In the male ultra-MTBers, the decrease of extracellular fluid could be due to the race intensity accompanied by the reduction of the glycogen

stores rather than due to dehydration. Ultra-MTBers in both sexes were not dehydrated, but they suffered a significant loss in solid masses. Limitations The limitation was the relatively small number of female ultra-endurance ultra-MTBers. Probably a high energy deficit occurred during 24-hour races and we did not determine energy intake, in future studies it should be recorded. Practical applications for coaches and ultra-MTBers Ultra-MTBers in both genders respond individualistically, although they had an equal access to fluid. These data support the finding that change in body mass during exercise may not reflect exact see more changes in hydration status, and higher losses of body mass did not impair race performance. Conclusions find more To summarize, completing a 24-hour

MTB race led to a significant decrease in total body mass and fat mass whereas skeletal muscle mass remained stable in both male and female competitors. The volume of the lower leg remained unchanged both in men and women. Body weight changes and increased plasma urea in both sexes under testing conditions do not reflect a change in body hydration, but rather represent a balance of both fluid and energy losses from both external and internal sources. Consent Written informed consent was obtained from all testing subjects for the publication of this report Sirolimus supplier and any accompanying images. Acknowledgements The authors gratefully acknowledge the athletes for their splendid cooperation without which this study could not have been done. We thank the organizers and the medical

crew of the ‘Czech Championship 24-hour MTB race’ in Jihlava and the ‘Bike Race Marathon Rohozec’ in Liberec for their generous support. A special thank goes to the laboratory staff of the University Hospital ‘U Svaté Anny’ in Brno, Czech Republic, for their efforts in analyzing haematological and biochemical samples even during the night-times. References 1. Zaryski C, Smith DJ: Training principles and issues for ultra-endurance athletes. Curr Sports Med Rep 2005, 4:165–170.PubMedCrossRef 2. Kao WF, Shyu CL, Yang XW, Hsu TF, Chen JJ, Kao WC, Polun C, Huang YJ, Kuo FC, Huang CI, Lee CH: Athletic performance and serial weight changes during 12- and 24-hour ultra-marathons. Clin J Sport Med 2008,18(2):155–158.PubMedCrossRef 3. Cheuvront SN, Kenefick RW, Charkoudian N, Sawka MN: Physiologic basis for Fosbretabulin understanding quantitative dehydration. Am J Clin Nutr 2013, 97:455–462.PubMedCrossRef 4. American College of Sports Medicine, Sawka MN, Burke LM, Eichner ER, Maughan RJ, Montain SJ, Stachenfeld NS: American College of Sports Medicine position stand. Exercise and fluid replacement. Med Sci Sports Exerc 2007,39(2):377–390.