Sleep regularity and predictors of sleep efficiency and sleep duration in elite team sport athletes

Background Many elite athletes have suboptimal sleep duration and efficiency, potentially due to factors that may impact sleep onset and offset times. Variability in sleep onset and offset may negatively influence sleep. The sleep regularity index (SRI) is a novel metric for sleep regularity, however there are no published descriptions of SRI in elite athletes. Further, contributors to sleep efficiency and duration in elite athletes using objective measures have not been explored. Methods Sleep was monitored over a minimum of seven consecutive days (7 to 43)—in 203 elite team sport athletes (age range = 19–36 years; female, n = 79; male, n = 124, total sleep nights = 1975) using activity monitoring and sleep diaries. The sleep regularity index (SRI) was calculated to reflect the night-to-night shifts in sleep by accounting for changes in sleep onset and sleep offset. Sleep characteristics were compared between regular and irregular sleepers and important contributors to sleep efficiency and total sleep time were assessed using multiple linear regression models. Results The median sleep regularity index and interquartile range were 85.1 (81.4 to 88.8). When compared to irregular sleepers, regular sleepers demonstrated (1) significantly greater sleep efficiency (p = 0.006; 0.31 medium effect size [ES]), (2) significantly less variability in total sleep time (− p ≤ 0.001; − 0.69, large ES) and sleep efficiency (− 0.34, small ES), (3) similar total sleep time and (4) significantly less variation in sleep onset (p ≤ 0.001; − 0.73, large ES) and offset (p ≤ 0.001; − 0.74, large ES) times. Sleep characteristics explained 73% and 22% of the variance in total sleep time and sleep efficiency, respectively. The most important contributor to total sleep time was a later sleep offset time, while the most important contributors to sleep efficiency were an earlier bedtime and less variable sleep onset times. Conclusions Bedtime and a consistent sleep onset time are important factors associated with sleep efficiency in athletes, while sleep offset is an important factor for total sleep time. Coaches and staff can assist their athletes by providing training schedules that allow for both regularity and sufficiency of time in bed where possible

