Aerobic Metabolism Chapter 3 PDF

Aerobic Metabolism ================== Learning Objectives =================== - Describe aerobic metabolism - Explain the role of oxygen and the mitochondria in aerobic metabolism - Explain the factors influencing different substrate utilization during aerobic exercise. - Descri...

Aerobic Metabolism ================== Learning Objectives =================== - Describe aerobic metabolism - Explain the role of oxygen and the mitochondria in aerobic metabolism - Explain the factors influencing different substrate utilization during aerobic exercise. - Describe how oxygen consumption changes during aerobic exercise and recovery. - Describe metabolic recovery after exercise and factors that influence this. - Describe the physiological adaptations that occur to enable greater ATP production via aerobic metabolism Metabolism Recap ================ - First 30 seconds of exercise emphasizes the ATP-PC system - Anaerobic Glycolysis generally provides most energy for the first 2-3 minutes after ATP-PC Reminder ======== - ### If exercise goes beyond ATP-PC system capacity then other systems are involved Glycolysis ========== **Glycolysis** - The breakdown of glucose/glycogen to pyruvate -- 3 carbon mlc Glycolysis overview =================== - Anaerobic (fast): not using oxygen oxygen - Aerobic (slower): using oxygen Only a little atp is Produced here Aerobic Metabolism ================== - Substrate -Carbs (glucose/glycogen) -fats (fatty acids/triglycerides) -Proteins (amino acids) -Lactate Byproducts: 1. CO~2~ expired by the lungs 2. H2O Aerobic Metabolism ================== - Carbohydrate substrate begins with glycolysis Regulation of Blood Glucose =========================== - Liver glycogenolysis - Role of Insulin - Uptake by muscle - But - During Exercise? -Contraction of muscle tells glucoses which muscle to enter How does glucose get from the blood and into the muscle? ======================================================== - Facilitated diffusion - At rest: - During exercise: How does muscle glycogen break down for glycolysis? =================================================== - Glycogen phosphorylase  Aerobic Metabolism ================== - Carbohydrate substrate begins with glycolysis Aerobic Metabolism ================== - Fat substrate: begins with beta oxidation - [ lipase] break down stored triglycerides - Glycerol - 3 FAs - Facilitated diffusion into the muscle - Long-chain fatty acids are broken down into two-carbon segments to form **acetyl CoA**  - Fatty acids and glycerol can be synthesized from glucose and acetyl CoA Aerobic Metabolism ================== - Protein substrate: Amino acids Acetyl CoA: Common pathway ========================== Krebs Cycle Function ==================== - Krebs Cycle function: - Transported by [H+] carrier molecules [(NAD/FAD)] Electron Transport Chain (ETC) Function ======================================= - Produce the majority of ATP during aerobic metabolism Krebs Cycle ===========  Krebs Cycle =========== - Starts and ends with oxaloacetate - Small amount of ATP produced Krebs Cycle: Hydrogen Carriers ============================== - Hydrogens (and electrons) removed and transported by NADH and FADH~2~ to the ETC - ETC produces lots of ATP using H+ and e- Why is the removal of H+ (and e-) and combination with NAD+ important to aerobic metabolism? ============================================================================================ - CO~2~ removed and then expired Krebs Cycle: End products ========================= - CO~2~: Expired - NADH: to ETC - FADH~2~:to ETC - [ 1] GTP/ATP: used by cell Electron Transport Chain ======================== - Takes place in the inner mitochondrial membrane  Electron Transport Chain ======================== - Both [e- and H+] are crucial to ATP production - Creates energy Electron Transport Chain ======================== - \> affinity for e- the further along the ETC - Oxygen is the last electron acceptor - With the greatest affinity -the further along the complex the greater the pull - Electrons need an empty complex ahead to move along the ETC so each complex has to do its job  Electron Transport Chain ======================== - Energy from electron transport is used to pump [H+] from inner to outer compartment Electron Transport Chain ======================== - More [H+] in outer compartment - Creates ATP Electron Transport Chain ======================== - What if there is no oxygen? Total ATP formed from Carbohydrate ========================================================= - FAs can vary in length - But most often make more acetyl CoA than one glucose molecule - But require oxygen - How does this affect rate/ capacity? The Role of Lactate =================== - During [high] intensity exercise lactate is produced - The cori cycle converts lactate into glucose - Lactate may also be used by other tissues to synthesize glycogen or converted to pyruvate Interaction of Substrates ========================= - Substrate used depends on: - What you eat: Interactions of Substrates ========================== - Anaerobic or ATP-PC: - Aerobic: - Preference depends on intensity and duration of exercise Interactions of Substrates ========================== Increasing carbohydrate metabolism during exercise ================================================== - Carbohydrate metabolism is [more efficent] - More [fast twitch] muscle fibers are recruited, - ↑ [epinephrine increases and] stimulates [glycolic] enzymes - ↑ [lactate] from glycolysis inhibits metabolism by reducing [triglyceride] availability  - The amount of fuel stored influences "capacity" -- how long fuel will last - Muscle glycogen stores can be depleted Influence of Duration ===================== - Low intensity, long duration activities, - ↑ epinephrine, norepinephrine, glucagon during exercise - Insulin suppression during exercise - Insulin inhibits hormone