Also low temperatures during night could increase carbohydrate metabolism, especially when shivering [63]. The reduction of glycogen stores along

with glycogen-bound water [46, 59] would result also in a loss of body mass. It is likely that the present male and female 24-hour ultra-MTBers started the race with full glycogen stores in both skeletal muscles and liver and the stores decreased during CHIR98014 order the race. We presume that the decrease in body mass could be the result of the metabolic breakdown of fuel, which includes a loss of fat, glycogen and water stored with glycogen. It is possible that the 24-hour race format may lead to a large energy deficit resulting in AZD2281 solubility dmso Increased Adriamycin nmr oxidisation of subcutaneous fat stores which coupled a decrease in extracellular fluid would result in the large body mass losses in male ultra-MTBers. Plasma urea, skeletal muscle damage, and protein catabolism In male ultra-MTBers, post-race body mass was related to significant losses in post-race fat mass, decreases in extracellular fluid and increases in plasma urea (Table  4). Plasma urea increased in men by 108% (Table  3) and in women by 46.9%. In a 525-km cycling race, plasma urea rose significantly by 97% [37]. In another study

investigating body composition and hydration status in one male ultra-endurance swimmer during a 24-hour swim, increases in plasma urea were associated with parameters of skeletal muscle mass damage [16]. We assume for the present male ultra-MTBers that the increase in plasma urea could be associated with skeletal muscle mass damage, because an increased plasma urea was related to changes in skeletal muscle mass in the present subjects. Nevertheless, due to the fact that absolute and percent changes in skeletal muscle mass were non-significantly, we assume that skeletal

muscle mass damage was moderate in the present athletes. In contrast to cycling, Fellmann et al. demonstrated that a 24-hour running race caused more muscular lesions than a triathlon, where ultra-cycling was a part of the event [41]. After a Double Iron ultra-triathlon, plasma urea increased significantly [6] and indicated a state of protein catabolism of the organism Selleckchem Abiraterone in the athlete. Faster 24-hour ultra-MTBers in the present study showed increases in plasma urea, therefore a post-race increase in plasma urea may be attributed also to enhanced protein catabolism during ultra-endurance performance as was reported after an ultra-cycling race [39]. We speculate that an increase in plasma urea cannot be solely attributed to skeletal muscle damage and protein catabolism. Increased plasma urea in both sexes suggests an increased metabolic activity [64]. Plasma urea increases also in cases of an impaired renal function [39].