This study investigates how energy availability affects performance, injury risk, and training outcomes in elite triathletes. Over two competitive seasons (2026-2027), 40 elite and sub-elite triathletes will be monitored through physiological tests, blood samples, and questionnaires. The goal is to identify markers of low energy availability and understand its impact on health and athletic performance. The study is observational and does not involve experimental treatments. Participants continue their regular training and diet while undergoing periodic assessments.