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Chapter 9 Nutrition and Performance. Questions about sports nutrition. Can diet improve athletic endeavor? What is the optimal diet for athletes? Does exercise increase the need for vitamin and mineral supplements? Do strength athletes need protein supplements to maximize size and power?

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Chapter 9 Nutrition and Performance


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    1. Chapter 9Nutrition and Performance Exercise Testing and Prescription: A Health-Related Approach by Nieman. McGraw-Hill.

    2. Questions about sports nutrition • Can diet improve athletic endeavor? • What is the optimal diet for athletes? • Does exercise increase the need for vitamin and mineral supplements? • Do strength athletes need protein supplements to maximize size and power? • What ergogenic aids are safe and beneficial? Exercise Testing and Prescription: A Health-Related Approach by Nieman. McGraw-Hill.

    3. Principles of Sports Nutrition • Prudent diet is the cornerstone • Increase total energy intake • Keep dietary carbohydrate intake high (55-70%) • Drink large amounts of fluid • Keep a close watch on iron deficiency • Vitamin & mineral supplements are not needed • Protein supplements do not benefit • Rest and emphasize carbohydrates prior to endurance events • Use of ergogenic aids is unethical • Fat loading is not recommended Exercise Testing and Prescription: A Health-Related Approach by Nieman. McGraw-Hill.

    4. Nutrition Basics • Six groups of essential nutrients (see page 283 and Table 9.1) • Carbohydrates • Fats • Proteins • Vitamins • Minerals • Water • RDA/DRI --- see Table 9.1 Exercise Testing and Prescription: A Health-Related Approach by Nieman. McGraw-Hill.

    5. Exercise Testing and Prescription: A Health-Related Approach by Nieman. McGraw-Hill.

    6. 10 Dietary guidelines for all Americans, Year 2000: –Aim, Build, Choose for Good Health (see pages 286-298) • Aim For Fitness • 1. Aim for a healthy weight. • 2. Be physically active each day. • Build A Healthy Base • 3. Let the Pyramid guide your food choices. • 4. Choose a variety of grains daily (whole grains). • 5. Choose a variety of fruits and vegetables daily. • 6. Keep food safe to eat. • Choose Sensibly • 7. Choose a diet low in saturated fat & cholesterol & moderate in total fat. • 8. Choose beverages & foods that limit intake of sugar. • 9. Choose and prepare foods with less salt. • 10. If you drink alcohol, do so in moderation. Exercise Testing and Prescription: A Health-Related Approach by Nieman. McGraw-Hill.

    7. See Box 9.3 for more detail. Figure 9.1 Exercise Testing and Prescription: A Health-Related Approach by Nieman. McGraw-Hill.

    8. Figure 9.2 Exercise Testing and Prescription: A Health-Related Approach by Nieman. McGraw-Hill.

    9. Figure 9.3 Exercise Testing and Prescription: A Health-Related Approach by Nieman. McGraw-Hill.

    10. Figure 9.4 Exercise Testing and Prescription: A Health-Related Approach by Nieman. McGraw-Hill.

    11. Exercise Testing and Prescription: A Health-Related Approach by Nieman. McGraw-Hill.

    12. Principle 1: Prudent Diet is the Cornerstone (Table 9.7): Dietary Practices of Athletes • Athletes tend to have high energy intakes (dependent on size and sport energy demands). (See Table 9.6). • Diet quality is similar to that of general population (too high in fat, low in carb), falling short of standards established for athletes. • Vitamin and mineral intake generally exceeds RDA standards, primarily because of high energy intake. • Athletes at risk of nutrient deficiency: sports that emphasize leanness (gymnasts, wrestlers, ballet dancers, body builders, female runners). See Box 9.4 for recommendations for wrestlers. Exercise Testing and Prescription: A Health-Related Approach by Nieman. McGraw-Hill.

    13. Exercise Testing and Prescription: A Health-Related Approach by Nieman. McGraw-Hill.

    14. Principle #2: Increase Total Energy Intake • Athletes are capable of amazingly high levels of energy output (see Figure 9.5). • In UK 24-h cycling time trial in a lab, one cyclist expended 20,166 kcal • Athletes are high energy expenders for two reasons: • High working capacities • Ability to work at a high % of maximal capacity • Expended in short period of time • High glycogen depletion • High sweat rates • Muscle and GI trauma • Energy and ATP Production (Figures 9.6, 9.7, 9.8) Exercise Testing and Prescription: A Health-Related Approach by Nieman. McGraw-Hill.

