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Exercise metabolism

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Exercise metabolism

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    1. Exercise metabolism ATP production available through: 1) high energy phosphate sources (PCr); 2) Glycolysis; 3) aerobic oxidation. Potential problems with lactate formation; A) Availability of “adequate” oxygen in cells; B) rate of “glycolytic flux” and H2 production-mismatch with transport into mitochondria; C) Activity of LDH; pyruvate accepts H2 and lactate forms;

    2. Metabolic Machinery Accepting pyruvate depends upon Mitochondrial reticulum (network). Activity of Krebs Cycle & Electron transport chain insulates cell from high pyruvate. Fiber-type specific LDH drives pyruvate to lactate. Fast-twitch fiber disadvantage for sedentary subjects.

    3. 3-4

    4. Response to Energy charge changes Rate of ATP production based on demand- Rising ADP and drop in ATP prime modulators. Creatine Kinase-high energy phosphate controller; Phosphofructokinase-glycolytic rate; “Dehydrogenases” of Krebs Cycle; Cytochrome oxidase of ETC controls rate of O2 acceptor of electrons in ETC.

    5. Fuel Sources during Exercise Intensity and Duration dependent; “Crossover Concept” -role of training status dictates how far into intensity spectrum fatty acids are predominate fuel source; Transition from rest to exercise-O2 deficit? Impact on short-term moderate to hi intensity exercise. VO2 drift with prolonged exercise.

    6. Fig 3-5 & 3-8

    7. Lactate Threshold Intensity dependent, training-specific change in metabolic response to exercise; Implications for ventilation, CO2 and muscle & blood pH changes; Ability to exercise at or above LT threatens exercise session.

    8. 3-10

    9. Ventilatory response Ventilatory threshold, anaerobic threshold, or Lactate threshold- Evaluate rise in Ve, VCO2, and/or Ve/VCO2 ratio. Jump in lactate concentrations in blood;

    10. Recovery from exercise-EPOC Re-establish dynamic equilibrium of body at rest; Core temperature; lactate metabolism; catecholamines; glycogen restoration; cardiac output, Contributes to overall exercise energy expenditure. Combines with exercise VO2 for total energy expenditure- VO2 & RER used to estimate kcals/ liter O2 consumed.

    11. Normal Cardiorespiratory Responses to Exercise

    12. Myocardial Response HR-influenced by SNS & PSNS & circulating hormones; As HR inc. diastole dec. and systoles stays about same. SV influenced by Frank-Starling mechanism/length-tension relationship of myocardial cells (Preload or LVEDV); Effect of afterload may hinder ventricular performance. Exercise inc LVEDV, small change in LVESV so SV increases.

    13. 3-12

    14. 3-13

    15. Cardiac Output Table 3-3: HR*SV- big difference is in SV.

    16. Peripheral Blood Flow MAP-balance of increased Q and greater vasodilation; Inc. cardiac output of heart raises SBP while peripheral vasodilation keeps diastolic fairly constant. TPR-vessel radius changes-combined efforts of vasoconstriction in inactive tissue beds by SNS-alpha receptors, and local vasodilatory substances (Nitric oxide) and beta receptors of SNS. Arm vs leg exercise also a factor.

    17. Dynamic vs static exercise Table 3-2

    18. Arms vs legs Absolute vs relative workload Arms can do less work (65-80% of VO2max of legs, HR 10 bpm lower) than legs, so same absolute workload is at a higher % of arm’s capacity than legs. See greater HR, SBP, DBP, Ve, VO2, lactate with lower SV. When arms & legs exercise at same relative workload, CV response quite similar.

    19. Myocardial Work 3-15

    20. Factors determining myocardial demand 3-16

    21. Cardiorespiratory Adaptations to Exercise Training Pulmonary-limited improvements-likely result of other adaptations-perhaps at maximal exercise or reduced respiratory muscle fatigue in prolonged exercise; Less lactate in blood may lower ventilatory drive; greater diffusion capacity makes lungs more efficient. Central Circulation-major change is greater SV. Blood volume expands which stresses ventricle, leads to larger ventricular cavity (LVEDV), greater ventricular mass improves Preload, which leads to greater SV. Improved contractility-greater SNS stimulation or Ca++ dynamics in cell.

    22. 22-1

    23. Training and Blood Lactate changes 22-1

    24. Peripheral Circulation Decrease in Total peripheral resistance;due to increase capillaries & improved vasodilator effects; Greater shunting of blood from splancnic & kidneys to skeletal muscle; maintains central venous pressure & filling of heart;

    25. 22-5

    26. Specificity Principle 22-7

    27. Muscle Adaptations Type of exercise dictates changes Endurance-oxidative enzymes-Krebs cycle, oxidases of ETC, shutttle of NADH2; fatty acid use (carnitine palmitoyal transferase); Glycogen and triglyceride storage; maintain lower ADP levels with more fuel choices; Fiber type determines magnitude of changes;migration toward oxidative;

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