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What is Energy?

What is Energy?. Energy is defined as the capacity to do work One of the more common ways to express energy is Calorie A calorie is a measure of heat There are 1000 calories in a kilocalorie A kilocalorie is commonly referred to as a Calorie. What is Energy?. 1 gram of carbohydrate = 4 C

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What is Energy?

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  1. What is Energy? • Energy is defined as the capacity to do work • One of the more common ways to express energy is Calorie • A calorie is a measure of heat • There are 1000 calories in a kilocalorie • A kilocalorie is commonly referred to as a Calorie

  2. What is Energy? • 1 gram of carbohydrate = 4 C • 1 gram of fat = 9 C • 1 gram protein = 4 C • The calories in food represent a form of potential energy

  3. How is energy stored in the body? • Energy is stored in the body in the form of adenosine triphosphate (ATP) • ATP is a complex molecule that contains a pair of high energy bonds • When the bond is split by enzymes, energy is quickly released • This energy is used to fuel body processes (eg. muscle contraction)

  4. ATP • ATP can be regenerated from ADP in three ways: • Interaction of ADP with CP • Anaerobic metabolism • Aerobic metabolism

  5. Creatine Phosphate • CP is another high-energy compound stored in the muscles • ADP + CP → C + ATP • CP donates its P to regenerate ATP • Process lasts around 10 seconds

  6. Creatine Phosphate • Recent creatine supp. studies have shown: • increases muscle total creatine (20 g/day for 5 days) • the extent of the increase that is normally observed is inversely related to the presupplementation level (e.g. vegetarians) • increased performance in situations where the availability of creatine phosphate is important (high intensity activity with short recovery)

  7. Carbohydrate (CHO) Metabolism • We will continue our discussion of ATP production with CHO metabolism • Why CHO? • Only food that can create energy anaerobically • Preferred fuel (requires less O2) • If you understand CHO metabolism, it’s easy to understand fat and protein metabolism

  8. Carbohydrates (CHO) • Monosaccharides, disaccharides, polysaccharides • Most come from plants (exception is lactose found in animal and human milk) • Most common monosaccharides are glucose and fructose • Complex CHO are polysaccharides: starch, glycogen, and cellulose

  9. Carbohydrate (CHO) Metabolism • All CHO must be broken down into glucose before it can continue through the metabolic pathways • The complete breakdown of glucose is afour-step process

  10. Carbohydrate (CHO) Metabolism • Imagine the four stages as the four quarters of a football game • Each step of the is like a single football play • String the series of plays (steps) together to form an offensive drive (metabolic pathway) • Two differences • Plays must follow the same order • The final score is predetermined

  11. Carbohydrate (CHO) Metabolism • First Quarter = Glycolysis • Second Quarter = Formation of Acetyl CoA • Third Quarter = Krebs Cycle • Fourth Quarter = Oxidative Phosphorylation

  12. First Quarter: Glycolysis • Prepares glucose to enter the next stage of metabolism • Glucose  Pyruvate (Lactate) • ATP is also produced

  13. First Quarter: Glycolysis Glucose 4 ATP 2 ATP 2 NAD+ 2 NADH 2 Pyruvate

  14. Second Quarter: Acetyl CoA 2 Pyruvate 2 Acetic Acid 2 CO2 2 NADH 2 Acetyl coenzyme A

  15. Third Quarter: Krebs Cycle • Krebs cycle begins and ends with the same substance • No ATP used • Forms • 2 ATP • 6 NADH • 2 FADH • 4 CO2

  16. Fourth Quarter: Oxidative Phosphorylation • Series of reactions where ATP is created from the hydrogen atoms that we have accumulated • Produces 3 ATP for every NADH & 2 ATP for every FADH

  17. The Final Score

  18. Lipids • 95% of lipids in our diet are triglycerides • Triglycerides are divided into: • Saturated fats • Unsaturated fats • Monounsaturated fats (olive and peanut oils) • Polyunsaturated fats (fish, safflower, sunflower, corn oil) • The more saturated the product, the harder it is at room temperature

  19. Lipids • How is percentage of fat in food calculated? • One gram of fat= 9 Calories • Multiply number of grams of fat by 9 and represent the number of Calories as a percentage of the total Calories per serving. • e.g. • Calories per serving = 120 Calories • Total fat = 7 grams • 7 x 9 = 63 Calories → 63 / 120 = 52.5% fat

