Sports performance encompasses the need to develop different cognitive and physical abilities, such as strength, power, speed, motor coordination, aerobic performance, and cognitive functions (perception, attention, memory, executive functions — inhibitory control, cognitive flexibility, decision-making —, for example). In recent years there has been growing interest in the relationship between sleep and its role in physical and cognitive performance, as well as in the mood and general health of athletes. During sleep, fundamental processes for muscle recovery occur, such as testosterone and growth hormone (GH) release and cortisol reduction. Thus, it is during sleep that athletes carry out physical and mental recovery processes.
IIn 2019, the International Olympic Committee (IOC) declared that sleep is essential for sports performance, as well as for the mental and general health of athletes (REARDON; HAINLINE; ARON; BARON et al., 2019).REARDON; HAINLINE; ARON; BARON et al., 2019This COI statement regarding quality sleep involves sleep duration (which must be at least over 7 hours), circadian alignment, sleep quality perceived as positive, and absence of sleep disturbances. Not only do they reinforce the need for specialized sleep education for athletes and coaching staff, as well as routines for screening and identifying possible sleep disorders and disorders for further treatment.
Sleep restriction leads to reduced reaction time (HURDIEL; VAN DONGEN; ARON; MCCAULEY et al., 2014),HURDIEL; VAN DONGEN; ARON; MCCAULEY et al., 2014increased subjective perception of exertion (MYLES, 1985)MYLES, 1985reduced synthesis of anabolic hormones (testosterone and growth hormone), in addition to worsening mood (ANDRADE; BEVILACQUA; COIMBRA; PEREIRA et al., 2016).ANDRADE; BEVILACQUA; COIMBRA; PEREIRA et al., 2016This scenario is unwanted by athletes. Leproult et al. demonstrated that one week of sleep restriction in young people was sufficient to reduce testosterone levels by 10-15% (LEPROULT; VAN CAUTER, 2011)LEPROULT; VAN CAUTER, 2011Milewski et al. demonstrated that athletes who sleep less than 8 hours per night have a 1.7 times greater risk of injury than athletes who sleep more than 8 hours per night (MILEWSKI; SKAGGS; BISHOP; PACE et al., 2014).MILEWSKI; SKAGGS; BISHOP; PACE et al., 2014Corroborating these results, Silva and collaborators demonstrated that athletes in a condition of sleep restriction and with poor quality of sleep are more likely to be injured and, in addition, when an injury occurs, it is likely to be more severe, causing a longer period of leave and more harm to the team (SILVA; NARCISO; SOALHEIRO; VIEGAS et al., 2020).SILVA; NARCISO; SOALHEIRO; VIEGAS et al., 2020).
However, despite this growth in research and knowledge, when compared to non-athletes, athletes have poor sleep and insufficient quantity. Furthermore, certain modalities and types of athletes are more predisposed to the onset of sleep disorders. For example, football players tend to be more likely to have obstructive sleep apnea due to their larger neck circumference (EMSELLEM; MURTAGH, 2005).EMSELLEM; MURTAGH, 2005Silva et al. evaluated 146 Olympic athletes through polysomnography and their data show that male athletes have a higher rate of apnea-hypopnea than female athletes (SILVA; NARCISO; ROSA; RODRIGUES et al., 2019).SILVA; NARCISO; ROSA; RODRIGUES et al., 2019).
Lastella et al. evaluated 124 athletes from team and individual sports, and found that the athletes had insufficient sleep (6.8 hours per night) (LASTELLA; ROACH; HALSON; SARGENT, 2015).LASTELLA; ROACH; HALSON; SARGENT, 2015Not only that, they compared the difference between team and individual sports athletes, and noticed that individual sports athletes had less total sleep time than team sports athletes, and this may be due to the different training demands between sports. These findings are in line with the results found by Sargent et al., who evaluated 70 national-level athletes through actigraphy, and found that, on average, athletes slept 6.5 hours per night (SARGENT; LASTELLA; HALSON; ROACH, 2014)SARGENT; LASTELLA; HALSON; ROACH, 2014In addition, Mah and collaborators evaluated collegiate athletes through questionnaires, and identified that the sleep of 42.4% of the athletes was classified as poor according to the Pittsburgh Sleep Quality Index (MAH; KEZIRIAN; MARCELLO; DEMENT, 2018).MAH; KEZIRIAN; MARCELLO; DEMENT, 2018Thus, these results demonstrate that it is important for the technical committee of sports teams to adopt a culture of promoting sleep quality among athletes.
