Here’s the paradox: The amount of oxygen your muscles, organs, and tissues are able to use is not entirely dependent on the amount of oxygen in your blood. Our red blood cells are saturated with between 95 and 99 percent oxygen, and that’s plenty for even the most strenuous exercise. (A few of my clients with serious pulmonary disease have a lower oxygen saturation level, but this is very rare.) What determines how much of this oxygen your body can use is actually the amount of carbon dioxide in your blood.
