Chapter 10 Nutrients, Physical Activity, and the Bodys Responses

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Chapter 10Nutrients, Physical Activity, and the
Bodys Responses
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Introduction

• Nutrition and physical activity are interactive
• As you improve your physical fitness, you not
  only feel better and stronger, but you look
  better

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Fitness

• Fitness depends on a minimum amount of
• Physical activity
• Exercise
• People who regularly engage in just moderate
  physical activity live longer (on average) than
  those who are inactive
• 25 of adults in the U.S. are inactive

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Benefits of Fitness

• More restful sleep
• Better nutritional health
• Physical activity expends energy and thus allows
  people to eat more food
• Improved body composition
• limits body fat and increases or maintains lean
  tissue
• Improved bone density
• builds bone strength and protects against
  osteoporosis
• Lower risk of some kinds of cancer
• Lifelong physical activity may help to protect
  against colon cancer, breast cancer

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Benefits of Fitness

• Lower risks of type 2 diabetes
• Reduced risk of gallbladder disease
• Stronger circulation and lung function
• Lower risks of cardiovascular disease
• Physical activity lowers BP, slows resting pulse
  rate
• Lower incidence and severity of anxiety and
  depression
• Stronger self-image
• Longer life and better quality of life

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Benefits of Fitness

• The American College of Sports medicine (ACSM)
• Specifies that people need to spend a minimum of
  30 minutes in some sort of physical activity on
  most days of the week
• The Dietary Guidelines for Americans, 2005
• The DRI committee recommends at least 60 minutes
  of moderately intense activity

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The Essentials of Fitness

• A variety of physical activities produces the
  best overall fitness
• Stretching enhances flexibility, the ability of
  the joints to move through a full range of motion
  and the ability to bend and recover without
  injury
• Weight training develops muscle strength and
  endurance, the ability of muscles to work against
  resistance
• Aerobic activity improves cardiorespiratory
  endurance-(oxygen- strengthens the heart and
  lungs by requiring them to work harder than
  normal to deliver oxygen to the tissues)

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What is Weight Training?

• The use of free weights or weight machines can
  provide resistance for developing muscle strength
  and endurance
• A persons own body weight may be used to provide
  resistance as when a person does push-ups,
  pull-ups, or sit-ups

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The Essentials of Fitness

• Benefits of weight training
• Prevent and manage several chronic
  diseases/cardiovascular disease
• Promotes strong muscles in the back and
  abdomen--Can improve posture and reduce the risk
  of back injury
• Prevents the decline in physical mobility as we
  age
• Can maintain bone mass/bone density
• Can emphasize either muscle strength or muscle
  endurance
• To emphasize muscle strength
• Combine high resistance with a low number of
  repetitions
• To emphasize muscle endurance
• Combine less resistance with more repetitions
• Enhances performance in other sports
• Swimmers can develop a more efficient
  stroke
• Tennis players can develop a more powerful
  serve

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The Essentials of Fitness

• How Does Cardiorespiratory Training Benefit the
  Heart?
• It determines how long you can remain active with
  an elevated heart rate
• It is the ability of the heart and lungs to
  sustain a given physical demand
• It is aerobic.
• Examples of activities---swimming,
  cross-country skiing, rowing, fast walking,
  jogging, fast bicycling, soccer, hockey,
  basketball, in-line skating, lacrosse, rugby

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The Essentials of Fitness

• As cardiorespiratory endurance improves, the
  body delivers oxygen more efficiently
• The total blood volume and the number of red
  blood cells increase
• The heart becomes stronger and larger
• The heart pumps more oxygen --Cardiac output
  increases
• The heart pumps more blood per beat-- Stroke
  volume increases
• Fewer beats pulse rate falls
• Breathing becomes more efficient
  

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The Essentials of Fitness
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The Active Bodys Use of Fuels

• Fuels/Energy that support body activity are
• Glucose--From carbohydrate
• Fatty acids--From fat
• To a small extent, amino acids--from protein
• The body uses different mixtures of fuels
  depending on the intensity and duration of its
  activities and prior training

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The Active Bodys Use of Fuels

