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Nutrition and Sport Chapter 13

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  1. Nutrition and SportChapter 13

  2. Learning Objectives • Review the six categories of nutrients and learn what amount of intake is necessary for normally active men and women • Discover the roles of CHOs, dietary fat, and PRO supplements in athletic performance • Found out which vitamins and minerals are most important in an athlete’s diet • Learn how dehydration affects performance, HR, and temperature

  3. Learning Objectives • Examine how the body regulates electrolyte balance during exercise and maximizes muscle glycogen storage • Find out what makes up a recommended pre-competition meal and how to properly load the muscles with glycogen before an endurance event • Learn the value of ingesting CHOs during and after endurance exercise and what constitutes the most effective sports drink

  4. Six Classes of Nutrients • Carbohydrates • Fats (lipids) • Proteins • Vitamins • Minerals • Water

  5. Recommended Balance of Nutrients • Carbohydate-55%-60% • Fat-no more than 35% (less than 10% saturated; avoid hydrogenated and trans fat) • Protein-10%-15%

  6. Carbohydrate (CHO) • Major energy source, particularly during high-intensity exercise • Helps regulate fat and protein metabolism • Nervous system relies exclusively on CHO for energy • Muscle and liver glycogen are synthesized from CHO

  7. Major Sources of CHO • Grains, fruits, vegetables, milk, and concentrated sweets • Refined sugar, syrup, and cornstarch are nearly pure CHOs • Many concentrated sweets such as candy, honey, jellies, molasses, and soft drinks contain few if any other nutrients

  8. Classifications of CHOs • Monosaccharide: • Simple one-unit sugars, such as glucose, fructose, and galactose • Simple CHOs-derived from processed foods or foods high in sugar • CHOs must be broken down to monosaccharides for body to use them

  9. Classifications of CHOs • Disaccharide: • composed of two monosaccharides, such as sucrose, maltose and lactose • e.g. sucrose = glucose + fructose • Oligosaccharides-short chains of 3-10 monosaccharides linked together

  10. Classifications of CHOs • Polysaccharide-large chains of linked monosaccharides (>10) • Glycogen is polysaccharide in animals • stored in muscle and liver • Starch and fiber are in plants • Referred to as complex CHOs

  11. CHO Consumption and Glycogen Storage • CHO consumption directly influences muscle glycogen storage and the ability to train and compete in endurance events • Athletes need 5 to 13g/kg per day in order to maintain glycogen stores

  12. Influence of Dietary CHO on Muscle Glycogen Stores

  13. Pre-exercise Muscle Glycogen and Exercise Time to Exhaustion

  14. Glycemic Index (GI) • The insulin response to ingesting glucose • High GI Foods (GI>70) • Sport drinks, jelly beans, baked potato, french fries, popcorn, cornflakes, Corn Chex, pretzels • Moderate GI Foods (GI 56-70) • Pastry, pita bread, white rice, bananas, Coca-Cola, and regular ice cream • Low GI foods (GI≤55) • White spaghetti, kidney and baked beans, milk, grapefruit, apples, pears, peanuts, M&M’s and yogurt

  15. GI for Sport Nutrition • Before exercise: low-GI preferred to reduce likelihood of hyperglycemia • During exercise: high-GI advantageous by helping maintain blood glucose levels • Recovery: high-GI-higher blood sugar level should increase muscle and liver glycogen storage

  16. CHO Intake and Performance • Glycogen loading the muscles may delay onset of fatigue. • Maintaining normal blood glucose levels may allow muscles to obtain more energy from blood glucose, sparing liver and muscle glycogen reserves • Activities >1 h can be enhanced when CHO is consumed within 5 min prior to, >2 h before, and at frequent intervals during the exercise.

  17. Pre-Exercise CHO Feeding

  18. Åstrand’s Glycogen Loading • Complete exhaustive training bout 7 days prior to competition • Eat fat and PRO for next 3 days and reduce training load- increases activity of glycogen synthase • Eat CHO-rich diet for remaining 3 days before competition and reduce training load, because of increased glycogen synthesis, greater muscle glycogen storage

  19. Sherman’s Glycogen Loading • 7 days prior to competition: reduce training intensity and eat normal, mixed diet with at least 55% CHO • 3 days prior to competition: reduce training to daily warm-up of 10 to 15 min of activity with CHO-rich diet

  20. Muscle Glycogen Loading

  21. Muscle Glycogen Resenthesis

  22. CHO Intake and Performance CHO and placebo drinks were taken every 15 min during exercise

  23. Hypoglycemic Effect During Exercise? • CHO intake during exercise does not have same hypoglycemic effect as pre-exercise intake • Might be caused by increased muscle fiber glucose uptake during muscle contraction that decreases the need for insulin, or insulin-binding sites may be altered during muscular activity

  24. Fat • Essential component of cell membranes and nerve fibers (myelin sheath) • Provides up to 70% energy at rest • Supports and cushions vital organs • Used to produce steroid hormones • Transports and stores fat-soluble vitamins • Helps preserve body heat (provides insulation)

  25. Fat in the Body • Exist in body as triglycerides, free fatty acids (FFAs), phospholipids, and sterols • Body stores most fat as triglycerides • Composed of 1 molecule of glycerol and 3 molecules of FAs • Most concentrated source of energy • Dietary fat (especially cholesterol and triglycerides) play major role in CV disease

  26. Fatty Acid • Basic unit of fat-used for energy production • Saturated FA: has no double bonds, has maximum amount of hydrogen bound to the carbons • Unsaturated: contain one (monounsaturated) or more (polyunsaturated) double bonds between carbon atoms

  27. Saturated Fat • Excessive saturated fat consumption is a risk factor for numerous diseases • More commonly found in fats from animals than from plants • Tend to be solid at room temperature • Limit to <10% of total caloric intake

  28. Fat Intake and Performance • The use of FFA for energy production can delay exhaustion during exercise. • Chronic endurance training results in an increased ability to use fats as an energy source.