sensitive lipase: ↓ available fatty acids - Less insulin [=] less inhibition of lipase = [more] fatty acids available  Carbohydrate Availability and Performance ========================================= - ↓ carbohydrate stores = ↑ fat use BUT at a Carbohydrate use and replenishment during periods of intense training --------------------------------------------------------------------- ### Carbohydrate Availability & Performance  Carbohydrate Loading ==================== - Beneficial in events [\>90] min - [ 10-12g/kg]of carbohydrates per 24 h for 36- 48 h prior - Practice during training Another Predictor of Performance: Lactate Threshold =================================================== - Exercise intensity at which blood lactate (La+) exceeds resting concentration. Another Predictor of Performance: Lactate Threshold ===================================================  - In trained individuals the lactate threshold is much higher than an untrained individual, therefore, the trained individual can train for a longer period of time without the accumulation of lactic acid. Another Predictor of Performance: Lactate Threshold =================================================== - Exercise intensity at which blood lactate (La+) exceeds resting concentration. Another Predictor of Performance: Lactate Threshold =================================================== - Where lactate production exceeds clearance ------------------------------------------ - Predictor of performance in aerobic events Lactate Threshold: Physiology ============================= - What accompanies an increase in lactate? - How will accumulating H+ affect performance? - Physiologically how does H+ affect performance? Lactate Threshold Vs. OBLA ========================== - Lactate Threshold - OBLA Metabolic Recovery After Exercise ================================= - Intramuscular PC stores need to be resynthesized - Intramuscular and blood acidity needs to be reduced - Elevated HR, elevate breathing rate, elevated metabolic rate - O~2~ Deficit:  - Steady state O~2~ consumption: - Excess Post Oxygen Consumption (EPOC): - Higher exercise intensity = higher EPOC  Causes of EPOC ==============  How Does Active Recovery Lower Blood Lactate? ============================================= - Lactate used for ATP production via aerobic metabolism during recovery - Maintains blood flow to the heart, liver and inactive muscles How Intense Should Active Recovery Be? ====================================== - Below lactate threshold - Due to more localized muscle involvement Are there any times when a prolonged active recovery may not be optimal? ======================================================================== -over tired, injured, muscles need time to heal =============================================== - ↑ [Mitochondrial Density]. - ↑ [Mitochondrial Enzyme Activity]. Aerobic Metabolic Adaptations to Exercise ========================================= - We need more capacity (e.g., substrate) and ATP synthesis at a faster rate to improve performance Aerobic Metabolic Adaptations to Exercise ========================================= - ↑ in [intramuscular] stores for aerobic and anaerobic use - ↑ in [intramuscular triglycerides] could increase aerobic triglyceride metabolism - Ability to metabolize fat at higher workloads (delayed crossover to carbohydrate) "glycogen sparing" - At a given submaximal exercise intensity, greater reliance on lipid metabolism spares glycogen stores, which could limit the fatigue at a given pace Aerobic Adaptations to Exercise =============================== - ↑ [relative intensity] at which lactate increases  Adaptations to Aerobic Exercise =============================== - What causes the ↑ in LT: Energy Systems Used During Sports ================================= **Duration** **Intensity** **Dominant energy source** **Example** -------------------- ---------------- --------------------------------- ----------------- \~ 8-10 S Very intense ATP-PC 100 m sprints \~ 10-30s Intense ATP-PC and anaerobic glycolysis 200 m sprints \~ 30 s -- 2/3 min High Anaerobic glycolysis Hockey shift 3min + Lower/moderate Aerobic metabolism Running cycling Metabolism: Applications ======================== - Why can a sprinter only sprint "all out" for a brief period of time? - How can a marathoner sustain a race pace for over 2 hours? - Where does this energy come from? - What factors limit performance and how can we overcome them? Measuring Aerobic Metabolism ============================ Oxygen Consumption ================== - VO~2~ - volume of oxygen used - Absolute measure - Used in rowing - Relative - Used in almost all other sports: running, cycling Respiratory Exchange Ratio (RER) ================================ - Ratio of oxygen used to carbon dioxide produced during metabolism - RER = [VCO2/VO2]. - RER changes depending on the substrate being metabolized RER Estimates ============= - When RER is between 0.7 -- 1.0 a mixture of both CHO and TG are being metabolized  Practical Example ================= Can RER exceed 1.0? =================== - May appear that the maximal value of RER is 1.0 - At higher intensities, some of the energy required is being obtained anaerobically - This can result in RER exceeding 1.0 (highest \~1.2) - Why/How? Can RER exceed 1.0? =================== - Bicarbonate buffering system in the blood H+ + HCO3 = H2CO3- = CO2 + H2O Endurance Event Metabolic Interactions ====================================== - Initially a reliance on anaerobic sources - Crossover from anaerobic to aerobic metabolism takes place approximately 15- 30 seconds into an activity  800 m ===== - Percentage of energy produced from aerobic metabolism continues to increase over time 1500 m ====== - Endurance events may use a high percentage of energy from anaerobic metabolism during periods of higher intensity (e.g., hills) or if the duration of the event is short