Assessment of sleep characteristics of elite team sport athletes

Despite the known restorative effects of sleep and the important role it may play in minimising fatigue and optimising adaptation from training, it has been suggested that athletes exhibit poorer sleep characteristics when compared to the general population. Whilst there have been investigations of the sleep characteristics exhibited during competition, analysis of the objective sleep characteristics of team sport athletes prior to and during important competition is limited, particularly in elite female athletes. In addition to the competition itself, there are a number of factors that may influence an athlete’s sleep. These include the training and competition schedule, phases of training and competition, internal and external training load, the athlete’s sleep environment, and domestic and international travel. However, the impact of a combination of these factors on objective sleep has rarely been explored in elite team sport athletes. Therefore, the main aim of this thesis was to investigate the objective sleep characteristics of elite male and female team sport athletes during competition. Three studies were conducted in a high performance sport environments to assess: (1) the impact of match start time and days relative to a match on sleep; (2) the relationships between sleep, training load and well-being; and (3) the impact of the quality and quantity of sleep obtained during a long-haul flight on competition sleep and perceptual measures including well-being and jetlag. Study 1 assessed the objective sleep characteristics, via wrist worn actigraphy, of 45 elite male Australian Football (AF) players during the pre-season (habitual) and across four home matches during the competitive season. For each match start time, the 22 participants who were selected to play were assigned an activity monitor to be worn the night before (-1), night of (0), one night after (+1), and two nights after (+2) each match. Differences observed in sleep onset latency (ES=0.11 ± 0.16), sleep rating (ES=0.08 ± 0.14) and sleep duration (ES=0.08 ± 0.01) between competition and habitual periods were trivial. Sleep efficiency (%) was almost certainly higher during competition than habitual, however this was not reflected in the subjective rating of sleep quality. In many cases, the differences between match start times were trivial or unclear. The evening match start time, compared to all other start times, resulted in the clearest differences (e.g., evening matches had a likely longer sleep latency and almost certainly lower sleep efficiency). The differences in sleep characteristics based on days relative to the match were primarily trivial, however there were almost certain decreases in sleep duration for the night of the match compared to +1 and +2 nights post-match. The findings of this study indicated that, in general, elite AF competition does not appear to cause substantial disruption to sleep characteristics when compared to habitual sleep. Whilst the match start time had some impact on sleep variables, it appears that any match, regardless of match start time, may cause disruption to players’ sleep characteristics. The clearest disruption to AF players’ sleep occurred in the nights (+1 and +2) immediately following a match, which provides an ideal opportunity for intervention to optimise sleep and recovery. Importantly, the subjective ratings of sleep from shortened well-being questionnaires, used routinely in the high performance environment appear limited in their ability to accurately provide an indication of sleep quality. It is recognised that numerous factors may influence the sleep characteristics of AF players, including player well-being and training and match day load. Nevertheless, the relationships between load, well-being and sleep prior to and following training and matches are not well understood.1 Study 2 assessed the association between objective sleep characteristics, self-reported measures of well-being and external load of 38 elite male AF players over a 15-day pre-season training period. External load was assessed during main field sessions and self-ratings of well-being were collected daily. Canonical correlations were moderate between pre training sleep and training load (r range = 0.32–0.49), pre training sleep and well-being (r = 0.32), and well-being and post training sleep (r = 0.36). Moderate-to-strong canonical correlations were observed between dimensions representing training load and post training sleep (r range = 0.31 to 0.67). Player Load TM (PL) and Player Load TM 2D (PL2D) showed the greatest association to pre and post training objective sleep characteristics and well-being. External load metrics PL and PL2D showed the greatest association between both objective sleep characteristics and well-being measures in AF players. This association was observed both prior to and following main AF training sessions. Fragmented sleep was associated with players completing the following training session with a higher PL2D, and increased wake bouts were associated with lower mood and higher soreness ratings. Our findings highlight that the relationship between objective sleep characteristics, training load and well-being are not defined by one measure (e.g., sleep duration). Instead, a complex interaction of sleep variables may influence both external load and the well-being of AF players. These findings have implications for practitioners, particularly when choosing variables to monitor AF players’ sleep to assist in the planning and evaluation of training. The sleep characteristics for both Study 1 and 2 were assessed in players’ habitual sleep environments, however it is often a requirement for an elite team sport athlete to travel both domestically and internationally for competition.2-5 In order to investigate the impact of international travel on the sleep characteristics, well-being and performance of elite team sport athletes,6 the participant group for Study 3 was extended to elite female cricket players, as players are required to travel both domestically and internationally for competition. There have been no assessments of the objective in-flight sleep characteristics when athletes have the ability to lie flat whilst travelling in business class, however the difficulties of obtaining good quantity and quantity of sleep during long-haul travel are well documented,4,7 Study 3 assessed the impact of the quality and quantity of sleep during an international flight on subsequent objective sleep characteristics, training and match day load, self-reported well-being, and perceptions of jetlag in 11 elite female cricketers during an International Cricket Council T20 Women’s World Cup. To our knowledge, Study 3 is the first objective assessment of the in-flight sleep of elite team sport athletes seated in business class during an international flight. The results of Study 3 indicate that maximising the opportunity for in-flight sleep quality and quantity by planning the team departure time and business class seat selection appear to benefit elite female cricket players’ recovery and sleep exhibited during competition. The quality of sleep obtained in-flight had an impact on the self-reported measures of fatigue during the tournament. Players with a lower in-flight sleep efficiency reported higher levels of fatigue during the tournament. Study 2 highlighted that fragmented sleep prior to a main training session was associated with lower ratings of mood and increased ratings of soreness. This further supports that the quality and quantity of in-flight sleep may have had a positive impact on an athlete’s overall well-being and readiness to train upon arrival at the international competition destination. The preservation of both the sleep quality and quantity during long-haul travel may also be an important strategy to manage jetlag.3,8 Players that slept for longer during the flight presented with minimal perceptions of jetlag and this was maintained across the monitoring period. In contrast, players with lower in-flight sleep duration reported some perceptions of jetlag, which improved two days after arrival at the destination. It is acknowledged that the financial constraints of travelling business class may be a limitation for elite team sporting organisations, however the investment to achieve sleep quality and quantity similar to habitual values prior to an important international competition may outweigh the costs associated with the alternative approach of an arriving days earlier (e.g., accommodation) to facilitate recovery from travel. In summary, the three studies in this thesis add to the knowledge of the objective sleep characteristics of elite male and female team sport athletes exhibited during competition. Our findings demonstrate that the sleep characteristics during competition are not compromised when compared to habitual. However, the habitual characteristics were not optimal, providing the greatest opportunity for intervention. The findings provide high performance practitioners and coaches with information to assist with the implementation of individualised and team strategies to optimise the sleep, well-being and performance of elite team sport athletes. Furthermore, preserving the sleep quality and quantity during international travel should be considered when planning travel and training upon arrival at the international competition destination

