Chapter 11 Concepts

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Chapter 11 Concepts

• The combination of good nutrition and regular
  exercise work together to promote fitness
• Activity requires ATP generated from
  carbohydrate, fat, and protein in the diet and
  body stores
• The ability of the heart and lungs to provide
  oxygen to tissues affects which nutrients can be
  used to produce ATP and how much is produced
• Physically active individuals need extra energy
  to fuel their activity but the recommended
  proportions of carbohydrate, fat, and protein are
  the same as for the general population
• Exercise increases the amount of water needed to
  transport nutrients, eliminate wastes, and cool
  the body
• Appropriate food choices before, during, and
  after competition can help optimize athletic
  performance
• Performance-enhancing (ergogenic) supplements are
  popular among athletes before they are used, the
  risks should be weighed against the benefits

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As exercise intensity increases, the proportion
of energy supplied by carbohydrate also
increases. Remember that during exercise the
total amount of energy expended is greater than
at rest. (Adapted from Horton, E. S. Effects of
low-energy diets on work performance.
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The source of ATP depends on how long you have
been exercising

• Stored ATP and creatine phosphate provide
  immediate energy
• As the ATP in muscle is used, enzymes break down
  another high-energy compound, called creatine
  phosphate
• Anaerobic metabolism uses glucose for fast energy
• Aerobic metabolism uses fat to fuel your long
  runs, bikes, and swims
• Once you have been exercising for 2 to 3 minutes
  your breathing and heart rate have increased to
  supply more oxygen to your muscles. When oxygen
  is available, ATP can be produced by aerobic
  metabolism
• Aerobic metabolism produces ATP at a slower rate
  than anaerobic metabolism but is much more
  efficient, producing about 18 times more ATP for
  each molecule of glucose
• Although protein is not considered a major energy
  source for the body, even at rest your body uses
  small amounts of amino acids for energy

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Nutrition, Fitness, and Physical Activity

• Exercise Improves Fitness and Health
• Regular exercise causes changes that increase
  fitness
• When you exercise it causes changes in your
  bodyyou breathe harder, your heart beats faster,
  and your muscles stretch and strain
• If you exercise regularly, you adapt to the
  exercise you perform so you can continue for a
  few minutes longer, lift a heavier weight, or
  stretch a millimeter farther. This is known as
  the overload principle the more you do, the more
  you are capable of doing
• Endurance is enhanced by regular aerobic
  exercise, the type of exercise that increases the
  heart rate and uses oxygen
• Resistance training makes your muscles stronger
• Stretching makes you more flexible
• Regular exercise makes it easier to keep body fat
  at a healthy level

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Exercise reduces the risk of chronic disease

• A regular exercise program can help to prevent or
  delay the onset of cardiovascular disease,
  hypertension, diabetes, osteoporosis, and colon
  cancer
• Exercise reduces the risk of obesity
• Exercise reduces the risk of cardiovascular
  disease
• Exercise helps to prevent and treat diabetes
• Weight-bearing exercise helps strengthen bones
  and reduces arthritis
• Exercise may reduce cancer risk
• When you exercise you feel better
• Physical activity increases your energy level and
  self-esteem.6 It has been shown to improve
  symptoms of depression, anxiety, and panic
  disorders. The exact mechanisms involved are not
  clear but one hypothesis has to do with the
  production of endorphins

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Everyone Should Get an Hour of Exercise Daily

• Most Americans do not exercise regularly 25 of
  American adults get no physical activity at all
  during their leisure time
• People who exercise moderately for more than 2.5
  hours per day or more intensely for more than 1
  hour per day are categorized as very active
• Exercise should include aerobic activities,
  stretching, and strength training
• Do something aerobic for 30 to 60 minutes most
  days
• An activity is aerobic if it raises your heart
  rate to 60 to 85 of its maximum
• Maximum heart rate The fastest your heart can
  beat, estimated by subtracting your age in years
  from 220
• Stretch at least 3 days a week
• Lift two to 3 days a week
• Build an activity pyramid

