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Responses to intermittent high intensity activity in tropical conditions and the development of pre-cooling protocols

Brearley, Matt B. (2006). Responses to intermittent high intensity activity in tropical conditions and the development of pre-cooling protocols. PhD Thesis, Charles Darwin University.

Document type: Thesis
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Author Brearley, Matt B.
Title Responses to intermittent high intensity activity in tropical conditions and the development of pre-cooling protocols
Institution Charles Darwin University
Publication Date 2006
Thesis Type PhD
Supervisor Finn, Paul
Subjects 1106 - Human Movement and Sports Science
PHYSICAL SCIENCES
Abstract Intermittent, high intensity activity is particularly susceptible to excess heat storage, while sports with mandatory protective clothing and/or rules that limit fluid consumption are likely to limit heat loss. This thesis therefore examined the physiological and perceptual responses to V8 Supercar driving and limited overs cricket in tropical conditions. Despite all four drivers receiving cooled air to their helmets and three drivers also utilising torso cooling, post-race mean (SD) core temperature was 39.0 (0.4)oC causing them to feel hot and uncomfortable. Batsmen and bowlers’ core temperature increased rapidly during short spells and although the sweat rates of 0.72 – 1.11L.h-1 were moderate, there were instances of substantial dehydration. The data of these field investigations demonstrated that physiological and perceptual strain result from relatively short bouts of physical activity in tropical conditions.

Three pre-cooling methods prior to intermittent high intensity activity in simulated tropical conditions were then assessed. Thirty minutes of water bath (28 – 25oC) pre-cooling and twenty minutes of rest during instrumentation resulted in a Trectal of 36.7oC compared to 37.2 – 37.4oC for the air jacket, control and ice jacket trials (p=0.000). An intermittent cycling protocol subsequently increased Trectal to 38.9oC for the air jacket, control and ice jacket trials, that was higher than the 38.6oC of the water bath trials (p=0.000) and contributed to the higher body heat storage of the water bath trials (p=0.000). Time to exhaustion at 100% V . O2max following the cycling protocol was not different between trials (p=0.992).

Attenuated thermal strain via lower Trectal following cool water immersion was therefore demonstrated. Water bath pre-cooling augmented heat storage reserve that increased the margin for attainment of hyperthermic internal temperatures, and therefore water bath precooling is recommended to minimise physiological and perceptual strain during intermittent high intensity activity in tropical conditions.


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