title: The effect of ice slushy ingestion and mouthwash on thermoregulation and endurance performance in the heat.
abstract: OBJECTIVE
  The purpose of this study was to establish whether sensory factors associated with cold-beverage ingestion exert an ergogenic effect on endurance performance independent of thermoregulatory or cardiovascular factors.
  
  
  METHODS
  Ten males performed three trials involving 90 min of steady state cycling (SS; 62% VO2max) in the heat (32.1 ± 0.9 °C, 40 ± 2.4% relative humidity) followed by a 4 kJ/kg body mass time trial (TT). During SS, participants consumed an identical volume (260 ± 38 g) of sports beverage (7.4% carbohydrate) every 15 min as either ice slushy (-1 °C; ICE), thermoneutral liquid (37 °C; CON), or thermoneutral liquid consumption with expectorated ice slushy mouthwash (WASH).
  
  
  RESULTS
  Rectal temperature, hydration status, heart rate, and skin blood flow were not different between trials. Gastrointestinal (pill) temperature was lower in ICE (35.6 ± 2.7 °C) versus CON (37.4 ± 0.7 °C, p = .05). Heat storage tended to be lower with ICE during SS (14.7 ± 8.4 W.m(-2), p = .08) and higher during TT (68.9 ± 38.6 W.m(-2), p = .03) compared with CON (22.1 ± 6.6 and 31.4 ± 27.6 W.m(-2)). ICE tended to lower the rating of perceived exertion (RPE, 12.9 ± 0.6, p = .05) and improve thermal comfort (TC, 4.5 ± 0.2; p = .01) vs. CON (13.8 ± 1.0 and 5.2 ± 0.2 respectively). WASH RPE (13.0 ± 0.8) and TC (4.8 ± 0.2) tended to be lower versus CON (p = .07 and p = .09 respectively). ICE improved performance (18:28 ± 1:03) compared with CON (20:24 ± 1:46) but not WASH (19:45 ± 1:43).
  
  
  CONCLUSIONS
  Improved performance with ICE ingestion likely resulted from the creation of a gastrointestinal heat sink, reducing SS heat storage. Although the benefits of cold-beverage consumption are more potent when there is ingestion, improved RPE, TC, and meaningful performance improvement with WASH supports an independent sensory effect of presenting a cold stimulus to the mouth.
authors.affiliation: Dept. of Exercise and Sport Science, University of Sydney, Sydney, Australia.
authors.forename: Catriona A
authors.initials: CA
authors.lastname: Burdon
authors.forename: Matthew W
authors.initials: MW
authors.lastname: Hoon
authors.forename: Nathan A
authors.initials: NA
authors.lastname: Johnson
authors.forename: Phillip G
authors.initials: PG
authors.lastname: Chapman
authors.forename: Helen T
authors.initials: HT
authors.lastname: O'Connor
mesh_terms: D000328:Adult; D001628:Beverages; D001642:Bicycling; D001831:Body Temperature; D001833:Body Temperature Regulation; D003080:Cold Temperature; D015444:Exercise / Q000502:physiology* / Q000523:psychology; D005080:Exercise Test; D041981:Gastrointestinal Tract / Q000502:physiology; D006358:Hot Temperature; D006801:Humans; D007053:Ice; D008297:Male; D009055:Mouth / Q000502:physiology; D010465:Perception; D010807:Physical Endurance / Q000502:physiology*; D005082:Physical Exertion / Q000502:physiology; D013696:Temperature; D013697:Thermosensing; D055815:Young Adult
chemical_list: D007053:Ice