    15. Figure 9.5 Exercise Testing and Prescription: A Health-Related Approach by Nieman. McGraw-Hill.

    16. Figure 9.6 Exercise Testing and Prescription: A Health-Related Approach by Nieman. McGraw-Hill.

    17. Figure 9.7 Exercise Testing and Prescription: A Health-Related Approach by Nieman. McGraw-Hill.

    18. Figure 9.8 Exercise Testing and Prescription: A Health-Related Approach by Nieman. McGraw-Hill.

    19. Factors That InfluenceFuel Utilization • Intensity and duration of exercise • % carb usage greater during high intensity exercise, with fat usage increasing as duration increases (Table 9.8, 9.9, Figures 9.9, 9.10). • Fitness status • At any given workload, fit people use a greater %fat for fuel, sparing glycogen (Figure 9.11). • Previous diet • If pre-event meal is high in carb, relatively more is stored and available, increasing exercise time (Figure 9.12). Exercise Testing and Prescription: A Health-Related Approach by Nieman. McGraw-Hill.

    20. Exercise Testing and Prescription: A Health-Related Approach by Nieman. McGraw-Hill.

    21. Exercise Testing and Prescription: A Health-Related Approach by Nieman. McGraw-Hill.

    22. Fig 9.9 Exercise Testing and Prescription: A Health-Related Approach by Nieman. McGraw-Hill.

    23. Figure 9.10 Exercise Testing and Prescription: A Health-Related Approach by Nieman. McGraw-Hill.

    24. Figure 9.11 Exercise Testing and Prescription: A Health-Related Approach by Nieman. McGraw-Hill.

    25. Figure 9.12 Exercise Testing and Prescription: A Health-Related Approach by Nieman. McGraw-Hill.

    26. Principle 3: Increase intake of carbohydrate (55-70%) • Glycogen found to play important role in intense exercise (70-85%) (e.g., running, cycling, soccer) (Figures 9.11 and Table 9.9). • Endurance training leads to a higher level of stored carbohydrate and a greater utilization of fat (Table 9.8, Figure 9.11). • Exhaustion is tied to low muscle glycogen levels and is limiting in bouts lasting longer than 60-90 minutes (Figure 9.14). • When muscle and liver glycogen is low, a high work output cannot be maintained. Exercise Testing and Prescription: A Health-Related Approach by Nieman. McGraw-Hill.

    27. Figure 9.14 Exercise Testing and Prescription: A Health-Related Approach by Nieman. McGraw-Hill.

    28. Principle 3: Carbohydrate (cont.) • During the first hour, most of the carb and fat come from within the muscle (Figures 9.10, 9.15). As exercise continues, more and more demands are placed on fat stores and blood glucose. • During strenuous training, muscle glycogen stores undergo rapid day-to-day fluctuation (Figures 9.16, 9.17). • Ingest 8-10 g/kg carbohydrate soon after long-term exercise to restore glycogen quickly (and consider high-glycemic-index foods (Figure 9.18, Box 9.5). Exercise Testing and Prescription: A Health-Related Approach by Nieman. McGraw-Hill.

    29. Figure 9.15 Exercise Testing and Prescription: A Health-Related Approach by Nieman. McGraw-Hill.

    30. Figure 9.16 Exercise Testing and Prescription: A Health-Related Approach by Nieman. McGraw-Hill.

    31. Figure 9.17 Exercise Testing and Prescription: A Health-Related Approach by Nieman. McGraw-Hill.

    32. Figure 9.18 Exercise Testing and Prescription: A Health-Related Approach by Nieman. McGraw-Hill.

    33. Exercise Testing and Prescription: A Health-Related Approach by Nieman. McGraw-Hill.

    34. Principle 4: Increase Fluid Intake • As the muscle burns fuel, 70-80% is transformed into heat (body heat can rise 1°C/5 min, causing death in 20-30 min). • During exercise, sweat evaporation accounts for >80% of heat loss (1 liter of sweat evaporation on the skin removes 600 kcal heat) (Figures 9.19, 9.20). • Sweat losses can range from 0.5-3.7 l/hr of exercise, depending on the workrate and environmental conditions (Figure 9.21). • Loss of >2% body water impairs performance (see Table 9.12, Figure 9.22). See Figure 9.23 for summary of how to attain water balance in the body. Box 9.6 summarizes ACSM position stand on exercise and fluid replacement. Exercise Testing and Prescription: A Health-Related Approach by Nieman. McGraw-Hill.

