Biomarkers for Noninvasive Assessment of Human Hydration

Inclusion Criteria: * Signed Informed Consent Form * Males and females between 18-40, healthy and aerobically fit determined by VO2max test. Minimum 45 ml/kg/min for males and 40 ml/kg/min for females * Willing to stop drinking any alcoholic beverages, taking all supplements and limit medications to those approved for the study * No heart conditions assessed by medical history and passing the PAR-Q * Complete and pass medical exam Exclusion Criteria: * Positive response to any PAR-Q questions * Physical problems/injuries associated with walking or cycling * VO2Max below 45 ml/kg/min for men and 40 ml/kg/min for women * Allergy to sulfa drugs * Existing heart and or lung conditions * Pregnant or breastfeeding * History of heat illness or heat injury * History of kidney stones or chronic renal problems * History of orthostatic hypotension, diabetes or gout * Taking certain medications: NSAIDS \[anti-inflammatory/pain medications\], digitalis \[a type of heart medication\], lithium and anti-depressants \[medications used in psychiatry\], anti-hypertensives \[medications to lower the blood pressure\], anti-fungals \[medications used to treat infectious type of mold\], supplements or anti-cholinergic drugs) * Taking any supplements, particularly creatine in 24 hours before the start of the study, or during the study * Alcohol consumption 24 hours before the start of the study, or during the study * Incapable to give informed consent * Anemia