Gender-Specific Hydration Practices During Cold-Weather Distance Running

Abstract

The risk of hyponatremia during distance running in the heat has been observed to be greater for women compared to men presumably due to over-drinking relative to sweat loss. PURPOSE: To examine hydration practices and risk factors associated with hyponatremia in non-elite male and female runners participating in a cold weather half-marathon and marathon. METHODS: Pre- and post-race measures were obtained on 17 marathon subjects (male: n=14; female: n=3) and 75 half-marathon subjects (male: n=34; female: n=41). All subjects completed survey and pre-race weights at the pre-race Expo and after a half- and marathon competition under race day conditions of 4oC. Post-race weight was measured within 5 minutes of crossing the finish line for 17 marathon and 75 half-marathon finishers. RESULTS:Marathon: Mean + SD weight change for all subjects was not significantly different (-0.56 + 1.25 kg; p=0.08) but was different for subjects who took NSAIDs prior to the race (+0.9 + 1.4 kg; p=0.012) compared to those who did not (-0.86 + 1.0 kg). Half-marathon: Mean weight change (pre-post) was also not significant (+0.14 + 1.2 kg; p=0.33). However, there was a significant gender difference (p <.01) in weight change between males (-0.57 + 0.94 kg) compared to females (+0.73 + 1.1 kg). Unlike the marathoners, there was no difference in weight change based on NSAID usage. Fluid consumption frequency was positively correlated with weight change in half-marathoners (r=0.36; p=0.006) and in female half-marathoners (r=0.41; p=0.015). Finishing time was positively correlated with weight change. As finishing time increased, weight increased (r=0.356, p=0.003) in half marathon subjects. CONCLUSION: These data suggest that females and those using NSAIDs prior to distance running in cold weather may be at greater risk for over-hydration (as measured by weight gain), a contributing factor in hyponatremia.