This book contains original and review article performed in our lab (Physical Activity and Performance Institude, Konkuk University, Korea). This content explains the effectiveness of various exercise training and intervention under hypoxia for enhancing athletic performance and various cardiometabolic health including obesity. By reading this textbook, it is believed that many readers will better understand the effectiveness of hypoxic training and hypoxic therapy.
Hypoxia remains a constant threat throughout life. It is for this reason that the International Hypoxia Society strives to maintain a near quarter century tradition of presenting a stimulating blend of clinical and basic science discussions. International experts from many fields have focused on the state-of-the-art discoveries in normal and pathophysiological responses to hypoxia. Topics in this volume include gene-environment interactions, a theme developed in both a clinical context regarding exercise and hypoxia, as well as in native populations living in high altitudes. Furthermore, experts in the field have combined topics such as skeletal muscle angiogenesis and hypoxia, high altitude pulmonary edema, new insights into the biology of the erythropoietin receptor, and the latest advances in cardiorespiratory control in hypoxia. This volume explores the fields of anatomy, cardiology, biological transport, and biomedical engineering among many others.
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
In the past, ‘traditional’ moderate-intensity continuous training (60-75% peak heart rate) was the type of physical activity most frequently recommended for both athletes and clinical populations (cf. American College of Sports Medicine guidelines). However, growing evidence indicates that high-intensity interval training (80-100% peak heart rate) could actually be associated with larger cardiorespiratory fitness and metabolic function benefits and, thereby, physical performance gains for athletes. Similarly, recent data in obese and hypertensive individuals indicate that various mechanisms – further improvement in endothelial function, reductions in sympathetic neural activity, or in arterial stiffness – might be involved in the larger cardiovascular protective effects associated with training at high exercise intensities. Concerning hypoxic training, similar trends have been observed from ‘traditional’ prolonged altitude sojourns (‘Live High Train High’ or ‘Live High Train Low’), which result in increased hemoglobin mass and blood carrying capacity. Recent innovative ‘Live Low Train High’ methods (‘Resistance Training in Hypoxia’ or ‘Repeated Sprint Training in Hypoxia’) have resulted in peripheral adaptations, such as hypertrophy or delay in muscle fatigue. Other interventions inducing peripheral hypoxia, such as vascular occlusion during endurance/resistance training or remote ischemic preconditioning (i.e. succession of ischemia/reperfusion episodes), have been proposed as methods for improving subsequent exercise performance or altitude tolerance (e.g. reduced severity of acute-mountain sickness symptoms). Postulated mechanisms behind these metabolic, neuro-humoral, hemodynamics, and systemic adaptations include stimulation of nitric oxide synthase, increase in anti-oxidant enzymes, and down-regulation of pro-inflammatory cytokines, although the amount of evidence is not yet significant enough. Improved O2 delivery/utilization conferred by hypoxic training interventions might also be effective in preventing and treating cardiovascular diseases, as well as contributing to improve exercise tolerance and health status of patients. For example, in obese subjects, combining exercise with hypoxic exposure enhances the negative energy balance, which further reduces weight and improves cardio-metabolic health. In hypertensive patients, the larger lowering of blood pressure through the endothelial nitric oxide synthase pathway and the associated compensatory vasodilation is taken to reflect the superiority of exercising in hypoxia compared to normoxia. A hypoxic stimulus, in addition to exercise at high vs. moderate intensity, has the potential to further ameliorate various aspects of the vascular function, as observed in healthy populations. This may have clinical implications for the reduction of cardiovascular risks. Key open questions are therefore of interest for patients suffering from chronic vascular or cellular hypoxia (e.g. work-rest or ischemia/reperfusion intermittent pattern; exercise intensity; hypoxic severity and exposure duration; type of hypoxia (normobaric vs. hypobaric); health risks; magnitude and maintenance of the benefits). Outside any potential beneficial effects of exercising in O2-deprived environments, there may also be long-term adverse consequences of chronic intermittent severe hypoxia. Sleep apnea syndrome, for instance, leads to oxidative stress and the production of reactive oxygen species, and ultimately systemic inflammation. Postulated pathophysiological changes associated with intermittent hypoxic exposure include alteration in baroreflex activity, increase in pulmonary arterial pressure and hematocrit, changes in heart structure and function, and an alteration in endothelial-dependent vasodilation in cerebral and muscular arteries. There is a need to explore the combination of exercising in hypoxia and association of hypertension, developmental defects, neuro-pathological and neuro-cognitive deficits, enhanced susceptibility to oxidative injury, and possibly increased myocardial and cerebral infarction in individuals sensitive to hypoxic stress. The aim of this Research Topic is to shed more light on the transcriptional, vascular, hemodynamics, neuro-humoral, and systemic consequences of training at high intensities under various hypoxic conditions.
