Chapter 16: Nutrition and Fitness

1. Chapter 16: Nutrition and Fitness

2. 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

3. 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

5. What Does a Successful Physical Fitness Program Look Like? • Incorporates activities based on the five components of fitness • Tailored to meet needs of individual

6. 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

7. 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

9. 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

10. 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

11. 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.

12. 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

13. Anaerobic Energy Metabolism Figure 16.2

14. 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

15. 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

16. 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

17. Energy Use During Various Intensities of Exercise Figure 16.3

18. 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

19. 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

20. 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

21. 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

22. 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

23. 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

24. 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

25. 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

27. 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

28. 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

29. Effects of Dehydration on Exercise Performance Figure 16.4

30. 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

31. 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

32. 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

33. 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

34. 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

35. 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

36. 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

37. 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

38. 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

39. 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

40. 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

41. 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