![Possible Explanations for EPOC
Reform ATP, PC, and replace tissue O2
stores.
Removal of Lactic Acid [to liver (Cori Cycle) or
Oxidation]
2Lactate (C3H6O3) + energy (from 16 ATP) glucose (C6H12O6)
2Lactate (C3H6O3) + 6O2 6CO2 + 6H2O + 619Kcal
Removal of excess CO2
Body Temp. and Catecholamines](https://image.slidesharecdn.com/lecture2-exercisemetabolism-150726203633-lva1-app6891/85/Lecture-2-exercise-metabolism-18-320.jpg)
Lecture 2 exercise metabolism
- 2. Overview Aerobic Exercise and Oxygen Consumption Substrate Utilization – Respiratory Exchange Ratio Anaerobic Exercise and the Lactate Threshold – Bicarbonate Buffer System – Definition, Possible Causes Causes of Fatigue Glycogen Depletion – Exercise Intensity – CHO intake
- 3. Aerobic Exercise and O2 Consumption
- 4. Maximal Duration of Energy System 30 sec 1 min 3 min 5 min 2-3 hr %Contribution ATP-PC Glycolysis Oxidative 10 sec
- 5. Aerobic Exercise and O2 Consumption Oxidative metabolism of CHO and FAT requires O2, produces CO2 Indirect calorimetry - calculated energy expenditure based on gas exchange (VO2 and VCO2) Must be primarily aerobic to be accurate – Anaerobic metabolism results in excess CO2 release from buffer systems Difference between inspired and expired air
- 6. Aerobic Exercise and O2 Consumption Energy Expenditure (kcals) Fitness Level Contribution of CHO Contribution of FAT
- 8. Fitness Level: VO2max Maximal Oxygen Uptake Measure of Aerobic Fitness Graded Exercise Test Maximal Effort VO2max= Inspired O2 – Expired O2
- 9. Bruce Protocol Stage Speed Incline 1 1.7 10% 2 2.5 12% 3 3.4 14% 4 4.2 16% 5 5.0 18% 6 5.5 20%
- 10. VO2max Data
- 11. Substrate Utilization Primary fuel source is CHO and Fat. Protein can serve as a secondary fuel source. Fat requires more O2 than CHO Relative Contribution determined by the Respiratory Exchange Ratio (RER)
- 12. Respiratory Exchange Ratio (RER) Non-invasive technique to determine relative Metabolic Contribution of Carbohydrate and Fat. RER = VCO2 VO2 Also called Respiratory Quotient (RQ) during Steady State Exercise. 1.0 = 100% CHO, 0.7 = 100% Fat
- 13. CHO vs. FAT 6 O2 + C6H12O6 6 CO2 + 6 H2O + 32 ATP CHO (Glucose = C6H12O6): 23 O2 + C16H32O2 16 CO2 + 16 H2O + 106 ATP FAT (Palmitic Acid = C16H32O2): Amount of O2 required is proportional to amount of C in the substrate! RER = VCO2/VO2 = 6/6 = 1.0 RER = VCO2/VO2 = 16/23 = 0.7
- 14. Crossover Effect % of max %Utilization CHO Fat35-40% of VO2 max
- 15. Oxygen Consumption Limitations Oxygen Deficit – Beginning of Exercise, Exercise Transitions Oxygen Debt/EPOC – End of Exercise Lactate Production – High Intensity Exercise
- 16. Exercise Transition Stage 1 Stage 2 Oxygen Deficit OxygenConsumption
- 18. Possible Explanations for EPOC Reform ATP, PC, and replace tissue O2 stores. Removal of Lactic Acid [to liver (Cori Cycle) or Oxidation] 2Lactate (C3H6O3) + energy (from 16 ATP) glucose (C6H12O6) 2Lactate (C3H6O3) + 6O2 6CO2 + 6H2O + 619Kcal Removal of excess CO2 Body Temp. and Catecholamines
- 19. Why is Lactate Produced during aerobic exercise? Glycolysis NADH Mitochondria Hydrogen Shuttle Pyruvate Lactate
- 20. Lactic Acid Metabolic by-product of Anaerobic Glycolysis. Immediately hydrolyzed into Lactate and H+(acid) Acid portion is removed from active tissue and buffered in the blood (bicarbonate system). Lactate can be reformed into glucose in the Liver via Cori Cycle (gluconeogenesis).