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Exercise for All Ages

• Children should also get an hour of
  age-appropriate exercise
• It is never too late to start an exercise program
• Exercise classes are taught in nursing homes.
  Heart patients, amputees, the blind, and those
  confined to wheelchairs compete in athletic
  events
• Find activities you enjoy
• Safety should be a concern in planning any
  exercise regimen
• Before beginning, you should check with your
  physician to be sure that your plans are
  appropriate considering your medical history
• The combination of exercise frequency, duration,
  and intensity that is needed to achieve a desired
  fitness level depends on your needs, goals, and
  abilities

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The Dietary Guidelines, 2000, recommends that
Americans Be physically active each day.
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Exercise Requires the Right Fuels from Food and
Body Stores

• Just as an automobile engine runs on energy from
  gasoline, the body machine runs on energy from
  the carbohydrate, fat, and protein in food and
  body stores
• But before they can be used to fuel activity,
  their energy must be converted into the
  high-energy compound ATP
• ATP is the immediate source of energy for all
  body functions, including muscle contraction
• ATP can be generated both in the presence of
  oxygen by aerobic metabolism and in the absence
  of oxygen by anaerobic metabolism

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The oxygen you breathe into your lungs is picked
up by the blood. Your heart pumps this
oxygen-rich blood throughout the body. Oxygen is
taken up by the muscles and other tissues and
used to generate ATP, producing carbon dioxide as
a waste product. Carbon dioxide is removed by
your blood and exhaled through your lungs. When
you exercise your muscles demand more oxygen. You
respond by increasing your heart rate and
breathing faster and deeper to take in and
deliver more oxygen.
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When exercise begins, ATP and creatine phosphate
stored in muscles provide ATP for muscle
contraction. As creatine phosphate stores are
depleted, anaerobic metabolism, which breaks down
glucose from the blood or from muscle glycogen,
becomes the predominant source of ATP. After
about 3 minutes, aerobic metabolism, which uses
fatty acids and glucose to produce ATP, takes
over as the predominate source.
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In the absence of oxygen, ATP is produced by the
anaerobic metabolism of glucose and lactic acid
is generated. When oxygen is present, ATP is
produced by the aerobic metabolism of glucose,
fatty acids, and amino acids. More ATP is
produced and no lactic acid accumulates.
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Whether an activity is aerobic depends how
intense it is

• When you exercise, ATP is produced by both
  anaerobic and aerobic metabolism
• The contributions made by each of these systems
  overlap to ensure that your muscles get enough
  ATP to meet the demand you are placing on them
• Anaerobic metabolism causes fatigue sooner
• When athletes run out of glycogen, they
  experience a feeling of overwhelming fatigue that
  is sometimes referred to as hitting the wall or
  bonking.
• Glycogen depletion is a concern for athletes
  because the amount of stored glycogen available
  to produce glucose during exercise is limited
• You can continue lower-intensity exercise for
  longer periods because it relies on aerobic
  metabolism, which is more efficient than
  anaerobic metabolism and uses both glucose and
  fatty acids for energy

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As exercise intensity increases, the proportion
of energy supplied by carbohydrate also
increases. Remember that during exercise the
total amount of energy expended is greater than
at rest. (Adapted from Horton, E. S. Effects of
low-energy diets on work performance.
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Exercise training allows you to perform more
intense activity without fatigue

• Training with repeated bouts of aerobic exercise
  causes physiological changes that increase the
  amount of oxygen that can be delivered to and
  used by the muscle cells
• The heart becomes larger and stronger so that the
  amount of blood pumped with each beat is
  increased
• Training also causes changes at the cellular
  level that affect the ability of cells to use
  different types of fuel to produce ATP
• There is an increase in the ability to store
  glycogen, and there is an increase in the number
  and size of muscle-cell mitochondria

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Good Nutrition is Essential for Optimal
Performance

