Credit: iStock Imagine this: A runner has just begun the Badwater Ultramarathon, the hottest, toughest ultramarathon in the world, which winds 135 miles through Death Valley in the middle of July. After hours of intense racing, she feels incredibly thirsty and quickly gulps down a lot of water at an aid station. Worried about her … Continue reading Marathon Runners: There’s a Downside to Drinking Too Much Water