During exercise in the heat, there is a need to replenish fluids in order to avoid dehydration and decrease the risk for heat illness. What drives this urge to drink is the thirst mechanism. Following ingestion of fluids, there is an inhibition of thirst before there is a replenishing of fluids. However, there is little scientific evidence of where thirst is inhibited, if this thirst inhibition is augmented by exercise and how thirst itself influence exercise performance. Further, during rehydration studies, it is very difficult to successfully blind a subject to their drinking/hydration protocol. Previous studies that have blinded a subject to their drinking have used various methods such as intravenous fluid administration and/or nasogastric tubes. Therefore, the purpose of this research is to examine the mechanistic roles thirst inhibition plays while exercising in the heat while undergoing intravenous fluid administration. Specific attention will be directed to the cardiovascular and thermoregulatory function of the individuals. All blood, cardiovascular, thermoregulatory, and perceptual measures are shown in the diagram below.

Inclusion Criteria:

• Cycling Racing History category 3 or higher USA cycling certification
• maximal oxygen uptake >55 ml/kg/min

Exclusion Criteria:

• History of heat stroke
• Renal, cardiovascular, metabolic diseases
• Regular medication