Aragon wrote:
sciencegirl wrote:
Oxygen delivery to the blood is almost 100% at barometric pressure, so increasing oxygen content in the air wouldn't improve performance that much...
Hemoglobin saturation is clearly lower than the rest value of 98-99 % during heavy exercise and closer to 90 % in many well-trained athletes, therefore breathing oxygen-rich air tends to enhance Vo2Max/performance.
Non-sequitur. The lower saturation is due to the lowered O2 affinity of the hemoglobin caused by the exercise. This lower affinity is necessary for the blood-to-muscle gas exchange to be rapid. If saturation at normal O2 pressure is near 100%, there's no reason to assume the saturation would drop less during exercise at higher O2 pressures, or that this would even be desirable.
Think of the blood as a subway train. One stop is the lungs. At normal traffic levels, it can function efficiently by loading up to near capacity and then a few passengers mosey off at each other stop. But if one of the other stops has a big event going on where half the passengers are going to get off, you'll want to err on the side of getting them off the train quickly. Put a bouncer on every car to throw the people off. The trade-off is the bouncers block a few people from getting on at the lungs too, but overall it's more efficient. Have more people trying to get on the train (higher O2 pressure) and it won't make any difference, the train is the bottleneck.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3824146/