Chapter 9- Sports Nutrition and Energy Metabolism

Chapter 9- Sports Nutrition and Energy Metabolism -...

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Jennifer Bishop March 27, 2008 Chapter 9: Sports Nutrition and Energy Metabolism Introduction 1. the body gets most of its energy from carbohydrates and fat (converted to mechanical energy) 2. respiration: the process of producing energy from fuels using oxygen and producing carbon dioxide and water 3. intensity of exercise determines how fast the body releases energy a. most energy production needs oxygen i. maximal oxygen consumption/VO 2 Max: the maximum amount of oxygen that can be supplied at any instant in an individual 1. training increases this; more oxygen supplied to cells b. aerobic : the condition of producing energy through processes that require oxygen; having sufficient oxygen to do so i. both fat and carbohydrates can be used c. anaerobic: the condition of producing energy through processes that do not require oxygen; not having sufficient oxygen to produce energy through other processes i. carbohydrates, but not fat used for energy 1. amount of CHO depends on how recently we ate, and duration of exercise 2. stored in liver/muscle cells as glycogen a. when cells run out of glycogen, body goes back to aerobic pathways (fat used for energy) ii. lactic acid produced (accumulates in muscle cells) iii. energy released depends on how fast lactic acid is carried away from muscle cells by bloodstream 4. Intensity/duration of activities determine which fuels the body uses An Ecological Perspective 1. energy demands of intense exercise can be high a. elite athletes may need > 1000 kcals/hour b. training and nutrition are the keys to optimal performance i. training: increases supply of oxygen to muscle cells ii. nutrition: affects availability of fuels cells can use 2. carbohydrates can be used as an energy source for anaerobic and aerobic paths a. when glycogen runs out, the body has to perform aerobically i. performance speed/strength decrease b. the body needs carbohydrates for speed and strength bursts 3. most people store 50,000 kcals of fat, and <2,000 kcals of carbohydrate a. fat is stored as energy since it has a higher energy density (9kcals/gram) b. the body spares carbs and uses fat for energy whenever possible Exercise Basics 1. Nutrition and Exercise a. Exercise helps you take in enough nutrients i. Increased energy expenditure = increased energy intake ii. The more food you eat, the more nutrients you take in iii. Sedentary people don’t need much food (few nutrients) b. exercise is important for weight control i. basal metabolism increases by building/maintaining muscle mass c. exercise helps regulate appetite i. when sedentary people exercise, they decrease energy intake
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ii. when they do intake energy, it matches their expenditure d. exercise helps prevent chronic disease i. increases levels of HDL cholesterol ii. body increases density of capillaries in muscles/heart to increase oxygen supply 1. if a heart attack occurs, these capillaries let blood flow to the affected area of the heart (survival!) iii. prevents type 2 diabetes and some cancers
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Chapter 9- Sports Nutrition and Energy Metabolism -...

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