Funding

No funding was received for the conduct of this research, nor for the preparation or publication of this article.

Conflicts of Interest

The authors do not have any conflicts of interest to declare.

Availability of Data and Materials

All data collected during the test have been presented here, except for data obtained from previously performed microbiota analyses.

Ethics Approval & Consent to Participate

KJ provided consent for the publication of their physiological data results analyzed during the UTMB race. The athlete was adequately informed about risks and benefits associated with study participation. The present study was approved by the Human Research Ethics Committee of the School of Science and Technology, University of the Basque Country (UPV/EHU) (M10 2021 191).

Author Contributions

Jesús Álvarez-Herms obtained the data directly during the race and drafted the manuscript. Kilian Jornet contributed to the revision and drafting of the manuscript.