Maintained Hydration Status After a 24-h Winter Mountain Running Race Under Extremely Cold Conditions

Abstract

Background: To date, no study has examined the hydration status of runners competing in a 24-h winter race under extremely cold environmental conditions. Therefore, the aim was to examine the effect of a 24-h race under an average temperature of -14.3°C on hydration status.Methods: Blood and urine parameters and body mass (BM) were assessed in 20 finishers (women, n = 6; men, n = 14) pre- and post-race.Results: Five (25%) ultra-runners had lower pre-race plasma sodium [Na+] and 11 (52%) had higher pre-race plasma potassium [K+] values than the reference ranges. Post-race plasma [Na+], plasma osmolality, urine osmolality and urine specific gravity remained stable (p > 0.05). The estimated fluid intake did not differ (p > 0.05) between women (0.30 ± 0.06 L/h) and men (0.46 ± 0.21 L/h). Runners with a higher number of completed ultra-marathons (r = -0.50, p = 0.024) and higher number of training kilometers (r = -0.68, p = 0.001) drank less than those with lower running experience. Pre-race and post-race plasma [Na+] were related to plasma osmolality (r = 0.65, p = 0.002, r = 0.69, p < 0.001, respectively) post-race, but not to fluid intake (p > 0.05). BM significantly decreased post-race (p = 0.002) and was not related to plasma [Na+] or fluid intake (p > 0.05). Post-race hematocrit and plasma [K+] decreased (p < 0.001) and transtubular potassium gradient increased (p = 0.008). Higher pre-race plasma [K+] was related to higher plasma [K+] loss post-race (p = -0.85, p < 0.001).Conclusion: Hydration status remained stable despite the extremely cold winter weather conditions. Overall fluid intake was probably sufficient to replenish the hydration needs of 24-h runners. Current recommendations may be too high for athletes competing in extremely cold conditions.

Body Composition Changes During a 24-h Winter Mountain Running Race Under Extremely Cold Conditions

“…Moreover, no significant differences between the male and female group regarding fluid intake were found. In the present 24-h ultra-runners no fluid overload occurred (Chlíbková et al, 2019) and therefore no disturbance of the body fluid homeostasis or of any other dimension could be determined. Pre-race carbohydrate loading, non-standardized diet, substrate intake, utilization and metabolism during the race and the extreme nature of this event probably altered the relationship between BM and body water (Olsson and Saltin, 1970).…”

“…Thus, with an average BM loss of 1.4% in males and stable BM in the female group, BIA appeared to have produced physiologically relevant values (Hew-Butler et al, 2015). Besides that, we were primarily interested in the changes between pre- and post-race values and not in the absolute values and plasma osmolality remained unchanged in present 24-h ultra-runners (Chlíbková et al, 2019). In addition, we did not measure energy expenditure and energy intake, because this would be problematic due to the character of this field study and extreme weather conditions which caused great physical exhaustion and inability of some competitors to cooperate in this direction.…”

“…To date, there is a limited number of studies on ultra-endurance athletes competing in cold temperatures ranging from -21°C to -2°C (Stuempfle et al, 2002, 2003; Chlíbková et al, 2019) and under very cold weather conditions with temperatures down to -48°C (O’Hara et al, 1977; Paulin et al, 2015; Coker et al, 2017; Johannsen et al, 2018; Schalt et al, 2018).…”

“…In ultra-marathon running, 24-h ultra-marathons enjoy great popularity (Fellmann et al, 1988; Kao et al, 2008; Knechtle et al, 2010b, 2011b; Waśkiewicz et al, 2012; Chlíbková et al, 2014, 2019; Costa et al, 2014). In the existing literature, the ambient temperature seems to be of importance for the changes in BM during such a race.…”

Exercise-Associated Hyponatremia in Endurance and Ultra-Endurance Performance–Aspects of Sex, Race Location, Ambient Temperature, Sports Discipline, and Length of Performance: A Narrative Review

“…However, women tended to drink less than men in the Houston Marathon, and had a prevalence of 22% for EAH [123]. In a 24-h run held in extreme cold, women drank no more than men [173]. The main role for women is most probably the lower body weight compared to men.…”