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Chapter 15

Chapter 15. Body Composition and Nutrition for Sport. Chapter 15 Overview. Body composition in sport Assessment Sport performance Weight standards Achieving optimal weight Nutrition and sport Classification of nutrients Water and electrolyte balance

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Chapter 15

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  1. Chapter 15 • Body Composition and Nutrition for Sport

  2. Chapter 15 Overview • Body composition in sport • Assessment • Sport performance • Weight standards • Achieving optimal weight • Nutrition and sport • Classification of nutrients • Water and electrolyte balance • Dehydration and exercise performance • Athlete’s diet • Sport drinks

  3. Body Composition in Sport • Body composition: body’s chemical and molecular composition • General models of body composition • Chemical model • Anatomical model • Two-compartment model

  4. Figure 15.1

  5. Body Composition in Sport:Assessment • Provides more information • Height and weight not enough to know fitness status –  Percent body fat,  performance • Body composition measured several ways • Densitometry/hydrostatic weighing • DEXA • Air plethysmography • Skinfold • Bioelectric impedance

  6. Body Composition in Sport:Assessment • Densitometry: measures body density • Hydrostatic (underwater) weighing • Muscle heavier than water, fat lighter than water • Most commonly used method • Limitations of hydrostatic weighing • Lung air volume confounding • Conversion of body density to percent fat • Fat-free density varies among people

  7. Figure 15.2

  8. Body Composition in Sport:Assessment • DEXA • Dual-energy X-ray absorptiometry • Quantifies bone and soft-tissue composition • Precise and reliable but expensive and technical • Air plethysmography (Bod Pod) • Another densitometry technique • Air displacement (instead of water) • Easy for subject, difficult for operator, expensive

  9. Figure 15.3a

  10. Figure 15.3b

  11. Figure 15.4

  12. Body Composition in Sport:Assessment • Skinfold • Most widely used field technique • Measures thickness at a minimum of three sites • Uses quadratic equations, reasonably accurate • Bioelectric impedance • Electrodes on ankle, foot, wrist, hand • Current passes from proximal to distal sites • Fat-free mass good conductor, fat poor conductor • Reasonably accurate, could be better

  13. Figure 15.5

  14. Figure 15.6

  15. Body Composition in Sport:Sport Performance • Fat-free mass (includes muscle) • Important variable for athletes to know –  Good for power, strength, muscle endurance • But bad for aerobic endurance (more mass to carry) • Relative body fat (percent body fat) • Fat: dead weight but useful energy store • Less fat usually = better performance • Exceptions: sumo wrestler, swimmer, weight lifter

  16. Body Composition in Sport:Weight Standards • Guide for optimal body size and composition for a given sport • Can be misleading • Elite athletes define optimal performance • But do elite athletes define optimal body? • Not always the case

  17. Figure 15.7

  18. Body Composition in Sport:Weight Standards • Inappropriate use of weight standards • Seriously abused by coaches, players • Misconception that small weight loss good, large weight loss better • Can lead to  performance, eating disorders • Making weight: severe weight loss • Wrestling, boxing, etc. • Weight classes can force extreme weight loss • Compete in class too low  injury, poor health

  19. Body Composition in Sport:Risks With Severe Weight Loss • Dehydration • Fasting, extreme caloric restriction  water loss • 2 to 4% weight loss as water  impaired performance • Risk of kidney, cardiovascular dysfunction, death • Chronic fatigue • Underweight  fatigue   performance, injury • Mimics overtraining and chronic fatigue syndromes • Underweight  substrate depletion

  20. Body Composition in Sport: Risks With Severe Weight Loss • Eating disorders • Weight standards can  disordered eating • Anorexia nervosa, bulimia nervosa • More prevalent with women in lean sports • Menstrual dysfunction • Delayed menarche, oligomenorrhea, or amenorrhea • Prevalent in low-body-weight sports • Due to caloric intake < caloric expenditure

  21. Body Composition in Sport: Risks With Severe Weight Loss • Bone mineral loss • Serious consequence of athletic amenorrhea • Anorexia  fracture rate 7 times higher • Female athlete triad • Eating + menstrual + bone mineral disorders • Seen with women in lean-physique, low-body-weight, or endurance sports • Skating, dance, gymnastics, running, swimming

  22. Body Composition in Sport:Weight Standards • Appropriate weight standards • Inappropriate standard risks athlete health • Body composition, not total body weight • Optimal range of percent body fat • Account for sex differences • Weight standards not always appropriate • Technical measurement errors • Not all athletes perform best at ideal composition

  23. Table 15.1

  24. Body Composition in Sport:Achieving Optimal Weight • Avoid fasting and crash diets • Cause more water and muscle loss, less fat loss • Ketosis accelerates water loss • Optimal weight loss:  fat mass,  FFM • Moderate caloric restriction + exercise • Caloric deficit ~200 to 500 kcal/day • Lose no more than 0.5 to 1 kg/week • When near goal, slow weight loss further

  25. Nutrition and Sport • Recommended macronutrient balance • Carbohydrate: 55 to 60% of daily kilocalories • Fat: <35% (<10% saturated) • Protein: 10 to 15% • Optimal for both performance and health

