Hardcore endurance athletes have tracked the metric for decades, but it is increasingly touted as a measure of fitness and health for the average person.

In short, you can think of this metric as the maximum amount of oxygen your body uses during exercise – V stands for volume, and O2 stands for oxygen, per Harvard Health. For some people, improving ...

The concentration of oxygen at sea level is about 21% and the barometric pressure averages 760 mmHg. As altitude increases, the concentration remains the same but the number of oxygen molecules per ...