Subject will enter a warm room with a temperature between 28-30°C (80-85°F). Then, subjects will undergo a 3-hour walk, cycle, and rest protocol. The exercise intensity is based on 70% of the subject's predicted heart rate using the formula: 220 beats per minute (bpm) - 10 years of age = 210 bpm, and 70% equals 147 bpm). This is an intensity in which the subject has an elevated breathing frequency but can still talk. During the 3-h period subject will complete the following one-hour test three times:
* 10 min walking on the treadmill at 70% of predicted max heart rate (\~147 bpm)
* 5 min rest
* 10 min cycling on the cycle ergometer at 70% of predicted max heart rate (\~147 bpm)
* 35 min rest
During the 3-h period, subjects will have free access to fluids Body weight and urine samples will be collected during the experiement
