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VENTILATION IN EXERCISE

VENTILATION IN EXERCISE. in exercise TV usually increses up to the level of 60% VC only then breathing rate starts to rise ventilation , VE = breathing frequency x TV. in maximal work a large male endurance athlete can have VE of more than 200 l/min.

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VENTILATION IN EXERCISE

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  1. VENTILATION IN EXERCISE

  2. in exercise TV usuallyincresesup to the level of 60% VC • onlythenbreathingratestarts to rise • ventilation, VE = breathingfrequency x TV • in maximalwork a largemaleenduranceathletecanhave VE of morethan 200 l/min

  3. lungvolume is notconnected to enduranceperformance • ventilation is alsonotusuallyenduranceperformanrelimitingfactor (MVV, maximalvoluntaryventilation, usually is 25% higherthanmaximalventilation in maximalwork • largelungs of swimmersarepropablycausedbystronginspirationmuscles (because of lungsbeingcompressedsmallerbywater)

  4. slowerbreathingrhythm and larger TV ensurebetteralveolarventilation • at restalveolarventilationappr.70% and in exerciseover 85% of VE

  5. VE in physicalexercise: • - VE firstincreasessharply (centralcommand + impulsesfrommuscles) • slowerrisestarts at about 20 s (as above + chemoreceptors) • steadylevel (chemoreceptorsimportant)

  6. Steady rate endurance exercise • - VE to VO2 ratio (non-athletes) usually about 20-25:1 ( 32:1 for children) • Progressive endurance exercise • - ventilatory treshold (aerobic treshold) is mainly caused by lactate removal (La to CO2 and expiration)

  7. (3) Weighttrainingexercise,socalledValsalvaeffect: • exhalingpressurewithclosedglottisincreasesstability of torso • pressure in abdominal/chestcavityrisesdramatically • venousreturn is greatlydiminishedbecause of compressedveinscausingloweredbloodpressurewithincreasingheartrate • afterglottisopens and intracavitypressuregoesdown BP increasesverymuchovernormalvalues

  8. VO2 of breathingmuscles: • at restoxygencost of breathingmuscles is verysmall • at maximalwork as much as 10-15 % of O2 is usedbybreathingmuscles

  9. Regulation of acidity • pH describes inversely and logarithmicly H+-ion concentration (change of 1.0 unit equals 10x change in concentration) • pH of purified water is neutral (pH = 7.0), digestive fluids 1.0-2.0 and blood 7.4 (at rest) • In extreme loading blood pH can go as low as 6.8 • Body buffers changes in pH by three mechanisms • 1.Chemical buffers • 2.Ventilation • 3.Kidneys

  10. Chemicalbuffers a) Sodiumbicarbonate  NaLA + H2CO3 HLA + NaHCO3  H20 + CO2 lungs H+ LA- Na+ HCO3- • H+-ionconcentrationand added PCO2stimulateventilation to getrid of eccess CO2

  11. b) Sodiumphosphate • actslikesodiumbicarbonatemainly in kidneys and extracellularspace • Proteins • - Hb in venousbloodaftergivingawayits O2 is morethanfivetimes as effective H+ reciever as someother plasma proteins

  12. Ventilation as buffermechanism • - potential of ventilation as buffer is double in power as compared to allchemicalbuffers • hyperventilationcanriseblood pH up to 7.4 → 7.6 • hypoventilationcanlowerblood pH to 7.4 → 7.2 Kidneys as buffers • in long termregulationirreplaceable • regulation of bicarbonate and H+levels

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