Optimising heat acclimation state and refining strategies for the acquisition of heat adaptations

  • Ash Willmott

Student thesis: Doctoral Thesis

Abstract

There were two aims of this thesis, the first included updating a heat acclimation state test (HAST), prescribed to determine changes in heat dissipation capacity and evaluate the effectiveness of heat acclimation (HA). The second aim refined and investigated the efficacy of novel and applied, short- and long-term HA protocols to optimise the acquisition of heat adaptations and alleviate the deleterious effect of heat stress and subsequent physiological strain during exercise.

Study 1 explored the reliability of a HAST prescribed from fixed rates of metabolic heat production (Ḣprod) per unit of body mass. The updated test was found to be reliable for heat acclimation state criteria (e.g. sweat setpoint and sweat gain).

Study 2 investigated the sensitivity of the refined HAST and prescribed long-term heat acclimation (HA) for construct validity purposes. Large physiological and perceptual heat adaptations were found following HA and the HAST was sufficiently sensitive to highlight meaningful changes in heat acclimation state.

Study 3 investigated a novel short-term, twice-daily heat acclimation (TDHA) protocol, to evoke heat adaptations within 2-days. Partial heat adaptations transpired, which alleviated heat strain and improved exercise tolerance (e.g. 3-km time trial).

Study 4 investigated a once-daily STHA protocol within ultra-endurance athletes preparing for the Marathon des Sables (a multi-stage, ~250 km ultra-marathon) across the Sahara Desert in hot, dry conditions. Partial heat adaptations transpired, without compromising the athletes’ immune function.

Study 5 and 6 built upon Study 1-4 and addressed some of the limitations found during this thesis. Study 5 and 6 investigated the efficacy of a non-consecutive TDHA protocol, compared to traditional consecutive once-daily HA, and matched temperate exercise groups. It was reported both HA protocols significantly enhanced heat acclimation state, induced large physiological heat adaptations and improved exercise tolerance in hot but not temperate conditions. No adverse effects in inflammatory or stress biomarkers were observed across HA protocols.

This thesis displays the benefits of updating exercise prescription methods to quantify physiological adaptations and responses following HA accurately. Similarly, this thesis reports the efficacy of new TDHA protocols, which may afford athletes and emergency personnel (e.g. firefighters and military) recovery days during HA interventions, minimising the risk of immune dysfunction and may provide the opportunity to continue their training quality.
Date of Award2018
Original languageEnglish
Awarding Institution
  • University of Brighton
SupervisorNeil Maxwell (Supervisor), Mark Hayes (Supervisor) & Jeanne Dekerle (Supervisor)

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