Abstract
Whole- (WBC) or partial-body cryotherapy (PBC) exposure (−110 to −140°C for periods of 1-3 min) has become a commonly used tool by athletes to recover from the physical demands of training and competition. However, there is a potential novel application of cryotherapy exposure using this modality in the 1-3 h before training, or competition, to elicit enhanced physical performance. Only a handful of observational and interventional studies have investigated pre-exercise cryotherapy exposure in athlete populations. Consequently, sport practitioners require further evidence to determine whether athletes can benefit from cryotherapy use, and for quantifying the effects on physical performance, physiological and perceptual variables. The aim of this thesis was to explore the novel application of pre-exercise PBC (3 min exposure at −140°C) on physical performance, salivary biomarkers, and self-reported performance readiness in male athletes. A comprehensive review of the literature was undertaken across two studies and reported in an expert commentary and a systematic review. Cryotherapy exposure prior to training or testing can elicit improvements in sit-and-reach scores, grip strength, and maximal effort elbow flexion peak torque. Studies also reported a dampened oxidative stress response, and decreased lysosomal enzymatic activity in athletes, when used both acutely and chronically over 7-10 days before regular training periods. Collectively, the review of the literature identified a lack of evidence on the effects of pre-exercise cryotherapy exposure in an athletic population. The literature review was complemented by a self-administered, online survey of high-performance sport practitioners, responsible for the training, preparation, and recovery of elite athletes. The survey indicated that sport practitioners employed a variety of both passive and active strategies in the window of preparation prior to both training and competition, such as: nutritional supplements, heating and cooling techniques, priming strategies, weights, and bands. There is a disconnect between the number of athletes anecdotally using cryotherapy as a recovery modality, and the lesser number of sport practitioners recommending its use. There is a need for further education and upskilling of practitioners in the applications of PBC in athlete populations given that it is becoming increasingly popular as a recovery, and/or a preparation strategy. The first experimental investigation found that a 3 min PBC exposure at −140℃ elicited improvements in countermovement jump (CMJ) performance, with peak velocity increasing 15 min (+4.7 ± 3.5%, mean ± 90% confidence limits) and 3 h (+2.3 ± 2.6%) post-exposure. Salivary α-amylase (a marker for blood catecholamine concentration and sympathetic nervous system activity) increased substantially 15 min post-exposure (+131 ± 109%), and self-reported variables of mental fatigue (-0.8 ± 0.6, Likert units 1-5 scale), mood (+0.3 ± 0.4), and overall well-being (+2.3 ± 1.8) also improved favourably after PBC exposure. In the second experimental study, the timing of cryotherapy exposure before exercise was investigated, finding that PBC exposure 2 h prior to CMJ testing elicited the greatest improvements in velocity (+1.9 ± 1.4%) and absolute power (+7.2 ± 4.2%) compared to a 1 h or 3 h exposure period. Salivary α-amylase concentration was elevated 15 min post-exposure in both the 1 h (+61 ± 14%) and 2 h groups (+55 ± 12%). Self-reported performance readiness in the 2 h group improved to a greater extent than both the 1 h (+0.9 ± 0.2) and 3 h groups (+1.3 ± 0.7). Mental fatigue favourably decreased at 2 h post-exposure (+0.3 ± 0.1). Finally, PBC did not elicit a performance improvement (+0.4 ± 5.9%) in a continuous, high-intensity 6 x 40 m shuttle run test 2 h post-exposure in male rugby league athletes. However, responses to PBC exposure were highly individual with a greater increase in salivary α-amylase concentration from baseline having a large relationship (r = 0.51 ± 0.46) with improvements in running performance. Self-reported mood (+0.6 ± 0.7) and muscle soreness (+0.6 ± 0.4) were improved over the 2 h post-exposure period. There are clear advantages for use of PBC prior to physical performance testing by athletes with selected physiological markers and self-reported well-being measures improving favourably. Collectively, this research adds substantially to the knowledge of using PBC as a passive strategy to enhance an athlete’s physical preparation, underpinned by favourable physiological and perceptual effects that promote an individual’s performance. We have prepared a framework of recommendations of practical applications for PBC use in the high-performance sport sector for sport practitioners.| Date of Award | 2021 |
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| Original language | English |
| Supervisor | Julie COOKE (Supervisor), Andrew MCKUNE (Supervisor) & David PYNE (Supervisor) |