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Respiratory Changes During Exercise, Oxygen Debt ,

Respiratory Changes During Exercise, Oxygen Debt ,. By Dr. Mudassar Ali Roomi. 2 main respiratory changes in exercise:. 1) increase in pulmonary ventilation 2) increase in both rate & depth of respiration. Regulation of Respiration during exercise:.

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Respiratory Changes During Exercise, Oxygen Debt ,

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  1. Respiratory Changes During Exercise, Oxygen Debt, By Dr. Mudassar Ali Roomi

  2. 2 main respiratory changes in exercise: • 1) increase in pulmonary ventilation • 2) increase in both rate & depth of respiration.

  3. Regulation of Respiration during exercise: • What causes intense ventilation during exercise?

  4. In healthy athlete  alveolar vent. is directly proportional to oxygen metabolism. The arterial PO2, PCO2 and pH remain almost normal. Conclusion: Hypoxia, hypercapnia & acidosis have no role in inducing hyperventilation during exercise!! O2 consumption in moderate & severe exercise:

  5. 4 main factors that increase rate of respiration during exercise: • Anticipatory increase in rate of ventilation: When a person intends to perform exercise impulses from cerebral cortex skeletal muscle to initiate contraction & simultaneously collateral impulses respiratory centre increase ventilation.

  6. 2. Impulses from proprioceptors: (receptors for position & movement present around joints, in the muscles, tendons and joint ligaments). This is the major stimulus for respiratory centre during exercise.

  7. 3. Increase in temperature: During exercise  metabolism increases  body temperature increases  stimulates respiration directly & indirectly.

  8. 4. Chemical factors: • Decrease in PO2 • Increase in PCO2 • Increase in H+ conc. • The effect of PO2, PCO2 & H+ is minimum to stimulate respiration in exercise because there is increased ventilation  so PO2 & PCO2 remain in normal limits.

  9. Metabolic systems during exercise: 3 types: • Phosphagen system: consist of ATP & Creatine phosphate in muscle (ATP can maintain muscle contraction for 5-6 sec; energy from creatine phosphate can sustain contraction for another 10 sec)

  10. 2) Glycogen-Lactic Acid System: (another 30-40 sec) Glucose stored as glycogen in the muscle undergoes glycolysis  ATP.

  11. 3) Aerobic System: (For long long time) Nutrients, Glucose, Amino Acids Fatty Acids are oxidized. It is the ultimate source of energy.

  12. Changes in Respiration during Exercise: 1) Normal respiratory minute volume (RMV) at rest = 500 x 12 = 6 L / min • in severe exercise: RMV = up to 100 – 110 L / min 2) Maximum Breathing Capacity (MBC): Up to 150 – 170 L / min

  13. 3) Oxygen Consumption (O.C): It is the percentage of arterial blood which gives its O2 while passing through the tissues. • 250 ml / min (at rest) • may increase to 4-5 L / min in exercise • 4) Utilization Co-efficient (U.C): 25% (at rest) 75 – 85 % in severe exercise

  14. 5) Diffusion Capacity for O2: • At rest: 20 – 30 ml / mm Hg / min • in exercise: 65 ml / mm Hg / min • 6) Chemical parameters in skeletal muscles: • PO2 decreases, • PCO2, H+, Temp increases  Right hand shift of oxy-Hb dissociation curve  easy dissociation of O2 to supply skeletal muscle.

  15. 7) Effect on Respiratory Quotient (RQ): • In moderate exercise: RQ remains about 1. • In severe exercise: May increase up to 1.5-2 due to extra CO2 formation • After severe exercise: RQ falls up to 0.5.

  16. At the onset of exercise  alveolar vent. increases instantaneously, without an initial increase in arterial PCO2 There is initial decrease in arterial PCO2 due to great increase in alv. Vent. Conclusion: brain  anticipatory stim. of resp. at the onset of exercise. Interrelation between chemical & nervous factors in control of respiration during exercise:

  17. Arterial PCO2 remain normal (40 mm Hg) at rest & during heavy exercise. If PCO2 does change from 40, there is stim. of vent. above 40 & depression of vent. below 40. This shift in exercise is partly a learned response that involves cerebral cortex. Conclusion: Neurogenic factor shifts the curve about 20- fold in upward direction so that vent. Matches the rate of CO2 release keeping normal level of Arterial PCO2 Neuro-genic drive from respiratory centre during heavy exercise

  18. Oxygen Debt: Definition: Extra amount of oxygen, that must be supplied to body after exercise, in order to restore metabolic system back to pre-exercise state.

  19. During exercise  oxygen consumption is increased by skeletal muscle. Oxygen is present: • In combination with Hb • In myoglobin & • In dissolved form

  20. Oxygen used in severe exercise: TOTAL OXYGEN = 2 L (approx.) This much oxygen must be repaid.

  21. Debts: • To restore phosphagen & glycogen system: 2 L is required. • To restore Aerobic system: 8 L is required. • So, a total of 10-12 L oxygen is used in exercise & is paid in 90 min after exercise  respiratory rate remain increased for 90 min after exercise to repay oxygen debt = 10-12 L.

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