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VO₂ max: the largest effect size in the longevity literature

No supplement, diet or drug in the published literature comes close to the mortality association attached to cardiorespiratory fitness. This is the number worth training, and it takes two different kinds of work to move it.

The mortality curve

In a cohort of 122,007 patients undergoing treadmill testing, moving from the "low" fitness band to "above average" was associated with roughly 70% lower all-cause mortality. The curve keeps improving into the elite band with no observed plateau — and, unusually for this literature, there was no upper limit at which more fitness stopped helping.

Training the top end: 4×4

The classic VO₂ max interval is 4 minutes at 90%+ of max heart rate, followed by 4 minutes of recovery, repeated 4 times. One to two sessions a week is enough — this is high-strain work and it competes with everything else you do.

Dose: 4 min at 90%+ max HR / 4 min recovery × 4 rounds · 1–2 sessions/week
Before you do this: Intervals at 90%+ of maximum heart rate are genuinely maximal effort. If you are over 40, sedentary, carry cardiovascular risk factors, or have any symptom on exertion — chest pain, unusual breathlessness, dizziness — get cleared by a doctor before doing max-effort work. Build an aerobic base first; this is not a starting point.

Training the base: Zone 2

Zone 2 is the intensity at which lactate production still matches clearance. It is associated with higher fat oxidation and mitochondrial efficiency, and world-class endurance athletes spend roughly 80% of their training volume there. The practical test: you can hold a full conversation, but not sing.

Dose: 3–5 sessions/week · 45–60 min · roughly 180 minus your age in bpm

The shortcut, and its limits

Sprint interval training gets you a large share of the cardiometabolic adaptation for a fraction of the time — three weekly sessions of 3×20-second all-out sprints matched 150 minutes of moderate exercise on several markers. It is not a full substitute: it targets different tissue and does not replace the Zone 2 base.

Common questions

What is the fastest way to raise VO₂ max?

The 4×4 protocol — 4 minutes at 90%+ of max heart rate, 4 minutes recovery, 4 rounds, once or twice a week — on top of a Zone 2 aerobic base.

What heart rate is Zone 2?

Roughly 180 minus your age in beats per minute, as a starting estimate. The practical test is that you can hold a full conversation but not sing.

How much does fitness actually matter for lifespan?

In Mandsager et al. (2018), going from low to above-average cardiorespiratory fitness was associated with about 70% lower all-cause mortality — among the largest associations in the literature.

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