000151674 001__ 151674 000151674 005__ 20250319155217.0 000151674 0247_ $$2doi$$a10.3390/biology14020136 000151674 0248_ $$2sideral$$a143233 000151674 037__ $$aART-2025-143233 000151674 041__ $$aeng 000151674 100__ $$0(orcid)0009-0002-1869-6854$$aGarcía-Giménez, Alejandro$$uUniversidad de Zaragoza 000151674 245__ $$aImpact of Ad Libitum Hydration on Muscle and Liver Damage and Electrolyte Balance in Ultra-Trail Events: A Heatmap Analysis of Biomarkers and Event Characteristics—A Pilot Study 000151674 260__ $$c2025 000151674 5060_ $$aAccess copy available to the general public$$fUnrestricted 000151674 5203_ $$aUltra-trail events (UTs) pose significant challenges to maintaining hydration and electrolyte balance, with risks of dehydration (DH), overhydration (OH), exercise-associated hyponatremia (EAH), and exertional rhabdomyolysis (ER). This study examined the effects of ad libitum (ADL) hydration on hydration status and muscle damage during a nine-stage UT (635 km, 40,586 m elevation gain). Four highly trained male athletes participated. Hydration was assessed via body weight loss (BWL), urine specific gravity (Usg), and serum sodium ([Na+]), while muscle damage markers included creatine kinase (CK), lactate dehydrogenase (LDH), and calcium (Ca), and liver damage biomarkers included aspartate aminotransferase (AST) and alanine aminotransferase (ALT). Our results showed no cases of EAH or hypernatremia ([Na+] > 145 mmol·L−1), with serum [Na+] maintained above 135 mmol·L−1. BWL exceeded the 2% DH threshold in early stages (p = 0.029), and Usg remained elevated (>1.020 g·mL−1). LDH and CK significantly increased at all stages (p < 0.05), persisting for 48 h post-event. Correlations showed BWL aggravated muscle damage (r = 0.47 with CK) and hypocalcemia (r = −0.68 with Ca). Elevation gain/loss amplified fluid loss and muscle injury. While ADL hydration mitigated EAH, it did not fully address DH or muscle damage. Personalized hydration and recovery protocols are crucial to optimizing performance and health in UT events. 000151674 540__ $$9info:eu-repo/semantics/openAccess$$aby$$uhttp://creativecommons.org/licenses/by/3.0/es/ 000151674 655_4 $$ainfo:eu-repo/semantics/article$$vinfo:eu-repo/semantics/publishedVersion 000151674 700__ $$0(orcid)0000-0002-6829-0775$$aPradas, Francisco$$uUniversidad de Zaragoza 000151674 700__ $$0(orcid)0000-0003-0454-6302$$aLecina, Miguel$$uUniversidad de Zaragoza 000151674 700__ $$aOchiana, Nicolae 000151674 700__ $$0(orcid)0000-0003-1121-6408$$aCastellar-Otín, Carlos$$uUniversidad de Zaragoza 000151674 7102_ $$13001$$2187$$aUniversidad de Zaragoza$$bDpto. Expres.Music.Plást.Corp.$$cÁrea Didáctica Expres.Corporal 000151674 7102_ $$11006$$2245$$aUniversidad de Zaragoza$$bDpto. Fisiatría y Enfermería$$cÁrea Educación Física y Depor. 000151674 773__ $$g14, 2 (2025), 136$$tBiology$$x2079-7737 000151674 8564_ $$s1656055$$uhttps://zaguan.unizar.es/record/151674/files/texto_completo.pdf$$yVersión publicada 000151674 8564_ $$s2584983$$uhttps://zaguan.unizar.es/record/151674/files/texto_completo.jpg?subformat=icon$$xicon$$yVersión publicada 000151674 909CO $$ooai:zaguan.unizar.es:151674$$particulos$$pdriver 000151674 951__ $$a2025-03-19-14:20:33 000151674 980__ $$aARTICLE