Maximal exercise at extreme altitudes on Mount Everest.

Area of Science:

• Physiology
• Altitude Medicine
• Exercise Science

Background:

• Extreme altitude research is crucial for understanding human physiological limits.
• The American Medical Research Expedition to Everest provided a unique opportunity to study these limits.

Purpose of the Study:

• To investigate maximal exercise responses at extreme altitudes.
• To determine the effects of reduced inspired oxygen partial pressure (PO2) on exercise capacity.
• To explain human physiological adaptation for reaching high altitudes.

Main Methods:

• Measurements of oxygen uptake, arterial oxygen saturation, and ventilation were taken at sea level and 6,300 m with varying inspired PO2 levels.
• Subjects were well-acclimatized and studied in a controlled laboratory environment.
• Alveolar gas samples were analyzed to assess gas exchange.

Main Results:

• Maximal oxygen uptake decreased significantly with lower inspired PO2.
• Arterial oxygen saturation dropped, and alveolar-arterial PO2 differences widened with increased work rate at high altitude, suggesting diffusion limitation.
• Maximal exercise ventilation decreased at very low inspired PO2.
• Alveolar CO2 partial pressure was found to be very low at extreme altitude, matching summit values.

Conclusions:

• Physiological responses to maximal exercise are severely impaired at extreme altitudes due to low inspired PO2.
• Diffusion limitation of oxygen transfer becomes apparent during exercise at high altitudes.
• The study provides insights into the physiological mechanisms enabling humans to perform strenuous activity on the summit of Mt. Everest.