1 Nutrition, Body Composition and Performance

2 Chapter OBJECTIVES Describe the effect of various carbohydrate diets on muscle glycogen and on endurance performance during heavy exercise. Discuss the method of achieving a supercompensation of the muscle glycogen stores. Describe the importance of blood glucose as a fuel in prolonged exercise, and the role of carbohydrate supplementation during performance. Describe the role of fats and proteins as fuel during performance. Explain the role of vitamins and minerals to the athlete and their importance to performance.

3 Nutrition and Sport Recommended macronutrient balanceCarbohydrate: 45 to 65% of daily kilocalories Meets needs of whole population Addresses special needs (type 2 diabetes) Athletes need more carbohydrates that the average person Fat: 20-35% (<10% saturated) Protein: 10 to 35% Optimal for both performance and health

4 Nutrition and Sport: Classification of NutrientsCarbohydrate (CHO) Fat (lipid) Protein Vitamins Minerals Water

5 Nutrition and Sport: Classification of Nutrients—CHOMolecular composition Monosaccharide, disaccharide, or polysaccharide Monosaccharides: glucose, fructose, galactose Functions in body Energy source (sole source for nervous system) Regulate fat and protein metabolism Consumption and storage Excess CHO stored as glycogen Dietary CHO intake determines glycogen stores

6 Nutrition and Sport: Classification of Nutrients—CHODeterminants of glycogen replacement CHO intake Exercise type (eccentric   glycogen synthesis) Glycogen maintenance Requires 5 to 13 g CHO/kg body weight per day In athletes, hunger often insufficient drive for CHO consumption Insufficient CHO intake  heavy, tired feeling

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9 Carbohydrate Diets and PerformanceMuscle 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

10 Muscle Glycogen SupercompensationClassical 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

11 Classic vs Modified Method of Supercompensation

12 Glycemic Index Glycemic index (GI) categorizes food based on glycemic (blood sugar) response High GI (GI >70): sport drinks, jelly beans, baked/fried potatoes, cornflakes, pretzels Moderate GI (GI 56-70): pastry, pita bread, white rice, bananas, soda, ice cream Low GI (GI ≤55): spaghetti, legumes, milk, apples/pears, peanuts, M&M’s, yogurt

13 CHO Intake Prior to PerformanceImproves performance by maintaining blood glucose Does not spare muscle glycogen utilization Allows maintenance of power output and lower RPE Pre-exercise 1-5 grams CHO/kg 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 https://www.youtube.com/watch?v=9-e5y-3dyUs https://www.youtube.com/watch?v=x3NimHt_shE

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15 CHO Intake During ExerciseCHO during exercise Unlike preexercise CHO, does not trigger hypoglycemia (can maintain plasma glucose even as glycogen is depleted) Improved muscle permeability to glucose? Insulin-binding sites altered during exercise? 30-60g CHO/hr is required ml/hr of 8% CHO solution (>8% slows gastric emptying)(Isotonic vs Hypotonic) Addition of caffeine increase CHO oxidation Adding protein could increase performance further

16 Blood Glucose Use During Prolonged Exercise

17 Protein During ExerciseDetermined 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 (positive caloric balance) The body’s carbohydrate stores Intensity, duration, and type of exercise Used to determine protein requirements for athletes

18 Protein and Sport PerformanceProtein essential for body function Cell structure, growth, repair, and maintenance Used to produce enzymes, hormones, antibodies, and as buffer Controls plasma volume via oncotic pressure

19 Recommended Protein IntakeRDA (adults) 0.8 g•kg-1•day-1 Met by diet having 12% calories from protein Endurance training 0.8 g•kg-1•day-1 for light to moderate exercise g•kg-1•day-1 for high-intensity exercise Strength training 0.9 g•kg-1•day-1 for maintaining strength 1.6–1.7 g•kg-1•day-1 for adding muscle mass Average athlete intake 16% calories from protein or 1.5 g•kg-1•day-1 Sufficient for most athletes

