chapter 16: nutrition and fitness
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Chapter 16: Nutrition and Fitness. What Is Physical Fitness and Why Is It Important?. Physical fitness is good health or physical condition as a result of exercise and proper nutrition Physical activity is body movement that expends energy (kilocalories) - PowerPoint PPT PresentationTRANSCRIPT
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Chapter 16: Nutrition and Fitness
© 2010 Pearson Education, Inc.
What Is Physical Fitness and Why Is It Important? Physical fitness is good health or physical condition as a
result of exercise and proper nutrition Physical activity is body movement that expends energy
(kilocalories) Exercise is formalized training or structured physical
activity
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What Is Physical Fitness and Why Is It Important? Five basic components of physical fitness which must be
considered to achieve optimal fitness• Cardiorespiratory endurance – ability to sustain
cardiorespiratory exercise for an extended period of time• Muscular strength – ability to produce force for a brief
period of time• Muscular endurance – ability to exert force over a long
period of time without fatigue• Flexibility – range of motion around a joint, improved
with stretching• Body composition – the proportion of muscle, fat, water,
and other tissues in the body
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What Does a Successful Physical Fitness Program Look Like? Incorporates activities based on the five components of
fitness Tailored to meet needs of individual
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Cardiorespiratory Exercise Can improve cardiorespiratory endurance and body
composition Cardiorespiratory fitness is measured by VO2max, the
maximum amount of oxygen muscles can consume during exercise• Gradual increases in exercise intensity will help increase
VO2max
Cardiorespiratory exercise also helps to maintain a healthy body weight, improves body composition, reduces stress, and reduces risk of heart disease
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Strength Training and Stretching Improve muscle strength, muscle endurance, and body
composition• A low number of repetitions using heavy weights will
increase muscle strength• To increase muscle endurance, perform a high number of
repetitions with lighter weights• Rest between sets of exercises and between workouts to
avoid overworking muscles and decrease risk of injury Stretching can improve flexibility; reduce muscle soreness
and risk of injury; and improve balance, posture, and circulation
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What Does a Successful Physical Fitness Program Look Like? The progressive overload principle can help improve
fitness over time• A gradual increase in exercise demands from
modifications to the frequency, intensity, time, or type of exercise
• Prevents a plateau of fitness level due to the body adapting to an exercise regimen
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Quick Review A successful fitness program incorporates the five
components of fitness Cardiorespiratory exercise improves cardiorespiratory
endurance and body composition Strength training improves muscle strength and endurance Stretching increases flexibility and reduces risk of injury An effective fitness program can be designed using the FITT
principle The 2008 Physical Activity Guidelines provide
recommendations for duration and intensity of exercise based on individual health goals such as weight management or improved physical fitness
Applying the progressive overload principle helps individuals achieve optimal fitness levels
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How Are Carbohydrate, Fat, and Protein Used During Exercise? Most energy production during cardiorespiratory exercise is
aerobic Anaerobic energy is generated for quick, intense activities
that require strength, agility and speed, or a sudden burst of energy.
