A revision of maximal oxygen consumption and exercise capacity at altitude 70 years after the first climb of Mount Everest

Abstract

On the 70th anniversary of the first climb of Mount Everest by Edmund Hillary and Tensing Norgay, we discuss the physiological bases of climbing Everest with or without supplementary oxygen. After summarizing the data of the 1953 expedition and the effects of oxygen administration, we analyse the reasons why Reinhold Messner and Peter Habeler succeeded without supplementary oxygen in 1978. The consequences of this climb for physiology are briefly discussed. An overall analysis of maximal oxygen consumption ( ${\dot{V}}_{O_2\max }$ ) at altitude follows. In this section, we discuss the reasons for the non-linear fall of ${\dot{V}}_{O_2\max }$ at altitude, we support the statement that it is a mirror image of the oxygen equilibrium curve, and we propose an analogue of Hill's model of the oxygen equilibrium curve to analyse the ${\dot{V}}_{O_2\max }$ fall. In the following section, we discuss the role of the ventilatory and pulmonary resistances to oxygen flow in limiting ${\dot{V}}_{O_2\max }$ , which becomes progressively greater while moving toward higher altitudes. On top of Everest, these resistances provide most of the ${\dot{V}}_{O_2\max }$ limitation, and the oxygen equilibrium curve and the respiratory system provide linear responses. This phenomenon is more accentuated in athletes with elevated ${\dot{V}}_{O_2\max }$ , due to exercise-induced arterial hypoxaemia. The large differences in ${\dot{V}}_{O_2\max }$ that we observe at sea level disappear at altitude. There is no need for a very high ${\dot{V}}_{O_2\max }$ at sea level to climb the highest peaks on Earth.

Keywords: altitude; exercise; hypoxia; maximal oxygen consumption.