1. © 2007 McGraw-Hill Higher Education. All Rights Reserved. Presentation revised and updated by Brian B. Parr, Ph.D. University of South Carolina Aiken Chapter 23 Nutrition, Body Composition, and Performance EXERCISE PHYSIOLOGY Theory and Application to Fitness and Performance, 6th edition Scott K. Powers & Edward T. Howley

2. © 2007 McGraw-Hill Higher Education. All Rights Reserved. Objectives 1.Describe the effect of various carbohydrate diets on muscle glycogen and on endurance performance during heavy exercise. 2.Contrast the “classic” method of achieving a supercompensation of the muscle glycogen stores with the “modified” method. 3.Describe some potential problems when glucose is ingested immediately prior to exercise. 4.Describe the importance of blood glucose as a fuel in prolonged exercise, and the role of carbohydrate supplementation during the performance.

3. © 2007 McGraw-Hill Higher Education. All Rights Reserved. Objectives 5.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. 6.Describe the need for protein during the adaptation to a new, more strenuous exercise level with the protein need when the adaptation is complete. 7.Defend the recommendation that a protein intake that is 12 to 15% of energy intake is sufficient to meet an athlete’s need. 8.Describe the recommended fluid replacement strategies for athletic events of different intensities and durations, citing evidence to support your position.

4. © 2007 McGraw-Hill Higher Education. All Rights Reserved. Objectives 9.Describe the salt requirement of the athlete compared to that of the sedentary individual, and the recommended means of maintaining sodium balance. 10.List the steps leading to iron deficiency anemia and the special problem that athletes have in maintaining iron balance. 11.Provide a brief summary of the effects of vitamin supplementation on performance. 12.Characterize the role of the pregame meal on performance and the rationale for limiting fats and proteins.

5. © 2007 McGraw-Hill Higher Education. All Rights Reserved. Objectives 13.Describe the various components of the somatotype and what the following rating signify: 171, 711, and 117. 14.Describe what the endomorphic and mesomorphic components in the Heath-Carter method of somatotyping represent in conventional body composition analysis. 15.Explain why one must be careful in recommending specific body fatness values for individual athletes.

6. © 2007 McGraw-Hill Higher Education. All Rights Reserved. Recommended Range of Nutrient Intakes  45–65% calories from carbohydrates –Meets needs of whole population –Addresses special needs (type 2 diabetes) –Athletes need more carbohydrates that the average person  20–35% calories from fat  10–35% calories from protein

7. © 2007 McGraw-Hill Higher Education. All Rights Reserved. Carbohydrate Diets and Performance  Muscle glycogen is depleted during heavy exercise –Time to exhaustion related to initial muscle glycogen store  Endurance performance is improved by a diet high in carbohydrates –Increases muscle glycogen and performance time  Muscle glycogen loading (“supercompensation”) –Goal is to maximize muscle glycogen in the days leading up to an event

8. © 2007 McGraw-Hill Higher Education. All Rights Reserved. Effect of Diet on Muscle Glycogen and Time to Exhaustion Figure 23.1

9. © 2007 McGraw-Hill Higher Education. All Rights Reserved. Muscle Glycogen Supercompensation  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 (90 to 40 minutes) over several days 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  Both methods increase muscle glycogen to high levels  Only one day with carbohydrate intake of 10 g/kg body weight from high glycemic index foods required for very high muscle glycogen levels

10. © 2007 McGraw-Hill Higher Education. All Rights Reserved. Modification of the Classic Glycogen Loading Technique Figure 23.2

11. © 2007 McGraw-Hill Higher Education. All Rights Reserved. Muscle Glycogen Replenishment  Takes about 24 hours to replenish muscle glycogen –Requires ingestion of 500–700 g carbohydrates –Limiting factor is glucose transport across cell membrane  Timing of glucose ingestion after exercise –Initiated immediately after exercise –Repeated each 2 hours for 6 hours  Type of carbohydrate –Glucose or glucose polymers better than fructose Fructose may be better for replenishing liver glycogen –Including protein may increase glucose uptake

12. © 2007 McGraw-Hill Higher Education. All Rights Reserved. Carbohydrates Prior to a Performance  Improves performance by maintaining blood glucose –Does not spare muscle glycogen utilization –Allows maintenance of power output and lower RPE  Pre-exercise –1-5 grams CHOkg -1 body weight –1-4 hours before exercise –Easily digestible solid or liquid food –Test for sensitivity to carbohydrate load in training  Carbohydrate intake immediately prior to exercise may impair performance –Hypoglycemia in sensitive individuals –Faster rate of muscle glycogen utilization

13. © 2007 McGraw-Hill Higher Education. All Rights Reserved. Carbohydrates During a Performance  Carbohydrate ingestion can maintain plasma glucose even as glycogen is depleted –Delays fatigue and improves performance  Can be ingested throughout exercise or 30 minutes prior to fatigue  30-60 g CHO/hour is required –375–750 ml/hr of 8% CHO solution >8% CHO slows gastric emptying CHO from glucose, sucrose, or glucose polymers –Addition of caffeine increases CHO oxidation –Adding protein increases performance further

14. © 2007 McGraw-Hill Higher Education. All Rights Reserved. Blood Glucose and Muscle Glycogen Use During Prolonged Exercise Figure 23.3

15. © 2007 McGraw-Hill Higher Education. All Rights Reserved. Protein Requirement During Exercise  Determined by: –Oxidation of individual amino acids (Leucine) Oxidation affected by carbohydrate intake Provide no rationale for increasing protein intake –Whole body nitrogen balance studies N excretion in urine and sweat 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 Used to determine protein requirements for athletes

