Transcript Chapter 11

Lecture
Outline
Chapter 11
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Nutrition for PhysicallyActive Lifestyles
Chapter 11
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Chapter Learning Outcomes
1. List five health benefits of a physically-active
lifestyle.
2. Differentiate between anaerobic and aerobic
use of energy, and identify advantages and
disadvantages of each.
3. Plan nutritionally adequate, high-carbohydrate
menus.
4. Estimate an athlete’s energy and protein needs.
5. List at least five ergogenic aids that athletes
often use, and describe their effects on health
and physical performance.
6. Design a personal fitness regimen that suits
your interests and lifestyle.
Quiz Yourself
True or False

1. People who exercise regularly can reduce their
risk of type 2 diabetes. T F
2. Sports drinks are not useful for fluid
replacement. T F
3. Protein is the body’s preferred fuel for muscular
activity. T F
4. Heatstroke is a serious illness that requires
immediate professional medical treatment. T F
5. While at rest, skeletal muscles metabolize more
glucose than fat for energy. T F
Quiz Yourself
True or False

1. True Engaging in exercise regularly can reduce
the risk of type 2 diabetes.
2. False Sports drinks can be useful for fluid
replacement.
3. False Protein is not the body’s preferred fuel for
muscular activity.
4. True Heatstroke is a serious illness that
requires immediate professional medical
treatment.
5. False While at rest, skeletal muscles
metabolize more fat for energy.
Key Terms
• Physical Activity
– Movement resulting from skeletal muscle
contraction
• Exercise
– Physical activities that are usually planned
and structured for a purpose
• Physical Fitness
– Ability to perform moderate- to vigorousintensity activities without becoming
excessively fatigued
Benefits of Regular Exercise
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11.1
Determining the Intensity of
Physical Activity
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11.1
Determining the Intensity of
Physical Activity
• Intensity
– Level of exertion used to perform an activity
• Factors that influence intensity:
– Duration
– Type of activity
– Body weight
• Methods of determining intensity:
– Assess breathing rate
– Assess heart rate
Calculating Age-Related
Maximum Heart Rate
To calculate your age-related maximum heart rate,
subtract your age from 220
– Target heart rate zone: range of heart rate that
reflects the intensity of exertion during physical
activity
Moderate intensity — target zone is 50 to 70% of
age-related maximum
Vigorous intensity — target zone is 70 to 85% of
age-related maximum
Physical Activity Pyramid
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Aerobic and Resistance Exercises
• Resistance exercise
• Aerobic exercise
– Sustained, rhythmic
contractions of large
muscle groups
– Raises heart rate
giving the heart an
effective workout
– Activities that increase
muscle mass and
strength
– Resistance exercises
also increase bone
mass.
Energy for Muscular Work
Cells obtain energy through a series of
chemical reactions
– Catabolism of glucose, fatty acids, amino
acids, or alcohol
• Energy stored in carbon-hydrogen bonds is
captured in the high energy compound ATP
• ATP forms when an inorganic phosphate
group (Pi ) bonds with ADP.
ATP
• Insert figure 11.4
Energy from Glucose
Glucose can be catabolizd anaerobically or
aerobically
– Catabolism involves oxidation, removal of
electrons from one compound to create
another.
• The first stage of glucose oxidation is glycolysis
— splitting of a glucose molecule to form two
pyruvate molecules.
– Occurs under anaerobic conditions
– A small amount of ATP is formed by glycolysis.
Glycolysis
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Figure 11.5
Further Oxidation of Glucose
If oxygen is available, pyruvate can enter
aerobic respiration pathways.
– Pyruvate moves from cytoplasm into
mitochondria — “powerhouses” of
cells.
– In mitochondria, pyruvate is completely
oxidized, forming ATP, CO2, and H2O.
Aerobic Respiration
• Insert
Figure 11.5
Summary of ATP Formation
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figure 11.6
How Do Cells Use ATP?
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Energy Systems for
Exercising Muscles
Why is glucose best biological fuel for
intense, brief exercise?
– Fatty acids have fewer oxygen atoms in
relation to carbons.
• Thus, cells require more oxygen to
metabolize fat.
• During brief bouts of intense exercise,
lungs and heart cannot deliver enough
oxygen to muscles for fatty acid oxidation.
Three Major Energy Systems
• Phosphocreatine (PCr)
– anaerobic
• Lactic acid
– anaerobic
• Oxygen
– aerobic
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man from bottom
of page 379
PCr-ATP Energy System
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Muscles contain enough ATP to last about 1 second.
