9/23/2008
Chapter 3
Optimal Nutrition for Exercise
Copyright © 2007 Lippincott Williams & Wilkins.
McArdle, Katch, and Katch: Exercise Physiology: Energy,
Nutrition, and Human Performance, Sixth Edition
Nutrient Requirements
• Recommended nutrient intake
– Protein
• 0.83 gg/kgg bodyy weight
g
– Lipid
• < 30% total kCals
– Carbohydrate
• 55 – 60% kCals
– Increased need for endurance athletes
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McArdle, Katch, and Katch: Exercise Physiology: Energy,
Nutrition, and Human Performance, Sixth Edition
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Nutrition, and Human Performance, Sixth Edition
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High-Fat Versus Low-Fat Diets
• High-fat diets may stimulate adaptive
responses that enhance fat use
– Controversial due to increased risks for CHD
• Research has not demonstrated benefits of a
high-fat diet for improving endurance
performance
• A high-carbohydrate diet is still
recommended over a high-fat diet
Copyright © 2007 Lippincott Williams & Wilkins.
McArdle, Katch, and Katch: Exercise Physiology: Energy,
Nutrition, and Human Performance, Sixth Edition
The Food Guide Pyramid
• The essentials of good nutrition are
displayed in this model
– The model has been modified to guide
modified diets
– Mediterranean Diet Pyramid
• Protection against CHD
– Vegetarian Diet Pyramid
• Complete nutrition without meat/fish
Copyright © 2007 Lippincott Williams & Wilkins.
McArdle, Katch, and Katch: Exercise Physiology: Energy,
Nutrition, and Human Performance, Sixth Edition
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Nutrition, and Human Performance, Sixth Edition
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Copyright © 2007 Lippincott Williams & Wilkins.
McArdle, Katch, and Katch: Exercise Physiology: Energy,
Nutrition, and Human Performance, Sixth Edition
Copyright © 2007 Lippincott Williams & Wilkins.
McArdle, Katch, and Katch: Exercise Physiology: Energy,
Nutrition, and Human Performance, Sixth Edition
Exercise and Food Intake
• Energy requirements vary depending upon
the volume of training
• Examples of events requiring increased
energy intake
– Tour de France
– Ultraendurance running competition
– Extreme ultraendurance sports
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Eat More, Weigh Less
• Compared to sedentary people, active
individuals
– Maintain a lower body weight
– Are leaner
– Have a better CHD risk profile
• This is true despite having an increased
intake of food.
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McArdle, Katch, and Katch: Exercise Physiology: Energy,
Nutrition, and Human Performance, Sixth Edition
Precompetition Meal
• The ideal meal
–
–
–
–
Provides adequate carbohydrate
Ensures optimal hydration
Is well tolerated by the athlete
Is easily digestible
• The meal should be consumed around 3
hours prior to competition.
Copyright © 2007 Lippincott Williams & Wilkins.
McArdle, Katch, and Katch: Exercise Physiology: Energy,
Nutrition, and Human Performance, Sixth Edition
Protein or Carbohydrate?
The evidence supports carbohydrate
– Carbohydrate is the main energy nutrient
– Carbohydrates
y
replenish
p
liver and muscle
glycogen
– Carbohydrate digestion and absorption are
faster
– High-protein meals elevate resting
metabolism
– Protein breakdown facilitates dehydration
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How Much Should Be Consumed?
• Carbohydrates
– 3 to 5 grams/kg body weight
• 150 – 300 grams total
– Consume 3 hours prior to exercising
– Contain relatively little fat and fiber
Copyright © 2007 Lippincott Williams & Wilkins.
McArdle, Katch, and Katch: Exercise Physiology: Energy,
Nutrition, and Human Performance, Sixth Edition
Liquid Meals
• Liquid meals are convenient.
• Other benefits of liquid meals
– Provide some lipid and protein
– Provide fluid and high carbohydrate content
– Digest rapidly
Copyright © 2007 Lippincott Williams & Wilkins.
McArdle, Katch, and Katch: Exercise Physiology: Energy,
Nutrition, and Human Performance, Sixth Edition
Prepackaged Meals
• Contain relatively high protein content
• May provide dietary supplements
– Weight loss
– Meal replacement
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Nutrition Powders and Drinks
• High protein content
• Dietary supplement ingredients
• Replace glycogen reserves before and
after exercise and competition
Copyright © 2007 Lippincott Williams & Wilkins.
McArdle, Katch, and Katch: Exercise Physiology: Energy,
Nutrition, and Human Performance, Sixth Edition
Carbohydrate Feedings
• Prior to exercise
– Should be consumed between 1 and 3 hours
prior to event to prevent rebound hypoglycemia
• The glycemic index and preexercise
feedings
– Fructose is absorbed more slowly than glucose
– If glucose is used, allow 1 hour for
reestablishment of hormone levels
Copyright © 2007 Lippincott Williams & Wilkins.
McArdle, Katch, and Katch: Exercise Physiology: Energy,
Nutrition, and Human Performance, Sixth Edition
Carbohydrate Feedings
• During prolonged high-intensity exercise
–
–
–
–
–
Spares muscle glycogen
Maintains more optimal
p
blood gglucose
Postpones fatigue
Improves endurance performance
Augments sprint capacity near the end of
performance
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Carbohydrate Feedings
• In recovery
– Use moderate- to high-glycemic index foods
– Keep lipid content low
• Consuming food after exercise increases
cellular uptake of glucose due to
– Increased activity of GLUT 1 and GLUT 4
– Lowered catecholamine levels and increased
insulin levels
– Increased activity of glycogen synthase
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McArdle, Katch, and Katch: Exercise Physiology: Energy,
Nutrition, and Human Performance, Sixth Edition
Postexercise Meals
• Consume high-glycemic carbohydrate-rich
foods as soon as possible after exercise.
– 50 – 75 grams every 2 hours
h
up to 500 grams
• Remain inactive to enhance glycogen
resynthesis
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McArdle, Katch, and Katch: Exercise Physiology: Energy,
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Glucose, Electrolytes, and Water
Uptake
• Glucose, water, and electrolytes are all
important.
• Glucose and water influence one another’s
uptake.
– Large fluid volume impairs carbohydrate uptake.
– Concentrated sugar solutions impairs fluid
replacement.
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Gastric Emptying & Intestinal Absorption
• High fluid volumes speed gastric emptying
– Consume 400 – 600 mL immediately preexercise
– Ingest 150 – 200 mL every 15 minutes during
exercise
– Carbonated beverages slow emptying
– Caffeine and alcohol promote diuresis
– Osmolarity
• Particles in solution
• Polymers may improve emptying rate
• Sodium reduces urine output
Copyright © 2007 Lippincott Williams & Wilkins.
McArdle, Katch, and Katch: Exercise Physiology: Energy,
Nutrition, and Human Performance, Sixth Edition
Copyright © 2007 Lippincott Williams & Wilkins.
McArdle, Katch, and Katch: Exercise Physiology: Energy,
Nutrition, and Human Performance, Sixth Edition
Fluid Replacement During Exercise
• Consume ~ 250 mL every 15 minutes
• Use a drink containing 5 – 8%
carbohydrates
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