title: Self-paced exercise performance in the heat after pre-exercise cold-fluid ingestion.
abstract: BACKGROUND
  Precooling is the pre-exercise reduction of body temperature and is an effective method of improving physiologic function and exercise performance in environmental heat. A practical and effective method of precooling suitable for application at athletic venues has not been demonstrated.
  
  
  OBJECTIVE
  To confirm the effectiveness of pre-exercise ingestion of cold fluid without fluid ingestion during exercise on pre-exercise core temperature and to determine whether pre-exercise ingestion of cold fluid alone without continued provision of cold fluid during exercise can improve exercise performance in the heat.
  
  
  METHODS
  Randomized controlled clinical trial.
  
  
  METHODS
  Environmental chamber at an exercise physiology laboratory that was maintained at 32°C, 60% relative humidity, and 3.2 m/s facing air velocity.
  
  
  METHODS
  Seven male recreational cyclists (age = 21 ± 1.5 years, height = 1.81 ± 0.07 m, mass = 78.4 ± 9.2 kg) participated.
  
  
  METHODS
  Participants ingested 900 mL of cold (2°C) or control (37°C) flavored water in 3 300-mL aliquots over 35 minutes of pre-exercise rest.
  
  
  METHODS
  Rectal temperature and thermal comfort before exercise and distance cycled, power output, pacing, rectal temperature, mean skin temperature, heart rate, blood lactate, thermal comfort, perceived exertion, and sweat loss during exercise.
  
  
  RESULTS
  During rest, a greater decrease in rectal temperature was observed with ingestion of the cold fluid (0.41 ± 0.16°C) than the control fluid (0.17 ± 0.17°C) over 35 to 5 minutes before exercise (t(6) = -3.47, P = .01). During exercise, rectal temperature was lower after ingestion of the cold fluid at 5 to 25 minutes (t(6) range, 2.53-3.38, P ≤ .05). Distance cycled was greater after ingestion of the cold fluid (19.26 ± 2.91 km) than after ingestion of the control fluid (18.72 ± 2.59 km; t(6) = -2.80, P = .03). Mean power output also was greater after ingestion of the cold fluid (275 ± 27 W) than the control fluid (261 ± 22 W; t(6) = -2.13, P = .05). No differences were observed for pacing, mean skin temperature, heart rate, blood lactate, thermal comfort, perceived exertion, and sweat loss (P > .05).
  
  
  CONCLUSIONS
  We demonstrated that pre-exercise ingestion of cold fluid is a simple, effective precooling method suitable for field-based application.
authors.affiliation: School of Sport and Health Sciences, University of Exeter, UK. c.byrne@exeter.ac.uk
authors.forename: Christopher
authors.initials: C
authors.lastname: Byrne
authors.forename: Craig
authors.initials: C
authors.lastname: Owen
authors.forename: Aurélien
authors.initials: A
authors.lastname: Cosnefroy
authors.forename: Jason Kai Wei
authors.initials: JK
authors.lastname: Lee
mesh_terms: D054874:Athletic Performance / Q000502:physiology*; D001628:Beverages; D001831:Body Temperature / Q000502:physiology; D004326:Drinking / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D006358:Hot Temperature; D006801:Humans; D008297:Male; D055815:Young Adult