• During rest
• The body gets a little more than half of its
  energy from fatty acids
• Most of the rest from glucose
• A little from amino acids
• During physical activity
• The body adjusts its fuel mix to use the stored
  glucose of muscle glycogen
• In the early minutes of activity, glycogen
  provides the majority of energy the muscles use
  to go into action
• As the activity continues epinephine signals the
  liver and fat cells to release glucose and fatty
  acids

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Glucose Use and Storage

• As activity continues
• Glucose from the livers stored glycogen and
  dietary glucose absorbed from the digestive tract
  also become important sources of fuel for muscle
  activity
• The body constantly uses and replenishes its
  glycogen
• The more carbohydrate a person eats
• The more glycogen muscles store (there is a limit
  to less than 2,000 calories of energy
• Fat stores can usually provide more than 70,000
  calories and fuel hours of activity without
  running out

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Glucose Use and Storage

• A classic study compared three diets used by
  three groups of runners, each on a different diet
• one groups ate a normal mixed diet-55 CHO
• a second group ate a high-carbohydrate diet-83
  CHO
• the third group ate a high-fat diet94 fat
• The high-carbohydrate diet enables the athletes
  to work longer before exhaustion

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Activity Intensity, Glucose Use, and Glycogen
Stores

• Anaerobic Use of Glucose
• Anaerobic
• Not requiring oxygen
• Anaerobic activity may require strength but does
  not work the heart and lungs very hard for a
  sustained period
• The muscles begin drawing on their limited
  glycogen supply
• Glucose can yield energy quickly
• Weight lifting, sprint

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Activity Intensity, Glucose Use, and Glycogen
Stores
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• Moderate physical activity uses glycogen
  slowly-Aerobic activity (easy jogging)
• The individual breathes easily and the heart
  beats at a faster pace than at rest
• During aerobic metabolism muscles get their
  energy from both glucose and fatty acids
• Moderate activity conserves glycogen stores

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Activity Intensity, Glucose Use, and Glycogen
Stores

• During intense activity, the anaerobic breakdown
  of glucose produces a by product called lactic
  acid
• Liver enzymes can convert the lactic acid back
  into glucose
• The glucose return to the muscles to fuel
  additional activity

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Activity Intensity, Glucose Use, and Glycogen
Stores

• At low intensities, lactic acid is cleared from
  the blood by the liver
• At higher intensities, lactic acid accumulates
• When the rate of lactic acid production exceeds
  the rate of clearance, intense activity can be
  maintained for only one to three minutes

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Activity Duration Affects Glucose Use

• Glucose use depends on the duration and intensity
  of the activity
• In the first 10 minutes
• muscles rely almost entirely on their own stores
  of glycogen
• Within the first 20 minutes of moderate activity
• About one-fifth of their available glycogen is
  used up
• Blood glucose also decreases and is used by the
  muscles

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Activity Duration Affects Glucose Use

• After 20 minutes less glucose and more fat is
  used for fuel
• If the activity goes on long enough and at a high
  enough intensity glycogen depletion occurs after
  about two hours
• When hypoglycemia and glycogen depletion occur
  activity stops

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Activity Duration Affects Glucose Use

• Maintaining Blood Glucose for Activity
• Eat a high-carbohydrate diet regularly
• Take glucose (usually in sports drinks)
  periodically during endurance activities
• Eat carbohydrate-rich foods after performance
• Train the muscles to maximize glycogen
  stores--Carbohydrate loading

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Activity Duration Affects Glucose Use

• Carbohydrate Loading
• A regimen of moderate exercise, followed by
  eating a high-carbohydrate diet
• It enables muscles to temporarily store double
  the glycogen beyond their normal capacity
• It can benefit athletes who must keep going 90
  minutes or longer

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Activity Duration Affects Glucose Use

• Glucose After Activity
• High-carbohydrate foods after physical activity
  replaces glycogen stores
• Eating a high-carbohydrate meal within 2 hours
  after physical activity accelerates the rate of
  glycogen storage by 300
• This is important to athletes who train hard more
  than one time a day
• High-carbohydrate energy drinks can be used to
  restore muscle glycogen after exercise or as a
  pregame beverage

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Should Athletes Eat More Fat?

