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. 2015 Mar;47(3):601-6.
doi: 10.1249/MSS.0000000000000428.

Effect of heat and heat acclimatization on cycling time trial performance and pacing

Sebastien Racinais  1 , Julien D Périard, Anders Karlsen, Lars Nybo
Affiliations

Effect of heat and heat acclimatization on cycling time trial performance and pacing

Sebastien Racinais et al. Med Sci Sports Exerc. 2015 Mar.

Abstract

Purpose: 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.

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Figures

FIGURE 1
FIGURE 1
Power output during a 43.4-km cycling TT in TTC (plain line) and in TTH-1 (long dashed line), TTH-2 (short dashed line), and TTH-3 (dotted line). Data are mean ± SD. *§†TTC was significantly (P< 0.05) higher than TTH-1, TTH-2, and TTH-3, respectively.
FIGURE 2
FIGURE 2
HR (upper panel) and rectal temperature (lower panel) during a 43.4-km cycling TT in TTC (plain line) and in TTH-1 (long dashed line), TTH-2 (short dashed line), and TTH-3 (dotted line). *TTH-1 > TTC and TTH-3. †TTH-1 > TTH-3; P < 0.05. NS, not statistically significant.
See this image and copyright information in PMC

Comment in

  • Time trial performance and pacing in heat is determined by rate of heat gain.
    Marino FE. Marino FE. Med Sci Sports Exerc. 2015 Jan;47(1):218. doi: 10.1249/MSS.0000000000000487. Med Sci Sports Exerc. 2015. PMID: 25501395 No abstract available.
  • Response.
    Périard JD, Racinais S, Karlsen A, Nybo L. Périard JD, et al. Med Sci Sports Exerc. 2015 Jan;47(1):219. doi: 10.1249/MSS.0000000000000488. Med Sci Sports Exerc. 2015. PMID: 25501396 No abstract available.

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