• Athletes have higher energy needs
• When you expend more energy you need to eat more.
  How much more depends on how intense the activity
  is and how often and how long you exercise
• The right mix of carbohydrate, fat, and protein
  fuels exercise
• In general, the diets of physically active
  individuals should contain the same proportion of
  carbohydrate, fat, and protein as is recommended
  to the general publicabout 45 to 65 of total
  energy as carbohydrate, 20 to 35 of energy as
  fat, and 10 to 35 of energy as protein
• Carbohydrate maintains blood glucose and restores
  glycogen
• Fat intake should be low enough to allow adequate
  dietary carbohydrate
• Protein is not a significant energy source,
  accounting for only about 5 of energy expended,
  but dietary protein is needed to maintain and
  repair lean tissues, including muscle

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Changing your activity level can have
a significant impact on your daily
energy expenditure.
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Most diets with enough energy also meet vitamin
and mineral needs

• Adequate vitamin and mineral intake is essential
  for optimal performance
• These nutrients are needed for energy production,
  oxygen delivery, antioxidant protection, and
  repair and maintenance of body structures
• Some nutritional problems are more common among
  athletes
• Weight loss diets can impair performance and
  health
• Pressure to perform optimally can lead to eating
  disorders
• Eating disorders and hormonal abnormalities
  combine to put bones at risk
• Low iron causes a decline in performance

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The female athlete triad includes disordered
eating, amenorrhea, and osteoporosis. Women with
these conditions typically have low body fat and
may experience multiple or recurrent stress
fractures. This syndrome is more common in women
who are perfectionists, highly competitive, and
have a low self-esteem.
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Adequate Water is Essential for Health and
Performance

• Do you drink enough when you are exercising?
• Most people only drink enough to assuage their
  thirst. Therefore they end their exercise session
  in a state of dehydration and must restore fluid
  balance during the remainder of the day
• Dehydration occurs when water loss is great
  enough for blood volume to decrease, thereby
  reducing the ability to deliver oxygen and
  nutrients to exercising muscles
• A 3 reduction in body weight can significantly
  reduce the amount of blood pumped with each heart
  beat because of the lower volume of fluid
• Dehydration increases the risk of heat-related
  illness
• An imbalance of water and salt is as dangerous as
  too little water
• A reduction in the level of sodium in the blood
  is referred to as hyponatremia

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As the degree of dehydration increases, the
adverse effects increase in severity. This can
occur rapidly if water losses are excessive, as
may occur with profuse sweating.
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Fluid needs depend on the length of your workout

• To ensure hydration adequate fluids should be
  consumed before, during, and after exercise
• For exercise lasting less than an hour, water is
  the only fluid needed
• For exercise lasting more than an hour add
  carbohydrate and salt to your water
• For exercise lasting more than 60 minutes,
  beverages containing a small amount of
  carbohydrate and electrolytes are recommended
• Small amounts of minerals, including sodium and
  chloride, are lost in sweat, but sweat consists
  mostly of water, so the amounts lost during
  exercise lasting less than 3 to 4 hours are
  usually not enough to affect health or
  performance, particularly if sodium was present
  in the previous meal
• the common belief that salt pills are necessary
  to replace the sodium lost in sweat and prevent
  dehydration is a misconception

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The Right Food and Drink Can Enhance
Performance

• Athletes may also need to plan when they eat and
  what they eat before, during, and after
  competition
• Food eaten at these times may give or take away
  the extra seconds that can mean victory or defeat
• Make sure you eat before you compete
• Ideally a pre-exercise meal should provide enough
  fluid to maintain hydration and be high in
  carbohydrate (60 to 70 of calories)
• In addition to being high in carbohydrate, the
  pre-exercise meal should contain about 300
  Calories and be moderate in protein (10 to 20)
  and low in fat (10 to 25) and fiber to minimize
  GI distress and bloating during competition
• Keep eating and drinking even when youre on the
  move
• When you stop exercising your body must shift
  from the task of breaking down glycogen,
  triglycerides, and muscle proteins for fuel to
  the job of restoring muscle and liver glycogen,
  depositing lipids, and synthesizing muscle
  proteins

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Do Supplements Enhance Athletic Performance?

