Water temperature, voluntary drinking and fluid balance in dehydrated Taekwondo athletes
 
 
Journal Title (Medline/Pubmed accepted abbreviation):  J. Sci. Sports Med.
Year: 2011
Volume: 10
Page numbers: 718-724

Summary of background and research design:

Background: It is known that the type of post-workout beverage can affect voluntary rehydration (for example, athletes tend to consume a greater amount of electrolyte beverage than water). However, there have been only a few studies investigating fluid intake in regard to beverage temperature.

Hypothesis: The temperature of the beverage that will be consumed in the greatest quantities will be cool or room temperature while beverage that are hot will not be consumed in as large quantities.

Subjects: Six male Taekwondo athletes, age 23.7 ± 0.6 y.

Experimental design: randomized, cross-over

Treatments: Water was consumed freely at temperatures of :
1) 5°C (41°F)
2) 16°C (61°F)
3) 26°C (79°F)
4) 58°C (136°F)
(Body temperature is about 37°C)

Protocol: The participants arrived at the laboratory at 4:00 pm after a light lunch at noon and did not drink any beverage since then. They rested for 30 min in a "thermo-neutral" room (28°C = 82°F) and a baseline blood sample was acquired. They were weighed and then, in order to become dehydrated, they cycled on a stationary bicycle at a moderate intensity in a warm environment (38-40°C, humidity 20-30%) for 120 min with scheduled breaks. Then, a post-workout blood sample was collected. The participants were offered water at the temperatures listed above. Intake was measured. Blood samples were acquired at 3, 9, and 15 min after drinking to assess hydration state and sodium concentration.


Summary of research findings:
  • Dehydration did not differ between trials.
  • Blood was the most concentrated post-workout before drinking any water (plasma osmolality 311.6 ± 5.5 mosmol/kg water vs. 304.4 ± 3.4 mosmol/kg water pre-workout). Plasma osmolality did not return to baseline within 15 min post-workout.
  • The most water was consumed when it was 16°C (about 500 mL), then 5°C (about 350 mL), then 24°C (about 250 mL), then 55°C (150 mL).
  • Voluntary intake was less than weight loss during exercise for all treatments.

Key practice applications:

Cold water tastes better (Boulze et al., 1983) but the volume consumed tends to be less than cool water. The temperature likely reduces hyperthermia caused by exercise (i.e. overheating). In order to balance fluid replacement and establishment of temperature regulation, "cool" water is best (16° C) is best. A main concern associated with this study, however, is the very limited sample size.
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