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

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

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

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

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

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

Supercompensation of Glycogen Stores 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

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

Classical and Modified Methods of Glycogen Super-compensation Fig 23.2

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

Muscle Glycogen & Blood Glucose Use During Prolonged Exercise Fig 23.3

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

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

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

Effect of Exercise on Nitrogen Balance Fig 23.4

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

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

Responses to Exercise With Different Volumes of Fluid Replacement Fig 23.7

Factors Affecting Fluid Absorption From the GI Tract Fig 23.8

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

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

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

Contrast of Somatotypes Between College Students and Athletes Fig 23.11

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

Chapter 23 Nutrition, Body Composition, and Performance