Figure 5.

The classic data from Mitchell, Sproule, and Chapman, demonstrating oxygen-carrying capacity, arterial oxygen saturation, and mixed venous oxygen saturation in an untrained young healthy subject at rest and during maximal exercise. This figure emphasizes that while only ∼33% of the oxygen leaving the heart is extracted during rest, ∼70–75% can be extracted during heavy exercise in an untrained subject. The increase in whole body systemic oxygen extraction with exercise is facilitated by very high levels of extraction across the exercising muscle beds in conjunction with redistribution of blood flow from less active muscles and visceral organs. For details, see Ref. 323.