  20. Lipids

  21. Lipids

  22. Lipids

  23. Lipids: An Important Energy Source • Lipids as an energy source • The part of the lipid molecule that is used for energy production is the free fatty acid (FFA) • FFA are metabolized by a process called beta-oxidation • Acetyl-CoA is formed from beta-oxidation

  24. Lipids: An Important Energy Source • Lipids as an energy source • Most of the acetyl-CoA enters the mitochondria and the Krebs cycle • During rest, nearly 60% of the energy supply is provided by the metabolism of fats

  25. Protein • Chains of amino acids • 20 different amino acids • Essential amino acids (9) • Non-essential amino acids • Used to synthesize protein in the body • Also used as a source of energy • Excess amino acids stored as glycogen or fat

  26. Cellular Respiration • Cellular respiration can be either anaerobic or aerobic • Not an “either/or” situation – both systems work concurrently • When we describe muscular exercise, aerobic and anaerobic refer to which system predominates

  27. The Energy Continuum • ATP-PC systempredominates in activitieslasting 10 seconds or less • Continues to provide at least 8% for maximal activities up to 2 minutes

  28. The Energy Continuum • Anaerobic metabolism (ATP-PC & LA) predominates in supplying energy for exercises lasting less than 2 minutes • Continues to provideup to 15% energyrequirements forexercise as longas 10 minutes

  29. The Energy Continuum • The O2 system is the dominant system five minutes into exercise • The longer the exercise, the more important it becomes

  30. The Energy Continuum

  31. Lactic Acid / Lactate Production • Lactic acid is produced in muscle cells • NADH + H+ transfers its hydrogen to pyruvate which forms lactic acid • The amount of lactic acid present depends on the balance between its production and its removal

  32. Lactic Acid / Lactate Production • What conditions lead to lactic acid production? • Muscle contraction results in lactic acid production • Fast twitch fibers produce lactic acid when they contract • Insufficient amounts of oxygen

  33. Why is Lactic Acid a Problem? • It is the H+ that comes from the lactic acid that is the problem • Normally we can buffer the H+ to maintain pH • When the amount of H+ exceeds the capacity to buffer, the pH becomes acidic • At this point, pain is perceived and performance suffers

  34. Why is Lactic Acid a Problem? • Pain sources: • Activities that rely on the ATP-PC and LA systems • H+ ions accumulate and stimulate pain nerve endings located in the muscle • Performance • Metabolic fatigue • Muscular fatigue

  35. Lactate Removal • Lactate is removed from the bloodstream relatively quickly following exercise • There are wide interindividual differences, but generally half of the lactate is removed in about 15 - 25 minutes (half-life) • Near-resting levels can be achieved in 30 - 60 minutes

  36. Lactate Removal • Evidence suggests that lactate removal occurs more quickly when individual exercises during recovery • Intensity of the exercise peaks at about 40% VO2max • Careful! Active recovery can deplete glycogen stores and delay glycogen resynthesis

  37. Lactate Threshold (LT) • The LT represents an exercise level where the production of lactic acid exceeds its removal • Function of LT • Indicator of aerobic training status • Predicts endurance performance • Establishes effective training intensity

  38. Aerobic Metabolism • The aerobic system provides long-term energy • Occurs in mitochondria • Includes Krebs cycle and oxidative phosphorylation (3rd & 4th quarters)

  39. Aerobic Metabolism Steady State Oxygen Consumption ml/kg/min Rest Exercise time (min)

  40. Steady State • Lactic acid does not accumulate in the blood under steady state conditions • Steady state is different for different people • Depends on • The capacity to deliver oxygen to the muscles • The ability of the muscles to use the oxygen

  41. Training the Anaerobic System • Anaerobic training (sprint/power training) • Increases in resting levels of ATP, CP, creatine & glycogen and increases in strength • Increases in the quantity of enzymes that control glycolysis • Increased capacity to generate high levels of blood lactate

  42. Training the Aerobic System • Aerobic training • Larger, more numerous mitochondria in muscle • Enhanced breakdown of fat (conserves glyocgen) • Enhanced ability to breakdown CHO during max exercise • Delay the onset of blood lactate during exercise of progressively increasing intensity • Body composition changes

  43. Training the Aerobic System • Aerobic training • Performance changes • Psychologic benefits

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