Chapter 10 Lecture

Chapter 10 Lecture Outline Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display

Physical Fitness “ The ability to perform moderate to vigorous activity without undue fatigue” Fat usage by the body Increased physical fitness means improved usage of fat for energy

Nutrition and Physical Activity Only 15% of adults are regularly physically active NUTRITION (intake) Physical Performance Nutrient Use

Healthy People 2010 Decrease inactivity in adults by 50% Increase the number of people who exercise regularly Increase the development of vigorous physical activity Increase adults who perform muscular strength and endurance activities

Beginning an Exercise Program Start out slowly Vary your workout — Make it fun Include others — Keep accountable Set attainable goals Set aside specific time Reward yourself Focus on long-term and not on occasional setbacks

2005 Dietary Guidelines for Americans 30 minutes/day physical activity Reduce risk of chronic disease 60 minutes/day physical activity Manage body weight and prevent weight gain 90 minutes/day physical activity Sustain weight loss

Fuel for Muscle Work ATP Chemical energy Used by cells for muscle contractions Only small amount is stored in resting cells 2-4 seconds worth of work Other sources of energy are needed

Phosphocreatine (PCr) High-energy compound Formed and stored in muscle cells PCr + ADP Cr + ATP Activated instantly Replenishes ATP Sustains ATP (work) for a few minutes

Anaerobic Glycolysis Limited oxygen — Intense physical activity (sprinting) Pyruvate is converted to lactate Produces 2 ATP per glucose ~5% of energy potential Replenishes ATP quickly Cannot sustain ATP production 30 seconds to 2 minutes of work Lactate build-up Changes acidity that inhibits glycolysis enzymes

Aerobic Glycolysis Plenty of oxygen available Low to moderate intensity (jogging) Produces 36-38 ATP per glucose 95% of energy potential ATP replenished slowly Sustained ATP production 2 minutes to 3 hours of work

Glycogen Temporary storage of glucose in liver and muscle Muscle glycogen Used only by that muscle Liver glycogen released into bloodstream During low to moderate intensity Can sustain work for up to 2 hours “Bonking” Depleted glycogen Work at ~50% of maximal capacity

Maintaining Normal Blood Glucose Level Important For activity lasting longer than 20-30 minutes Intake of 30-60 gm carbohydrates per hour During strenuous endurance activity Delays fatigue by 30-60 minutes

Fat Fuel (Fatty Acid) Majority of stored energy in the body Fatty acids Converted to ATP by muscle cells 12 ATP produced Per each turn of the Citric Acid Cycle 108 ATP for each 16 C fatty acid chain Trained muscles Have more mitochondria Have greater ability to use fat as fuel

Fat Fuel Rate of fat use Dependent on concentration of fatty acids in the bloodstream Prolonged exercise Fat becomes main fuel source Intense activity Fat is not a major source of fuel Requires more oxygen for aerobic breakdown (than glucose)

Protein — Minor Source of Fuel During rest and low/moderate exercise Provides 2%-5% of energy needs During endurance exercise Provides 10%-15% of energy needs Branched-chain amino acids provide most of the energy Resistance exercise uses protein less Average diet Provides ample amount of these amino acids Supplements not needed

Fuel Use During Physical Activity

Calorie Needs Individual needs vary Monitoring weight and body fat If weight falls, increase intake If body fat increases, cut back in fat (& kcal) and maintain activity Desirable body fat for male athletes: 5%-18% Desirable body fat for female athletes: 17%-28%

Carbohydrate Needs Main fuel for many types of activity Consume ~60% of total kcal from carbohydrate Adhere to the Food Guide Pyramid > 5 gm of carbohydrate/kg body weight Aerobic and endurance athletes 7-10 gm carbohydrates/kg body weight ~ 500-600 gm of carbohydrates/day

Carbohydrate Loading Events lasting longer than 60-90 minutes Maximize glycogen stores Tapering of exercise while increasing carbohydrate intake Additional water weight

Carbohydrate (CHO) Loading 600 600 600 450 450 450 CHO (grams) rest 20 20 40 40 60 Exercise Time 1 2 3 4 5 6 Days Before Com- petition

