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Energy Balance

“Aside from the limits imposed by heredity and the physical improvements associated with training, no factor plays a bigger role in exercise performance than does nutrition.” Dr. David Costill, 1988. Energy Balance. Hypothetical daily energy needs of an Ironman triathlete in training.

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Energy Balance

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  1. “Aside from the limits imposed by heredity and the physical improvements associated with training, no factor plays a bigger role in exercise performance than does nutrition.” Dr. David Costill, 1988

  2. Energy Balance

  3. Hypothetical daily energy needs of an Ironman triathlete in training. Activity METS Duration (h) Energy Expenditure (kcal) Sleep 0.9 8.0 540 Office work 1.5 8.0 900 Running (7.5 mph)* 13.5 0.8* 810 Swimming (2 mph)* 8.0 0.5* 318 Bicycling (18.6 mph)* 12.0 1.7* 1,530 Home activities (e.g. cooking, washing dishes, etc.) 2.5 3.0 563 Miscellaneous activities (reading newspaper, talking on phone, etc.) 1.3 2.0 195 4,856 *Based on data from O’Toole, 1989. Energy expenditure calculated as: (METS  75 kg body weight  hours of activity = kcal)

  4. Daily Energy Intakes of Elite Athletes

  5. Map of the Trek WR 2,928 km Unsupported Ski Trek March - June, 1996 Torry Larsen Rune Gjeldnes

  6. WR 2,928 km Ski Trek Details • 2,928 km (1,815 miles) in 83 days • 9 hrs/d of trekking (~22 miles/d) • Each pulling 150 kg (330 lb sled) • Average energy intake was 6,000 kcal/d • Average weight loss was only 5.3 kg (~12 lbs) and 4% reduction in body fat (DEXA) • Average weight loss of Army Rangers during 64 days of training is 10 – 20 kg (22 – 44 lbs)!

  7. Macronutrients

  8. Macronutrient Composition and Performance: Overview 60 -70% of kcal 350-600g/d 5-10g/kg/d 15-25% of kcal FAT PRO CHO 15% of kcal 1.2-1.8g/kg/d

  9. Dietary Protein

  10. Meredith et al., 1989 80 60 40 20 0 -20 -40 -60 -80 Nitrogen Balance (mg/kg/d) RDA Mean = .94g/kg/d 0.3 0.5 0.7 0.9 1.1 1.3 1.5 Protein Intake (g/kg/d)

  11. Tarnopolsky et al., 1992 Sedentary 300 250 200 150 100 50 Strength Athletes * * Whole Body Protein Synthesis (mg/kg/hr) 0.9 1.4 2.4 Protein Intake (g/kg/d)

  12. Current Protein Intake Recommendations

  13. Protein and Amino Acid Contents of Common Foods and Popular Supplements

  14. Dietary Carbohydrate

  15. Why Are Carbohydrates So Important? • Carbohydrates are the primary muscular fuel source for intense exercise

  16. FAT CHO The “Crossover Concept” Adapted from: Brooks and Mercier, 1994

  17. Adapted from: Romijn et al., 1993

  18. Why Are Carbohydrates So Important? • Carbohydrates are the primary muscular fuel source for intense exercise • Carbohydrate body stores are limited; when depleted, athletes cannot exercise intensely and experience fatigue

  19. Adapted from: Bergstrom and Hultman, 1967

  20. Adapted from: Gollnick, 1974

  21.  Low CHO Diet  Normal Diet  High CHO Diet Adapted from: Bergstrom et al., 1967

  22. Why Are Carbohydrates So Important? • Carbohydrates are the primary muscular fuel source for intense exercise • Carbohydrate body stores are limited; when depleted, athletes cannot exercise intensely and experience fatigue • Athletes who train regularly and intensely require more dietary carbohydrates to replenish what is used

  23. Adapted from: Costill, 1985

  24. Are athletes eating enough carbohydrates?

  25. Recommendations for Training • Absolute CHO intakes should approach 350-600g/d or 5-10g/kg/d • The % of calories coming from CHO is not as important as long as absolute needs are met

  26. Adapted from: Nieman et al., 1989

  27. Data from: Lamb et al., 1990

  28. Why Are Carbohydrates So Important? • Carbohydrates are the primary muscular fuel source for intense exercise • Carbohydrate body stores are limited; when depleted, athletes cannot exercise intensely and experience fatigue • Athletes who train regularly and intensely require more dietary carbohydrates to replenish what is used • Carbohydrates consumed before, during, and after exercise maximize performance

  29. Sports Drinks

  30. Adapted from: McConell et al., 1999

  31. Adapted from: Tsintzas et al., 1993

  32. Adapted from: Wright et al., 1991

  33. Carbohydrates and Performance Dorando Pietri, 1908 Olympic Marathon

  34. Carbohydrates in the post-exercise period: Glycogen Resynthesis

  35. * Adapted from: Fallowfield et al., 1993

  36. Nutrition and Athletic Performance:Summary • Number one nutritional priority is maintaining energy balance • Athlete protein needs are higher than the RDA, but athletes* already consume even more than the upper scientific recommendations • Carbohydrate needs are best expressed on a g/kg/d basis (or in absolute terms: 350-600g/d) • Carbohydrates improve athletic performance for endurance exercise (> 90 continuous minutes)

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