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

What wrist should you wear your actigraphy device on? Analysis of dominant vs. non-dominant wrist actigraphy for measuring sleep in healthy adults

OBJECTIVE: Differences in sleep results due to the placement of actigraphy devices (non-dominant vs. dominant wrist) are yet to be determined. METHODS: 65 nights of data from 13 adult participants was collected while participants wore two actigraphy devices, one on each wrist. Sleep indices including total sleep time (TST), total time in bed (TTB), sleep efficiency (SE%), sleep latency (SL), wake after sleep onset (WASO), sleep onset time (SOT) and wake time (WT) were assessed between the two devices. RESULTS: There were no significant differences between devices for any of the measured sleep variables (p>0.05). SE%, SL and WASO resulted in high correlations between devices (0.89, 0.89 and 0.76, respectively), with all other sleep variables resulting in very high correlations (>0.90) between devices. CONCLUSIONS: Based on our results, it does not seem critical which wrist the actigraphy device is worn on for measuring key sleep variables

The Influence of Match-Day Napping in Elite Female Netball Athletes

Purpose: To assess the effect of match-day napping and duration of naps on perceptual and performance indices in elite female netball players over two consecutive netball seasons. Methods: Fourteen elite female netball athletes (mean ± SD; age = 23 ± 6 yr) participated in an observational study over 26 competition matches. On each match day, athletes provided information on their napping habits, perceived energy levels, and then performed 3 countermovement jumps (CMJ) 3h30 prior to the start of the match. One hour following the match, subjective player performance ratings from the players and two members of the coaching staff were obtained. Naps were characterized into 3 conditions for analysis; No Nap (NN), <20 min Nap (SHORT), and ≥20 min Nap (LONG). Results: A significant difference in peak jump velocity was observed between the SHORT and the NN condition in favor of the shorter nap (3.23 ± 0.26 and 3.07 ± 0.36 m.s-1, respectively, d = 0.34, p < 0.05). A moderate, significant difference (d = 0.85; p < 0.05) was observed for the coach rating of performance (out of 10) between the SHORT and the NN condition (7.2 ± 0.8 and 6.4 ± 0.9, respectively) in favor of SHORT. Conclusion: The findings from the study would suggest that a short nap (<20 min) on the day of competition can enhance jump velocity and improve subjective performance in elite netball players, as assessed by coaching staff

Melatonin and sleep responses following exercise in elite female athletes

To determine the melatonin concentrations and subsequent sleep indices of elite netball athletes following a training day when compared to a control day. Ten elite female netball athletes (mean ± SD; age = 23 ± 6 yrs) provided saliva samples PRE (17:15h) and POST (22:00h) a training session, and a day with no training (CONTROL). Sleep monitoring was performed using wrist actigraphy to assess total time in bed (TTB), total sleep time (TST), sleep efficiency (SE) and sleep latency (SL). Melatonin levels were significantly lower (p < 0.05), both PRE and POST the training condition (6.2 and 17.6 pg/mL, respectively) when compared to the CONTROL (14.8 and 24.3 pg/mL, respectively). There were no significant differences observed between conditions for any of the sleep variables. However, a small reduction in TST could be observed following the training session condition compared to the CONTROL condition. The scheduling of netball training in the evening is shown to suppress salivary melatonin levels. This may have an influence on subsequent sleep following night-time exercise

