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CHAPTER 14
NUTRITION AND NUTRITIONAL
ERGOGENICS
Six Nutrient Classes
w Carbohydrate
w Fat
w Protein
w Vitamins
w Minerals
w Water
Recommended Balance of Nutrients
w 55% to 60% carbohydrate
w Less than 30% fat (less than 10% saturated)
w 10% to 15% protein
Carbohydrate (CHO)
w Provides energy, particularly during high-intensity exercise
w Regulates fat and protein metabolism
w Exclusive energy source for the nervous system
w Synthesized into muscle and liver glycogen
w Sources include grains, fruit, vegetables, milk, and sweets
DIETARY CARBOHYDRATES AND
GLYCOGEN
MUSCLE GLYCOGEN AND EXHAUSTIVE
EXERCISE
CHO Types
Simple sugars
w Elevate blood glucose levels
w Rely on insulin to move them to cells
w When intake exceeds usage, stored within the cells as fat
Complex CHOs
w Require more time to breakdown
w Produce smaller and slower rise in blood glucose
w Have less impact on blood lipid levels
CHO INTAKE AND PERFORMANCE
PRE-EXERCISE CHO FEEDING
Fat
w Makes up cell membranes and nerve fibers
w Provides up to 70% energy at rest
w Cushions vital organs
w Produces all steroid hormones
w Transports and stores fat-soluble vitamins
w Preserves body heat
Protein
w Makes up cell structure
w Helps develop, repair, and maintain tissues
w Produces hemoglobin, enzymes, and many hormones
w Maintains normal blood osmotic pressure
w Forms antibodies
w Can be energy source, but it is a minor contributor
w Breaks down into amino acids to be used
by the body
Vitamins
Fat soluble
w A, D, E, and K
w Absorbed from digestive tract and bound to lipids
w Excessive intake can cause toxic accumulations
Water soluble
w B-complex and C
w Absorbed from digestive tract with water
w Excess is excreted
B-Complex Vitamins
w Include more than 1 dozen vitamins
w Involved in energy production
w If deficiency, supplementation may facility performance
Vitamin C
w Formulates and maintains collagen in connective tissue
w Helps metabolize amino acids
w Helps synthesize epinephrine, norepinephrine, and
corticoids
w Promotes iron absorption
w May help fight infection and function as an antioxidant
w Supplementation does not appear to
improve performance if no deficiency
exists
Vitamin E
w Stored in muscle and fat
w Prevents oxidation of vitamins A and C
w Acts as an antioxidant to disarm free radicals
w May decrease risk of coronary artery disease
w Supplementation has not been proven to improve
performance
Minerals
Electrolytes—mineral compounds that can dissociate into
ions in the body
Macrominerals—minerals that your body needs 100 mg of
per day
Microminerals—minerals that your body needs less than
100 mg of per day
Calcium
w Most abundant mineral in the body
w Stored in the bones
w Facilitates bone growth and maintenance
w Essential in nerve impulse transmission
w Activates enzymes and regulates cell membrane
permeability
w Essential for normal muscle function
Phosphorus
w Commonly linked to calcium in form of calcium phosphate
w Provides strength and rigidity to bones
w Essential to metabolism and component of ATP
w Part of cell membrane structure
w Helps maintain constant blood pH
Iron
w Helps form hemoglobin and myoglobin
w Deficiency is relatively common, more so in women
w If deficiency, supplementation can improve aerobic
capacity
Sodium, Potassium, and Chloride
w Separates electrical charge across neuron and muscle
cell membranes
w Maintain body's water balance and distribution
w Maintain normal osmotic equilibrium and pH
w Maintain normal cardiac rhythm
BODY WATER AT REST
Water
w Makes up blood plasma, which transports and delivers
nutrients to tissues
w Makes up body fluids that regulate pH
w Dissipates excess body heat during exercise
w Maintains blood pressure
Key Points
Water Balance During Exercise
w Metabolic water production increases as
metabolic rate increases—water gain.
w Water loss increases during exercise due
to sweating.
w Blood flow to the kidneys decreases to
prevent dehydration—reduced urine output.
w If dehydration exceeds 2% body weight,
physical performance is impaired.
DEHYDRATION AND PERFORMANCE
Key Points
Electrolyte Balance During Exercise
w Loss of water via sweating disrupts
electrolyte balance.
w Sodium and chloride are the most
abundant electrolytes in sweat.
w Excess electrolytes are excreted in the
urine during rest, but less so during
exercise.
w Dehydration causes aldosterone to
promote renal retention of sodium and
chloride ions, raising their concentrations
in the blood. This, in turn, triggers thirst.
DEHYDRATION AND HEAT
PERFORMANCE
Key Points
Replacing Fluid Losses
w The need to replace body fluids is greater
than the need to replace electrolytes.
w Our thirst mechanism does not match our
hydration state, so it is best to consume
more fluid than thirst dictates.
w Water intake during prolonged exercise
reduces the risk of dehydration and
optimizes performance.
w Drinking too much fluid can result in
hyponatremia (low levels of plasma
sodium), which can cause confusion,
disorientation, and seizures.
Key Points
The Athlete’s Diet
w There is no one typical diet of an athlete;
yet, it is important that athletes and active
people alike meet their RDA of nutrients.
w Athletes can get the nutrition they need
with a strictly vegetarian diet as long as the
foods they select include a balance of
essential nutrients and calories.
w The precompetition meal can ensure a
normal blood glucose level and prevent
hunger; it should include 200 to 500 kcal of
foods that are easily digestible and are
eaten no less than 2 hours before
competition.
°
Astrand’s
Glycogen Loading
1. Complete an exhaustive training bout 7 days before
event.
2. Eat fat and protein for next 3 days and reduce training
load; this increases glycogen synthesis (low CHO).
3. Eat a CHO-rich diet for remaining 3 days before event
and reduce training load; because of increased glycogen
synthesis, more glycogen is stored.
Sherman’s Glycogen Loading
7 days before competition
w Reduce training intensity
w Eat a normal, healthy mixed diet with 55% CHO
3 days before competition
w Reduce training to daily warm-up of 10 to 15 minutes
w Eat a CHO-rich diet
MUSCLE GLYCOGEN LOADING
MUSCLE GLYCOGEN RESYNTHESIS
Effects of Solution Characteristics on
the Rate of Gastric Emptying
Solution characteristic
Rate of emptying
Volume of the solution
Increases with larger volumes
Caloric content
Decreases as the caloric density
increases
Osmolarity
Decreases with hyperosmolar
solutions
Temperature
Faster for cooler fluids than
warm solutions
pH
Decreases with more acidic
solutions
Gastric Emptying
.
w Slows at exercise intensities above 70% to 80% VO2max
w Is same
. rate at rest as it is at exercise intensities below
70% VO2max
w Affected by an individual's fitness—the more fit, the less
exercise affects it
w Not affected by exercise duration
w Affected differently by different types of
activities
Key Points
Designing Sports Drinks
w Fructose, glucose, and maltodextrin may
empty fastest from digestive tract.
w Concentrations less than 11 g of CHO per
100 ml empty faster, but don't supply the
full energy needed for prolonged exercise.
w Athletes prefer a drink with a light flavor
and no strong aftertaste.
w During prolonged exercise, water intake is
primary, but drinking 4 g to 8 g of CHO per
100 ml solution every 10 to 15 minutes
reduces risk of dehydration and provides a
partial energy supplement.