Bioelectrical impedance analysis (BIA) is a simple, noninvasive technique to determine body composition. The fundamental principle of determining body composition via bioelectrical impedance is to determine the resistance to, or conductance of, a low voltage current applied to biological tissue. Bioelectrical impedance analysis is well correlated to total body water. Bioelectrical impedance is sensitive to fluid shifts namely changes in blood flow, changes in electrolyte concentration, and changes in hydration status and consequently bioelectrical impedance has been used as a tool to measure such changes. Thirty college-aged students, 18-25 years old, 18 men and 12 women were subjects for this study. Bioelectrical impedance was determined with the Tanita BC-418 at two time points. Subjects were instructed to drink 490ml of water then exercised on the treadmill for 30mins. Our results show a significant decrease in resistance in both the sum of the upper limbs and the sum of the lower limbs indicating a fluid shift that is related to the fluid consumed by the subjects, but independent of tonicity.