Aim: to assess the effect of water temperature on post-rehydration urine output and fluid retention.
Methods: on three different days, one week apart, 11 physically active men (24±4 years old, 1.73±0.05 m and 70.2±9.0 kg) (x ± S.D.) exercised intermittently in a temperature-controlled room (Dry bulb temperature = 30-32°C, relative humidity = 50-60%) until dehydrated to 1.96±0.2% of body mass (BM) on three separate occasions. They were rehydrated in random order with cold (4-6°C), ambient (23-25°C) or warm (38-40°C) water, equivalent in volume to 120% of weight loss. Fluid was consumed in one hour in 6 equal aliquots, one every 10 minutes. Following rehydration, urine samples were collected every 30 minutes for 4 hours, analyzing volume and Urine Specific Gravity (USG).
Results: no interaction was found between water temperature (TEMP) and diuresis (P=.726), or USG (P=.140) over time. There was no significant effect of TEMP on the total volume of urine eliminated (882±380, 973±341, and 1006±407 mL for cold, ambient, and warm water, respectively; P=.541), or on fluid retention (45.0±22, 41.9±14 and 37±28%; P=.588).
Conclusion: when men are rehydrated with a volume of water equivalent to 120% of weight loss, after dehydration to 2% BM, water temperature (within this range) has no effect on diuresis or fluid retention.
