Cumulative pre-cooling methods do not enhance cycling performance in tropical climate

For the cycling performance (see Table 3), a Friedman ANOVA indicated no between-con- dition differences neither before (Friedman χ2 = 0.67; df = 2; p = 0.72) nor at the end of the performance (Friedman χ2 = 1.88; df = 2; p = 0.39). The pairwise comparisons within condi- tion revealed no difference of TC’measures from T0 to T20 for ICE-VEST (T = 7.00, Z = 0.74, p = 0.46), MEN-VEST (T = 4.00, Z = 0.37, p = 0.72) and NO-VEST (T = 0.00, Z = 1.34, p = 0.18). Discussion The aim of this study was to determine in a tropical climate (1) whether combined internal pre-cooling with menthol and external pre-cooling with or without menthol during a warm- up would improve the cycling performance, perceptions (i.e., thermal environment, RPE) and core temperature of athletes more than only internal pre-cooling with menthol, and (2) in the mixed conditions, whether adding menthol to the external pre-cooling would further improve the cycling performance, perceptions and core temperature. No between-condition differences were found for physiological parameters, perception of exertion, thermal comfort and thermal sensation during either the warm-up or the performance. Nevertheless, an increase of the ther- mal sensation was observed during the performance only in NO-VEST condition. This study failed to show between-condition differences for the cycling performance for either the total distance traveled nor the distance traveled per 2-min block. Regarding the lat- ter, a period effect was observed, suggesting a variation in pace during the cycling performance

trial. Visually only, the Fig 1 shows more variation in pace in the NO-VEST condition than the mixed conditions, suggesting a better consistent performance with the both external cooling methods. These could have had an impact on effort regulation leading to the subject to provide a homogeneous and constant effort over time. Furthermore, the Fig 1 also allows to notice that the evolution of the curves of the two mixed conditions are relatively close. A study with cyclists focused on the effects of a precooling during an active warm-up on a short distance time trials in hot conditions and has shown, at the end of the warm-up, that an upper body precooling (head, neck and torso) enhances cycling performance time and limits increase of skin temperature, mean body temperature, and thermal comfort ratings [38]. Our study failed to show the effectiveness of precooling during the warm-up on short-distance cycling performance, cooling rate and perceptions, probably due to some differences in the protocol. Indeed, as our warm-up time was longer (30 min versus 20 min) and our perfor- mance task more demanding (time trial events versus 65% _VO2peak), our precooling meth- ods, which also differed (ice vest with or without menthol + internal menthol cooling versus ice vest + head and neck), were not sufficiently effective in such conditions, particularly faced with the tropical humid climate that impact the evaporation process by limiting the dissipation of the heat load. In our protocol, it was expected that (1) the combination of internal and external cooling,

and/or (2) the addition of menthol to this combination, would improve the thermal perception and the cooling rate during warm-up, and improve the distance covered and the perception of effort during this performance. Given the more demanding and longer warm-up on the one hand, and the performance of a task in a more humid and ecological environment on the other hand, it is possible that the skin surface directly covered by the precooling was insuffi- cient to improve subsequent performance and the thermal sensation, especially considering the physiological responses warm-up-induced. Indeed, in a review on the precooling methods (Rodriguez et al.), the body surface exposed, its sensibility and the time of application need to be considered. In addition, the neck, the head and the face, due to the proximity to the thermo- regulatory center of the central nervous system [39], are regions of high alliesthesial PLOS ONE Tropical cycling performance and cumulative pre-cooling PLOS ONE | https://doi.org/10.1371/journal.pone.0291951 October 12, 2023 9 / 15