic vascular tone which may confer additional beneficial vascular effects in a post-stretch resting period. Alterations in NIRS-derived microvascular parameters may reveal a causal role for this phenomenon which serves to regulate how the upstream conduit artery blood flow profiles manifest.
This presentation describes various aspects of the regulation of tissue oxygenation, including the roles of the circulatory system, respiratory system, and blood, the carrier of oxygen within these components of the cardiorespiratory system. The respiratory system takes oxygen from the atmosphere and transports it by diffusion from the air in the alveoli to the blood flowing through the pulmonary capillaries. The cardiovascular system then moves the oxygenated blood from the heart to the microcirculation of the various organs by convection, where oxygen is released from hemoglobin in the red blood cells and moves to the parenchymal cells of each tissue by diffusion. Oxygen that has diffused into cells is then utilized in the mitochondria to produce adenosine triphosphate (ATP), the energy currency of all cells. The mitochondria are able to produce ATP until the oxygen tension or PO2 on the cell surface falls to a critical level of about 4–5 mm Hg. Thus, in order to meet the energetic needs of cells, it is important to maintain a continuous supply of oxygen to the mitochondria at or above the critical PO2 . In order to accomplish this desired outcome, the cardiorespiratory system, including the blood, must be capable of regulation to ensure survival of all tissues under a wide range of circumstances. The purpose of this presentation is to provide basic information about the operation and regulation of the cardiovascular and respiratory systems, as well as the properties of the blood and parenchymal cells, so that a fundamental understanding of the regulation of tissue oxygenation is achieved.
The aim of this treatise is to summarize the current understanding of the mechanisms for blood flow control to skeletal muscle under resting conditions, how perfusion is elevated (exercise hyperemia) to meet the increased demand for oxygen and other substrates during exercise, mechanisms underlying the beneficial effects of regular physical activity on cardiovascular health, the regulation of transcapillary fluid filtration and protein flux across the microvascular exchange vessels, and the role of changes in the skeletal muscle circulation in pathologic states. Skeletal muscle is unique among organs in that its blood flow can change over a remarkably large range. Compared to blood flow at rest, muscle blood flow can increase by more than 20-fold on average during intense exercise, while perfusion of certain individual white muscles or portions of those muscles can increase by as much as 80-fold. This is compared to maximal increases of 4- to 6-fold in the coronary circulation during exercise. These increases in muscle perfusion are required to meet the enormous demands for oxygen and nutrients by the active muscles. Because of its large mass and the fact that skeletal muscles receive 25% of the cardiac output at rest, sympathetically mediated vasoconstriction in vessels supplying this tissue allows central hemodynamic variables (e.g., blood pressure) to be spared during stresses such as hypovolemic shock. Sympathetic vasoconstriction in skeletal muscle in such pathologic conditions also effectively shunts blood flow away from muscles to tissues that are more sensitive to reductions in their blood supply that might otherwise occur. Again, because of its large mass and percentage of cardiac output directed to skeletal muscle, alterations in blood vessel structure and function with chronic disease (e.g., hypertension) contribute significantly to the pathology of such disorders. Alterations in skeletal muscle vascular resistance and/or in the exchange properties of this vascular bed also modify transcapillary fluid filtration and solute movement across the microvascular barrier to influence muscle function and contribute to disease pathology. Finally, it is clear that exercise training induces an adaptive transformation to a protected phenotype in the vasculature supplying skeletal muscle and other tissues to promote overall cardiovascular health. Table of Contents: Introduction / Anatomy of Skeletal Muscle and Its Vascular Supply / Regulation of Vascular Tone in Skeletal Muscle / Exercise Hyperemia and Regulation of Tissue Oxygenation During Muscular Activity / Microvascular Fluid and Solute Exchange in Skeletal Muscle / Skeletal Muscle Circulation in Aging and Disease States: Protective Effects of Exercise / References
Exercise training provokes widespread transformations in the human body, requiring coordinated changes in muscle composition, blood flow, neuronal and hormonal signaling, and metabolism. These changes enhance physical performance, improve mental health, and delay the onset of aging and disease. Understanding the molecular basis of these changes is therefore important for optimizing athletic ability and for developing drugs that elicit therapeutic effects. Written and edited by experts in the field, this collection from Cold Spring Harbor Perspectives in Medicine examines the biological basis of exercise from the molecular to the systemic levels. Contributors discuss how transcriptional regulation, cytokine and hormonal signaling, glucose metabolism, epigenetic modifications, microRNA profiles, and mitochondrial and ribosomal functions are altered in response to exercise training, leading to improved skeletal muscle, hippocampal, and cardiovascular function. Cross talk among the pathways underlying tissue-specific and systemic responses to exercise is also considered. The authors also discuss how the understanding of such molecular mechanisms may lead to the development of drugs that mitigate aging and disease. This volume will therefore serve as a vital reference for all involved in the fields of sports science and medicine, as well as anyone seeking to understand the molecular mechanisms by which exercise promotes whole-body health.
