1. VENTILATION IN EXERCISE

3. - 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

4. - lung volume is not connected to endurance performance - ventilation is also not usually endurance performanre limiting factor (MVV, maximal voluntary ventilation, usually is 25% higher than maximal ventilation in maximal work - large lungs of swimmers are propably caused by strong inspiration muscles (because of lungs being compressed smaller by water)

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

6. - VE first increases sharply (central command + impulses from muscles) - slower rise starts at about 20 s (as above + chemoreceptors) - steady level (chemoreceptors important) VE in physical exercise:

7. (1)Steady rate endurance exercise - VE to VO 2 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)

8. (3) Weight training exercise,so called Valsalva effect: - exhaling pressure with closed glottis increases stability of torso - pressure in abdominal/chest cavity rises dramatically - venous return is greatly diminished because of compressed veins causing lowered blood pressure with increasing heart rate - after glottis opens and intracavity pressure goes down BP increases very much over normal values

9. VO2 of breathing muscles: - at rest oxygen cost of breathing muscles is very small - at maximal work as much as 10-15 % of O2 is used by breathing muscles

10. 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

11. HLA + NaHCO 3 H+H+H+H+ LA - NaLA + H 2 CO 3 NaLA + H 2 CO 3 H 2 0 + CO 2 H 2 0 + CO 2 lungs lungs Chemical buffers a) Sodiumbicarbonate - H+-ion concentration and added PCO 2 stimulate ventilation to get rid of eccess CO2 Na + HCO3 -

12. b) Sodium phosphate - acts like sodiumbicarbonate mainly in kidneys and extracellular space - Proteins - Hb in venous blood after giving away its O2 is more than five times as effective H+ reciever as some other plasma proteins

13. Ventilation as buffer mechanism - potential of ventilation as buffer is double in power as compared to all chemical buffers - hyperventilation can rise blood pH up to 7.4 7.6 - hypoventilation can lower blood pH to 7.4 7.2 Kidneys as buffers - in long term regulation irreplaceable - regulation of bicarbonate and H + levels