• When endurance athletes fat load by consuming
  high-fat, low-carbohydrate diets for 1 to 3 days
• performance is impaired because their small
  glycogen stores are depleted quickly
• Endurance athletes who fat load for more than a
  week
• Adapt to relying on more fat to fuel activity
• Performance benefits have not been consistently
  shown

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Should Athletes Eat More Fat?

• High-fat diets carry risks of heart disease
• Physical activity offers some protection against
  CV disease however athletes can suffer heart
  attacks and strokes
• A diet that restricts fat is not recommended
• Endurance athletes should consume 20-30 of
  their energy from fat
• As fuel for activity, body fat stores are more
  important than fat in the diet
• Fat stores can fuel hours of activity without
  running out, even for marathoners

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Should Athletes Eat More Fat?

• Early in activity muscles draw on fatty acids
  from two sources
• Fats stored within the working muscles
• Fats under the skin
• Areas with the most fat to spare donate the
  greatest amounts of fatty acids to the blood

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Should Athletes Eat More Fat?

• Intensity and Duration Affect Fat Use
• The intensity of physical activity affects the
  percentage of energy contributed by fat
• Fat can be broken down for energy only by aerobic
  metabolism
• When the intensity of activity becomes so great
  that energy demands surpass the ability to
  provide energy aerobically, the body cannot burn
  more fat instead, it burns more glucose

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Should Athletes Eat More Fat?

• The duration of activity also matters to fat use
• At the start of activity, the blood fatty acid
  concentration falls
• But a few minutes into an activity norepinephrine
  signals fat cells to break apart their stored
  triglycerides and to liberate fatty acids into
  the blood
• After about 20 minutes of activity, the blood
  fatty acid concentration rises above normal
  resting concentrations
• It is during this phase that fat cells begin to
  shrink in size

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Should Eat More Fat?

• Degree of Training Affects Fat Use
• Training stimulates muscles to develop more
  fat-burning enzymes
• Aerobically trained muscles burn fat more readily
  than untrained muscles
• With aerobic training, the heart and lungs become
  stronger and better able to deliver oxygen to the
  muscles during high-intensity activities

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Can Physical Training Speed Up an Athletes
Metabolism?

• Athletes in training expend huge amounts of
  energy each day while practicing
• Research suggests that the athlete uses more
  energy at rest than a sedentary person or a
  casual exerciser
• Intense endurance activity can increase BMR for
  anywhere from 5 minutes to hours

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Using Protein and Amino Acids

• Athletes use dietary protein to build and
  maintain muscle and other lean tissue structure
• The body handles protein differently during
  activity than during rest
• During rest muscles speed up their rate of
  protein synthesis to remodel muscle

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Using Protein and Amino Acids

• Protein for Fuel
• Athletes retain more protein, and use a little
  more protein as fuel
• Studies of nitrogen balance show that the body
  speeds up its use of amino acids for energy
  during physical activity
• Protein contributes about 10 of the total fuel
  used
• A carbohydrate-rich diet spares excess protein
  from being used as fuel
• Some amino acids can be converted into glucose
  when needed
• If the diet is low in carbohydrate, much more
  protein will be used in place of glucose

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Using Protein and Amino Acids

• Intensity and Duration Affect Protein Use
• Endurance athletes training more than an hour a
  day may deplete their glycogen stores by the end
  of their training period and become more
  dependent on body protein for energy

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How Much Protein Shouldan Athlete Consume

• The protein needs of endurance and strength
  athletes are higher than those of sedentary
  people
• Athletes in training should take care of protein
  and carbohydrate needs
• Otherwise, they will use protein as fuel rather
  than to retain muscle
• The DRI committee does not recommend
  greater-than-normal protein intakes for athletes
• Other authorities do
• The American Dietetic Association and the
  Dietitians of Canada recommend protein intakes
  higher than the 0.8 gram of protein per kilogram
  of body weight recommended for sedentary people

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Vitamin and Minerals - Keys to Performance

• Many vitamins (Bs) and minerals assist in
  releasing energy from fuels and transporting
  oxygen
• Vitamin C is needed for the formation of the
  protein collagen
• The foundation material of bones and the
  cartilage that forms the linings of joints and
  other connective tissues
• Folate and vitamin B12 help build red blood cells
• Calcium and magnesium help make muscles contract

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Do Nutrient Supplements Benefit Athletic
Performance?

