During each testing session heart rate (HR), work output and core temperature (CT) were monitored. HR and CT were monitored by a CorTemp™ temperature pill which was ingested by the athletes prior to the trial (http://www.hqinc.net/pages/pill_page.html). In addition, blood was drawn at baseline (before depletion trial), immediately after the time trial, and again at 1h and 5h. Blood was analyzed for indices of training intensity (lactate), muscle damage (creatine kinase, cytokines), and gut barrier dysfunction (lipopolysaccharide, cytokines). In addition, immediately after the run athletes consumed a beverage with two carbohydrates (lactulose, and rhamnose). During the following six hours urine was collected and these sugars were measured via gas chromatography to determine the permeability of the gut.