There’s a fight on the internet about VO2Max. One camp treats it as the single number that rules your healthspan — get it as high as humanly possible, no matter the cost. Another camp says it’s overhyped, mismeasured, and not worth your attention at all. As usual, the loudest voices are the least useful.

So I brought the question to someone I actually trust: Dr. Mike T. Nelson, back on the show for — I think we’ve lost count — his fourth conversation with me. Mike is the rare internet fitness voice with both the science and the scruples, and he’s written about this exact controversy. My question for him was simple and a little selfish: I’m 64. I don’t have unlimited time or unlimited recovery. How much should someone like me actually be chasing VO₂max — and once I’ve got “enough,” where should my effort go instead?

His answer is what this episode is about, and it comes down to a sweet spot. Yes, VO2Max is one of the most powerful longevity predictors we’ve ever measured — climbing out of the bottom of the pack buys you more protection than almost anything else you can do. But the benefit curve flattens. There’s a point where squeezing out another few percent costs enormous effort for very little return — effort that would do far more good aimed at whatever your real weak link is.

Along the way Mike takes apart some sacred cows. Why zone 2, for most of us, is not the magic everyone says it is. How to actually program intervals so you’re building speed instead of just collecting misery. Why your fading max heart rate might be partly a use-it-or-lose-it problem. And how something as quiet as your breathing rate while you sleep can tell you whether you’re sabotaging your own oxygen delivery.

If you’ve ever stared at the VO2Max number on your watch and wondered whether to celebrate it, panic about it, or ignore it — this one’s for you.