Pre-race characteristics and race performance in hyponatremic and normonatremic finishers of Czech ultra-races

Objective: The aim of the study was to compare pre-race characteristics, race performance and plasma sodium [Na+] levels of hyponatremic and normonatremic ultra-endurance athletes and chosen variables in all finishers (N = 138). We assessed age, gender, club membership, pre-race training history and experience, pre-race body mass and body mass index (BMI) in 138 finishers of ultra-races (stage mountain bikers, 24 hours mountain bikers, 24 hours ultra-runners and 100 km ultra-runners) and post-race plasma [Na+] in a subgroup of 113 ultra-athletes.

Methods: The 138 participants completed a pre-race questionnaire survey and underwent body mass measurement, of those, 113 provided blood samples pre and post-race.

Results: There were no group differences between hyponatremic and normonatremic ultra-athletes in age, gender, club membership, pre-race BMI, regular training, experience or race placement. Pre-race body mass and BMI related to race placement in the normonatremic group (r = .30, p < .01; r = .43, p < .01). Faster finishers were older (r = -.28, p = .001) and more experienced (r = -.19, p = .02) than slower finishers (N = 138). Lower pre-race body mass and BMI (r = .28, p < .01; r = .49, p < .001) was associated with lower absolute order; however, did not related to age (N = 138). A higher weekly training volume was associated with a lower pre-race body mass (r = -.49, p < .01) in female racers; however, it did not relate to pre-race BMI (r = -.21, p = .41) or race placement (r = -.20, p = .56).

Conclusion: Pre-race characteristics did not distinguish those finishers developing EAH from those not developing EAH.