20 Water and Electrolyte BalanceDehydration during exercise Sweat  due to higher body temperature Water loss > water gain 2% total body weight Body temperature and sweating affected by Environmental temperature, radiant heat load Humidity Air velocity Body size Metabolic rate

21 Physiological Effects of DehydrationDecreases in: SV, HR, Q Peak blood lactate Buffering capacity of the blood Lactate threshold Muscle and liver glycogen Sweat rate Skin blood flow Increase in: Core temperature

22 Dehydration and Exercise PerformanceThirst Osmoreceptors (high blood osmolality) Baroreceptors (low blood volume) Thirst not well calibrated to hydration levels 24 to 48 h to completely rehydrate Benefits of fluids before and during ex Minimize dehydration and water loss Performance and cardiovascular function maintained

23 Hydration Before Exercise During ExerciseFor exercise less than one hour ml water (10-16oz) Containing g CHO For exercise durations more than one hour 300–500 ml water only During Exercise Fluid replacement during exercise associated with: Lower HR, core temp and RPE Recommendations: Events <1 hour: 500–1,000 ml water only (16-33oz) Events of 1–3 hrs: 500–1,600 ml water + Na+, Cl-, and glu Events >3 hours: 500–1,000 ml water + Na+, Cl-, and glu

24 Effect of Fluid ReplacementFluid replacement during exercise associated with: Lower exercise HR Lower core temp Lower RPE (objective AND subjective benefits)

25 Factors Affecting Absorption of Fluid

26 Classification of Nutrients—VitaminsSmall but essential organic molecules Enable use of other ingested nutrients Act as catalysts and cofactors in chemical reactions Coenzymes associated with aerobic metabolism Fat soluble versus water soluble Fat soluble stored, can reach toxic accumulations Water soluble excrete, toxicity difficult to reach In general, unless vitamin deficiency exists, supplementation NOT helpful

27 Classification of Nutrients—VitaminsB-complex vitamins (12+ total) Essential for cellular metabolism, ATP production Needed for pyruvate  acetyl-CoA, formation of FAD and NADP, erythropoiesis Vitamin C Important for collagen maintenance, antioxidant Also, adrenal hormone synthesis, iron absorption Vitamin E Stored in muscle and fat Potent antioxidant

28 Classification of Nutrients—AntioxidantsFree radicals Cellular by-product of oxidative phosphorylation Highly reactive, may precipitate fatigue Antioxidants Quench free radicals, prevent oxidant damage Muscle antioxidant enzymes Dietary antioxidants: vitamins E and C, b-carotene

29 Classification of Nutrients—MineralsInorganic substances needed for cellular function Calcium Bone density, nerve and muscle function Concerns: osteopenia, osteoporosis Sodium, potassium, chloride Na+, Cl- found primarily in interstitial fluid K+ in intracellular fluid Needed for nerve impulses, cardiac rhythm, fluid and pH balance Excess intake can be dangerous

30 Classification of Nutrients—MineralsIron Critical for hemoglobin, myoglobin (O2 transport) Deficiency  anemia Deficiency affects VO2max and endurance Component of hemoglobin and cytochromes Iron deficiency in athletes Due to decreased intake and decreased absorption Due to increased loss Iron supplementation Rapidly restores hematocrit and VO2max Slower increase in mitochondrial activity and endurance Increase iron intake through foods Supplements may be indicated

31 The Athlete’s Diet Vegetarian diets Vegan, lacto, lacto-ovoLacto-ovo fewer nutrition deficiencies Need sufficient essential amino acids, total kilocalories, vitamin A, riboflavin, vitamin B12, vitamin D, Ca2+, zinc, iron **ExPhysRules

32 Precompetiton Meal Purposes Content Provide adequate hydrationProvide 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

33 Body Somatotypes Endomorphy Mesomorphy EctomorphyRelative 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 Body Fat and PerformanceOptimal 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

35 Somatotypes Ath vs Adults