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Scand J Med Sci Sports. 2017 Jan;27(1):55-65. doi: 10.1111/sms.12629. Epub 2015 Dec 17.

Heat-acclimatization and pre-cooling: a further boost for endurance performance?

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French National Institute of Sport, Expertise and Performance (INSEP), Research Department, Laboratory of Sport, Expertise and Performance (EA 7370), Paris, France.
Sport & Exercise Discipline Group, Faculty of Health, University of Technology Sydney (UTS), Moore Park, Australia.
Medical Department, National School for Mountain Sports, Site of the National School for Skiing and Mountaineering (ENSA), Chamonix, France.
Department of Biological Toxicology, University Hospital Lariboisière (AP-HP), Paris, France.


To determine if pre-cooling (PC) following heat-acclimatization (HA) can further improve self-paced endurance performance in the heat, 13 male triathletes performed two 20-km cycling time-trials (TT) at 35 °C, 50% relative humidity, before and after an 8-day training camp, each time with (PC) or without (control) ice vest PC. Pacing strategies, physiological and perceptual responses were assessed during each TT. PC and HA induced moderate (+10 ± 18 W; effect size [ES] 4.4 ± 4.6%) and very large (+28 ± 19 W; ES 11.7 ± 4.1%) increases in power output (PO), respectively. The overall PC effect became unclear after HA (+4 ± 14 W; ES 1.4 ± 3.0%). However, pacing analysis revealed that PC remained transiently beneficial post-HA, i.e., during the first half of the TT. Both HA and PC pre-HA were characterized by an enhanced PO without increased cardio-thermoregulatory or perceptual disturbances, while post-HA PC only improved thermal comfort. PC improved 20-km TT performance in unacclimatized athletes, but an 8-day HA period attenuated the magnitude of this effect. The respective converging physiological responses to HA and PC may explain the blunting of PC effectiveness. However, perceptual benefits from PC can still account for the small alterations to pacing noted post-HA.


Heat-dissipating strategies; cycling; pacing; time-trial; tropical climate

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