• Nutrient supplements do not enhance the
  performance of well-nourished athletes or active
  people
• Deficiencies of vitamins and minerals adversely
  effect performance
• Taking vitamin or mineral supplements just before
  competition will not enhance performance

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Do Nutrient Supplements Benefit Athletic
Performance?

• Athletes who lose weight making weight to meet
  low body-weight requirements may consume so
  little food that they fail to obtain all the
  nutrients they need
• A daily multivitamin-mineral tablet that provides
  the DRI recommendations can be beneficial
• Athletes who eat well-balanced meals generally do
  not need vitamin or mineral supplements

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Nutrients of Special ConcernVitamin E and Iron

• During prolonged, high-intensity physical
  activity, the muscles use of oxygen increases
  tenfold or more
• increasing the production of free radicals in the
  body
• Vitamin E an antioxidant protects cells membranes
  against oxidative damage
• Some athletes take megadoses of vitamin E to
  prevent oxidative damage to muscles
• Supplementation with vitamin E does seem to
  protect against exercise-induced oxidative stress
  
• There is little evidence it improve performance

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Nutrients of Special Concern

• Iron deficiency impairs performance by reducing
  aerobic capacity
• Physically active young women are prone to iron
  deficiency due to
• Iron losses in sweat
• Small blood losses through the digestive track
• Low intakes of high iron foods and
• High iron losses through menstruation

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Nutrients of Special Concern

• Vegetarian female athletes are vulnerable to low
  iron and iron deficiency
• The bioavailability of iron is often poor in
  plant-based diets because of
• The high fiber and phytic acid
• The iron in plant foods is not as easily absorbed
  as the heme iron in animal based foods
• Good dietary sources of iron (fortified cereals,
  legumes, nuts, and seeds)
• vitamin C rich foods should be included with each
  meal

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Nutrients of Special Concern

• Who needs iron supplements?
• Many menstruating women border on iron
  deficiency.
• Teens of both genders because of growth, have
  high iron needs
• Both groups may need supplements to correct an
  iron deficiency

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Temperature Regulation Water

• During physical activity
• Dehydration is a real threat
• A water loss of 1-2 of body weight can reduce a
  persons capacity to do muscular work
• A person with a water loss of 7 is likely to
  collapse
• The exercising body loses water via sweat and
  exhaled vapor
• Sweat cools the body
• If heat builds up heat stroke may occur
  (increases body heat with loss of body fluid)

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Temperature Regulation

• Measures to prevent heat stroke
• Drink enough fluid before and during activity
• Rest in the shade
• Wear lightweight clothing that encourages
  evaporation
• Heat stroke symptoms
• Clumsiness, Confusion or loss of consciousness,
  Dizziness, Headache Internal temperature above
  104F, Nausea, Stumbling, Sudden cessation of
  sweating (hot, dry skin)
• This condition needs medical attention.

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Temperature Regulation

• Hypothermia
• Below-normal body temperature in cold weather can
  pose as serious health threat
• Early symptoms are shivering and euphoria
• As body temperature falls
• Shivering stops
• Weakness, disorientation, and apathy set in
• Even in cold weather, the body sweats and needs
  fluids
• The fluids should be warm or at room temperature
  to help prevent hypothermia

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Fluid Needs

• Endurance athletes can lose 2 or more quarts of
  fluid in every hour of activity
• athletes must hydrate before and rehydrate during
  and after activity to replace all the lost fluid
• Athletes are often advised to drink extra fluids
  in the last few days of training before an event
• Extra fluid is not stored but ensures maximum
  tissue hydration
• Thirst awareness occurs after fluid stores are
  depleted
• Dont wait to feel thirsty before drinking

