Transcript Chapter 11: Sports Nutrition: Eating For Peak Performance

Chapter
14
Sports Nutrition
Nutrition and Physical Performance
• Cardiorespiratory fitness
• Muscular strength
• Muscular endurance
Guidelines for Physical Activity
Energy Systems, Muscles, and
Physical Performance
• ATP–CP energy system
• Quick source of ATP
• Cellular ATP and creatine phosphate
• Fuel for 3–15 seconds of maximal effort
Energy Systems, Muscles, and
Physical Performance
• Lactic acid energy system
• Breakdown of glucose to
lactic acid (lactate)
• Doesn’t require oxygen
• Rise in acidity triggers
muscle fatigue
Energy Systems, Muscles, and
Physical Performance
• Oxygen energy system
• Breakdown of carbohydrate
and fat for energy
• Requires oxygen
• Produces ATP more slowly
Energy Systems, Muscles, and
Physical Performance
• Teamwork in energy production
• Anaerobic systems for short duration activities,
early part of endurance activities
• Aerobic systems for endurance activities
• Training
• Decreases reliance
on anaerobic systems
• Extends availability
of glycogen
Energy Systems, Muscles, and
Physical Performance
• Glycogen Depletion
• Initial, primary energy source with gradual
depletion
• “Hit the wall”
• Endurance Training
• Enhances aerobic capacity
• Decreases reliance on anaerobic energy
system
Muscles and Muscle Fibers
• Slow-twitch (ST) fibers
• Breakdown carbohydrate and fat via
aerobic pathways
• Fast-twitch (FT) fibers
• Anaerobic pathways
• Fiber type and the athlete
• Genetics
Optimal Nutrition for Athletic
Performance
• Underlying foundations are similar to
the basic principles in the Dietary
Guidelines for Americans
• Differences
• Increase fluid needs
• Increase energy needs
Energy Intake and Exercise
• Priority = Adequate energy intake by
eating small, frequent meals
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Maintain metabolism
Improve nutrient intake
Achieve desirable body composition
Support a training schedule
Reduce injuries
Carbohydrate and Exercise
• High-carbohydrate diets
• Increase glycogen
stores
• Extend endurance
• Carbohydrate loading
• Carbohydrate intake
• Before exercise
• During exercise
• Following exercise
Dietary Fat and Exercise
• Major fuel source during
exercise
• High-fat diet not needed
• Recommendations
• Moderate fat intake with
focus on monounsaturated
and polyunsaturated
sources
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Protein and Exercise
• Protein recommendations
• Adults: 0.8 grams/kg body weight
• Endurance athletes: 1.2–1.4 grams/kg
• Strength athletes: 1.6–1.7 grams/kg
• Protein sources
• Foods: lean meats, fish, low-fat dairy, egg whites
• Protein intake after exercise
• Helps replenish glycogen
• Dangers of high protein intake
• diuresis
Vitamins, Minerals, and Athletic
Performance
• B vitamins
• Needed for energy metabolism
• Choose variety of whole grains, fruits, vegetables
• Calcium
• Needed for normal muscle function, strong bones
• Low-fat dairy products
• Adequate intake may be a problem for females
Vitamins, Minerals, and Athletic
Performance
• Iron
• Needed for oxygen delivery and energy production
• Athletes have higher losses
• Lean red meats, vegetables, enriched grains
• Other Trace Minerals
• Copper
• zinc
Fluid Needs During Exercise
• Exercise and fluid loss
• Increased losses from sweat
• Increased with heat, humidity
• Risk for dehydration
• Hydration
• Adequate fluids before,
during, after exercise
• Water vs. sports drinks
Nutrition Needs of Young Athletes
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Short stature and delayed puberty
Nutrient deficiencies and dehydration
Menstrual irregularities
Poor bone health
Increases incidence of injuries
Increased risk of developing eating
disorders
Nutrition Supplements and
Ergogenic Aids
• Most are unnecessary for athletes who
select a variety of foods and meet their
energy needs
• Although some have been well
researched, most lack vigorous clinical
trials
Nutrition Supplements and
Ergogenic Aids
• Regulation and concerns about dietary
and herbal supplements
• Dietary Supplement Health and Education
Act
• Contamination of products
• Purchases from other countries
• May contain substances not shown on
the package label
Nutrition Supplements and
Ergogenic Aids: Types
• Convenience supplements
• Weight gain powders
• Amino acids
• Branched chain amino acids
• HMB
• Glutamine
• Creatine
• Antioxidants
Nutrition Supplements and
Ergogenic Aids: Types
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Caffeine
Sodium bicarbonate
Iron
Beta-alanine
Weight and Body Composition
• Weight gain
• Build Muscle, Lose Fat
• Weight loss
• Lose fat, maintain muscle
• Avoid dangerous weight
loss practices
• Female athlete triad
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Disordered eating
Amenorrhea
Premature osteoporosis
Breaking the triad
Slow-Twitch Fibers
• With a sufficient supply of oxygen, slow-twitch
(ST) fibers can maintain muscular activity for
a prolonged time. This ability is known as
aerobic endurance.
• Because ST fibers have high aerobic
endurance, your body predominantly relies on
them during low-intensity endurance events,
such as a marathon, and during everyday
activities, such as walking.
Fast-Twitch Fibers
• Compared to slow-twitch fibers, fast-twitch
(FT) fibers have poor aerobic endurance.
They are optimized to perform anaerobically
(when the oxygen supply is limited).
• The body recruits both ST and FT fibers
during shorter, higher-intensity endurance
events, such as the mile run or the 400-meter
swim.
Pound for Pound?
• Women’s muscles have smaller muscle
fiber cross sections and less muscle
mass then men.
• For a given amount of muscle, however,
there is no difference in strength
between men and women.
Structure of Skeletal Muscle
Fiber Type and the Athlete
• Genes determine the relative proportion of
muscle fiber types in athletes. Although
distance runners who have a high percentage
of ST fibers are well suited for endurance
events, they will not succeed as elite
sprinters.
• Conversely, sprinters who have
predominantly FT fibers are better equipped
for explosive events, but they will not become
competitive marathon runners.
Fat Intake and the Athlete
• Fat intake should not be overly restricted.
There is no performance benefit in
consuming a diet with less than 15 percent of
energy from fat. Extreme fat restriction limits
food choices, especially sources of protein,
iron, zinc, and essential fatty acids.
• Sports nutritionists recommend that any extra
fat calories come from monounsaturated and
polyunsaturated sources.
Making Weight
• Wrestlers, weight lifters, boxers, jockeys, rowers, and
coxswains face competitive pressures to “make
weight” to compete or to be certified in a lower
weight classification.
• In order to make weight, such athletes often resort to
pathogenic weight-control behaviors such as fasting,
using diet pills, following a fat-free diet, using
diuretics or laxatives, or excessive exercise.
• Repeated cycles of rapid weight loss and subsequent
regain increase risk of disordered eating, fatigue,
psychological distress (anger, anxiety, depression),
dehydration, and sudden death.
Glycogen Depletion and Fatigue
Sensation
American Heart Association:
Physical Activity
• Physical inactivity is a major risk factor
for developing coronary artery disease.
• Even moderately intense physical
activity such as brisk walking is
beneficial when done regularly for a
total of 30 minutes or longer most days.