No compromise of competition sleep compared with habitual sleep in elite Australian footballers

Purpose: To assess the impact of match-start time and days relative to match compared with the habitual sleep characteristics of elite Australian Football (AF) players. Methods: 45 elite male AF players were assessed during the preseason (habitual) and across 4 home matches during the season. Players wore an activity monitor the night before (−1), night of (0), 1 night after (+1), and 2 nights (+2) after each match and completed a self-reported rating of sleep quality. A 2-way ANOVA with Tukey post hoc was used to determine differences in sleep characteristics between match-start times and days relative to the match. Two-way nested ANOVA was conducted to examine differences between competition and habitual phases. Effect size ± 90% confidence interval (ES ± 90% CI) was calculated to quantify the magnitude of pairwise differences. Results: Differences observed in sleep-onset latency (ES = 0.11 ± 0.16), sleep rating (ES = 0.08 ± 0.14), and sleep duration (ES = 0.08 ± 0.01) between competition and habitual periods were trivial. Sleep efficiency was almost certainly higher during competition than habitual, but this was not reflected in the subjective rating of sleep quality. Conclusions: Elite AF competition does not cause substantial disruption to sleep characteristics compared with habitual sleep. While match-start time has some impact on sleep variables, it appears that the match itself is more of a disruption than the start time. Subjective ratings of sleep from well-being questionnaires appear limited in their ability to accurately provide an indication of sleep quality

A complex relationship : Sleep, external training load, and well-being in elite Australian footballers

Purpose: To assess relationships between objective sleep characteristics, external training loads, and subjective ratings of well-being in elite Australian football (AF) players. Methods: A total of 38 elite male AF players recorded objective sleep characteristics over a 15-day period using an activity monitor. External load was assessed during main field sessions, and ratings of well-being were provided each morning. Canonical correlation analysis was used to create canonical dimensions for each variable set (sleep, well-being, and external load). Relationships between dimensions representing sleep, external load, and well-being were quantified using Pearson r. Results: Canonical correlations were moderate between pretraining sleep and external training load (r = .32–.49), pretraining sleep and well-being (r = .32), and well-being and posttraining sleep (r = .36). Moderate to strong correlations were observed between dimensions representing external training load and posttraining sleep (r = .31–.67), and well-being and external training load (r = .32–.67). Player load and Player load 2D (PL2D) showed the greatest association to pretraining and posttraining objective sleep characteristics and well-being. Fragmented sleep was associated with players completing the following training with a higher PL2D. Conclusions: Maximum speed, player load, and PL2D were the common associations between objective sleep characteristics and well-being in AF players. Improving pretraining sleep quality and quantity may have a positive impact on AF players’ well-being and movement strategy during field sessions. Following training sessions that have high maximum speed and PL2D, the increased requirement for sleep should be considered by ensuring that subsequent sessions do not start earlier than required

Establishing the incidence and prevalence of injury and illness in Australian sailing athletes over a full year of training and competition to help determine prevention priorities

