title: Temperature of Ingested Water during Exercise Does Not Affect Body Heat Storage.
abstract: OBJECTIVE
  The objective of this study was to examine the effect of ingested water temperature on heat balance during exercise as assessed by direct calorimetry.
  
  
  METHODS
  Ten healthy males (25 ± 4 yr) cycled at 50% V˙O2peak (equivalent rate of metabolic heat production (M-W) of 523 ± 84 W) for 75 min under thermocomfortable conditions (25°C, 25% relative humidity) while consuming either hot (50°C) or cold (1.5°C) water. Four 3.2 mL·kg⁻¹ boluses of hot or cold water were consumed 5 min before and at 15, 30, and 45 min after the onset of exercise. Total heat loss (HL = evaporative heat loss (HE) ± dry heat exchange (HD)) and M-W were measured by direct and indirect calorimetry, respectively. Change in body heat content (ΔHb) was calculated as the temporal summation of M-W and HL and adjusted for changes in heat transfer from the ingested fluid (Hfluid).
  
  
  RESULTS
  The absolute difference for HL (209 ± 81 kJ) was similar to the absolute difference of Hfluid (204 ± 36 kJ) between conditions (P = 0.785). Furthermore, the difference in HL was primarily explained by the corresponding changes in HE (hot: 1538 ± 393 kJ; cold: 1358 ± 330 kJ) because HD was found to be similar between conditions (P = 0.220). Consequently, no difference in ΔHb was observed between the hot (364 ± 152 kJ) and cold (363 ± 134 kJ) conditions (P = 0.971) during exercise.
  
  
  CONCLUSIONS
  We show that ingestion of hot water elicits a greater HL relative to cold water ingestion during exercise. However, this response was only compensated for the heat of the ingested fluid as evidenced by similar ΔHb between conditions. Therefore, our findings indicate that relative to cold water ingestion, consuming hot water does not provide a thermoregulatory advantage. Both hot and cold water ingestion results in the same amount of heat stored during prolonged moderate-intensity exercise.
authors.affiliation: Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, CANADA.
authors.forename: Dallon T
authors.initials: DT
authors.lastname: Lamarche
authors.forename: Robert D
authors.initials: RD
authors.lastname: Meade
authors.forename: Ryan
authors.initials: R
authors.lastname: McGinn
authors.forename: Martin P
authors.initials: MP
authors.lastname: Poirier
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Friesen
authors.forename: Glen P
authors.initials: GP
authors.lastname: Kenny
mesh_terms: D000328:Adult; D000886:Anthropometry; D001833:Body Temperature Regulation / Q000502:physiology*; D002151:Calorimetry / Q000379:methods; D004326:Drinking; D005080:Exercise Test; D006801:Humans; D008297:Male; D013696:Temperature; D014867:Water
chemical_list: D014867:Water