Sleeping to perform: examining sleep and exercise in elite female athletes
Sleep plays an essential role in biological functions, and is fundamental for human health and wellbeing. Sleep is also widely recognised as playing an important role in the sporting environment, with an increasing awareness of the importance of sleep in elite athletes. Although sleep research in athletes is increasing, elite athletes are still largely underrepresented in the literature, especially female athletes. Through a series of six studies, this PhD thesis aimed to enhance the understanding of sleep habits of elite athletes, specifically female team sport athletes. The main aim of the thesis was to investigate the sleep habits of elite female team sport athletes in both training and competition environments and also to evaluate interventions to improve sleep and subsequent exercise performance. Study One assessed the reliability and validity of a linear position transducer device as a performance tool for further studies within the thesis. Study Two subjectively and objectively assessed sleep indices in the night leading up to and the nights following competition over a netball season. Study Three investigated perceived and hormonal stress markers and sleep responses following a match, training and control condition. Study Four assessed difference between the melatonin and sleep responses to training and non-training days. Study Fix, objectively assessed the effect of an acute sleep hygiene education session on sleep indices via wrist-actigraphy. Finally, Study Six, an observational and longitudinal study, examined the influence of match-day napping on various performance and perceptual markers. In Study One, a linear position transducer (GymAware, Kinetic Performance Technology, Canberra, Australia), was shown to be a reliable tool for measuring countermovement squat jump performance in female athletes, with a mean intraclass correlation of 0.70 for jump height, 0.90 for peak velocity, and 0.91 for mean velocity. It was also shown to have a Pearson correlation of r = 0.90 and a typical error of ~2.4 cm when compared to a force plate, however the linear position transducer overestimated jump height by an average of 7.0 ± 2.8 cm. In Study Two, 10 elite female athletes completed a survey on their perceived sleep duration and quality on three consecutive nights; the night before the game, the night of the game and the night following the game on 15 separate occasions over a netball season. In addition, on two separate occasions, 11 elite female athlete’s sleep was monitored via an actigraph device for the three consecutive nights. Results showed the athletes perceived sleep duration was significantly different on the night of the game (6:52 h:m) from the night before a game (8:29 h:m). Similarly, when sleep duration was measured using actigraphy, total sleep time was observed to be significantly lower on the night of a game (6:46 h:m) compared to the night before a game (8:31 h:m). Furthermore, total sleep time remained significantly reduced on the night following the game (7:23 h:m). Findings from Study Three provide further support for poor sleep in athletes following evening competition and training. Ten elite female netballers’ sleep was monitored following a netball competition match (MATCH), a netball match simulation session (TRAIN) and a rest day (CON). Salivary cortisol was collected immediately pre and post session, and at 22:00pm. Total sleep time was significantly reduced following the MATCH (6:03 h:m) compared to TRAIN (8:03 h:m) and CON (8:46 h:m). Sleep efficiency was also significantly reduced by 7.7% following the match compared to the training, with sleep latency significantly increased following the game (50.3 minutes) compared to the rest day. Cortisol levels were significantly higher immediately after the match (0.700 μg/dL) compared to training (0.178 μg/dL) and rest (0.077 μg/dL) and remained significantly elevated at 22:00pm. Study Four compared salivary melatonin levels and sleep behavior of 10 elite female athletes between a training session and a control session (rest day). Significant reductions (p < 0.05) in melatonin levels both pre and at 22:00pm were observed in the training condition (6.2 and 17.6 pg/mL, respectively) compared to the control condition (14.8 and 24.3 pg/mL, respectively). The 26 female athletes in Study Five performed one week of baseline sleep monitoring (PRE), followed by a sleep hygiene education session, and a further week of sleep monitoring (POST). Total sleep time significantly increased by 22.3 minutes (p < 0.05), following a one-hour sleep hygiene education session from the PRE week to the POST week. Furthermore, wake variance and wake episode duration were significantly increased from the PRE week to the POST week. Lastly, in Study Six, on each match day, 14 female athletes provided information on their durations of naps and perceived energy levels before performing 3 countermovement jumps 3.5 hours prior to the start of the match on 26 occasions, over two netball seasons. One hour following the match, subjective player performance ratings and coaching staff player performance ratings were obtained. Improved jump performance and ratings of netball performance were observed following nap durations of 20 minutes or less on match-day in elite female athletes, when compared to no nap or naps lasting longer than 20 minutes. In summary, the series of studies in this thesis provides a foundation for understanding sleep in elite female team-sport athletes. Sleep disturbances are prevalent around training and further disturbed around competition environments. These disturbances were also associated with perturbations in different salivary hormones. Furthermore, results show sleep can be acutely improved following a single sleep hygiene education session. And finally, match-day naps of varying duration may have an effect on subsequent match performance, with naps lasting <20 minutes being associated with the most favorable results. The studies provide valuable information on the sleep habits of elite female athletes, which can be used by coaches and practitioners to monitor sleep and establish individualized sleep hygiene protocols. Moreover, the sleep patterns around training and competition should be factored in by practitioners when designing training and recovery programs.
Networked Digital Library of Theses and Dissertations