[Work of breathing during high altitude exercise]

Measurements of oxygen consumption, ventilation and dynamic respiratory work in three males during ergometer bicycle exercise at sea level and at 3500 m altitude are reported. At submaximal work load, dynamic respiratory work proved 140-180% greater at 3500 m than at sea level; at a given ventilation, on the other hand, dynamic respiratory work is 20% less at 3500 m. During maximum oxygen consumption, this respiratory work reaches its peak value at 5800 m a.s.l. (30% more than what it is at sea level). It can be stated that the altitude ventilation cost during exercise is nothing but a small portion of total oxygen expenditure because the energy required for a given work load is not significantly different from sea level controls.