1 Integrated Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, Københavns Universitet2 Athlete Health and Performance Research Centre, Aspetar, Qatar Orthopaedic and Sports Medicine Hospital, Doha3 Institut for Idræt og Ernæring, Københavns Universitet4 Integrated Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, Københavns Universitet
PURPOSE: To determine the effects of heat-acclimatization on performance and pacing during outdoor cycling time-trials (TT, 43.4km) in the heat. METHODS: Nine cyclists performed 3 TTs in hot ambient conditions (TTH, ∼37ºC) on the first (TTH-1), sixth (TTH-2) and fourteenth (TTH-3) days of training in the heat. Data were compared to the average of two TTs in cool condition (∼8ºC) performed pre and post heat acclimatization (TTC). RESULTS: TTH-1 (77±6min) was slower (p=0.001) than TTH-2 (69±5min) 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 TTs 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 following six days of acclimatization and further reduced after fourteen days. HR was higher during the first 20% of TTH-1 than in the other TTs (p<0.05), but there were no differences between conditions from 30% onward. Final rectal temperature was similar in all TTHs (40.2±0.4ºC, p=1.000) and higher than in TTC (38.5±0.6ºC, p<0.001). CONCLUSION: Following two weeks of acclimatization, trained cyclists are capable of completing a prolonged TT in a similar time in the heat compared to cool conditions, whereas in the unacclimatized state they experienced a marked decrease in power output during the TTHs.
Medicine and Science in Sports and Exercise, 2015, Vol 47, Issue 3, p. 601-606