VO2max Training: The Fitness That Best Predicts a Long Life, and How to Build It
VO2max is how much oxygen your body can use at full effort, and it tracks with how long you live more tightly than almost any other fitness measure you can train. It is hard to raise: the method that works is short, hard interval training.
The number reflects everything working at once: heart, lungs, blood, and muscle. A higher VO2max means an ordinary effort, stairs, a hill, a long day on your feet, uses a smaller share of your capacity, so it feels easier and tires you out less.
You raise VO2max with short, hard intervals. One weekly session near your limit, a few minutes of hard effort broken into pieces, does most of it. Keep the rest of your cardio easy and conversational, the pace where you can still talk.
You can estimate VO2max without a lab: a hard one-mile walk, a 12-minute run, or the figure your watch reports all get close enough to track your own trend over time. Give it a couple of months and the same hill will feel easier.
Almost everyone gains, and the people who start with the lowest fitness gain the most. If you have a heart condition or have been inactive for a long time, build an easy aerobic base first, then add the hard intervals once that feels steady.