Members of our research group are conducting the first phase of the TRIATHLON Project, a series of studies intended to be the doctoral thesis of Anna Barrero (BSc, MSc), supervised by professors Ferran A. Rodríguez and Xavier Iglesias. The project aims at characterizing the bioenergetic requirements of different triathlon events. The first study will focus on long-distance triathlon (3800 m swim, 180 km cycling, 42.2 km running), where 15 athletes will be monitored throughout an official competition. The Extreme Man Salou-Costa Daurada is the selected race, to be held on the 5th of June. With more than 370 registered athletes from eleven countries, this triathlon is one of the hardest races due to the Ironman distance and over 2600 meters accumulated elevation in the cycling leg. Prior to the competition, the group of athletes will perform three maximal graded tests in the laboratory with gas exchange analysis, so as to assess the subjects’ physiological profile in all three modes of exercise. During the race, heart rate and kinematical parameters, as well as food intake will be continuously monitored. We thank Win Sports Factory, Polar Ibérica, C.N. Montjuïc and the Catalan Federation of Triathlon for their support and collaboration in the project.