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Effect of combined stressors on heat acclimation and temperate exercise

Student thesis: Doctoral Thesis

Recent evidence suggests heat acclimation (HA) may improve exercise performance under cooler conditions and that combined-stressor approaches might optimise HA. Accordingly, the studies presented in this thesis examined strategies for optimising HA in well-trained athletes through the use of combined-stressor approaches and the subsequent effects on exercise in a temperate environment (cross-stressor).
The first two studies examined the effect of dehydration in combination with exercise-heat stress on HA over the short- and longer-term and its subsequent decay, as well as investigating thermoregulation, parameters related to endurance performance and performance, in temperate conditions. Study three examined the addition of an overnight hypoxic stressor on short- and longer-term HA and endurance exercise performance in a temperate environment, after HA and following a 2-week decay. The final study comprehensively explored the ergogenic potential of heat acclimation for endurance performance in a temperate environment, relative to a cool exercise control group.
Together these studies demonstrated that the majority of the alterations associated with HA are rapidly induced (5-days) but longer programmes (10-days) are necessary to optimise these adaptations; they are well maintained over a short decay period (7-days). Combined stressor approaches (addition of dehydration or hypoxia) did not meaningfully affect the rate or magnitude of the induction of HA. Finally, HA did not induce any greater ergogenic benefit than a cool exertion matched exercise programme in a temperate environment.
In conclusion, HA is rapidly induced, robust, and the HA phenotype is minimally influenced by combined stressors (dehydration or hypoxia) when thermal strain is clamped. Moreover, when compared to an ecologically valid control, HA does not notably influence endurance performance or its related parameters in a temperate environment. These extensive findings provide useful guidance for athletes utilising environmental stressors in preparation for competition in various conditions.
Original languageEnglish
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Award dateMay 2017
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