Sports Nutrition for Peak Performance

1. Sports Nutrition for Peak Performance

2. We have been discussing basic concepts of nutrition: - Food choices and nutritional guidelines - Digestion - Carbohydrates, lipids, and proteins - Energy balance and body composition - Vitamins - Water and mineral balance

3. We have been discussing basic concepts of nutrition: - Food choices and nutritional guidelines - Digestion - Carbohydrates, lipids, and proteins - Energy balance and body composition - Vitamins - Water and mineral balance For the rest of this course, we will discuss some specific applications of those concepts: - Sports nutrition - Nutrition in pregnancy and various life stages - Food safety and technology - Global nutrition

4. As we have discussed many times, maintaining an active lifestyle is an important part of maintaining energy balance, normal weight, and healthy eating habits.

5. As we have discussed many times, maintaining an active lifestyle is an important part of maintaining energy balance, normal weight, and healthy eating habits. Humans evolved for both intensive short-term (anerobic) exercise such as sprinting to overtake prey, and long-term (aerobic) endurance exercise such as chasing prey over long distances. These adaptations include how the body obtains various nutrients, as well as how the body uses these nutrients under different physiological conditions.

6. As we have discussed many times, maintaining an active lifestyle is an important part of maintaining energy balance, normal weight, and healthy eating habits. Thus, nutrition and physical activity are intricately linked and must be considered together: - changes in physical activity result in changes in nutritional needs - changes in nutrition are reflected in changes in physical activity

7. Nutrition in Exercise and Sports Performance Unfortunately, in modern life our physical activity and our our dietary habits have not remained in balance.

8. Nutrition in Exercise and Sports Performance Unfortunately, in modern life our physical activity and our our dietary habits have not remained in balance. We eat more food and more types of food, particularly high-calorie carbohydrates and fats.

9. Nutrition in Exercise and Sports Performance Unfortunately, in modern life our physical activity and our our dietary habits have not remained in balance. We eat more food and more types of food, particularly high-calorie carbohydrates and fats. At the same time, we have become more sedentary, getting less exercise in both duration and intensity. The result it that we are becoming increasingly out-of-shape physically and increasingly obese, and we are experiencing more health problems because of these.

10. Nutrition in Exercise and Sports Performance To combat that, a variety of recommendations have been developed through both public and private organization to encourage us to get adequate exercise and to develop eating habits which are better aligned with modern lifestyles.

11. Nutrition in Exercise and Sports Performance Exercise places strong demands on the body to provide - Energy for strenuous and/or sustained muscle use - Building blocks for muscle and bone growth - Pathways to remove waste products of activity

12. Nutrition in Exercise: Muscle We need to start out with a review of the structure and contraction of muscles and muscle cells.

13. Nutrition in Exercise: Muscle We need to start out with a review of the structure and contraction of muscles and muscle cells. In a muscle such as your rectus femoris or gastrocnemius (both in the lower limb) the muscle cells (“myocytes”, “fibers”) are all arranged in the same direction so they all pull in the same direction.

14. Nutrition in Exercise: Muscle We need to start out with a review of the structure and contraction of muscles and muscle cells. In a muscle such as your rectus femoris or gastrocnemius (both in the lower limb) the muscle cells (“myocytes”, “fibers”) are all arranged in the same direction so they all pull in the same direction. Within each cell are bundles of contractile proteins called myofibrils. There are also many mitochondria.

15. Nutrition in Exercise: Muscle Those myofibrils are composed of thousands of smaller structures called myofilaments which slide past each other during contraction. That requires the release of large amounts of calcium inside the cell, and it requires a large amount of energy.

16. Nutrition in Exercise: Muscle Those myofibrils are composed of thousands of smaller structures called myofilaments which slide past each other during contraction. That requires the release of large amounts of calcium inside the cell, and it requires a large amount of energy. You will recall that energy for all cellular processes, including muscle contraction, is provided by a molecule called adenosine triphosphate (ATP).

17. Nutrition in Exercise: ATP Muscle cells contain a lot of pre-formed ATP. However, in exercise they quickly deplete all of that stored ATP. They have a related molecule called creatine phosphate (CP) which can be used to quickly make more ATP, but that too will be used up in just a few seconds of strenuous exercise. (Your book calls this the “ATP-CP Energy System”)

18. Nutrition in Exercise: ATP Once ATP and CP are depleted, your muscle cells begin to break apart glycogen to release glucose molecules.

19. Nutrition in Exercise: ATP Once ATP and CP are depleted, your muscle cells begin to break apart glycogen to release glucose molecules. Through glycolysis, each molecule of glucose is converted to two molecules of pyruvate, forming two molecules of ATP in the process. This does not require oxygen, that is, it is anaerobic. Glucose ATP ATP 2 Pyruvate

20. Nutrition in Exercise: ATP Once ATP and CP are depleted, your muscle cells begin to break apart glycogen to release glucose molecules. Through glycolysis, each molecule of glucose is converted to two molecules of pyruvate, forming two molecules of ATP in the process. This does not require oxygen, that is, it is anaerobic. In the absence of oxygen, pyruvate is converted to lactic acid, which interferes with contraction. It must be removed from the muscle cells and sent to the liver. Glucose ATP ATP 2 Pyruvate 2 Lactic Acid (Your book calls this the “Lactic Acid Energy System”)

21. Nutrition in Exercise: ATP This anaerobic system of glycolysis can produce a small amount of ATP quickly, so it is sufficient for short periods of exercise. However, it can not produce enough to sustain long-term exercise. For that, oxygen is needed. Oxygen is delivered to the muscle cells in the blood, and some was stored by attachment to the molecule myoglobin.