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How Are Carbohydrate, Fat, and Protein Used During Exercise? During the first few minutes of physical activity, the body
relies heavily on anaerobic energy production from ATP and creatine phosphate (PCr)
PCr stored in muscles is depleted after 10 seconds of maximum intensity exercise; stored ATP can only support a few seconds of intense exercise
Once stores are depleted, the body relies on aerobic production of ATP
Figure 16.2
Anaerobic Energy Metabolism
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Carbohydrate and Exercise Carbohydrate is the primary energy source during high-
intensity exercise• Obtained from blood glucose and from stored glycogen in
muscles and liver• ~2,000 kcals of energy as carbohydrate is available;
enough to perform 2 hours of moderate-intensity exercise• As intensity of exercise increases, lactate is formed and
can begin to accumulate in muscle tissue- New research suggests it can be an important fuel
during exercise Eat simple carbohydrates during and/or immediately after
exercise• Athletes use carbohydrate loading before competition
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Fat and Exercise Fat (as fatty acids) is the primary energy source during low-
to moderate-intensity exercise• Derived from fatty acids stored in muscle tissue and free
fatty acids in the blood from adipose stores• Use of fat for energy increases throughout the duration of
low- to moderate-intensity exercise• Endurance training increases muscle fatty acid stores
which can increase amount of fat used for energy
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Protein and Exercise Protein is primarily needed to build and repair muscle
• Exercise increases cortisol which stimulates protein turnover
• All active people use small amounts of protein for energy• When kilocalorie intake and carbohydrate stores are
insufficient, the body relies on protein• If protein breakdown exceeds protein synthesis, muscle
atrophy can occur• Most recreational exercisers can easily meet protein
needs (0.8 g/kg) with a balanced diet- Endurance athletes and those doing significant
resistance/strength training may need more protein
Figure 16.3
Energy Use During Various Intensities of Exercise
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Food Intake and Exercise The timing of meals affects fitness and athletic performance
• Important to allow sufficient time for food to digest before exercise- Large meals 3–4 hours - Smaller meals 2–3 hours- Liquid supplement or small snack 30 min–1 hour
• Food intake is important to maintain blood glucose supply in exercise lasting greater than 1 hour- Carbohydrate intake recommended at 15–20 min
intervals- 30–60 g of carbohydrate should be consumed per hour
• Food eaten after exercise will affect how the body recovers
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Food Intake and Exercise Optimal foods before exercise
• 1–4.5 g/kg carbohydrate 1–4 hours prior to exercise• Consumption of protein and carbohydrate recommended• High-fat foods should be avoided several hours before
exercise Optimal foods during exercise
• Sports drinks, bars, and gels• Fructose (fruit sugar) may cause GI distress• Consuming carbohydrate and protein improves net
protein balance for endurance athletes
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Food Intake and Exercise Optimal foods after exercise
• Consuming carbohydrate after exercise helps to replenish muscle and liver glycogen. It is most effective 30–45 minutes after exercise.
• Consuming protein and carbohydrate after exercise increases muscle protein synthesis- Low-fat chocolate milk is a low-cost option to provide
whey protein and carbohydrate to assist in recovery• A high-carbohydrate, moderate-protein, low-fat meal
should be consumed within 2 hours
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Quick Review Carbohydrate from blood glucose and muscle and liver
glycogen are the main source of energy during high-intensity exercise
Fat is the main energy source for low- to moderate-intensity exercise
Protein promotes muscle growth and repair of muscle breakdown caused by exercise
Both the timing of meals and the foods eaten can affect exercise performance and recovery time
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Vitamins and Minerals in Fitness Intense, prolonged exercise increases production of free
radicals• Antioxidants such as vitamins E and C protect cells from
the damage of free radicals• Research has not shown that supplementation above the
RDA improves athletic performance or decreases oxidative stress
Unless the body is deficient in a nutrient, vitamin and mineral supplements will not improve athletic performance
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Vitamins and Minerals in Fitness Certain minerals may be a concern in highly active people
• Iron- Necessary for energy metabolism and oxygen
transport- Levels may be low due to menstruation in women,
intravascular hemolysis, or sports anemia• Calcium
- Lost in sweat, thus losses may be high in athletes- Supplementation not recommended unless intake from
food and beverage is inadequate to meet the RDA
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Quick Review Antioxidants such as vitamins E and C are thought to
protect cells from free radical damage though research has not shown that supplementation is beneficial to athletes
Certain minerals may be a concern to athletes including calcium and iron
Adequate amounts of nutrients can be consumed in foods, so supplementation is usually not necessary
Anyone should consult a physician or Registered Dietitian before taking dietary supplements
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How Does Fluid Intake Affect Fitness? Consuming adequate fluid during exercise is essential for
preventing dehydration and promoting optimal performance
