The results of this study will provide mechanistic insight for how dehydration (intra- or extracellular) impairs systemic whole body and local small muscle performance in vivo. This Basic Science study seeks to understand how volume and osmolality impact MSNA and CAC as a basis for improving potential countermeasures, such as a more optimally formulated rehydration beverage. Therefore, this study directly complements Task Area T10 (Hot Weather Operations and Hydration: Injury and Performance Optimization) and impacts virtually all 14 Military Operational Medicine Research Program Drivers.