One of extra fitness lowers by 10–15%.
You listed cardiovascular fitness or general health as a goal — is where the evidence is strongest.
TL;DR
In a cohort of 122,007 adults, higher was associated with dramatically lower . Elite-level fitness carried a 5x lower risk of death than low fitness — and unlike most health markers, there was no upper limit to the benefit.
What the study found
Mandsager and colleagues followed people who had done a maximal treadmill test. Each 1 (roughly one Bruce-protocol stage) was linked to a 10–15% lower . The gap between 'low' and 'below-average' fitness was as large as smoking versus not smoking.
Why it matters for you
is trainable. Even sedentary adults can raise it by 15–20% in 8–12 weeks. Because the relationship is dose-responsive, small improvements add years of healthy life expectancy.
How to apply it
Two levers, both needed. First, a base of cardio — 2–3 sessions a week where you can just about hold a conversation, 30–45 minutes each. Second, one hard interval session weekly — minutes at 90% effort, 3 minutes easy between. The intervals push the ceiling; zone 2 raises the floor.
Caveats
This is observational data, so 'fitness causes longer life' is inference, not proof. But the , dose-response and biological plausibility all point the same way, and no RCT will ever run for the decades needed to test it directly.
Association of cardiorespiratory fitness with long-term mortality among adults
Mandsager K et al. · 2018 · JAMA Network Open
Cohort of 122,007 patients: cardiorespiratory fitness (VO2 max) was inversely associated with all-cause mortality, with elite-level fitness conferring a 5x lower risk than low fitness — and no upper limit to benefit observed.
Read the full paper