Evening exercise and cold water immersion: effect on subsequent sleep

    Research output: ThesisDoctoral Thesis

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    Abstract

    Post-exercise recovery strategies are commonly used with elite athletes to minimise fatigue experienced post-training. Sleep is widely considered to be the most important period for achieving optimal recovery post-exercise, however, sleep research in athletes is limited. One of the most popular post-exercise recovery techniques is cold water immersion (CWI). While there has been some research into the subsequent performance benefits (~60 min to 72 h) of post-exercise cold water immersion, there has been limited research into the physiological responses in the post-immersion (~90 min) period. As athletes often perform CWI in the evening post-exercise, research is needed to investigate the effects of CWI on subsequent sleep quality and quantity. The purpose of this thesis was to investigate the effect of evening high-intensity exercise, plus any effect of CWI performed post-exercise, on subsequent sleep quality and quantity. Specifically, study 1 investigated the core temperature and salivary melatonin responses to 15 min of either cold (14°C) or warm water immersion (WWI: 34°C) after a high-intensity cycling protocol in the evening. Study 2 investigated the effect of early evening high-intensity training sessions (over a training phase) on the sleep of elite youth soccer players in their normal sleeping environment using wrist actigraphy, by comparing high-intensity and low-intensity/no training nights. Additionally, as the players regularly engaged in CWI post-training (15 min in 14°C) it was possible to explore any effects of CWI on subsequent sleep. Study 3 combined elements of study 1 and study 2 together, by investigating the effect of evening highintensity cycling with and without the addition of CWI (15 min in 14°C) performed post-exercise compared to a control (no-exercise, no CWI) condition on the sleep of healthy male athletes. Sleep was measured using polysomnography (PSG), the gold standard of sleep measurement. Core temperature, skin temperature and salivary melatonin were also measured as these have all been linked to sleep mechanisms and there has been limited research surrounding their response to evening exercise and CWI. The results from these studies show that performing CWI post-exercise will decrease core temperature at a greater rate than both WWI and a control condition, with the effect lasting for ~2 h post-exercise. In addition, salivary melatonin is unaffected by both high-intensity exercise and CWI, even when controlling for light exposure, which usually inhibits the secretion of melatonin. However, most importantly, high-intensity exercise performed in the evening with or without the addition of CWI performed postexercise does not affect whole night sleep quality and quantity of athletes as measured by both actigraphy and PSG. Therefore, athletes and coaches can be confident that performing CWI post-exercise in the evening does not negatively affect the subsequent sleep of athletes.
    Original languageEnglish
    QualificationDoctor of Philosophy
    Publication statusUnpublished - 2013

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