Prolonged exercise in hot environmental conditions places the body under far greater physiological and perceptual strain than when exercising at the same intensity in temperate conditions, resulting in an impaired exercise performance or capacity. The exact mechanisms that limit exercise performance are a complex interplay between the physiological and the behavioural systems, likely governed by a rising core temperature (hyperthermia). The three main interventions; hydration, cooling and heat acclimation (HA) have been investigated in an attempt to offset the reduction in exercise performance and capacity observed. The current thesis examined the effect of perceived hydration status (Chapter 3) and pre and per-cooling in isolation or in combination (Chapter 4) on the physiological and perceptual responses during a preload and 15 min timetrial (TT) performance in the heat (35 ºC to 40 °C, 50% rh). In Chapter 5, Chapter 6 and Chapter 7 a daily 60 min isothermic HA protocol was investigated on the physiological, perceptual, cognitive function and lipopolysaccharide responses. To further compare whether there was a time course effect over short-term (five days) and medium-term (ten days) upon these responses. Perceived euhydration status when hypohydrated had no effect on 15 min TT performance in moderately trained individuals, when the physiological and perceptual consequences of hypohydration existed. Neither external pre- nor per-cooling in isolation or in combination improved 15 min preloaded TT performance in the heat in highly trained athletes (Chapter 4). Pre-cooling via whole-body cold water immersion (CWI); 22 °C) for 30 min was successful at lowering overall strain for a limited period during the preload; however, by the time participants commenced the TT, the majority of these benefits had worn off, with combined external per-cooling not providing any additional benefit. A short-term (five days) 60 min daily isothermic (target rectal temperature ~38.5 °C) HA protocol provided a sufficient thermal impulse to elicit the necessary thermal adaptations to reduce physiological and perceptual strain when exercising in the heat, without inducing an endotoxin response with medium-term (ten days) offering a more complete adaptation to some systems and offering protection to working memory function.
- endotoxin response
- Hydration
- cooling
- heat acclimation
- interventions
- endurance performance
- heat strain
- exercise capacity
- thermoregulation
- cognitive function
Maximising endurance performance in the heat: investigating the effects of hydration, cooling and heat acclimation interventions
Moss, J. (Author). 19 Jun 2020
Student thesis: Doctoral Thesis