22. Nutrition in Exercise: ATP In the presence of oxygen, the pyruvate is converted to a molecule called acetyl CoA. Within the mitochondria, this is sent into a series of reactions called the Kreb’s Cycle or Tricarboxylic Acid Cycle, which generates another 18 molecules of ATP from each acetyl CoA, or 36 molecules of ATP from each glucose molecule. Glucose ATP ATP 2 Pyruvate 2 Acetyl CoA 36 ATP 6 O2 6 CO2

23. Nutrition in Exercise: ATP In the presence of oxygen, the pyruvate is converted to a molecule called acetyl CoA. Within the mitochondria, this is sent into a series of reactions called the Kreb’s Cycle or Tricarboxylic Acid Cycle, which generates another 18 molecules of ATP from each acetyl CoA, or 36 molecules of ATP from each glucose molecule. While that produces a lot more ATP than glycolysis alone, it is much slower Glucose ATP ATP 2 Pyruvate 2 Acetyl CoA 36 ATP 6 O2 6 CO2 (Your book calls this the “Oxygen Energy System”)

24. Nutrition in Exercise: ATP Another advantage of the Kreb’s Cycle is that it can also be used to produce energy from fats (and, if absolutely necessary, proteins) through acetyl CoA. Glycogen Triglycerides (Proteins) Glucose Fatty Acids (Amino Acids) Pyruvate Acetyl CoA ATP O2 CO2

25. Nutrition in Exercise: ATP Another advantage of the Kreb’s Cycle is that it can also be used to produce energy from fats (and, if absolutely necessary, proteins) through acetyl CoA. However, it takes a longer time for the body to mobilize fats and send them to the muscle cells, so at least the early stages of exercise depend on the muscle cells’ store of glycogen. Glycogen Triglycerides (Proteins) Glucose Fatty Acids (Amino Acids) Pyruvate Acetyl CoA ATP O2 CO2

26. Nutrition in Exercise: ATP During exercise, of course, all of these systems of producing energy (in the form of ATP) are used by muscle cells as long as glycogen is available.

27. Nutrition in Exercise: ATP During exercise, of course, all of these systems of producing energy (in the form of ATP) are used by muscle cells as long as glycogen is available. Eventually, the stored glucogen will be depleted and muscle fatigue occurs. The muscle cells can obtain some glucose from the blood, but this is not enough to sustain prolonged exercise.

28. Nutrition in Exercise and Sports Performance Endurance training increases the number of mitochondria within the muscle cells, and it increases their ability to store glucose as glycogen and to store oxygen attached to myoglobin, so it - Decreases reliance on anaerobic systems - Extends availability of glycogen - Delays fatigue

29. Nutrition in Exercise: Muscle Cells In reality, we have been oversimplifying things a bit. It turns out that not all muscle cells are the same. All of your skeletal muscles (the organs, such as your biceps brachii or trapezius) have two types of muscle cells (“myocytes” or “fibers”) 1. Fast twitch cells have large amounts of glycogen but few mitochondria and small amounts of myoglobin. They can generate ATP quickly by the anaerobic pathway and contract quickly, but they fatigue easily.

30. Nutrition in Exercise: Muscle Cells In reality, we have been oversimplifying things a bit. It turns out that not all muscle cells are the same. All of your skeletal muscles (the organs, such as your biceps brachii or trapezius) have two types of muscle cells (“myocytes” or “fibers”) 2. Slow twitch cells have moderate amounts of glycogen, many mitochondria, and large amounts of myoglobin. They generate a lot more ATP but do it more slowly by the aerobic pathway, contracting more slowly, but fatiguing less easily.

31. Nutrition in Exercise: Muscle Cells Exercise training can change the proportion of slow-twitch and fast-twitch cells in your muscles. Consequently, you can make your muscles more efficient for either short-term or long-term exercise.

32. Nutrition in Exercise and Sports Performance Production of ATP for energy (from creatine phosphate, through glycolysis, and through the Kreb’s cycle) is certainly an important part of nutrition for exercise, but of course it is not the only thing which is important.

33. Nutrition in Exercise and Sports Performance Production of ATP for energy (from creatine phosphate, through glycolysis, and through the Kreb’s cycle) is certainly an important part of nutrition for exercise, but of course it is not the only thing which is important. During exercise you need to: - consume adequate calories for your energy needs - consume adequate amino acids to maintain proteins - consume adequate vitamins and minerals - maintain fluid balance & avoid dehydration Long-term, you also need to: - maintain proper body mass and body fat - recover from muscle damage from exercise

34. Nutrition in Exercise and Sports Performance The most important nutritional concern of exercise and athletic performance is adequate energy intake from two primary sources: - carbohydrates - lipids

35. Nutrition in Exercise and Sports Performance The most important nutritional concern of exercise and athletic performance is adequate energy intake from two primary sources: - carbohydrates - lipids These are important both - short term to provide glucose and fatty acids for immediate use, and - long term to provide the molecules needed to replenish glygocen and triglycerides.

