The regulation of exercise, a process known as pacing, is considered an essential determinant of athletic performance. Pacing is the distribution of energy during an exercise task and manifests through pre-determined ‘templates’ built through prior experience and recalled for future performances. Once the exercise task begins, internal and external feedback is integrated to determine if the current work-rate should be maintained or adjusted. Despite a wide range of investigations examining the pacing phenomenon, the probability that environmental and feedback manipulations change pacing remains largely unknown. In addition, whether accurate or inaccurate knowledge of the fraction of inspired oxygen content (FiO2) or series of oxygen deception trials can build psycho-physiological belief in cyclists to improve performance has not yet been explored. Moreover, whether an exercise reserve exists and can be used in hyperoxia to improve performance in hyperoxic time-trials (TT) and in subsequent normoxic TT’s is unclear. Therefore, this thesis aimed to examine how environmental and performance feedback manipulations could affect exercise regulation and performance in trained cyclists. A meta-analysis was conducted for Study One and the effects of five extrinsic factors on TT performance were examined: hypoxia, hyperoxia, heat-stress, pre-cooling strategies and various forms of feedback. Only studies that reported power output for self-paced cycling TT’s in a manner that allowed for the segmentation of performances into start, middle and end sections were included. In Study Two, participants were informed during a series of 4000-m oxygen deception TT’s they were inspiring either normoxia or hyperoxia, however, in two trials participants were deceived of the FiO2. Trials were completed in a double-blinded and randomised order, allocating participants to one of four possible trial orders, before negative performance deception was revealed in a final, self-paced normoxic TT. Participants in Study Three completed seven 4000-m TT’s: two self-paced, normoxic familiarisation trials; a self-paced hyperoxic and competive hyperoxic trial; a further self-paced trial in normoxia, a hyperoxic competitive-performance deception trial; and a competitive, normoxic trial after deception was revealed. The novel findings of this research were: i) self-paced TT’s undertaken in hypoxia or heat-stress had no effect on cycling compared with normoxic or cool conditions until the middle section of trials where exercise intensity was downregulated (Study One); ii) provision of negative deceptive feedback may enable upregulation of MPO during the middle stages of a trial improving overall trial performance (Study One); iii) performance improvements in a previous negative deceptive feedback trial may be retained in a subsequent TT after negative performance deception is revealed (Study One); iv) cycling performance improves in hyperoxia, and mechanisms are likely physiological, however, improvement in a deception trial suggests a placebo effect might be present. (Study Two); v) a particular sequence of oxygen deception trials might build psycho-physiological belief to improve performance in a subsequent normoxic trial (Study Two); vi) further performance improvement can occur when receiving negative deceptive feedback in hyperoxia which indicates an exercise reserve still exists in hyperoxia (Study Three); and vii) performance improvements after negative performance deception in hyperoxia can be retained in a subsequent normoxic TT after deception is revealed (Study Three). These findings contribute to our knowledge of how exercise is modulated and offer mechanistic understanding of how trained cyclists can change their routine pacing strategy to enhance performance from exposure to increased FiO2, oxygen deception trials and negative performance deception.
|Date of Award||2018|
|Supervisor||Kevin Thompson (Supervisor), Brad Clark (Supervisor) & Laura Garvican (Supervisor)|