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Water

• The best drink for most active people is plain
  cool water
• Endurance athletes need more from their fluids
  than plain water
• The first priority for endurance athletes should
  be replacement of fluids
• To prevent heat stroke
• The body also looses electrolytes in sweat
• The minerals sodium, potassium, and chloride

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Electrolyte Losses and Replacement

• To replenish electrolytes in events lasting more
  than 1 hour
• Sports drinks may be needed to replace fluids and
  electrolytes
• Sports drinks supply about 7 glucose
• A carbohydrate concentration greater than 8 can
  delay fluid emptying from the stomach and slow
  down the delivery of water to the tissues

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Consumer Corner What Do Sports Drinks Have to
Offer?

• Sports drinks offer sodium and other electrolytes
  to help replace those lost during physical
  activity
• Sports drinks taste good
• If the drinks tastes good, people may drink more,
  ensuring adequate hydration
• Fitness water does not provide glucose and
  electrolytes

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Sodium Depletion

• When athletes compete in endurance sports lasting
  longer than three hours
• Sweating over a long period of time can cause
  sodium depletion (hypoatremia)
• Hypoatremia symptoms are similar to
  dehydrationBloating, Puffiness from water
  retention, Confusion, Seizure, Severe headache,
  Vomiting
• To prevent hypoatremia, endurance athletes should
  use sports drinks over water and eat salted
  pretzels in the last half of a race
• Some may need beverages with higher sodium
  concentrations than commercial sports drinks

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Other Beverages

• Caffeine
• Moderate amounts of caffeine one hour prior to an
  activity may assist athletic performance and at
  other times seem to have no effect
• Athletic competitions limit the amount of
  caffeine that can be consumed within two hours of
  an event
• Carbonated Drinks
• The air bubbles from the carbonation make a
  person feel full quickly and may limit fluid
  intake

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Other Beverages

• Alcoholic beverages are inappropriate as fluid
  replacements
• Alcohol is a diuretic
• It promotes the excretion of water, thiamin,
  riboflavin, folate, calcium, magnesium, and
  potassium
• Alcoholic beverages
• Impair temperature regulation
• Alter perception and reaction time
• Reduce strength and endurance
• Impair judgment

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Food FeatureChoosing a Performance Diet

• Many different diets can support an athletes
  performance
• Athletes should eat for energy and full glycogen
  stores
• Endurance athletes should aim for an average
  intake of 50 calories /kg of body weight
• high in carbohydrate (60-70 of total calories)
• moderate in fat (20-39),
• adequate in protein (10-20)

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Food FeatureChoosing a Performance Diet

• Recommendations for a pregame meal
• The foods should be high in carbohydrate
• Easy to digest and contain fluids
• It should be eaten 3 - 4 hours before competition
  to allow time for the stomach to empty

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Food FeatureChoosing a Performance Diet

• Drinks or candylike sport bars claim to provide
  complete nutrition
• Mixtures of carbohydrate, protein, fat, some
  fiber, and certain vitamins and minerals
• Usually taste good
• Provide additional food energy before a game or
  for those needing to gain weight

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Controversy Ergogenic Aids

• Ergoenic aids
• Appeal to performance-conscious people
• Thought to enhance performance
• Protein powders, amino acid supplements, caffeine
  pills, steroid replacers, muscle builders,
  vitamins, etc.

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Controversy Ergogenic Aids

• Ergogenic Aids
• For the large majority of ergogenic aids,
  research findings do not support the claims made
  for them
• Almost anything can be sold under the label of
  dietary supplement with little regulation
• They may contain added substances, lack purity
• Consistent training and sound nutrition serve an
  athlete better than any pill, powder, or
  supplement

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Controversy Ergogenic Aids

• Amino Acid Supplements
• Are unnecessary
• Healthy athletes eating a well-balanced diet
  never need them
• In a few cases these supplements have proved
  dangerous
• Amino acids complete for carriers
• An overdose of one can limit the availability of
  some other amino acid

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Controversy Ergogenic Aids

• Caffeine
• Provides mental stimulation and a physical boost
  during endurance sports
• Some research supports this idea
• Potential benefits from caffeine must be weighed
  against known adverse effects Upset stomach,
  nervousness, irritability, headaches,
  dehydration, and diarrhea
• HYPERTENSION???

