1. The collection of blood and urine before and after exercise-heat stress and dehydration provides an opportunity to measure and characterize cytokine and intestinal barrier integrity marker (I-FAB, claudin-3) responses (blood) and renal stress biomarkers (urine) in humans. This descriptive research 'sub-study' directly complements Task Area T10 (Hot Weather Operations and Hydration: Injury and Performance Optimization) near and mid-term research goals of identifying biomarkers of heat stress for protection against heat injury. There are no hypotheses associated with this sub-study.