  29. Protein • Major structural component of the cell • Used for growth, repair, and maintenance of body tissues-builds fat-free muscle mass • Main constituent of hemoglobin, enzymes, and many hormones • Helps maintain normal blood osmotic pressure (‘oncotic’ pressure) • Used to form antibodies

  30. Protein • Can provide energy, but contribution is minor except during fasting or starvation • Made up of 20 amino acids • 11 nonessential (our bodies synthesize them) • 9 essential (must be obtained via diet) • Complete: contains all the essential aa’s • Meat, fish, poultry, eggs, and milk • Incomplete: in vegetables and grains

  31. Essential Nonessential Phenylalanine Alanine Valine Arginine Threonine Asparagine Tryptophan Aspartic acid Isoleucine Cysteine Methionine Glutamic acid Glutamine Histidine (children)a Glycine Leucine Proline Lysine Serine Tyrosine Histidine (adult)* aHistidine is not synthesized in infants and young children, so it is an essential amino acid for children but not for adults. Essential and Nonessential Amino Acids

  32. Recommended Daily Allowance (RDA) • General population: 0.8 g/kg per day • Strength training: 1.6-1.7 g/kg per day • Endurance training: 1.2-1.4 g/kg per day • No scientific evidence that PRO intake exceeding 1.7g/kg per day provides additional advantages • May place greater demands on kidneys

  33. PRO After Exercise • Adding PRO to CHO solutions enhances glycogen synthesis after aerobic exercise • PRO supplementation after resistance training helps stimulate PRO synthesis

  34. Vitamins • Unrelated organic compounds that perform specific functions to promote growth and maintain health • Act primarily as catalysts in chemical reactions • Enable us to use the other nutrients we ingest • Essential for energy release, tissue building, and metabolic regulation

  35. Vitamins • Fat soluble-absorbed from digestive tract bound to lipids (fat) • A, D, E, K • Stored in body so excessive intake can cause toxic accumulations • Water soluble-absorbed from digestive along with water • B-complex vitamins, biotin, pantothenic acid, folate, and vitamin C • Excess is excreted

  36. Fat-Soluble Vitamins • A: crucial for normal growth and bone development • D: essential for intestinal absorption of calcium and phosphorus and therefore bone development and strength; neuromuscular function • K: intermediate in ETC and oxidative phosphorylation

  37. B-Complex Vitamins • Include more than a dozen vitamins • Important components of enzymes involved in energy production • e.g. niacin and riboflavin • If deficient in diet, supplementation may facilitate performance

  38. Vitamin C • Important in synthesis and maintenance of collagen in connective tissue • Helps metabolize amino acids • Helps synthesize epinephrine, norepinephrine, and corticoids • Promotes iron absorption

  39. Vitamin C • May help fight infection and function as an antioxidant • Supplementation does not appear to improve performance if no deficiency exists • Sever deficiency results in scurvy (why were British sailors called “limeys?”)

  40. Vitamin E • Stored in fat, including cell membranes • Prevents oxidation of vitamins A and C • Acts as an antioxidant to disarm free radicals • May decrease risk of CAD and cancer • Supplementation has not been proven to improve performance

  41. Minerals • Electrolytes- mineral compounds that can dissociate into ions in the body • Macrominerals- minerals the body needs ≥100 mg of per day • Microminerals- minerals the body needs <100 mg of per day

  42. Calcium • Most abundant mineral in body; second most common mineral deficiency (after iron) • Stored in the bones • Facilitates bone growth and maintenance

  43. Calcium • Essential in nerve impulse and transmission • Activates enzymes and regulates cell membrane permeability • Essential for normal muscle function

  44. Phosphorus • Commonly linked to calcium in form of calcium phosphate • Provides strength and rigidity to bones • Essential to metabolism and component of ATP • Part of cell membrane structure (phospholipids) • Helps maintain constant blood pH

  45. Iron • Essential component of hemoglobin and myoglobin; O2 specifically binds to the Fe2+ in these proteins • Deficiency is relatively common, more so in women because of menstruation and tendency of women to eat less

  46. Iron • Estimated ~25% of world’s population has iron-deficiency anemia-most common mineral deficiency • If deficiency present, supplementation can improve aerobic capacity

  47. Sodium, Potassium, Chloride • Separation across neuron and muscle cell membranes results in the membrane potential • Maintain body’s water balance and distribution • Maintain normal osmotic equilibrium and pH • Maintain normal cardiac rhythm

  48. Rule of Thumb • Vitamins and minerals do not appear to have any ergogenic value in amounts beyond the (RDA), which is achieved by eating a good, balanced diet. • Taking them in amounts greater than RDA will not improve performance and may be dangerous.

  49. Body Water • Intracellular-in the cells, 67% • Extracellular-outside the cells, 33% • Makes up plasma, which transports and delivers nutrients to tissues • Main component of cytoplasm in cells • Dissipates excess body heat during exercise • Body fluids regulate pH • Maintains BP

  50. Body Water at Rest and During Exercise