Chapter 23 Nutrition, Body Composition, and Performance

1. Chapter 23Nutrition, Body Composition, and Performance EXERCISE PHYSIOLOGY Theory and Application to Fitness and Performance, 6th edition Scott K. Powers & Edward T. Hawley

2. Objectives • Describe the effect of various carbohydrate diets on muscle glycogen and on endurance performance during heavy exercise • Contrast the “classic” method of achieving a super compensation of muscle glycogen stores with the “modified” method • Describe some potential problems when glucose is ingested immediately prior to exercise • Describe the importance of blood glucose as a fuel in prolonged exercise, and the role of carbohydrate supplementation during the performance

3. Objectives • Contrast the evidence that protein is oxidized at a faster rate during exercise with the evidence that the use of labeled amino acids may be an inappropriate methodology to study this issue • Describe the need for protein during the adaptation to a new, more strenuous exercise level with the protein need when the adaptation is complete • Defend the recommendation that a protein intake that is 12% to 15% of energy intake is sufficient to meet an athlete’s need • Describe the recommended fluid replacement strategies for athletic events of different intensities and duration, citing evidence to support your position

4. Objectives • Describe the salt requirement of the athlete, compared to the sedentary individual, and the recommended means of maintaining sodium balance • List steps leading to iron deficiency anemia and special problems that athletes have in maintaining iron balance • Provide a brief summary of the effects of vitamin supplementation on performance • Characterize the role of the prename meal on performance and the rationale for limiting fats and proteins

5. Objectives • Describe the various components of the somatotype and what the following rating signify: 171, 711, 117 • Describe what the endomorphic and geomorphic components in the Heath-Carter method of somatotyping represent in conventional body composition analysis • Explain why one must be careful in recommending specific body fatness values for individual athletes

6. Carbohydrates and Performance • Endurance performance is improved by a diet high in carbohydrates • Increases muscle glycogen • 58% of caloric intake as carbohydrates provides for adequate muscle glycogen • Muscle glycogen loading (“super compensation”) • Goal is to maximize muscle glycogen • Replenishing muscle glycogen • Glucose or glucose polymers better than fructose

7. Classical method Prolonged strenuous exercise to deplete glycogen stores A high fat/protein diet for three days while continuing to train 90% CHO diet for three days with inactivity Modified plan Tapering workouts over several days from 90 to 40 minutes while eating 50% CHO diet Two days of 20 minute workouts while eating 70% CHO diet Day of rest eating 70% CHO diet before event Supercompensation of Glycogen Stores

8. Effect of Diet on Muscle Glycogen and Time to Exhaustion Fig 23.1

9. Classical and Modified Methods of Glycogen Super-compensation Fig 23.2

10. Carbohydrate Intake Before and During Exercise • Improves performance by elevating blood glucose • Does not spare muscle glycogen utilization • Pre-exercise • 1-5 grams CHO•kg-1 body weight • 1-4 hours before exercise • During exercise • CHO ingestion can maintain plasma glucose even as glycogen is depleted

11. Muscle Glycogen & Blood Glucose Use During Prolonged Exercise Fig 23.3

12. Protein Requirement for Training • Endurance training • RDA of 0.8 g•kg-1•day-1 is sufficient for light to moderate exercise • 1.2-1.4 g•kg-1•day-1 for high-intensity endurance exercise

13. Protein Requirement for Training • Resistance training • 0.9 g•kg-1•day-1 for maintaining strength • 1.4-1.8 g•kg-1•day-1 for increasing strength and lean body mass • Average protein intake is ~1.5 g•kg-1•day-1 • Enough to meet requirements for athletes

14. Nitrogen Balance During Exercise • Dependent upon: • Training state of the subject • Quality and quantity of protein consumed • Total calories consumed • The body’s carbohydrate stores • Intensity, duration, and type of exercise

15. Effect of Exercise on Nitrogen Balance Fig 23.4

16. Effect of Muscle Glycogen Levels on Sweat Urea Nitrogen Excretion Fig 23.5

17. Water Replacement • Before exercise • 300-500 ml water • Include 30-50 g CHO for duration <1 hour • During exercise • Duration less than one hour - Water only • Duration greater than one hour • Water plus Na+, Cl-, and glucose • Cold drinks absorbed faster than warm drinks • Gastric emptying slower at intensities above 65-70% VO2max

18. Responses to Exercise With Different Volumes of Fluid Replacement Fig 23.7

19. Factors Affecting Fluid Absorption From the GI Tract Fig 23.8

20. Salt and Mineral Replacement • Salt needs are met or exceeded by meals • Iron - Deficiency due to decreased intake or increased loss • Supplementation recommended for female athletes • Vitamins - Supplementation is not necessary on well-balanced diet unless clear deficiency is known

21. Pregame Meal • Purposes • Provide adequate hydration • Provide carbohydrates to “top off” liver stores • Avoid the sensation of hunger • Minimize GI tract problems • Content • 500-1,000 kcals • Mostly complex carbohydrates

22. Somatotypes • Endomorphy • Relative predominance of soft roundness and large digestive viscera • Mesomorphy • Relative predominance of muscle, bone, and connective tissue • Ectomorphy • Relative predominance of linearity and fragility

23. Contrast of Somatotypes Between College Students and Athletes Fig 23.11

24. Body Fatness and Performance • Optimal body fatness for health • Males: 10-25% • Females: 15-25% • Optimal body fatness for performance differs between men and women and varies within gender and sport • It is natural for some athletes to have higher body fatness than others in order to perform optimally

25. Chapter 23 Nutrition, Body Composition, and Performance