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.

VENTILATION IN EXERCISEVENTILATION IN EXERCISE

- in exercise TV usually increses in exercise TV usually increses up to the level of 60% VC up to the level of 60% VC - only then breathing rate starts only then breathing rate starts to riseto rise- ventilation, VE = breathing ventilation, VE = breathing frequency x TVfrequency x TV

- in maximal work a large male in maximal work a large male endurance athlete can have VE endurance athlete can have VE of more than 200 l/min of more than 200 l/min

- lung volume is not lung volume is not connected connected to endurance to endurance performance performance- ventilation is also not usually ventilation is also not usually

endurance performanre endurance performanre limiting factor (MVV, limiting factor (MVV, maximal voluntary maximal voluntary ventilation, usually is 25% ventilation, usually is 25%

higher than maximal higher than maximal ventilation in maximal workventilation in maximal work- large lungs of swimmers are large lungs of swimmers are

propably caused by strong propably caused by strong inspiration muscles inspiration muscles

(because of lungs being (because of lungs being compressed smaller by compressed smaller by water) water)

- slower breathing rhythm and larger TV ensure better alveolar ventilation slower breathing rhythm and larger TV ensure better alveolar ventilation - at rest alveolar ventilation appr. 70% and in exercise over 85% of VEat rest alveolar ventilation appr. 70% and in exercise over 85% of VE

- VE first increases sharply - VE first increases sharply (central (central

command + impulses command + impulses from muscles)from muscles)- slower rise starts at about slower rise starts at about 20 s (as above + 20 s (as above + chemoreceptors)chemoreceptors)- steady level steady level (chemoreceptors (chemoreceptors important)important)

VE in physical exercise:VE in physical exercise:

(1) Steady rate endurance exercise- VE to VO2 ratio (non-athletes) usually about 20-25:1 ( 32:1 for children)

(2) Progressive endurance exercise- ventilatory treshold (aerobic treshold) is mainly caused by lactate removal (La to CO2 and expiration)

(3) Weight training exercise,so called Valsalva (3) Weight training exercise,so called Valsalva effect:effect:

- exhaling pressure with closed glottis increases exhaling pressure with closed glottis increases stability of torsostability of torso- pressure in abdominal/chest cavity rises pressure in abdominal/chest cavity rises dramaticallydramatically- venous return is greatly diminished because of venous return is greatly diminished because of compressed veins causing lowered blood pressure compressed veins causing lowered blood pressure with increasing heart ratewith increasing heart rate- after glottis opens and intracavity pressure goes after glottis opens and intracavity pressure goes down BP increases very much over normal valuesdown BP increases very much over normal values

VO2 of breathing muscles:VO2 of breathing muscles:

- at rest oxygen cost of breathing muscles is very smallat rest oxygen cost of breathing muscles is very small- at maximal work as much as 10-15 % of O2 is used by breathing musclesat maximal work as much as 10-15 % of O2 is used by breathing muscles

Regulation of acidityRegulation 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 mechanisms1.Chemical buffers2.Ventilation3.Kidneys

HLA + NaHCOHLA + NaHCO33

HH++ LALA--

NaLA + HNaLA + H22COCO33 HH220 + CO0 + CO22 lungslungs

Chemical buffersChemical buffers

a) Sodiumbicarbonatea) Sodiumbicarbonate

- H+-ion concentration and added PCOH+-ion concentration and added PCO22

stimulate ventilation to get rid of eccess CO2 stimulate ventilation to get rid of eccess CO2

NaNa++ HCO3HCO3--

b) Sodium phosphateb) Sodium phosphate

- acts like sodiumbicarbonate mainly in kidneys and extracellular spaceacts like sodiumbicarbonate mainly in kidneys and extracellular space

- ProteinsProteins

-- Hb in venous blood after giving away its O2 is more than five times as Hb in venous blood after giving away its O2 is more than five times as effective H+ reciever as some other plasma proteinseffective H+ reciever as some other plasma proteins

Ventilation as buffer mechanismVentilation as buffer mechanism

- potential of ventilation as buffer is double in power as compared to all - potential of ventilation as buffer is double in power as compared to all chemical buffers chemical buffers

- hyperventilation can rise blood pH up to 7.4 hyperventilation can rise blood pH up to 7.4 → → 7.67.6- hypoventilation can lower blood pH to 7.4 → 7.2hypoventilation can lower blood pH to 7.4 → 7.2

Kidneys as buffersKidneys as buffers

- in long term regulation irreplaceablein long term regulation irreplaceable- regulation of bicarbonate and Hregulation of bicarbonate and H++ levels levels