36. Nutrition in Exercise: Carbohydrate For most athletes, smaller more frequent meals containing complex carbohydrates works best. These take longer to be digested to release mosaccharides, slowing their absorption from the intestine into the blood and producing a more stable level of glucose in the blood. This helps increase glycogen storage in liver and muscle cells as well as ensuring that a continuous supply of glucose is availabe in the blood for immediate energy needs. Food with complex carbohydrates have the additional advantage of often also providing vitamins and minerals.

37. Nutrition in Exercise: Carbohydrate If you start early enough, you can significantly increase the amount of glycogen stored in your muscles by a process called carbohydrate loading in which you alternate shorter, less intense periods of exercise with high carbohydrate meals.

38. Nutrition in Exercise: Carbohydrate If you start early enough, you can significantly increase the amount of glycogen stored in your muscles by a process called carbohydrate loading in which you alternate shorter, less intense periods of exercise with high carbohydrate meals. Since the muscles of most athletes have enough glycogen to last at least 60-90 minutes, this is only effective for periods of activity longer than that.

39. Nutrition in Exercise: Carbohydrate Two to four hours before strenuous exercise, meals should contain up to 65% of their calories as complex carbohydrates with low or moderate glycemic indices, and 10% to 20% each from lipids and proteins.

40. Nutrition in Exercise: Carbohydrate Two to four hours before strenuous exercise, meals should contain up to 65% of their calories as complex carbohydrates with low or moderate glycemic indices, and 10% to 20% each from lipids and proteins. Just before exercise, eat easily digestable carbohydrates with higher glycemic indices.

41. Nutrition in Exercise: Carbohydrate Two to four hours before strenuous exercise, meals should contain up to 65% of their calories as complex carbohydrates with low or moderate glycemic indices, and 10% to 20% each from lipids and proteins. Just before exercise, eat easily digestable carbohydrates with higher glycemic indices. During exercise, eat or drink small amounts (large meals can cause digestive problems) of foods with high glycemic indices.

42. Nutrition in Exercise: Carbohydrate Immediately after strenuous exercise you should begin eating foods with moderate to high glycemic indices to immediately begin to replenish glycogen, and you should continue to eat carbohydrates for a few hours.

43. Nutrition in Exercise: Carbohydrate Immediately after strenuous exercise you should begin eating foods with moderate to high glycemic indices to immediately begin to replenish glycogen, and you should continue to eat carbohydrates for a few hours. Of course, exercise causes significant loss of water and minerals, so it is important to also remain hydrated during exercise to maintain fluid balance. Without this, your muscle cells can not effectively use glycogen, produce energy through glycolysis or the Kreb’s cycle, or remove waste products such as lactic acid or CO2.

44. Nutrition in Exercise: While carbohydrates are critical to peak performance during exercise, they are not the only important nutrients. Fats, proteins, vitamins, and minerals are also involved.

45. Nutrition in Exercise: Fats At all times, carbohydrates and fats are the two primary fuels: fats should contribute 20%-30% of calories. Glycogen Triglycerides Glucose Fatty Acids Pyruvate Acetyl CoA ATP O2 CO2

46. Nutrition in Exercise: Fats At all times, carbohydrates and fats are the two primary fuels: fats should contribute 20%-30% of calories. This is particularly true during exercise. In low-intensity exercise after glycogen is depleted from cells, fats often become the primary fuel source if carbohydrates are not consumed. Glycogen Triglycerides Glucose Fatty Acids Pyruvate Acetyl CoA ATP O2 CO2

47. Nutrition in Exercise: Fats However: - fat is digested and absorbed more slowly than carbohydrates with high glycemic indices - fatty acids are not transported as easily in the blood as glucose - fatty acid are not absorbed from the blood into muscle cells as easily as glucose

48. Nutrition in Exercise: Fats However: - fat is digested and absorbed more slowly than carbohydrates with high glycemic indices - fatty acids are not transported as easily in the blood as glucose - fatty acid are not absorbed from the blood into muscle cells as easily as glucose Thus, fatty acids are more difficult for muscle cells to use, but

49. Nutrition in Exercise: Fats Like any other times: dietary fats during exercise should - include monounsaturated & polyunsaturatedfatty acids - minimize trans fatty acids - include omega-3 and omega-6 fatty acids - be part of foods that also include proteins, vitamins, and minerals

50. Nutrition in Exercise: Fats A word of caution: Fat is sometimes erroneously seen by athletes as something “bad” to be avoided in the diet and removed from the body. While excess fat is indeed unhealthy, too little body fat is also unhealthy Fat: Provides fatty acids for energy Protects internal organs Insulates against heat loss Regulates a number of hormones Stores some vitamins Forms phospholipids for cell membranes