PHYSIOLOGICAL ADAPTATIONS TO HEAT ACCLIMATION; REPERCUSSIONS ON CYCLING PERFORMANCE
The aims of this thesis were to 1) investigate the haematological adaptations to a novel long-term, progressive, work-matched heart rate clamp protocol, 2) to ascertain the neuromuscular adaptations to intermittent sprint training during heat acclimation and the effect on intermittent sprint performance and 3) to examine the phenomena of cross- acclimation where the stressors of one environment (heat), might convey a performance benefit in alternative environments (cool and hypoxia). Results from chapter 4 and 5 characterised the haematological adaptations of heat acclimation, and provided evidence of alterations in the red blood cell compartment of the total blood volume. Whilst modification of the plasma volume compartment is well researched, little is known regarding the red cell compartment, with no study previously measuring haemoglobin mass during heat acclimation. While training in a temperate environment led to a stable haemoglobin mass, training in a warm environment led to a transient drop in haemoglobin mass within 4 days of heat exposures, although this response was generally reversed within one week following the heat acclimation procedure. In chapter 6, all out intermittent sprint performance was shown to be not different between temperate and warm environments, and heat acclimation had no additional performance benefits over the same training when completed in cool environments. As such no differences were observed in electromyographic activity or tissue oxygen saturation either between environments or throughout acclimation. Chapter 7 revealed that heat acclimation led to enhancement of cycle time trial performance in hot, cool and hypoxic environments, where completing work matched training in a cool environment had no effect on exercise performance in any of the tested environments. Given that we only observed an increase in maximal aerobic capacity in the heat after 9 heat acclimation, but improvements in maximal aerobic power and time trial performance in all three environments, it is possible that heat acclimation either led to enhancement of anaerobic energy supply, or increased sub-maximal cycling efficiency, beyond that which cool training alone achieved.
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