NATIONAL QUALIFICATIONS CURRICULUM SUPPORT
Biology Physiology, Health and Exercise Student Monograph [ADVANCED HIGHER] Fiona Andersen
Glasgow Caledonian University
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First published 2000 Electronic version 2001 Š Scottish Consultative Council on the Curriculum 2000 This publication may be reproduced in whole or in part for educational purposes by educational establishments in Scotland provided that no profit accrues at any stage. Acknowledgement Learning and Teaching Scotland gratefully acknowledge this contribution to the Higher Still support programme for Biology. The author and publisher wish to record their thanks to Jim Stafford, Biology Editor, of the Higher Still Development Unit. Drawings are by Douglas McConnach. ISBN 1 85955 853 4 Learning and Teaching Scotland Gardyne Road Dundee DD5 1NY www.LTScotland.com
CONTENTS
Preface
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Introduction Section 1
Section 2
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Exercise and the cardiovascular system (CVS) 1.1 Structure and function of the cardiovascular system 1.2 Pathology of cardiovascular disease (CVD) 1.3 Role of exercise in prevention and treatment of CVD
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Exercise and metabolism 2.1 Energy 2.2 Body composition and weight control 2.3 Diabetes mellitus 2.4 Osteoporosis
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1 9
Bibliography
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Useful websites
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Glossary
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PREFACE
The aim of this monograph is to provide support material for the AH unit Physiology, Health and Exercise . The unit deals with the beneficial effects of physical activity both on the general health of the individual and in the prevention of, or rehabilitation from, certain disease conditions, e.g. cardiovascular disease (CVD), obesity, Type 2 diabetes mellitus and osteoporosis. For these reasons, exercise has been described as the best public health buy . The precise mechanisms by which exercise may confer such health benefits are in many cases still unclear and are the subject of on-going research. Given the wide spectrum of topics to be covered in this unit in a relatively short time, this text can provide only limited coverage of several important areas in such a rapidly expanding field. Despite the strong evidence that regular physical activity benefits health and well-being, surveys in the UK indicate that most adults do not take enough exercise for optimum health, with most having sedentary lifestyles with little leisure-time physical activity. Advances in technology also mean that there has been a marked decrease in physical activity associated with most occupations. Children too are at risk. Childhood obesity rates are increasing due mainly to inactivity. Children now seldom walk or cycle to school and many leisure activities are increasingly being replaced by sedentary pastimes, e.g. computer games, television, etc. Girls especially become less active as they move through adolescence, thereby increasing their risk of becoming obese, and of developing coronary heart disease (CHD), high blood pressure and diabetes in adulthood. For these reasons and many others, not least the considerable cost to the health service, increasing activity levels at all ages in the population has been identified as an important health priority.
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INTRODUCTION
Exercise and coronary heart disease There is now a worldwide consensus that physical activity not only protects against coronary heart disease but is an independent risk factor, along with smoking, high blood pressure and high blood cholesterol. There is growing evidence that even moderate levels of activity, such as brisk walking, may confer a benefit. Physical activity is also important in the treatment and management of individuals with known cardiovascular disease, including those who have already suffered a heart attack, have angina or heart failure. Regular activity reduces the risk of a second heart attack and therefore plays an important role in cardiac rehabilitation programmes. The mechanisms by which physical activity reduces CHD risk are not fully understood, but alteration in lipid metabolism and blood clotting mechanisms are thought to be important. This text starts by reviewing the physiology of the cardiovascular system and describes some aspects of the basic pathophysiology of heart disease. The role of exercise in the prevention and treatment of CHD is discussed and some well established tests of aerobic fitness are described. Exercise and metabolism Obesity is now a significant health problem in many developed countries including the UK, and its prevalence is increasing in both adults and children. Although there has been a decline in average food intake in these populations, this has been counterbalanced by an even greater decline in physical activity levels. Evidence suggests that weight loss achieved through an increase in physical activity, combined with a reduction in food intake, is more likely to be maintained than weight lost by dieting alone. In addition, increased physical activity ensures that the weight lost is mainly fat, whereas weight lost on very low energy diets alone tends to be about 50% lean tissue.
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INTRODUCTION
The text explores the concept of energy balance and describes methods of measuring energy expenditure. Examples of the energy cost of some activities are given, and also how fat loss may be achieved on different regimes. The importance of measuring body composition rather than body weight only is discussed, and some commonly used methods of measuring body composition are described. Exercise and non-insulin dependent (Type 2) diabetes mellitus Regular physical activity helps to control blood glucose levels and insulin activity in both the Type 2 diabetic and non-diabetic subjects. Physically active Type 2 diabetics are at lower risk of some of the vascular complications of the disorder than their sedentary counterparts. Active individuals are less likely to develop diabetes with age, therefore regular physical activity plays an important role in the prevention as well as the treatment of Type 2 diabetes. The text discusses the normal control of blood glucose levels and briefly describes some of the symptoms and causes of both types of diabetes. The protective role of exercise is also described. Exercise and osteoporosis The decrease in bone density with age is partly due to declining levels of physical activity. In particular, post-menopausal women are at high risk of developing osteoporosis which increases their risk of bone fractures, particularly of the wrist, vertebrae and hip. It has been shown that regular, moderate weight-bearing activity such as brisk walking can help deter these age related changes in bone density.
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