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Nutrients, Physical Activity, and the Body’s Responses
Chapter 10
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Learning Objectives Provide examples of how regular physical activity benefits the body, and explain how the Physical Activity Guidelines for Americans can be incorporated into anyone’s lifestyle. Describe in brief how fitness develops, and explain the beneficial effects of both resistance and cardiorespiratory exercise on the body.
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Learning Objectives Explain the importance of glucose, fatty acids, and amino acids to a working athlete before, during, and after vigorous exercise. Explain why iron is of special significance for some athletes, and describe the proper roles for nutrient supplements.
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Learning Objectives Identify hazards associated with inadequate fluid replacement in the exercising body, and compare the fluid needs of a casual exerciser and an endurance athlete. Design a nourishing and adequate diet for an athlete, including snacks and pregame meals.
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Learning Objectives Evaluate whether dietary ergogenic aids are useful for increasing sports performance or obtaining an ideal body composition for sports.
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Introduction Physical activity and nutrition Needs Results
Energy-yielding nutrients Vitamins and minerals Results Regulation of energy-yielding nutrients Body composition Daily calorie allowance
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Fitness Depends on physical activity or exercise
Signs you are physically fit Longer, healthier life Sedentary lifestyle Benefits of fitness Chronic disease Disease resistance Numerous other benefits
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Physical Activity Guidelines
Physical Activity Guidelines for Americans Aerobic activity & resistance training Time and intensity Health benefits Higher intensity, greater frequency, and longer duration Weekly totals Healthy body weight maintenance Sport performance
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Physical Activity Guidelines for Americans
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Intensity of Physical Activity
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American College of Sport Medicine’s Guidelines for Physical Fitness
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The Essentials of Fitness
Components of fitness Adaptations Athletes Muscle power Agility Reaction times Muscle fatigue
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How Do Muscles Adapt to Physical Activity?
Activity choices Overload Hypertrophy Atrophy Balance of activity and rest Work different muscle groups Muscles need rest Replenish and adapt Specific training
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A Sample Balanced Fitness Program
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Resistance Training Progressive weight training
Prevent and manage chronic disease Muscle strength & size, power, and endurance Resistance and repetitions Appearance One to two days per week
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How Does Aerobic Training Benefit the Heart?
Enhances capacity Heart, lungs, and blood Enhances efficiency Delivery of oxygen VO2 max Removal of wastes Cardiac output Stroke volume
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How Does Aerobic Training Benefit the Heart?
Effective training activity characteristics Elevate heart rate Use most of the large-muscle groups
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Delivery of Oxygen by the Heart and Lungs to the Muscles
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The Active Body’s Use of Fuels
Need for food energy Excess postexercise oxygen consumption (EPOC) High intensity activities VO2max Energy deficit Moderate-intensity aerobic endurance training
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Glucose: A Major Fuel for Physical Activity
Muscle glycogen Retains glycogen for own use Liver glycogen Glycogen stores are not inexhaustible Glycogen and endurance High-carbohydrate diets Glucose from the digestive tract
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The Effect of Diet on Physical Endurance
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Glucose: A Major Fuel for Physical Activity
Anaerobic use of fuel Quick energy Muscle glycogen reserves Aerobic use of fuel Energy from glucose and fatty acids Lactate Role of the liver Accumulation coincides with fatigue
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Glucose and Fatty Acids in Their Energy-Releasing Pathways in Muscle Cells
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Glucose: A Major Fuel for Physical Activity
Glycogen use Duration of activity Intensity of activity Degree of training Muscles store more glycogen Muscles burn more fat
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Glycogen – Before and After Physical Activity
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Carbohydrate Recommendations for Athletes
Postpone fatigue and maximize performance Need for abundant carbohydrate Glucose before activity Glucose during activity Glucose after activity
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Suggested Daily Carbohydrate Intakes for Athletes
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Lipid Fuel for Physical Activity
Unlimited (theoretically) source of energy Sources of fat Aerobic metabolism Intensity and duration Degree of training Fat in the athlete’s diet Performance Omega-3 fatty acids
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Protein for Building Muscles and for Fuel
Muscle protein synthesis Up to two days after activity Intensity and pattern of muscle contraction Muscle cells only build proteins as needed Amino acids Protein-building limits Supplements Protein timing Two hours post exercise
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Protein for Building Muscles and for Fuel
Use in physical activity Regulatory factors Diet Exercise intensity and duration Degree of training Sufficient carbohydrate Recommendations for athletes Greater need for protein Dangers of excess protein
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How Much Protein Should An Athlete Consume?
DRI vs. other authorities Nature of chosen activity Benefits of nutritious eating pattern Problem with insufficient carbohydrate intake
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Recommended Protein Intakes for Athletes
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Do Nutrient Supplements Benefit Athletic Performance?
Well-nourished athletes More food means more nutrients Supplement timing Body use takes hours or days Preventing deficiencies Impede performance
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Iron – A Mineral of Concern
Deficiency impairs performance Myoglobin Sports anemia Groups at risk for deficiency Vitamin C
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Fluids and Temperature Regulation in Physical Activity
Water losses Breathing and sweating Dehydration Symptoms Sweat and temperature regulation Heat stroke Potentially fatal Hypothermia
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Symptoms of Heat Stroke
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Fluid and Electrolyte Needs during Physical Activity
Hydrate and rehydrate Hourly sweat rate Thirst signal Water Endurance athletes Electrolyte losses and replacement Minerals Sports drinks vs. regular diet
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Suggested Hydration Schedule for Physical Activity
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Sodium Depletion and Water Intoxication
Replenishing electrolytes Crucial time Hyponatremia Differs from dehydration Heat cramps Sodium
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Hyponatremia: Symptoms and Risk Factors
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Other Beverages Carbonated beverages Alcoholic beverages Caffeine
Moderate doses Alcoholic beverages Diuretic
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Selecting Sports Drinks
Fluid Glucose Percentage glucose Sodium and other electrolytes Read labels Psychological edge
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Choosing a Performance Diet
Nutrient density Carbohydrate Carbohydrate sources Liquid carbohydrate supplements Protein Lean proteins
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Nutritious High-Carbohydrate Meals for Athletes
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Choosing a Performance Diet
Pregame meals Easily digested High in carbohydrates Timing of activity and body size Recovery meals Several small meals Liquid form Homemade shakes Commercial products
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Examples of High-Carbohydrate Pregame Meals
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Commercial and Homemade Recovery Drinks Compared
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Ergogenic Aids: Breakthroughs, Gimmicks, or Dangers?
Controversy 10
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Ergogenic Aids Advertorials Dietary supplements Legitimate research
Escape regulation Legitimate research Large majority of ergogenic aid claims are not supported
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Ergogenic Aids Antioxidant supplements Caffeine Carnitine
Oxidative stress Caffeine Endurance vs. high-intensity activities Adverse effects Carnitine Nonessential nutrient Dietary sources
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Ergogenic Aids Chromium picolinate Creatine
Carbohydrate and lipid metabolism Safety concerns Creatine Hypothesized benefits Confirmed effect Weight gain
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Ergogenic Aids Buffers Amino acid supplements Sodium bicarbonate
Unpleasant side effects Amino acid supplements Essential amino acids in system prior to physical work Best source Food Reasons against supplements
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Ergogenic Aids Whey protein By product of cheese making
Timing of protein intake No clear benefits
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Hormones and Hormone Imitators
Anabolic steroid hormones Illegal and dangerous Human growth hormone Steroid alternatives DHEA Drugs posing as supplements DMAA
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More Substances Promoted as Ergogenic aids
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More Substances Promoted as Ergogenic aids
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