PCr provides the energy by providing Pi to ADP
forming ATP .
PCr supplies muscles with ~ 6 seconds of energy.
Lactic Acid Energy System
• In anaerobic conditions, glucose is converted
to pyruvate and then lactic acid.
– Enough ATP is formed to last 30 to 40 sec.
• Lactic acid releases hydrogen ions, and
becomes lactate.
– Certain muscles can use some lactate for
energy.
– Most lactate enters the bloodstream.
• Liver removes lactate and converts it to glucose.
Lactic Acid
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11.9
Oxygen Energy System
• During low- to moderateintensity exercise (aerobic
conditions), muscle cells
can completely metabolize
glucose.
Produces ~18 times
more ATP than during
anaerobic conditions
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runner from
page 383
Fat or Carbohydrate for
Fueling Exercise?
Intensity of activity influences type of fuel
use
–Fat predominates when at rest and
during low- to moderate-intensity
activities
–Carbohydrate is main fuel for highintensity activities
–Protein contributes a small amount of
energy, with slightly more during
endurance exercise
General Dietary Advice for Athletes
Factors that influence athletic performance:
• Genetic endowment
• Physical training
• Diet
– Many athletes and coaches believe sports nutrition
misinformation often in advertisements, magazines
articles, and the Internet.
– Sports nutrition: applying nutrition principles
and research findings to improving athletic
performance
Energy for Athletic Performance
Most athletes need at least 3000 kcal/day.
– Males generally need 50 kcal/kg/day.
– Females generally need 45-50 kcal/kg/day.
Methods to determine adequate caloric
intake:
– Keep a food log
– Monitor body weight
Fat should supply 20 to 35% of energy.
Focusing on Carbohydrate
Intake
• Athletes should consume >60% of kcal from
carbohydrates.
Do the math to determine % kcal from
carbohydrates:
A person consumes 3000 kcal/day:
– Step 1 Determine 60% of 3000 kcal:
• 60% = 0.60
• 0.60 x 3000 = 1800 kcal
– Step 2 Determine grams of carbohydrate in 1800 kcal by
dividing kcal by 4. (Note: 1 g of “carbs” supplies 4 kcal)
• 1800 kcal  4 kcal/g = 450 g
Carbohydrate Intake
• To maintain adequate glycogen stores,
athletes need 6 to 10 g of carbohdrate/kg
body weight
To determine carbohydrate intake range:
Example: A person weighs 145 lbs.
– Step 1. Convert lbs to kg by dividing weight by 2.2
• 145  2.2 = 66 kg
– Step 2. To determine the range of carbohydrate
intake, multiply body wt in kg by 6 and then by 10
• For 6 g/kg  6 g x 66 kg = 396 g of “carbs”
• For 10 g/kg  10g x 66 kg = 660 g of “carbs”
Pre-Event Meal
Recommendations:
– About 2 to 4 hrs before event, eat a low-fat meal.
• Provides ~ 100 g of carbohydrate
• Total meal should supply ~ 500 to 600 kcal
• Insert
Table
11.3
Energy and
Macronutrient
Content of
Selected
Foods
• Insert Table 11.4
What Is Carbohydrate Loading?
CHO loading: manipulating physical activity and
dietary patterns, a few days before an event
Goal is to increase muscle glycogen stores
• Typical technique: 7 days before event
– Day 1 - Train intensely
– Days 2 to 4 - Gradually taper off training with
moderate carbohydrate (~ 300 g) intake
– Days 5 to 7 - Exercise lightly and rest on the last
day with high carbohydrate (400 to 700 g) intake
• The diet and training manipulation greatly
increase glycogen stores.
Consuming Carbohydrate
During and After Events
During
After
• Vigorous exercise >60
minutes depletes
glycogen stores:
• Trained athletes can
replenish most of their
glycogen stores in a few
days.
• Recommendation: 8 to 10
g carbohydrate/kg body
wt/day
• To replenish glycogen
quickly after intense
exercise: sports drinks,
sugar-sweetened soft
drinks, fruit, or fruit juices
– Athletes “hit the wall”
• Recommendation:
Consume 30 to 60 g
carbohydrates/hr.
• Food sources: Sports
drinks, sports gels, or
other sources of
carbohydrate
Raising the Bar?
What about energy bars, gels and drinks?
• Energy bars are made from soy or milk
proteins fortified with vitamins, minerals, and
fiber.
