Nu fsp chapter 4

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  • 1. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chapter 4 Lecture Slides
  • 2. Dietary Carbohydrates • One of the most important nutrients in your diet, from the standpoint of both health and athletic performance, is dietary carbohydrate.
  • 3. What are the different types of dietary carbohydrate? • Carbohydrates – Carbon, hydrogen and oxygen • Simple carbohydrates – Monosaccharides • Name them – Disaccharides • Name them and the monosaccharides for each
  • 4. What are some common foods high in carbohydrate content?
  • 5. How much carbohydrate do we need in the diet? • Recommended Dietary Allowance (RDA) – 130 grams • Acceptable Macronutrient Distribution Range (AMDR) – 45-65% of energy intake • Daily Value (DV) – 60% of daily energy needs – 300 grams on a 2,000 Calorie diet – 25 grams of fiber
  • 6. Recommended carbohydrate in the diet • Sport nutritionists – Recommend high end of AMDR – 60-70% or higher – Diet containing 3,000 Calories • 450 grams of carbohydrate at 60% level
  • 7. Figure 4.4
  • 8. What happens to the carbohydrate after it is absorbed into the body? • Most dietary carbohydrates eventually are converted to glucose which circulates in the blood • Carbohydrate foods have different effects on blood glucose levels • The glycemic index and glycemic load
  • 9. Fates of blood glucose • May be used for energy • May be converted to liver or muscle glycogen • May be converted to and stored as fat in adipose tissues • May be excreted in the urine if in excess
  • 10. Figure 4.6
  • 11. Carbohydrate storage in the body
  • 12. Carbohydrates for Exercise • Carbohydrate as an energy source during exercise • Effect of training on carbohydrate metabolism • Methods of providing carbohydrate – Before competition – During competition – After competition – During training
  • 13. In what type of activities does the body rely heavily on carbohydrate as an energy source? • Carbohydrate contributes about 40% of energy needs at rest • Fat is main energy source during low exercise intensity, such as 40-50% VO2max • Carbohydrate is major source during – Very high intensity anaerobic exercise – High intensity (>65% VO2max) aerobic exercise – Prolonged aerobic exercise events – Intermittent high-intensity exercise sports
  • 14. Carbohydrate sources for exercise • Muscle glycogen is a very important source • Liver glycogen is converted to blood glucose • Blood glucose is delivered to muscles
  • 15. Hypoglycemia • The human body attempts to prevent hypoglycemia • Hormone activity – Insulin – Glucagon
  • 16. Hormones and glucose metabolism Hormone Gland Stimulus Action Insulin Pancreas Increase in blood glucose Helps transport glucose into cells; decreases blood glucose levels Glucagon Pancreas Decrease in blood glucose; exercise stress Promotes gluconeogenesis in liver; helps increase blood glucose levels Epinephrine Adrenal Exercise stress; decrease in blood glucose Promotes glycogen breakdown and glucose release from the liver Cortisol Adrenal Exercise stress; decrease in blood glucose Promotes breakdown of protein; stimulates gluconeogenesis
  • 17. How is low muscle glycogen related to the development of fatigue? • Low muscle glycogen and aerobic exercise – Muscle glycogen is the primary fuel for endurance athletes, such as marathon runner • Studies have shown physical exhaustion to be associated with very low muscle glycogen levels. However, other studies have shown fatigue with some muscle glycogen remaining.
  • 18. Optimal supplementation protocol • Consume carbohydrates both before and during the exercise task.
  • 19. When, how much, and in what form should carbohydrates be consumed before or during exercise? • Athletes who may benefit from carbohydrate intake – Endurance exercise – Intermediate high-intensity exercise • Fluid replacement is also an important consideration
  • 20. What is the importance of carbohydrate replenishment after prolonged exercise? • Rapid restoration of muscle glycogen important for some athletes – Repeated bouts of prolonged, intense exercise on the same day – Prolonged, intense exercise on consecutive days
  • 21. Carbohydrate-rich diets for athletes • Sport nutritionists recommend that athletes consume about 8-10 grams of carbohydrate per kilogram body weight daily • For a 70-kg athlete, this would amount to 560 to 700 grams of carbohydrate daily, or the equivalent of 2,240 to 2,800 Calories • On a 3,500-Calorie daily intake, the carbohydrate would provide 65-80% of daily energy intake. • This amount of daily carbohydrate would help restore muscle glycogen levels
  • 22. Carbohydrates during training • There is no evidence that low-carbohydrate diets improve exercise performance • A diet rich in healthy carbohydrates may help guarantee optimal energy sources for daily training • Train high and compete high is the concept of training and competing with high carbohydrate intake.
  • 23. Carbohydrate loading What is carbohydrate, or glycogen, loading? • Method of increasing muscle glycogen levels – Also known as muscle glycogen supercompensation
  • 24. What type of athlete would benefit from carbohydrate loading? • Athletes who sustain high levels of continuous energy expenditure for prolonged periods – Long-distance runners – Cross-country skiers – Endurance triathletes – Tournament play in intermittent high-intensity exercise sports
  • 25. How do you carbohydrate load? • Athlete should be fully trained • Classic procedure not necessary: – Depletion stage – Low carbohydrate diet – Carbohydrate loading • Have about 3-4 days of high carbohydrate intake, about 8-10 grams/kg body weight, or more • Low and high glycemic index carbohydrates are equally effective • Taper exercise training over the course of a week or longer
  • 26. Carbohydrate loading procedures
  • 27. Will carbohydrate loading increase muscle glycogen concentration? • Most studies report increased muscle glycogen levels following carbohydrate loading procedures • Both males and females will increase glycogen levels if adequate energy and carbohydrate are consumed • Muscle glycogen levels may increase two to three times above normal • Experiment with the protocol during training
  • 28. Will carbohydrate loading improve exercise performance? • In general, the procedure is not needed for exercise tasks of short duration • In general, research supports the use of carbohydrate loading as a means to enhance performance in prolonged endurance exercise tasks – Helps maintain an optimal pace longer – Extra body water may help during exercise in the heat • Most appropriate protocol is to use both carbohydrate loading and consumption of carbohydrate during the event
  • 29. Carbohydrates: Ergogenic Aspects • Metabolic by-products – Pyruvate – DHAP (Pyruvate and dihydroxyacetone) – Lactate salts – Ribose – Multiple carbohydrate products
  • 30. Soluble and insoluble fiber • The issue of soluble and insoluble fiber – Difficult to generalize on different health effects of soluble and insoluble fiber; health effects are due to total fiber, but it may be illustrative to discuss soluble and insoluble fiber effects on health.