Respiratory Muscle Training: theory and practice is the world's first book to provide an "everything-you-need-to-know" guide to respiratory muscle training (RMT). Authored by an internationally-acclaimed expert, it is an evidence-based resource, built upon current scientific knowledge, as well as experience at the cutting-edge of respiratory training in a wide range of settings. The aim of the book is to give readers: 1) an introduction to respiratory physiology and exercise physiology, as well as training theory; 2) an understanding of how disease affects the respiratory muscles and the mechanics of breathing; 3) an insight into the disease-specific, evidence-based benefits of RMT; 4) advice on the application of RMT as a standalone treatment, and as part of a rehabilitation programme; and finally, 5) guidance on the application of functional training techniques to RMT. The book is divided into two parts – theory and practice. Part I provides readers with access to the theoretical building blocks that support practice. It explores the evidence base for RMT as well as the different methods of training respiratory muscles and their respective efficacy. Part II guides the reader through the practical implementation of the most widely validated form of RMT, namely inspiratory muscle resistance training. Finally, over 150 "Functional" RMT exercises are described, which incorporate a stability and/or postural challenge – and address specific movements that provoke dyspnoea. Respiratory Muscle Training: theory and practice is supported by a dedicated website (www.physiobreathe.com), which provides access to the latest information on RMT, as well as video clips of all exercises described in the book. Purchasers will also receive a three-month free trial of the Physiotec software platform (via www.physiotec.ca), which allows clinicians to create bespoke training programmes (including video clips) that can be printed or emailed to patients. - Introductory overviews of respiratory and exercise physiology, as well as training theory - Comprehensive, up-to-date review of respiratory muscle function, breathing mechanics and RMT - Analysis of the interaction between disease and respiratory mechanics, as well as their independent and combined influence upon exercise tolerance - Analysis of the rationale and application of RMT to over 20 clinical conditions, e.g., COPD, heart failure, obesity, mechanical ventilation - Evidence-based guidance on the implementation of inspiratory muscle resistance training - Over 150 functional exercises that incorporate a breathing challenge - www.physiobreathe.com - access up-to-date information, video clips of exercises and a three-month free trial of Physiotec's RMT exercise module (via www.physiotec.ca)
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.
Over the last decade the science and medicine of high altitude and hypoxia adaptation has seen great advances. High Altitude: Human Adaptation to Hypoxia addresses the challenges in dealing with the changes in human physiology and the particular medical conditions that arise from exposure to high altitude. In-depth and comprehensive chapters cover both the basic science and the clinical consequences of exposure to high altitude. Genetic, cellular, organ and whole body system responses to high altitudes are covered and chapters discuss these effects on a wide range of diseases. Expert authors provide insight into the care of patients with pre-existing medical conditions that fail in some cases to adapt as well as offer insights into how high altitude research can help critically ill patients. High Altitude: Human Adaptation to Hypoxia is an important new volume that offers a window into greater understanding and more successful treatment of hypoxic human diseases.
Intermittent hypoxia can cause significant structural and functional impact on the systemic, organic, cellular and molecular processes of human physiology and pathophysiology. This book focuses on the most updated scientific understanding of the adaptive (beneficial) and maladaptive (detrimental) responses to intermittent hypoxia and their potential pathogenetic or prophylactic roles in the development and progression of major human diseases. This is a comprehensive monograph for clinicians, research scientists, academic faculty, postgraduate and medical students, and allied health professionals who are interested in enhancing their up-to-date knowledge of intermittent hypoxia research and its translational applications in preventing and treating major human diseases.
The 14th volume in the series will focus on cutting edge research at the interface of hypoxia and exercise. The work will cover the range from molecular mechanisms of muscle fatigue and muscle wasting to whole body exercise on the world’s highest mountains. State of the art papers on training at high altitude for low altitude athletic performance will also be featured.
