Ventilatory work during exercise at high altitude

Oxygen consumption, ventilation, and dynamic respiratory work were measured in three male subjects during cycling at 122 and 3500 mm above sea level (ASL). At a given ventilation the dynamic respiratory work was 20% less at 3500 m ASL; this change was due to a decrease of airway resistance. At a given submaximal exercise intensity, the respiratory work was significantly higher at 3500 m ASL (+ 140%-180%); hence, the increase of ventilation was not compensated for by the decrease of airway resistance. At V̇(O2)max the respiratory work was predicted to reach its maximal value at 5800 m ASL where it was 30% higher than at sea level.