16. © 2007 McGraw-Hill Higher Education. All Rights Reserved. Effect of Exercise on Nitrogen Balance Figure 23.4

17. © 2007 McGraw-Hill Higher Education. All Rights Reserved. Effect of Initial Muscle Glycogen Levels on Sweat Urea Nitrogen Excretion Figure 23.5

18. © 2007 McGraw-Hill Higher Education. All Rights Reserved. Effect of Glucose Ingestion on the Rate of Leucine Metabolism Figure 23.6

19. © 2007 McGraw-Hill Higher Education. All Rights Reserved. Dietary Goals for Athletes  RDA –0.8 gkg -1 day -1 Met by diet having 12% calories from protein  Endurance training –0.8 gkg -1 day -1 for light to moderate exercise –1.2-1.4 gkg -1 day -1 for high-intensity exercise  Strength training –0.9 gkg -1 day -1 for maintaining strength –1.6–1.7 gkg -1 day -1 for adding muscle mass  Average athlete intake –16% calories from protein or 1.5 gkg -1 day -1 –Sufficient for most athletes

20. © 2007 McGraw-Hill Higher Education. All Rights Reserved. Water Replacement—Before Exercise  For exercise less than one hour –300-500 ml water –Containing 30-50 g CHO  For exercise durations more than one hour –300–500 ml water only

21. © 2007 McGraw-Hill Higher Education. All Rights Reserved. Water Replacement—During Exercise  Fluid replacement during exercise associated with: –Lower HR –Lower body temperature –Lower RPE  Recommendations: –Events <1 hour 500–1,000 ml water only –Events of 1–3 hours 500–1,600 ml water plus Na +, Cl -, and glucose –Events >3 hours 500–1,000 ml water plus Na +, Cl -, and glucose

22. © 2007 McGraw-Hill Higher Education. All Rights Reserved. Responses to Exercise With Different Volumes of Fluid Replacement Figure 23.7

23. © 2007 McGraw-Hill Higher Education. All Rights Reserved. Water Replacement—During Exercise  Factors affecting fluid absorption –Glucose concentration Gastric emptying slower above 139 mM –Fluid volume Optimal volume is 600 ml –Temperature Cold drinks absorbed faster than warm drinks –Exercise intensity Gastric emptying slower above 65-70% VO 2max

24. © 2007 McGraw-Hill Higher Education. All Rights Reserved. Factors Affecting Fluid Absorption From the Gastrointestinal Tract Figure 23.8

25. © 2007 McGraw-Hill Higher Education. All Rights Reserved. Hyponatremia  Dangerously low Na + concentration  Caused by rehydration with water or hyponatremic drinks during long (4+ hours) events –May lead to weight gain during event  Recommendations: –Work to minimize risk of both hyponatremia and dehydration –Drink to match fluid loss on a schedule Match fluid intake to sweat loss and thirst –Consume salty foods and beverages

26. © 2007 McGraw-Hill Higher Education. All Rights Reserved. Salt  Athletes require more salt than sedentary individuals –Must replace salt lost in sweat –Most people consume more salt than is required  Salt needs should be met at meals –Not by consuming salt tablets  Body weight is the best test of salt/water balance –Constant body weight indicates adequate salt intake

27. © 2007 McGraw-Hill Higher Education. All Rights Reserved. Iron  Deficiency affects VO 2max and endurance –Component of hemoglobin and cytochromes  Iron deficiency in athletes –Due to decreased intake and decreased absorption –Due to increased loss Through sweat, feces, and urine  Iron supplementation –Rapidly restores hematocrit and VO 2max –Slower increase in mitochondrial activity and endurance –Increase iron intake through foods Supplements may be indicated

28. © 2007 McGraw-Hill Higher Education. All Rights Reserved. Stages of Iron Deficiency Table 23.1

29. © 2007 McGraw-Hill Higher Education. All Rights Reserved. Recovery of Various Physiological Capacities with Iron Repletion Figure 23.9

30. © 2007 McGraw-Hill Higher Education. All Rights Reserved. Vitamins  Important for energy production –Coenzymes associated with aerobic metabolism  Supplementation –Not necessary on well-balanced diet unless clear deficiency is known –Toxicity with large doses of fat-soluble vitamins and vitamin C

31. © 2007 McGraw-Hill Higher Education. All Rights Reserved. Pre-Competition Diet  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, 3 hours prior to event –Mostly complex carbohydrates –Low in fat Slowly digested –Low in protein Contributes to acids in blood

32. © 2007 McGraw-Hill Higher Education. All Rights Reserved. Example of Pregame Meals Table 23.2

33. © 2007 McGraw-Hill Higher Education. All Rights Reserved. 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

34. © 2007 McGraw-Hill Higher Education. All Rights Reserved. Extremes of Somatotypes Figure 23.10

35. © 2007 McGraw-Hill Higher Education. All Rights Reserved. Contrast of Somatotypes Between College Students and Athletes Figure 23.11

36. © 2007 McGraw-Hill Higher Education. All Rights Reserved. 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 –Varies within gender and sport –It is natural for some athletes to have higher body fatness than others in order to perform optimally –Should be based on individual health status, not on team average

37. © 2007 McGraw-Hill Higher Education. All Rights Reserved. Percent Body Fat in Male and Female Athletes Table 23.3