Objectives To investigate the prevalence, incidence rate (IR) and burden of health problems (injuries and illnesses) in Australian Olympic class and State Sailing Pathway Program (SSPP) athletes over 12-months of training and competition. Design Descriptive epidemiological study. Methods Ninety-two Australian Sailing and SSPP athletes were prospectively followed during the 2019–2020 season. Medical attention injuries and illnesses were prospectively recorded, and further sub-categorised according to time loss. The IR and burden were calculated per 365 athlete-days, with differences in IR between sexes compared using negative binomial generated rate ratios. Results Three hundred and forty-nine injuries were reported in 53 athletes (57.6 %), with 14.3 % resulting in time loss. Injury IR was 3.71 (95%CI = 3.33–4.12) injuries per 365 athlete–days, with no difference observed between sex (IRR = 1.64; 95%CI = 0.81–3.34). Shoulder injuries were found to have the greatest burden. Fifty-four illnesses were reported in 27 athletes (29.3 %), with 39.0 % resulting in time loss. Respiratory infection (n = 22, 40.7 %) was the most common illness reported. Illness IR was 0.57 (95%CI = 0.43–0.75) illnesses per 365 athlete days, with females found to have a 3.6 fold increase in illness compared to males (IRR = 3.6; 95%CI = 2.0–6.7). Conclusions The majority of health problems reported in sailing athletes did not result in time loss. There were no differences in the injury IR between sexes, however females had a 3.6-fold increase in reported illness. These results can inform future strategies to reduce key health problems in sailors. Future research investigating whether performance is impacted by the high rate of non-time loss health problems is warranted

Business class travel preserves sleep quality and quantity and minimizes jet lag during the ICC Women’s T20 World Cup

Purpose: To determine the impact of the quality and quantity of sleep during an international flight on subsequent objective sleep characteristics, training and match-day load, self-reported well-being, and perceptions of jet lag of elite female cricketers during an International Cricket Council Women’s T20 World Cup. Methods: In-flight and tournament objective sleep characteristics of 11 elite female cricketers were assessed using activity monitors. Seated in business class, players traveled west from Melbourne, Australia, to Chennai, India. The outbound flight departed Melbourne at 3:30 AM with a stopover in Dubai for 2 hours. The arrival time in Chennai was 8:10 PM local time (1:40 AM in Melbourne). The total travel time was 19 hours 35 minutes. Perceptual ratings of jet lag, well-being, and training and competition load were collected. To determine the impact of in-flight sleep on tournament measures, a median split was used to create subsamples based on (1) in-flight sleep quantity and (2) in-flight sleep quality (2 groups: higher vs lower). Spearman correlation coefficients were calculated to assess the bivariate associations between sleep measures, self-reported well-being, perceptual measures of jet lag, and internal training and match-day load. Results: Mean duration and efficiency of in-flight sleep bouts were 4.72 hours and 87.45%, respectively. Aggregated in-flight sleep duration was 14.64 + 3.56 hours. Players with higher in-flight sleep efficiency reported higher ratings for fatigue (ie, lower perceived fatigue) during the tournament period. Tournament sleep duration was longer, and bed and wake times were earlier compared with habitual. Compared with other nights during the tournament, sleep duration was shorter following matches. Conclusions: Maximizing in-flight sleep quality and quantity appears to have implications for recovery and sleep exhibited during competition. Sleep duration was longer than habitual except for the night of a match, which suggests that T20 matches may disrupt sleep duration

Sports Dietitians Australia Position Statement: Nutrition for Exercise in Hot Environments

It is the position of Sports Dietitians Australia (SDA) that exercise in hot and/or humid environments, or with significant clothing and/or equipment that prevents body heat loss (i.e., exertional heat stress), provides significant challenges to an athlete’s nutritional status, health, and performance. Exertional heat stress, especially when prolonged, can perturb thermoregulatory, cardiovascular, and gastrointestinal systems. Heat acclimation or acclimatization provides beneficial adaptations and should be undertaken where possible. Athletes should aim to begin exercise euhydrated. Furthermore, preexercise hyperhydration may be desirable in some scenarios and can be achieved through acute sodium or glycerol loading protocols. The assessment of fluid balance during exercise, together with gastrointestinal tolerance to fluid intake, and the appropriateness of thirst responses provide valuable information to inform fluid replacement strategies that should be integrated with event fuel requirements. Such strategies should also consider fluid availability and opportunities to drink, to prevent significant under- or overconsumption during exercise. Postexercise beverage choices can be influenced by the required timeframe for return to euhydration and co-ingestion of meals and snacks. Ingested beverage temperature can influence core temperature, with cold/icy beverages of potential use before and during exertional heat stress, while use of menthol can alter thermal sensation. Practical challenges in supporting athletes in teams and traveling for competition require careful planning. Finally, specific athletic population groups have unique nutritional needs in the context of exertional heat stress (i.e., youth, endurance/ultra-endurance athletes, and para-sport athletes), and specific adjustments to nutrition strategies should be made for these population groups