This narrative review synthesizes 60 years of evidence on cardiorespiratory fitness (CRF) and longevity, centering on VO2 max as the single strongest predictor of all-cause and cardiovascular mortality. Each 1-MET increase in exercise capacity correlates with a 12–15% mortality reduction. Vigorous exercise follows a J-shaped dose-response curve — 3–5 sessions per week yielding 1–2.4 hours of vigorous activity produces the lowest mortality risk, while chronic extreme endurance training raises atrial fibrillation risk 5.3-fold. The review also argues that optimal exercise type shifts across the lifespan and proposes a structured four-step clinical framework for personalized, age-adapted exercise prescription.
