Abstract
Hot water immersion initiates some thermo-physiological responses that can be complimentary to or similar to that of exercise. These responses can be utilised within sport through targeted heating protocols to elicit a desired response for a range of reasons, including promotion of acute recovery or chronic adaptation. This thesis aimed to explore the potential positive and negative effects of the utility of hot water immersion and provide some evidence as to the different physiological responses that occur to different immersion protocols.Surveyed athletes and practitioners reported hot water immersion is the most common modality of passive heating (Chapter 3). Athletes reported primarily using heating to promote recovery, whereas with practitioners this was heat acclimation. The majority of users perceiving passive heating to be beneficial for its intended purpose. However, negative symptoms, such as dizziness, tiredness, or vomiting, are common when using passive heating and this prevalence increases with perceptions of thermal sensation or discomfort. Thermal and orthostatic intolerance were shown experimentally to be prevalent during prolonged hot water immersion, however, can be reduced with simple mitigation strategies of facial fan cooling or non-submersion of the arms (Chapter 4).
Despite athletes perceiving heating to be beneficial for recovery, previous research has shown residual fatigue following passive heating that may negatively impact training or performance outcomes. Symptoms of tiredness were present in 38% of participants during 60 minutes of immersion in Chapter 4. However, a shorter, 30-minute immersion bout post-exercise was insufficient to impact perceptions of effort during subsequent exercise, perceived recovery, or any associated neuroendocrine biomarkers despite differences in expected recovery, rectal temperature, heart rate, and blood flow (Chapter 5). This demonstrates an increased thermal stimulus for adaptation can be applied using post-exercise hot water immersion without negatively impacting subsequent training outcomes.
Finally, differences in water temperature and immersion depth can effect the thermo-physiological, vascular, perceptual, and inflammatory responses to hot water immersion (Chapter 6). This demonstrates that optimal protocol selection may differ depending on the desired outcome, and factors beyond rectal temperature should be taken into consideration.
In summary, this thesis shows that the responses to acute bouts of hot water immersion are dependent on the immersion protocol and context in which it is used, with key considerations required for thermal and orthostatic intolerance and the desired physiological outcome.
| Date of Award | Aug 2024 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Tom Cullen (Supervisor), Neil Clarke (Supervisor), Charles Steward (Supervisor) & Doug Thake (Supervisor) |