During exercise, the body loses water and electrolytes (sodium, chloride, and potassium) in sweat• In hot, humid weather sweat may not evaporate and risk
of hyperthermia increases• Cold weather, especially if wet, can contribute to
hypothermia• The body sweats when exercising both in hot and cold
weather, so meeting fluid needs is always a concern
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How Does Fluid Intake Affect Fitness? Fluids are needed before, during, and after exercise
• Healthy adult women require 9 cups water/day• Healthy adult men require 13 cups water/day• To determine fluid needs for exercise
- Weigh yourself before and after exercise- Consume 16–24 ounces of fluid for every pound of
body weight lost during exercise
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How Does Fluid Intake Affect Fitness? Sports drinks contain 6–8% carbohydrate and sodium and
potassium• Most beneficial for exercise lasting longer than 60
minutes Certain beverages are suboptimal for hydration during
physical activity• Juice and juice drinks• Carbonated drinks• Alcohol• Caffeine
Figure 16.4
Effects of Dehydration on Exercise Performance
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How Does Fluid Intake Affect Fitness? Consuming too little or too much fluid can be harmful
Too little fluid• To prevent acute dehydration follow a regimented
hydration schedule before, during, and after exercise• Chronic dehydration is due to inadequate fluid
consumption over a long period of time and may be indicated by very dark urine and infrequent bathroom trips
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How Does Fluid Intake Affect Fitness? To much fluid
• Taking in too much water without sufficient electrolytes can dilute the blood and cause hyponatremia- Symptoms of hyponatremia include rapid weight gain,
nausea, vomiting, swollen hands and feet, headache, dizziness, and confusion
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Quick Review Adequate hydration before, during, and after exercise is
important to sustain fluid and electrolyte balance and normal body temperature
Consuming too little or too much fluid can be harmful and impair performance
Water is the preferred beverage for hydration, but sports drinks can be beneficial during moderate- or vigorous-intensity exercise of a longer duration
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Can Dietary Supplements Contribute to Fitness? An ergogenic aid is any substance that is used to improve
athletic performance Most commonly used aids include
• Creatine• Caffeine• Anabolic steroids• Growth hormone• Erythropoietin
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Creatine Improves athletic performance in high-intensity, short-
duration activities such as weight training Shown to increase muscle strength and muscle mass No negative effects on blood pressure, kidney, or liver
function in healthy people
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Caffeine Stimulates the central nervous system and decreases
perception of effort • May increase metabolism of fatty acids for energy and
spare glycogen stores Enhances athletic performance during endurance events NCAA classifies as a banned substance when urine
concentrations exceed 15 micrograms per milliliter
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Anabolic Steroids Testosterone-based substances that promote muscle
strength and development Many negative side effects including
• Impotence in men • Amenorrhea in women • Changes in hair growth• Extreme mood swings and aggressiveness
Use is prohibited by most professional agencies
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Growth Hormone Increases protein synthesis, causing an increase in muscle
mass but not strength • Could impair performance by reducing power, speed, and
endurance Decreases glycogen
breakdown and increases the use of fatty acids for energy which can decrease body fat
Abuse of growth hormone can lead to development of diabetes, atherosclerosis, hypertension, or acromegaly
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Erythropoietin Hormone produced by the kidneys that stimulates synthesis
of red blood cells• Synthetic versions used to increase oxygen carrying
capacity of blood Synthetic erythropoietin is a banned substance in most
athletic organizations• Blood doping (red blood cell reinfusion) is an older
method used to increase oxygen-carrying capacity of blood
• Both blood doping and synthetic erythropoietin increase blood viscosity and could cause stroke or heart attack
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Meal Replacements Sports bars and shakes are not defined as dietary
supplements by the FDA• Main energy source is carbohydrate with some protein
and fat• Offer convenience, but are often expensive• Should not replace whole, nutritious foods in the diet
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Quick Review Dietary supplement and ergogenic aids such as creatine,
caffeine, anabolic steroids, growth hormone, erythropoietin and blood doping, may enhance performance, but can have serious side effects
Sports bars and shakes are convenient energy sources, but can be costly and should only be included as a minor part of an overall healthy diet
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Putting It All Together Cardiorespiratory endurance, muscle strength, muscle
endurance, flexibility, and body composition are the components of fitness
Effective conditioning programs can be designed using the FITT and progressive overload principles
Both the timing of meals and the foods eaten can affect exercise performance and recovery time
Certain vitamins and minerals are a concern to athletes; supplementation is not usually necessary as adequate amounts can generally be consumed in foods
Sports drinks may be beneficial for moderate to vigorous activities or endurance sports
Dietary supplements and ergogenic aids may enhance performance, but can have negative side effects