Abstract
Objective. Prior studies of full-marathon participants have demonstrated a higher incidence of hyponatraemia in runners with completion times of 4 hours or more. Our primary aim was to determine if slower pace is associated with increased prevalence of hyponatraemia. Secondly, we evaluated the prevalence of hyponatraemia in full-marathoners v. halfmarathoners.Methods. This observational, cross-sectional study comprised consenting runners in the 26.2 With Donna, The National Marathon to Finish Breast Cancer, in Jacksonville Beach, Florida, February 2008. On race day, participants completed a questionnaire, provided finger-stick blood samples, and were weighed both pre- and post-race.Results. A significant negative association was found between pace and post-race sodium level (p<0.001). A negative correlation was found between finishing time and post-race sodium level (p<0.001). The prevalence of post-race hyponatraemia was 4% (4/106) among half-marathoners and 13% (12/89) among full-marathoners (P=0.02). An inverse correlation was found between sodium change and weight change, significant in fullmarathoners (r=-0.55, p<0.001) but not half-marathoners (r=- 0.23, p=0.042).Conclusions. Slower race pace and longer finishing times were associated with lower post-race sodium levels. Full-marathoners had a significantly higher prevalence of hyponatraemia. The development of hyponatraemia was associated with weight gain. Our data indicate that the relationship between post-race sodium concentration and pace differs according to the distance of the event. We can extrapolate from this data that longer racedistance with increased availability of fluid stations combined with a slower pace may increase the risk of developing exerciseinduced hyponatraemia.
Highlights
Hydration status and its role in the performance of endurance athletes remains a popular topic of debate in sports medicine
An inverse correlation was found between sodium change and weight change, significant in fullmarathoners (r=-0.55, p
Slower race pace and longer finishing times were associated with lower post-race sodium levels
Summary
Hydration status and its role in the performance of endurance athletes remains a popular topic of debate in sports medicine. Newer recommendations, including the 2007 American College of Sports Medicine Position Stand on Exercise and Fluid Replacement, warn athletes not to lose >2% body weight during exercise as it may adversely affect performance.[1] the same paper recommends drinking to thirst, the unfounded fear of dehydration and/or heat illness may have prompted athletes in the USA to continue to follow protocols that promote overzealous hydration. Current hydration strategies may be based on individual sweat rate, as monitored by body weight change during exercise, but most importantly should be gauged by thirst to maximise performance.[1,3,4,5,6,7]
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