Muscle Cramping in Ultra-Trail: Dehydration and Electrolyte Depletion versus Muscle Damage

Abstract Martinez-Navarro, I, Vicente-Mampel, J, López-Grueso, R, Collado-Boira, E, Recacha-Ponce, P, Gómez-Seré, T, and Hernando, C. Muscle cramping in ultra-trail: Dehydration and electrolyte depletion versus muscle damage. J Strength Cond Res XX(X): 000–000, 2026—Our aim was to compare dehydration variables, electrolyte and muscle damage serum markers, race pacing, and training background between runners who suffered exercise-associated muscle cramps (EAMC) and those who not in an ultra-trail race. Fifty-eight finishers (37 men and 21 women) from 2 editions of the same race (Penyagolosa Trails CSP) were analyzed. Blood and urine samples were collected, and body mass (BM) was measured before and after the race. Exercise-associated muscle cramps were diagnosed immediately after the race. Nine subjects developed EAMC (16%). Although it was not significantly different, the incidence in men was 4 times greater than in women (males: 22%, females: 5%). Body mass change, postrace urine specific gravity, and serum sodium levels did not differ between crampers and noncrampers. Conversely, postrace potassium was higher among crampers (5.04 ± 0.39 mmol·L −1 vs. 4.66 ± 0.48 mmol·L −1 ; p = 0.029; d = 0.83). At 24 h and 48 h postrace, creatine kinase (5,166 ± 3067 U·L −1 vs. 1940 ± 1523 U·L −1 , p = 0.002, d = 1.80; 3,194 ± 2340 U·L −1 vs. 894 ± 775 U·L −1 , p = 0.001, d = 2.05) and lactate dehydrogenase (565 ± 118 U·L −1 vs. 420 ± 185 U·L −1 , p = 0.030, d = 0.83; 582 ± 140 U·L −1 vs. 401 ± 179 U·L −1 , p = 0.006, d = 1.06) were greater among crampers. Pacing indices were not different between crampers and noncrampers. The percentage of runners who underwent regular lower-limb strength training was different (crampers: 55.6%, noncrampers: 87.5%; p = 0.021). Therefore, runners who suffered EAMC did not exhibit a greater degree of postrace dehydration and sodium depletion but displayed higher concentrations of muscle damage biomarkers from 24 to 48 h after the race.