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

Abstract

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 alleviation strategies for athletic performance: A review and practitioner guidelines

“…The two studies to combine techniques in endurance performance revealed encouraging findings, although no performance advantage. Utilizing an ice-vest prior to a 20 km cycling time trial, following 10 d of acclimatization did not improve overall performance above acclimatization alone, although transient, beneficial pacing alterations were observed until the dissipation of pre-cooling effects indicating a more aggressive cooling approach may prolong this effect [20]. Implementing a 20 min mixed-method external pre-cooling following 5 d of STHA, afforded large differences in T CORE , T SKIN , T CORE :T SKIN gradient, TS and HR during the first half of a 5 km running trial, but without any change in initial self-selected running speed [21].…”

“…As with all competition day strategies, cooling must be meticulously planned and practiced from both athlete and practitioner perspectives. Anecdotally, athletes take time to identify a preferred pacing strategy within endurance events, not always utilizing the apparent alleviated physiological strain [20,21] and find the transition from cool to "very hot" is expedited when pre-cooled, challenging planned pacing strategies. Whilst "more is better" may be a pertinent cooling mantra, some are also better than none.…”

“…Whilst the efficacy of acute techniques is robust, the authors are of the opinion that adopting robust chronic techniques cannot be understated. Indeed, there is good evidence to suggest chronic heat alleviation will be more effective [20,21]. Well-rehearsed, acute techniques to optimize thermoregulatory and performance physiology in the heat and minimize risks to health should not be considered as a "quick fix" alternative, but complementary to pre-planned and well-considered chronic alleviation strategies.…”

A Matter of Degrees: A Systematic Review of the Ergogenic Effect of Pre-Cooling in Highly Trained Athletes

“…Overall, 240 subjects were included in the qualitative analysis. The number of participants ranged from 6 [41] to 20 [25]. All the studies assessed only men, except three which used a mix-sex sample [20,21,26] and two studies that included only women [44,45].…”

“…The average age of participants was 24.6 years (ranging between 19.9 [32] and 34.8 [22]), and the VO 2 max varied from 55.7 [33,38] to 71.6 mL/kg/min [40]. Regarding sport modality, studies included a wide variety of athletes, both individual (cyclists [18,19,24,30,[37][38][39][40][41][42], runners [20][21][22]43], triathletes [23][24][25]42], and tennis players [26]), and team-sport players (covering cricket [27][28][29], soccer [31], lacrosse [32], and other non-specified team sports [33]). Furthermore, three studies included volunteers who recreationally practice various sport activities [34][35][36].…”