The Triathlon Project is a research initiative focused on the determining factors of triathlon performance. In its first phase, led by Dr. Ferran A. Rodríguez, the project focused on specific physiological aspects of this multi-sport discipline. Currently, in its second phase under the direction of Dr. Diego Chaverri, the study focuses on the relationship between oxygen uptake and muscle oxygen saturation. One of the most innovative and recent aspects of our research includes the use of near-infrared spectroscopy (NIRS) technology, which makes it possible to analyse muscle oxygen saturation in training or simulated-competition situations.