Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 8 Nutritional Considerations for Intense Training and Sports Competition

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins The Precompetition Meal  Readily digestible foods  Should contribute to energy and fluid requirements  Meals high in carbohydrates and relatively low in lipids and proteins  Three to four hours to digest and absorb the precompetition meal

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Ideal Precompetition Meal  The ideal precompetition meal: Contains 150 to 300 grams of carbohydrates Is consumed 3 to 4 hours before the event Contains little fat Contains little fiber

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Liquid Meals  High carbohydrate content  Supply fluids  Digest rapidly  Can be used for day-long events  Supplement calorie intake in those with difficulty maintaining body weight

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Nutrition Bars  High protein content  Approximately 25 g of carbohydrate  Often include vitamins and minerals  May contain dietary supplements  Should not substitute for normal food intake

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Nutrition Powders and Drinks  High protein content  Contain vitamins, minerals, and other dietary supplements  Come in powdered form or premixed  Contain fewer calories per serving than nutrition bars

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Carbohydrates before Exercise  If simple sugars are consumed, they should be consumed at least 60 minutes before exercising. This time gives hormones the chance to rebalance.  Fructose absorbs more slowly compared to glucose or sucrose. High-fructose beverages can produce significant gastrointestinal distress.

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Carbohydrates during Exercise  Allows for a greater intensity during prolonged activities  Consuming about 60 g of liquid or solid carbohydrates each hour benefits: High-intensity, long-duration aerobic exercise Repetitive short bouts of near-maximal effort  Spares muscle glycogen  Helps maintain a more optimal blood glucose level

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Carbohydrates after Exercise  High-glycemic carbohydrate-rich foods  Either a single large meal or small frequent meals will replenish glycogen stores.  Should be consumed as soon as possible after the activity  Avoid legumes, fructose, and milk products.

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Glycemic Index  Indicates how a carbohydrate-containing food affects blood glucose levels  High-glycemic index  Moderate-glycemic index  Low-glycemic index  Affected by food preparation, ripeness, and how foods are combined

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Glycogen Depletion  High-intensity aerobic exercise for 1 hour decreases liver glycogen by about 55%.  A 2-hour strenuous workout nearly depletes the glycogen content of the liver and specifically exercised muscles.

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Hydration Solutions  Carbohydrate-containing solutions consumed during exercise enhance endurance performance by maintaining blood sugar concentration.  Glucose supplied in the blood can: Spare existing glycogen in active muscles Serve as “ reserve ” blood glucose for later use should muscle glycogen become depleted

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Oral Rehydration Solutions  Provide additional glucose  Minimize the effects of dehydration on: Cardiovascular dynamics Temperature regulation Exercise performance  Adding electrolytes aids in: Maintaining thirst mechanism Reducing the risk of hyponatremia

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Carbohydrate-Electrolyte Beverages  The ideal hydration solution contains between 5% and 8% carbohydrates.  This permits carbohydrate replenishment without adversely affecting fluid balance and thermoregulation.  Maintains glucose metabolism and preserves glycogen during prolonged exercise

Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Hydration during Exercise  Adding moderate amounts of sodium to the ingested fluid helps to maintain plasma sodium concentration.  This benefits the ultra-endurance athlete at risk for hyponatremia.  Maintaining plasma osmolality with added sodium in the hydration beverage reduces urine output and sustains the sodium-dependent osmotic drive to drink.

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High-Fat Diets  Conflicting research findings  Detrimental health risks are possible.  Heath risks may not apply to athletes.  Significant restrictions in fat impair exercise endurance.