  26. Nutrition and Sport:Classification of Nutrients • Recommended Daily Allowance (RDA) • Outdated—not bad, just insufficient • Estimated safe, adequate dietary intakes and minimum vitamin and mineral requirements • Daily Recommended Intake (DRI) • Current standard • Groups intakes by nutrient function, classification • Four reference values: EAR, RDA, UL, AI

  27. Nutrition and Sport:Classification of Nutrients • Carbohydrate (CHO) • Fat (lipid) • Protein • Vitamins • Minerals • Water

  28. Nutrition and Sport:Classification of Nutrients—CHO • Molecular 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

  29. Nutrition and Sport:Classification of Nutrients—CHO • Determinants 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

  30. Figure 15.8

  31. Figure 15.9

  32. Nutrition and Sport:Classification of Nutrients—CHO • 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

  33. Nutrition and Sport:Classification of Nutrients—CHO • GI not perfect • Individual GI response varies • Some complex CHOs have high GI • Fat + high GI = lower GI • GI calculations differ depending on reference food (glucose vs. white bread) • Glycemic load (GL) • Improved CHO index • GL = (GI x CHO, g)/100

  34. Nutrition and Sport:Classification of Nutrients—CHO • CHO factors that  exercise time • Normoglycemia, low-GI preexercise snack • CHO loading (1-3 days prior) • CHO feedings during exercise • CHO factors that  exercise time • Hypoglycemia, high-GI preexercise snack • No CHO loading (lower glycogen stores) • No CHO feeding during exercise

  35. Figure 15.10

  36. Figure 15.11

  37. Nutrition and Sport:Classification of Nutrients—CHO • CHO during exercise • Unlike preexercise CHO, does not trigger hypoglycemia • Improved muscle permeability to glucose? • Insulin-binding sites altered during exercise? • CHO intake after exercise essential • Glycogen resynthesis high <2 h after exercise • Protein + CHO intake enhances glycogen stores • Stimulates muscle tissue repair

  38. Figure 15.12

  39. Nutrition and Sport:Classification of Nutrients—Fat • Fat essential for body function • Fuel substrate (triglycerides  FFAs + glycerol) • Component of cell membranes and nerve fibers • Required by steroid hormones and fat-soluble vitamins • Saturated versus unsaturated FFAs • Total fat <35% of total daily kilocalories (0 trans fat) • Saturated fat <10% total daily kilocalories • Cholesterol <300 mg/day

  40. Nutrition and Sport:Classification of Nutrients—Fat • FFAs important fuel during exercise • Delay exhaustion after glycogen depletion • Body cannot metabolize triglycerides (dietary fat) • Must break down triglycerides into FFAs • High-fat versus high-CHO diets • High-fat intake   circulating FFAs (good) • High-fat intake   glycogen storage (bad) • No conclusive evidence on high-fat diets

  41. Nutrition and Sport:Classification of Nutrients—Protein • Protein 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 • 20 amino acids: essential versus nonessential • Protein consumption • 15% of total daily kilocalories • ~0.80 g protein/kg body weight per day

  42. Table 15.2

  43. Nutrition and Sport:Classification of Nutrients—Protein • Protein requirements higher for athletes • 1.2 to 1.7 g protein/kg body weight per day • Endurance training: may use as fuel substrate • Strength training: needed for building muscle • Excessive protein intake  health risks • CHO + protein after exercise  improved glycogen and muscle protein synthesis

  44. Nutrition and Sport:Classification of Nutrients—Vitamins • Small but essential organic molecules • Enable use of other ingested nutrients • Act as catalysts and cofactors in chemical reactions • 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

  45. Nutrition and Sport:Classification of Nutrients—Vitamins • B-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

  46. Nutrition and Sport: Classification of Nutrients—Antioxidants • Free 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

  47. Nutrition and Sport:Classification of Nutrients—Minerals • Minerals • Inorganic substances needed for cellular function • Macrominerals versus microminerals (trace elements) • Calcium • Bone density, nerve and muscle function • Concerns: osteopenia, osteoporosis • Phosphorus • Bound to calcium in bones • Important for metabolism, cell membranes, buffers, bioenergetics

  48. Nutrition and Sport:Classification of Nutrients—Minerals • Iron • Critical for hemoglobin, myoglobin (O2 transport) • Deficiency  anemia • Excess iron  toxicity • 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 dangerous

  49. Nutrition and Sport:Classification of Nutrients—Water • 50 to 60% of total body weight • Fat-free mass 73% water versus fat mass 10% water • 1 to 6% body weight loss in sweat common for athletes • 9 to 12% loss can be fatal • 2/3 body water intracellular, 1/3 extracellular • Medium for transportation, diffusion • Regulates temperature • Maintains blood pressure

  50. Nutrition and Sport:Water and Electrolyte Balance • Water gain at rest (33 ml/kg/day) • 60% from beverages • 30% from food • 10% from cellular respiration • Water loss at rest • Evaporation from skin, respiratory tract (30%) • Excretion from kidneys (60%) • Excretion from large intestine (5%) • Sweat (5%)

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