Adam Naylor

The primary aim of this thesis was to advance the current field of knowledge regarding whole-body cryotherapy (WBC) and its influence on fatigue and recovery in elite rugby players. The secondary aim of this thesis was to explore the perceptions and current use of WBC in an elite contact sport population.
A systematic review analysed fifteen studies specific to the use of WBC following fatiguing physical activity. Despite the body of evidence reflecting low-to-moderate quality, WBC appears to result in perceived and symptomatic benefits, with some indications of positive change to recovery via physiological and inflammatory measures. Endocrinological responses were shown to be vastly under-researched and required clarification.
A qualitative survey formed the basis of exploring the beliefs and perceptions of fatigue, recovery and current practice of WBC within elite contact sport environments.
The key findings highlighted that (i) recovery from evening match or training activity was frequently impacted due to reduced perceived sleep quality; (ii) the perceived benefits of WBC enhanced sleep quality for those who had experienced WBC; (iii) the beliefs of those who had not experienced WBC was that they would highly likely adopt its use on the basis that sleep quality and psychological wellbeing would be enhanced in order to benefit recovery; (iv) the adoption of WBC as a regular practice-based modality for recovery is low mainly due to cost, logistics and lack of evidence-based information supporting parameters of implementation.
Two experimental, field-based studies were conducted using an elite Rugby League team from the European Super League. The first was an observational study and had the purpose of analysing the endocrinological (cortisol and testosterone) responses to a nine-day period of competition involving match and training activity and regular WBC exposures. These have been shown to be reliable indicators of catabolic and anabolic basal control in response to high intensity physical activity. The use of WBC post-training appeared to attenuate anabolic status, whereas following matches, anabolic signaling was enhanced following WBC. The second study was a participant controlled design comparing post-match recovery inclusive of WBC to regular recovery processes without WBC. Two, three-minute exposures to WBC showed significant alteration to the endocrine profile of players at 60 h post-match in that greater concentrations of testosterone were found without concurrent change in cortisol. A significant effect was shown after one exposure to WBC, albeit to a lesser degree. Without WBC, the recovery of endocrine and biochemical profile was not reached by the end of the 60-h sample period.
In summary, this thesis supports the use of WBC in that it appears to hold benefits for athletes in their recovery from elite level collision sport. Greater benefits appear more supported following matches, with a lesser extent, post-training sessions. Medical practitioners, coaches and sport scientists/conditioners should look to optimise the influence of WBC though applying two, 3-minute exposures as close to the cessation of high-fatiguing activity as possible. WBC has the potential to improve the wellbeing and recovery of collision sport athletes, however, the underlying mechanisms involved remain undetermined despite the observation of a desirable change in endocrinological profile.
Further study should look to specifically investigate the effects of WBC relative to the time of day of activity given that indications in this study from a perceived perspective suggest that effects may be relative to activity and time of day. This area currently holds negligible supporting evidence and will assist to inform the implementation strategy of WBC in the team environment.