• Citius, altius, fortiusfaster, higher,
  strongerthe Olympic motto
• For as long as there have been competitions,
  athletes have yearned for somethinganythingthat
  would give them the competitive edge
• Vitamin supplements are promoted to increase
  energy and antioxidant protection
• As long as athletes do not consume antioxidant
  supplements in amounts that exceed the Tolerable
  Upper Intake Levels (ULs), there is little risk
  associated with their use
• However, a diet that includes plenty of fruits
  and vegetables will ensure adequate intakes of
  these nutrients as well as provide other
  antioxidants
• Mineral supplements are marketed to improve body
  composition or endurance
• Chromium, vanadium, selenium, zinc, and iron all
  sound tough and strong and all are marketed to
  harden muscles or enhance endurance. As with
  vitamin supplements, many of the claims made
  about these minerals are based on their
  physiological functions. And as with vitamins,
  there is little evidence that consuming more than
  the recommended amount provides any benefits

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Protein and amino acid supplements claimto
provide fuel and build muscle

• Hundreds of protein supplements are available,
  from powders you mix in your beverage to bars you
  put in your backpack
• Supplements of individual amino acids are also
  marketed to build muscle. In general these
  supplements are not recommended
• Ornithine, arginine, and lysine are amino acids
  that are sold with the promise that they will
  increase the production of growth hormone and, in
  turn, enhance the growth of muscles
• Glutamine supplements promise to increase muscle
  glycogen deposition after intense exercise, to
  enhance immune function, and to prevent the
  adverse effects of over-training such as fatigue
  and increased incidence of certain infections
• The branched-chain amino acidsleucine,
  isoleucine, and valineare the predominant amino
  acids used for fuel during exercise

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Some supplements promise to help endurance by
sparing glycogen

• Carnitine is needed to get fatty acids into the
  mitochondria
• Medium chain triglycerides get into the blood
  quickly
• Much of the fat used by the muscle to generate
  ATP is delivered in the blood, so theoretically,
  higher levels in the blood increase the
  availability of fat as a fuel for exercise
• Caffeine can wake you up and keep you going
• Caffeine, the stimulant found in coffee, tea, and
  some soft drinks, not only wakes you up, but may
  enhance your endurance. Caffeine has been shown
  to enhance performance during prolonged
  moderate-intensity endurance exercise and
  short-term intense exercise
• Athletes who are unaccustomed to caffeine respond
  better than those who routinely consume it
• In some athletes caffeine may impair performance
  by increasing water loss in the urine or by
  causing gastrointestinal upset
• Regardless of its effectiveness, athletes should
  know that consuming excess caffeine before a
  competition is illegal

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Creatine and bicarbonate can help for short-term
intense exercise

• Creatine supplements increase muscle creatine
  phosphate
• Creatine phosphate gives you instant energy. More
  of it should therefore increase the amount of
  short-term intense exercise that can be performed
• A number of studies have suggested that creatine
  supplements are safe, but controlled toxicology
  studies have not been done and the safety and
  efficacy of the long-term use of high-dose
  supplements is unknown
• Bicarbonate boosts buffering capacity
• Intense anaerobic exercise produces lactic acid
• If too much accumulates in the muscles it impairs
  muscle function and causes pain and fatigue

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Healthy eating helps performance more thanherbs
or hoaxes

• The foundation of good athletic performance is a
  healthy diet, talent, and hard work
• A healthy diet is one that provides the right
  number of calories to keep your weight in the
  desirable range the proper balance of
  carbohydrate, protein, and fat to fuel your
  activity and maintain your tissues plenty of
  water and sufficient but not excessive amounts
  of essential vitamins and minerals
• It is rich in whole grains, fruits, and
  vegetables, high in fiber, moderate in fat and
  sodium, and low in saturated fat, cholesterol,
  trans fat, and added sugars
• Your performance can be further improved by using
  appropriate foods and fluids to help you refuel
  and rehydrate during workouts and events

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This pyramid illustrates the relative value of
various nutrition strategies for exercise
performance. The most significant benefit is
achieved by eating a healthy overall diet. Foods
and beverages used to supply energy and ensure
hydration during an event can provide additional
benefits but ergogenic aids provide little or no
performance boost. (Adapted from Burke, L.
Supplements in sport-nutritional ergogenic aids.
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