    35. Figure 9.19 Exercise Testing and Prescription: A Health-Related Approach by Nieman. McGraw-Hill.

    36. Figure 9.20 Exercise Testing and Prescription: A Health-Related Approach by Nieman. McGraw-Hill.

    37. Figure 9.21 Exercise Testing and Prescription: A Health-Related Approach by Nieman. McGraw-Hill.

    38. Exercise Testing and Prescription: A Health-Related Approach by Nieman. McGraw-Hill.

    39. Figure 9.22 Exercise Testing and Prescription: A Health-Related Approach by Nieman. McGraw-Hill.

    40. Figure 9.23 Exercise Testing and Prescription: A Health-Related Approach by Nieman. McGraw-Hill.

    41. Box 9.6 ACSM Position Stand on Exercise & Fluid Replacement • Emphasize fluid intake before exercise by drinking adequate fluids during the day before the event, and drink about 500 ml 2 hours before exercise. • Urine should be light-colored, good volume, no strong smell. • Athletes should start drinking early and at regular intervals during exercise to replace nearly all the water lost from sweating. • 2% drop in body wt from fluid impairs exercise • 0.5-2 cups fluid / 10-15 min of exercise • 2 cups / pound of weight loss • Gastric emptying is promoted by >600 ml gastric volume (maintain largest fluid volume in stomach that is tolerable) • Fluids should be sweetened (6-8% carb), flavored, and cooled to stimulate intake Exercise Testing and Prescription: A Health-Related Approach by Nieman. McGraw-Hill.

    42. ACSM Position Stand on Exercise & Fluid Replacement (cont.) • If the event is longer than 1 hour, carbohydrates and electrolytes should be included in fluids ingested (F 9.24). • Peformance enhanced (fatigue delayed) (Figures 9.25, 9.26) • Water delivery to body not impaired • Enhance palatability • Carbohydrates should be ingested at a rate of 30-60 g/hr (0.6-1.2 lof most sports drinks with 4-8% carb) (T 9.13). • The carbohydrates can be glucose, sucrose, or maltodextrin (fructose can cause GI distress) • Inclusion of sodium (0.5-0.7 g/l water) enhances palatability, promotes fluid retention (less urination), and helps prevent hyponatremia in certain athletes who drink excessive plain water during ultra events • 1 liter sweat has 0.4-1 g sodium Exercise Testing and Prescription: A Health-Related Approach by Nieman. McGraw-Hill.

    43. Exercise Testing and Prescription: A Health-Related Approach by Nieman. McGraw-Hill.

    44. Figure 9.24 Exercise Testing and Prescription: A Health-Related Approach by Nieman. McGraw-Hill.

    45. Figure 9.25 Exercise Testing and Prescription: A Health-Related Approach by Nieman. McGraw-Hill.

    46. Figure 9.26 Exercise Testing and Prescription: A Health-Related Approach by Nieman. McGraw-Hill.

    47. Principle 5: Watch for Iron Deficiency • In the human body, iron is present in all cells and has several vital functions. Too little iron can interfere with these vital functions and lead to morbidity and mortality. Iron has these functions: • carrier of oxygen to the tissues from the lungs in the form of hemoglobin • facilitator of oxygen use and storage in the muscles as myoglobin • transport medium for electrons within the cells in the form of cytochromes • integral part of enzyme reactions in various tissues. Exercise Testing and Prescription: A Health-Related Approach by Nieman. McGraw-Hill.

    48. Principle 5: Watch for Iron Deficiency • 10-80% female athletes (depending on sport and study design) have mild iron deficiency (serum ferritin <12 g/l). Reasons: • Inadequate dietary iron • Increased hemolysis (trauma, temperature, increased blood flow, acidosis, catecholamines) • Increased iron loss in sweat and feces (GI bleeding most important cause) • Extremely rare to find that athletes have anemia (hemoglobin <12 mg/dl for females) (Figure 9.28). (See Table 9.14 & Figure 9.27 for review of iron deficiency). • Mild iron deficiency does not impair health or performance in most female athletes (unlike anemia). Exercise Testing and Prescription: A Health-Related Approach by Nieman. McGraw-Hill.

    49. Exercise Testing and Prescription: A Health-Related Approach by Nieman. McGraw-Hill.

    50. Figure 9.27 Exercise Testing and Prescription: A Health-Related Approach by Nieman. McGraw-Hill.