- 21. Bicarbonate System CO2+H2OH+ From Lactic Acid HCO3+ Bicarbonate H2CO3 Carbonic Acid
- 22. Lactate Threshold Lactic acid accumulates with prolonged, high-intensity exercise Lactate Threshold is the systematic rise in blood lactate concentration – Production exceeds clearance Often used as a measure of aerobic fitness level
- 23. Lactate Threshold LT Exercise Intensity BloodLactate
- 24. Does Lactic Acid Cause Fatigue? • No, lactic acid DOES NOT directly cause fatigue! • Acidosis (H+) causes fatigue • Inhibits PFK (rate limiting enzyme) and energy production • Inhibits actin-myosin cross bridges for muscle contraction • Benefits of Lactic Acid: • Maintains cytosolic redox potential • Can be converted to glucose and used for energy production (Cori Cycle)
- 25. Cytosolic Redox Potential Lactic Acid Pyruvic Acid NADH+H+ NAD+ Lactate Dehydrogenase Pyruvic Acid accepts H+; is reduced by NADH forming a molecule of lactic acid. C3H4O3 + NADH + H+ → C3H6O3 + NAD+ (Pyruvic Acid) (Lactic Acid)
- 26. Causes of Fatigue Energy System Failure – PC Depletion – Glycogen Depletion Metabolic By-Products – Pi (inorganic phosphate) – Heat and Muscle Temperature – Acidosis (H+) Neuromuscular Fatigue – Peripheral (neural transmission) – Central (CNS)
- 27. Quick check When _________ runs out, endurance exercise simply can’t continue…… A. Steam B. Muscle glycogen C. The trail ….. unless ______ is ingested. A. Really strong coffee B. Air C. Carbohydrates
- 28. Substrate Use in Prolonged Exercise Coggan and Coyle, 1991 Fat: 100,000 kcals 40 kcals 400 kcals Liver glycogen: 200 kcals
- 29. Glycogen Depletion Muscle Glycogen used for energy production (glycolysis, oxidative phosphorylation) Depletion selective within muscle fiber : type I to type II (intensity low to high) Glycogen depletion does not directly cause fatigue
- 30. Glycogen Depletion and Exercise Intensity
- 31. CHO and Glycogen Storage
- 32. CHO and Glycogen Storage
- 33. CHO Loading
- 34. CHO during Exercise Delays fatigue by: – Maintaining blood glucose levels (especially important for prolonged exercise) – “Sparing” glycogen stores – Glycogen synthesis during low-intensity exercise 6-8% CHO solution is ideal ~16g CHO/hour
Editor's Notes
- #14: Chemical reactions Fats require more oxygen than carbohydrates An RER of 0.95 during steady-state exercise is suggestive of a(n) High rate of carbohydrate metabolism. An RER of 0.75 during steady-state exercise is suggestive of a(n) High rate of fat metabolism.
- #23: Lactate Threshold is the best predictor of aerobic exercise performance.
- #24: Lactate threshold is point at which production exceeds clearance; systemic increase in lactate concentration in the blood
- #29: CHO sources are enough to power 25% of a marathon (20 kcals/min). Fat can’t keep up.
- #31: The influence of exercise intensity (31% to 150% of VO2max) on the reduction in muscle glycogen stores. At relatively high intensities, the rate of muscle glycogen use is extremely high compared to that at the moderate and lower intensities.
- #32: The relation between pre-exercise muscle glycogen content and exercise time to exhaustion. The exercise time to exhaustion and muscle glycogen were nearly four time greater when the subjects ate a carbohydrate rich diet than when the diet was composed of low carbohydrate (high fat and protein diet)
- #33: The influence of dietary carbohydrate on muscle glycogen stores during repeated days of training. Note that when a low CHO diet was consumed, muscle glycogen gradually declined over the three days of study, whereas the CHO-rich diet was able to return the glycogen to near normal each day.
- #34: Astrand, 1979; Two regiments for muscle glycogen loading. In one regimen, the subjects were depleted of muscle glycogen (day 0) and then ate a low-carbohydrate (CHO) diet for three days. They then switched to a CHO-rich diet, which caused muscle glycogen to increase to about 200mmol/kg. In the other regimen, the subjects ate a normal, mixed diet and reduced their training volume for the first three days. They then changed to a high-CHO diet and further reduction in training volume for three days, which also resulted in muscle glycogen of about 200mmol/kg.