Emphasizes the research activities of Germany’s Nauheim Institute of the Max Planck Society and its group of investigators both past and present, in the field of collateral artery growth. Incorporates a multidisciplinary in vivo approach to the study of arteriogenesis that includes molecular approaches with classical physiology and immunohistochemistry. Full color throughout and well illustrated.
Research centering on blood flow in the heart continues to hold an important position, especially since a better understanding of the subject may help reduce the incidence of coronary arterial disease and heart attacks. This book summarizes recent advances in the field; it is the product of fruitful cooperation among international scientists who met in Japan in May, 1990 to discuss the regulation of coronary blood flow.
In this manuscript, practitioners and students who are concerned with sports and rehabilitation medicine, kinesiology, as well as coaches and athletes, are introduced to numerous concepts, including mechanotransduction, inflammation, pro- and anti-inflammatory cytokines, calpains, the extracellular matrix, neutrophils and macrophages, and their relevance to stretching, particularly stretching intensity. Although the quantitative parameters of training, duration, and frequency are important, it is the qualitative criterion of intensity (“how much”) that the author suggests is ultimately of greater concern. Intensity, the rate and magnitude of force, may be responsible for the proper recovery, regeneration, and adaptation of the musculoskeletal tissues from training, competition, or rehabilitation from injuries. Research suggests that too much force results in the stimulation of an inflammatory response, one associated with a biochemical feedback emerging from a mechanical stimulus. The intent of this manuscript is twofold: to initiate the discussion of the importance of stretching intensity with regard to proper recovery, regeneration, and adaptation, and to suggest that researchers need to explore its potential role in addressing numerous inflammatory (RA) and non-inflammatory (OA, recurrent tendinitis etc.) musculoskeletal conditions as well.
Every year workers' low-back, hand, and arm problems lead to time away from jobs and reduce the nation's economic productivity. The connection of these problems to workplace activities-from carrying boxes to lifting patients to pounding computer keyboards-is the subject of major disagreements among workers, employers, advocacy groups, and researchers. Musculoskeletal Disorders and the Workplace examines the scientific basis for connecting musculoskeletal disorders with the workplace, considering people, job tasks, and work environments. A multidisciplinary panel draws conclusions about the likelihood of causal links and the effectiveness of various intervention strategies. The panel also offers recommendations for what actions can be considered on the basis of current information and for closing information gaps. This book presents the latest information on the prevalence, incidence, and costs of musculoskeletal disorders and identifies factors that influence injury reporting. It reviews the broad scope of evidence: epidemiological studies of physical and psychosocial variables, basic biology, biomechanics, and physical and behavioral responses to stress. Given the magnitude of the problem-approximately 1 million people miss some work each year-and the current trends in workplace practices, this volume will be a must for advocates for workplace health, policy makers, employers, employees, medical professionals, engineers, lawyers, and labor officials.
The partition of fluid between the vascular and interstitial compartments is regulated by forces (hydrostatic and oncotic) operating across the microvascular walls and the surface areas of permeable structures comprising the endothelial barrier to fluid and solute exchange, as well as within the extracellular matrix and lymphatics. In addition to its role in the regulation of vascular volume, transcapillary fluid filtration also allows for continuous turnover of water bathing tissue cells, providing the medium for diffusional flux of oxygen and nutrients required for cellular metabolism and removal of metabolic byproducts. Transendothelial volume flow has also been shown to influence vascular smooth muscle tone in arterioles, hydraulic conductivity in capillaries, and neutrophil transmigration across postcapillary venules, while the flow of this filtrate through the interstitial spaces functions to modify the activities of parenchymal, resident tissue, and metastasizing tumor cells. Likewise, the flow of lymph, which is driven by capillary filtration, is important for the transport of immune and tumor cells, antigen delivery to lymph nodes, and for return of filtered fluid and extravasated proteins to the blood. Given this background, the aims of this treatise are to summarize our current understanding of the factors involved in the regulation of transcapillary fluid movement, how fluid movements across the endothelial barrier and through the interstitium and lymphatic vessels influence cell function and behavior, and the pathophysiology of edema formation. Table of Contents: Fluid Movement Across the Endothelial Barrier / The Interstitium / The Lymphatic Vasculature / Pathophysiology of Edema Formation
New updated edition first published with Cambridge University Press. This new edition includes 29 chapters on topics as diverse as pathophysiology of atherosclerosis, vascular haemodynamics, haemostasis, thrombophilia and post-amputation pain syndromes.