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Physical Activity and Nutrition Readings: Chapter 14, pages 466 and 467, 471 - 487 Next Lecture: Chapter 10, pages 307 - 335 • an estimated 57% of Canadians are not physically active enough to benefit their health (2001 data) • physical inactivity declined from 62% in 1994 to 55% in 1998 • British Columbia has the lowest inactivity rate of Canadian provinces at 46% • it’s estimated that reducing the percent of the population that is physically inactive to 10% would save approximately $5 billion in lifetime costs for medical care, sick leave, and lost tax revenues • sedentary individuals have 50% more health problems than active individuals • over one half of Canadians aged 5 - 17 are not active enough for healthy growth and development Canadian Fitness and Lifestyle Research Institute: www.cflri.ca What is Physical Fitness? Definition • the characteristics that enable the body to perform physical activity • the ability to meet routine physical demands with enough reserve energy to rise to a physical challenge Benefits of physical fitness • • • • • • • • • • • improved sleep nutritional health healthy body composition healthy bone mineral density improved immune function reduced risk of cardiovascular disease, Type II diabetes, and some cancers reduced stress and anxiety improved self-esteem and lowered risk of depression improved cognitive functioning, alertness and memory injury reduction and low back pain greater longevity and quality of life Sources of Energy During Physical Activity Physical activity increases the energy needs of working tissues including the muscles and the heart…where does this energy come from? 1. : Quick Energy Compounds • very small pool of ATP available in cells • CP (creatine phosphate) can release phosphate which combines with ADP to form ATP but supplies are limited • anaerobic creatine phosphate + ADP creatine + ATP Sources of Energy During Physical Activity 2. Carbohydrate: • derived from muscle and liver glycogen stores • in activities of extreme intensity (20s to 3 minutes): – oxygen needs of muscle exceed the ability of cardiovascular system to supply oxygen – glucose is used to produce ATP – by product is • in activities of high intensity (3 to 20 minutes): – glucose is used AEROBICALLY to produce ATP • in activities of moderate intensity (> 20 minutes): – glucose oxidation is supplemented with Sources of Energy During Physical Activity 3. Fat • initially during exercise blood [fatty acid] decreases • after 20 minutes there is an increase in release of fatty acids from stores – due to actions of hormone (adrenalin) • endurance training produces adaptations that – increased size and number of is muscles – increased number of capillaries to supply oxygen and nutrients to muscles Sources of Energy During Physical Activity 4. Protein • • contributes about 10% to energy expenditure both during activity and at rest Factors that influence protein use during activity: • high dietary protein use of protein as a fuel • increased duration of activity protein use as a fuel • increased intensity of activity protein use as fuel • increased training (especially strength training) use of protein as fuel Influence of Intensity and Duration on Fuel Use increased duration fatty acid oxidation decreased intensity glucose utilization decreased duration fatty acid oxidation increased intensity glucose utilization Duration Intensity 8 – 10 seconds EXTREME 20 sec – 3 min VERY HIGH 3 – 20 minutes HIGH > 20 minutes MODERATE Preferred Fuel Source Effect of Diet on Physical Endurance Maximum Endurance Time fat and protein diet normal mixed diet high carbohydrate diet Figure 14-3, page 473 Diet to Support Physical Activity Water • nutrient required in largest amounts by the body • needs increase during physical activity Body can lose water in four ways: 1. urine 2. feces 3. sweat 4. respiration Diet to Support Physical Activity Water and Temperature Regulation • heat production increases 15-20x during exercise compared to rest • body cools itself by sweating – 1 L of sweat dissipates about 600 kcal of heat – prevents an increase in body temperature of about 10°C • of sweat cools the body • blood is rerouted through capillary beds that lie just beneath surface of skin to cool the blood • endurance athletes can lose of water or more during each hour of activity Diet to Support Physical Activity Water and Temperature Regulation cont. • in hot humid weather, need for water increases even more • dehydration not only decreases performance but can cause dizziness, cardiac arrhythmias, muscle spasms, delirium, and death Hydration Schedule 2 hrs before 2 – 3 cups 15 min before 1 – 2 cups every 15 min during ½ - 1 cup after at least 2 cups for each lb body weight lost Diet to Support Physical Activity Electrolytes • in addition to contributing to water loss, sweat also results in loss of ELECTROLYTES – electrically charged minerals – sodium, potassium, chloride, and magnesium • minerals are important for water balance • losses normally replaced through regular • for exercises lasting longer than one hour, replacement of fluids with water AND electrolytes may provide a slight performance advantage • more important for athletes in competitions lasting 4+ hours with heavy sweating Diet to Support Physical Activity Energy Bars and Drinks • during endurance activities lasting longer than one hour, glycogen supplies risk • maintaining blood glucose levels can prolong time to exhaustion Replenishing Energy DURING activity… • glucose replacement (200 g) useful in activities lasting longer than 2 hours • sports drinks with 6 - 10% carbohydrates (50 - 100 kcal per cup) Diet to Support Physical Activity Replenishing Energy AFTER activity… • a high carbohydrate meal eaten within 15 minutes accelerates rate of glycogen storage by 300%, called “glycogen window” Are energy bars or drinks necessary? Diet to Support Physical Activity Protein • discuss previously in Lectures 8 and 9 • athletes have increased need for protein – due to need to repair and build muscles after activity – see Table 14-4 for recommended intakes Too much protein? • supplements may result in – dehydration – displacement of carbohydrates from diet, may result in insufficient replenishment of glycogen stores – kidney problems Diet to Support Physical Activity Vitamins and Minerals • many vitamins and minerals are important for energy metabolism • supplements DO NOT enhance physical performance • impair performance Iron • physically active young women prone to iron deficiency • multiple contributing factors • supplementation should be based on blood tests, not self-assessment