title: Effect of heat and heat acclimatization on cycling time trial performance and pacing.
abstract: OBJECTIVE
  This study aimed to determine the effects of heat acclimatization on performance and pacing during outdoor cycling time trials (TT, 43.4 km) in the heat.
  
  
  METHODS
  Nine cyclists performed three TT in hot ambient conditions (TTH, approximately 37°C) on the first (TTH-1), sixth (TTH-2), and 14th (TTH-3) days of training in the heat. Data were compared with the average of two TT in cool condition (approximately 8°C) performed before and after heat acclimatization (TTC).
  
  
  RESULTS
  TTH-1 (77 ± 6 min) was slower (P = 0.001) than TTH-2 (69 ± 5 min), and both were slower (P < 0.01) than TTC and TTH-3 (66 ± 3 and 66 ± 4 min, respectively), without differences between TTC and TTH-3 (P > 0.05). The cyclists initiated the first 20% of all TT at a similar power output, irrespective of climate and acclimatization status; however, during TTH-1, they subsequently had a marked decrease in power output, which was partly attenuated after 6 d of acclimatization and was further reduced after 14 d. HR was higher during the first 20% of TTH-1 than that in the other TT (P < 0.05), but there were no differences between conditions from 30% onward. Final rectal temperature was similar in all TTH (40.2°C ± 0.4°C, P = 1.000) and higher than that in TTC (38.5°C ± 0.6°C, P < 0.001).
  
  
  CONCLUSIONS
  After 2 wk of acclimatization, trained cyclists are capable of completing a prolonged TT in a similar time in the heat compared with cool conditions, whereas in the unacclimatized state, they experienced a marked decrease in power output during the TTH.
authors: 1Athlete Health and Performance Research Centre, Aspetar, Qatar Orthopaedic and Sports Medicine Hospital, Doha, QATAR; and 2Department of Nutrition, Exercise and Sports, Section of Integrative Physiology, University of Copenhagen, DENMARK.
authors: Sebastien
authors: S
authors: Racinais
authors: Julien D
authors: JD
authors: Périard
authors: Anders
authors: A
authors: Karlsen
authors: Lars
authors: L
authors: Nybo
mesh_terms: D000064:Acclimatization; D000328:Adult; D000392:Air Movements; D054874:Athletic Performance / Q000502:physiology*; D001642:Bicycling / Q000502:physiology*; D001833:Body Temperature Regulation; D006339:Heart Rate; D006358:Hot Temperature; D006801:Humans; D008297:Male