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Anaerobic Threshold (OBLA)

Anaerobic Threshold (OBLA). accumulation of lactate due to excessive amount produced, compared to amount removed 4 mmol/l in the horse rest - 1 mmol/l low-moderate exercise, no build-up V LA4 = velocity of travel when lactate at 4 mmol/l % of VO 2 max

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Anaerobic Threshold (OBLA)

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  1. Anaerobic Threshold (OBLA) • accumulation of lactate due to excessive amount produced, compared to amount removed • 4 mmol/l in the horse • rest - 1 mmol/l • low-moderate exercise, no build-up • VLA4 = velocity of travel when lactate at 4 mmol/l • % of VO2 max • ex: OBLA @ 80%VO2 max to 60% VO2 max

  2. lactic acid in blood • diffusion • active transport from active skeletal muscle • lactate production • TB race 25-30 mmol/l • trot/3 day event 8 mmol/l • endurance race 2 mmol/l

  3. Integration of Aerobic and Anaerobic Pathways • regulated by: • relative concentrations of substrates and end products • availability of enzymes • effect of feedback mechanisms • activate or inhibit enzyme activity • most important regulators • availability of O2 • ratio of ATP/ADP

  4. Energy System • ATP-Pcr • glycogen • muscle glycogen used more rapidly first minute • liver glycogen • fats

  5. Onset of Exercise • reserves of O2 (myoglobin and hemoglobin) • ATP and CPr reserves • along with glycogen • O2 available • O2 re-oxidizes NADH2 produced in cytoplasm • energy production continues via aerobic pathway • increased energy demand • ATP/ADP ratio declines • stimulates glycolytic pathway, increase in NADH2 and pyruvate • stimulate activity of PFK

  6. low-mod exercise • most pyruvate enters TCA cycle • b-oxidation stimulated • critical intensity of exercise • NADH2 re-oxidized via pyruvate • anaerobic pathway • producing lactate • above maximal O2 uptake • all anaerobic metabolism

  7. Interplay of Systems • maximal intensity • 0-20 sec - ATP-PCr primary system • some glycolytic • > 20 sec - glycolytic primary system • longer efforts - aerobic primary system • increasing intensity • aerobic primary with addition of anaerobic as needed • aerobic continues to rise to VO2 max (HR 200) • above VO2 max - anaerobic primary system • intermittent intensity • aerobic primary • bursts either ATP-PCr and/or glycolytic pathway

  8. Fatigue • depletion of energy system • depletion of PCr and ATP • glycogen • accumulation of metabolic by-products • failure of fibers to contract mechanically • nervous system

  9. Toxic By-Products • lactic acid • H+ accumulation causes muscle acidification (acidosis) • buffers (HCO3) bicarbonate • pH of muscle 7.1 to 6.6 (6.4 exhaustion) • below 6.9 - decrease in glycolysis and ATP production • 6.4 - glycogen and ATP breakdown stop • unfit horse - 400 m/min or 150 HR • fit horse - 500 m/min or 170 HR

  10. Conditioning • no conditioning effect on ATP-PCr system • more skilled, energy demand to activity decreases • more efficient in movement • “mass action effect” • large amounts of one fuel causes cells to rely more on that source • increase concentration of enzymes used for fat metabolism • increase muscle ability to use fats

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