Effect of footwear on Y-Balance Test performance & risk categorisation

Introduction: The Y-Balance Test (YBT) assesses dynamic balance and screens for injury risk. However, there are inconsistent recommendations regarding footwear use during testing. Methods: Forty-two volunteers (26 females, 16 males) performed the YBT with their habitual athletic footwear and barefoot on both legs. In a single-legged stance, participants reached with the contralateral limb in the anterior, posteromedial, and posterolateral directions three times. Leg- length normalised composite scores (%) and anterior-reach differences (cm) were extracted and used to identify high-risk participants (i.e., anterior-reach difference ≥4 cm or composite score ≤94%). Results: Anterior, posteromedial, and anterior-reach difference measures were similar between conditions (P>0.05). Posterolateral (2.8±7.6 cm, P=0.001) and composite scores (93.4 vs 94.8%, P=0.018) were greater barefoot. The proportion of individuals at high-risk based on anterior- reach difference (odds ratio: 1.6, McNear test P =0.58) and composite scores (odds ratio: 2.2, P=0.21) was similar between conditions, although risk categorisation was inconsistent in 31 and 19% of cases, respectively. Discussion: Footwear altered the composite score such that the group average exceeded the high-risk threshold. While testing in athletic footwear may be more valid, researchers should be aware that risk categorisation is affected. Take home message: Care should be taken when comparing studies with different protocols

From pillow to podium: a review on understanding sleep for elite athletes

Sleep is considered vital to human health and well-being, and is critical to physiological and cognitive functioning. Elite athletes experience high training and competition demands, and are often exposed to various factors, situations, and environments that can cause sleep impairments. Previous research has shown that athletes commonly experience sleep loss in the lead up to and following competition, which could have significant impacts on their preparation, performance, and recovery. In particular, the results from previous research show significant reductions in total sleep time (~1:40 h:min) and significant increases in sleep latency (~45 minutes) following evening competition. Napping is common in both the training and competition setting in athletes; however, research on the effect of napping on physiology and performance is limited. In contrast, research on strategies and interventions to improve sleep are increasing in the athletic population, with sleep hygiene research resulting in significant improvements in key sleep indices. This review investigates the physiological importance of sleep in athletes, current tools to monitor athletes’ sleep, the role of sleep for cognitive functioning and athletic performance, the prevalence of sleep disturbances and the potential mechanisms causing sleep disturbances, the role of napping, and different intervention strategies to improve sleep

Sleep and stress hormone responses to training and competition in elite female athletes

Stress hormone and sleep differences in a competition versus training setting are yet to be evaluated in elite female team-sport athletes. The aim of the current study was to evaluate salivary cortisol and perceptual stress markers during competition and training and to determine the subsequent effects on sleep indices in elite female athletes. Ten elite female netball athletes (mean ± SD; age: 23 ± 6 years) had their sleep monitored on three occasions; following one netball competition match (MATCH), one netball match simulation session (TRAIN), and one rest day (CONTROL). Perceived stress values and salivary cortisol were collected immediately pre- (17:15 pm) and post-session (19:30 pm), and at 22:00 pm. Sleep monitoring was performed using wrist actigraphy assessing total time in bed, total sleep time (TST), efficiency (SE%), latency, sleep onset time and wake time. Cortisol levels were significantly higher (p < .01) immediately post MATCH compared with TRAIN and CONTROL (mean ± SD; 0.700 ± 0.165, 0.178 ± 0.127 and 0.157 ± 0.178 μg/dL, respectively) and at 22:00 pm (0.155 ± 0.062, 0.077 ± 0.063, and 0.089 ± 0.083 μg/dL, respectively). There was a significant reduction in TST (−118 ± 112 min, p < .01) and SE (−7.7 ± 8.5%, p < .05) following MATCH vs. TRAIN. Salivary cortisol levels were significantly higher, and sleep quantity and quality were significantly reduced, following competition when compared to training and rest days

COVID-19 Host Genetics Initiative. A first update on mapping the human genetic architecture of COVID-19

The COVID-19 pandemic continues to pose a major public health threat, especially in countries with low vaccination rates. To better understand the biological underpinnings of SARS-CoV-2 infection and COVID-19 severity, we formed the COVID-19 Host Genetics Initiative1. Here we present a genome-wide association study meta-analysis of up to 125,584 cases and over 2.5 million control individuals across 60 studies from 25 countries, adding 11 genome-wide significant loci compared with those previously identified2. Genes at new loci, including SFTPD, MUC5B and ACE2, reveal compelling insights regarding disease susceptibility and severity.</p