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Controversy Ergogenic AidsCarnitine

• A nonessential nutrient- the body can make plenty
  when needed
• Marketed as a fat burner
• In the body it helps transfer fatty acids across
  the membrane that encases the cells mitochondria
• In scientific studies, carnitine supplementation
  for 7 to 14 days did not raise muscle carnitine
  concentrations or influence fat or carbohydrate
  oxidation
• Supplements do not enhance exercise performance
• Milk and meat products are good sources of
  carnitine

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Controversy Ergogenic AidsChromium Picolinate

• Chromium is an essential trace mineral involved
  carbohydrate and lipid metabolism
• The great majority of studies show no effects of
  chromium picolinate on body fatness, lean body
  mass, strength, or fatigue

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Controversy Ergogenic Aids Creatine

• Creatine safety
• Long-term studies are lacking
• Some studies suggest that creatine
  supplementation may enhance performance of
  high-intensity strength activity--weight lifting
  or repeated sprinting
• Other studies have found no effect on strength
  performance
• There is concern that children as young as 9
  years old take creatine with unknown consequences
• Even diets high in creatine do not approach the
  amount athletes take in supplement form

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Controversy Ergogenic Aids

• Protein Powders/ Whey protein
• Can supply amino acids to the body
• Offers no special benefits beyond those provided
  by ordinary milk or yogurt
• Extra protein
• Will not stimulate muscle growth
• Muscle growth is stimulated by physically
  demanding activity
• Complete Meal Replacers
• These bars and drinks taste good and provide
  extra food energy, largely as added fats and
  sugars
• They fall short of providing complete nutrition

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Controversy Ergogenic Aids Anabolic Steroid
Hormones

• Often athletes take these drugs and related
  products without any medical supervision or
  testing
• The testes and adrenal glands in men and the
  adrenal glands in women make anabolic steroid
  hormones naturally
• In the body, these steroids produce accelerated
  muscle bulking in response to physical activity
• Injections of these fake hormones produce
  muscle size and strength far beyond that
  attainable by training alone
• At the price of great risks to health

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Controversy Ergogenic Aids Anabolic Steroid
Hormones

• The AAcademy of Ped the Amer Coll Sports Med, and
  the International Olympic Com maintain that
  taking these drugs is a form of cheating
• Steroids produce changes in the brain that in
  some people bring on overly aggressive behavior,
  called steroid rage

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Controversy Ergogenic Aids Steroid Alternative
Supplements

• Andro or DHEA claim
• They reduce fat, build muscle, slow aging--
  are unsupported by research
• Some effects of steroid alternatives include
• Oily skin, Acne, Body hair growth, Liver
  enlargement
• Irreversible masculine changes in females
• Irreversible feminine changes in males
• Aggressive behavior
• Long-term effects, such as serious liver damage,
  may occur after years of use
• Particularly vulnerable to these effects are
  children and adolescent athletes

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Controversy Ergogenic Aids Human Growth Hormone
(HGH)

• The U.S. Olympic Committee bans HGH use and
  maintains that it is a form of cheating
• It can induce huge body size
• It is less readily detected in drug tests than
  steroids
• Athletes in power sports are most likely to
  experiment with HGH
• HGH causes the disease acromegaly
• Widened jawline and nose, protruding brow, buck
  teeth, huge body, abnormally enlarged bones and
  organs

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Controversy Ergogenic Aids

• Drugs Posing As Supplements
• Some ergogenic aids sold as dietary supplements
  can be powerful drugs
• TRIAC a potent thyroid hormone has been recalled
  by the FDA
• TRIAC interferes with normal thyroid functioning
  and has caused heart attack and stroke

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Controversy Ergogenic Aids

• Conclusion
• Researchers identified over 300 products
  containing 235 different ingredients advertised
  as beneficial for muscle growth in a dozen health
  and body building magazines
• None had been scientifically shown to be
  effective
• Consistent training and sound nutrition are the
  best combination for athletic success