• No scientific evidence for benefits to performance
• Regular granola bars are cheaper source of
nutrients and fiber.
• Energy drinks typically contain sugars and
caffeine.
• Some contain ginseng
– may enhance effects of caffeine
What About Proteins?
For many athletes, protein intakes are higher
than recommendations.
• Protein recommendations for athletes:
• Endurance: 1.2 to 1.4 g/kg of body
weight/day
• Resistance: 1.6 to 1.7 g/kg of body
weight/day
Popular Energy Bars and Gels
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table 11.5
Focusing on Fluids
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man drinking
water from
page 390
Adequate Intake for Total
Water:
– 11 cups for young women
– 15.5 cups for young men
Water needs vary, depending on:
– Sport
– Fitness level
– Environmental conditions
Heat-Related Illnesses
• Insert table 11.6
Replenishing Fluids
To reduce risk of heat-related illness:
 Avoid exercising in extremely hot, humid weather
and replace lost fluids.
To estimate fluid needs, weigh yourself prior to
exercising and again after.
• If difference is >2%, fluid replacement is needed.
• General recommendation: Drink 20 to 24 oz of
fluids for each 1 pound of body weight lost
during exercise.
Do I Need a Sports Drink?
Sports drinks provide benefits over plain water
• Carbohydrate
– Sports drinks provide desirable carbohydrate content
(6%)
– Soft drinks and juices provide >10% carbohydrate
• Sodium and electrolytes
– Enhance water and carbohydrate absorption
and stimulate thirst
• Sports drinks generally recommended when
event lasts longer than 30 minutes
Antioxidant Vitamins
Free radical formation increases during aerobic
exercise.
– Oxidative stress may contribute to muscle
fatigue and damage.
• Intense exercise may stimulate the body’s natural
antioxidant defense system .
– Taking antioxidant supplements may block this
process.
• Therefore, taking antioxidant supplements is not
recommended.
Iron
Iron is needed to produce red blood cells, transport
oxygen, and obtain energy.
– Athletes at risk for iron deficiency include:
• Females
• Distance runners
• Vegetarians (especially vegans)
• Sports anemia — temporary condition resulting
from an increase in plasma (liquid portion of
blood)
– May be difficult to distinguish between sports
anemia and true anemia
Calcium
• Vegans and people who restrict intake of milk
and milk products are at risk for calcium
deficiency.
– Weak bones or osteoporosis may result.
• Female athletes who have irregular or no
menstrual cycles may be deficient in estrogen.
– Weight bearing exercise increases bone
density, but estrogen is needed to maintain
healthy bones.
Ergogenic Aids
What are ergogenic aids?
– Foods, devices, dietary supplements, or drugs used
to improve physical performance
– Are they effective?
• Little reliable scientific evidence supports
effectiveness of most dietary supplements.
• Sufficient water and electrolytes,
carbohydrates, and a balanced and varied diet
are the most important ergogenic aids.
Evaluation of Some Ergogenic Aids
• Insert table 11.7
Caffeine
Caffeine -- most widely used ergogenic aid
– How caffeine affects athletic performance:
• Benefits
– Raises blood fatty acid levels
– Enhances contraction of skeletal and heart muscles
– Increases mental alertness
• Adverse effects
–
–
–
–
Shakiness
Rapid heart beat
Sleep disturbances
Diarrhea and frequent urination
Caffeine Content
of Selected Beverages
• Insert Table
11.8
Chapter 11 Highlight: Developing a
Personal Physical Fitness Plan
• Most healthy people can gradually increase
physical activity levels.
• Older adults or those with any chronic health
condition should consult a physician before
starting a physical fitness program.
Stages of Fitness Plan
• Initiation—first 3to 6 weeks
– Incorporate short periods of activity to total 30
minutes on most days. (For example, gardening or taking
the stairs instead of elevators)
• Improvement—the next 5 to 6 months
– Increase intensity and duration of exercises.
– Exercise near the lower end of target heart rate zone.
• Maintenance—at 5 to 6 months
– Fitness goals are reached
– Continue present program
Components of a Workout
Regimen
• Warm-up
• Aerobic workout
–
–
–
–
–
Type
Duration
Frequency
Intensity
Progression
• Cool down
Types of Training
• What about strength (resistance) training?
– Include strength training 2 to 3 days per week
– May use weight, machines or elastic exercise cords
• Mixing it up
– Include several types of physical activity each week.
– Having an exercise partner provides motivation and
encouragement.
– Include variety, balance, and moderation in the
exercise routine.