Fat Needs ~35% of total kcal Rich in monounsaturated fats Limit saturated fats Limit trans fat

Protein Needs Recommend 1.0 - 1.6 gm protein/kg body weight Up to 1.7 gm/km body weight for athletes beginning strength training Needs are easily met by a normal diet Protein supplements are not necessary Excessive protein has not been shown to be beneficial

Current Protein Recommendations

Vitamins and Minerals Vitamin E and C Slightly higher needs Antioxidant properties Thiamin, riboflavin, vitamin B-6, potassium, magnesium, iron, zinc, copper, and chromium needs May also be higher (role in metabolism or sweat) Increase intake of fruits and vegetables

Iron Needs Iron deficiency affects performance Sports anemia Increase in plasma volume but not RBCs Women at risk because of menstruation Focus on iron-rich foods Use of iron supplement may cause toxic effects

Calcium Needs Restriction of dairy products by women Irregular menstruation/Amenorrhea Severe bone loss and osteoporosis Extra calcium does not compensate for effects of menstrual irregularities Compromises bone health Calcium deficiency increases risk of stress fractures

Fluid Needs Needs of average adults 9 cups per day for women 13 cups per day for men Athletes need more Maintenance of body’s cooling system Water helps dissipate heat from working muscles Avoid losing more than 2% of body weight during exercise For every 1lb. lost replace 2.5-3 cups of fluid

Hydration Thirst: Not reliable indicator of fluid needs General guidelines: Drink 3 C of fluids per each pound of weight loss during activity Check urine color Drink fluid freely 24 hours before event Drink 1 ½ -2 ½ C 2-3 hours before event Consume ½ - 1 ½ C every 15 minutes for events lasting longer than 30 min. Lose no more than 2% of body weight

Heat Exhaustion Heat stress causes depletion of blood volume due to fluid loss Body heat is dissipated through evaporation of sweat (fluid) Fluid loss (sweat): ~3-8 C per hour Humidity interferes with sweat production Dehydration decreases endurance, strength, performance Signs: Profuse sweating, headache, dizziness, nausea, weakness, visual disturbances

Heat Cramps Frequent complication of heat exhaustion Exercising in heat Significant sweating Consuming water without sodium Painful muscle contractions 1-3 minutes at a time Ensure adequate salt and fluid intake Exercise moderately at first in the heat

Heat Stroke High blood flow to working muscles Overloads body’s cooling system Sweating ceases Internal body temperature reaches 104 ° F Fatality rate high Symptoms: Nausea, confusion, irritability, poor coordination, seizures, coma Replace fluids Monitor weight change (fluid loss) Avoid exercising in hot humid conditions

Sports Drinks For Endurance Exercise Recommended for activity > 60 minutes Help maintain blood glucose level and blood volume Delay “bonking” Supply electrolytes <60 minutes Nutrients are easily replaced by diet

Gels and Bars Provide additional fuel Should be taken with fluids Expensive source of nutrients Ideal bars for endurance athletes Contain 40 gm carbohydrate, 10 gm of protein, 4 gram fat, 5 gm of fiber Fortified with vitamins and minerals Toxicities possible with overuse

Content of Energy Bars and Gels

Hyperhydration Excessive intake of water Intake without sodium and chloride During prolonged low-intensity activities Results in low blood sodium and low blood chloride

Pre-Endurance Event Meal Light meal 2-4 hours prior to event Consisting primarily of carbohydrate (top off glycogen stores) Low fat (<25% of energy intake) Little fiber (prevent bloating, gas) Moderate protein Avoid fatty, fried foods Blended or liquid meal recommended for meals eaten 1-2 hours prior

Recovery Meal Carbohydrate-rich meal within 2 hours after endurance event Glycogen synthesis is the greatest 1-2 gm CHO/kg body weight Repeat meal over the next 2 hours Choose high glycemic index foods Aim for 3:1 carbohydrate-to-protein Fluid and electrolyte replacement

Replenishing Muscle Glycogen Availability of adequate carbohydrate Ingestion of carbohydrate soon after exercise Selection of high-glycemic-load carbohydrate Combination of carbohydrate and protein foods

Chapter 10 Lecture

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Chapter 10 Lecture