The Physiological Paradox of Extreme Endurance Exercise: A Comprehensive Analysis of Biochemical Alterations, Cardiovascular Adaptations, and Mortality Outcomes in Marathon, Ultramarathon, and Ironman Athletes

Abstract

The dramatic proliferation of participation in extreme endurance sports—marathons, ultramarathons, and Ironman triathlons—has precipitated a critical re-examination of the dose-response relationship between physical activity and health outcomes. While the cardioprotective benefits of moderate exercise are incontrovertible, the physiological consequences of chronic, high-volume endurance training present a considerably more nuanced and paradoxical paradigm. This comprehensive academic review synthesises contemporary evidence across three fundamental domains: the acute biochemical perturbations induced by extreme exertion, the epidemiological patterns of mortality and cardiovascular morbidity, and the mathematical frameworks employed to model these complex relationships.