Naps
Taking naps is a valid strategy to alleviate sleep debt and improve sports performance. Due to circadian factors, the best time to nap is in the afternoon, while there are 2 definitions of ideal nap duration: 20 or 90 minutes. The reason for this is that taking a 20-minute nap reduces the probability of waking up during slow-wave sleep, which would increase sleep inertia (PETIT; MOUGIN; BOURDIN; TIO et al., 2014).PETIT; MOUGIN; BOURDIN; TIO et al., 2014On the other hand, 90-minute naps are also positive as they allow the entire sleep cycle (REM and NREM) to be complete, which also reduces sleep inertia (DAVIES; GRAHAM; CHOW, 2010).DAVIES; GRAHAM; CHOW, 2010Waterhouse and collaborators found better performance in the 2 m and 20 m sprints after a 30-minute nap when compared to the condition without a nap (WATERHOUSE; ATKINSON; EDWARDS; REILLY, 2007).WATERHOUSE; ATKINSON; EDWARDS; REILLY, 2007The results of O'Donnell and collaborators demonstrate that the performance of jumping with countermovement and the perception of performance in competition, observed by the coach, improved after a nap of up to 20 minutes, when compared to the condition without a nap (O'DONNELL; BEAVEN; DRILLER, 2018).O’DONNELL; BEAVEN; DRILLER, 2018).
Causes of sleep restriction and poor sleep quality among athletes
Several factors lead to poor sleep among athletes, including pressure to perform well in competitions, constant travel, sleeping in unfamiliar rooms and with roommates, competitions too late at night or too early in the morning, jet lag, as well as pain and fatigue resulting from training and competitions. jet lag, assim como dor e fadiga decorrentes de treinos e competições.
Competitions
Lastella and collaborators evaluated 103 athletes before a competition and their results indicate that 70% of the evaluated athletes presented losses in the quality of their sleep, and the most common causes for poor quality sleep were anxiety, noise, need to use the bathroom and beginning of tests very early in the morning (LASTELLA; LOVELL; SARGENT, 2014)LASTELLA; LOVELL; SARGENT, 2014Also, some sports competitions take place at night or very early in the morning. This leads to a drag on the athletes' sleep phase, which causes losses in the quality of sleep, as well as pre- and post-competition sleep restriction. Not only, the psychological effects of competition (support and pressure to perform well) also influence the quality of sleep and, specifically in the case of night competitions, the bright lighting in stadiums contributes to the dragging of the post-competition sleep phase.
Travel and Jet lag
Elite athletes often travel to compete and are exposed to travel fatigue and jet lag jet lag. O jet lag occurs when time zones change abruptly, such as when traveling by plane across the South. Thus, there is not enough time for the organism to adapt, resulting in circadian desynchronization. Symptoms of this phenomenon include excessive daytime sleepiness, gastrointestinal disturbances, problems with concentration and attention, insomnia and impaired sleep quality (LEE; GALVEZ, 2012)LEE; GALVEZ, 2012Added to this, poor quality sleep adds to the damage observed. The literature demonstrates that it takes approximately one day to adapt to each time zone crossed (REILLY; WATERHOUSE; EDWARDS, 2005)REILLY; WATERHOUSE; EDWARDS, 2005Thus, athletes leaving Brazil to compete in Japan need, on average, 12 days to adapt to their new destination.
Travel fatigue has similar symptoms, however, unlike Jet Lag Jet Lag, , it occurs due to long hours of travel, dehydration, uncomfortable seats and poor diet during the journey. Thus, fatigue usually dissipates after a bath, adequate nutrition and a good night's sleep (SAMUELS, 2012).SAMUELS, 2012Therefore, travel fatigue occurs after long journeys, whether by air or land transport, in the North-South direction, and vice versa) while Jet Lag Jet Lag occurs after abrupt time zone changes (i.e., travel in the East-West direction, and vice versa).
Furthermore, jet lag jet lag impacta diretamente no desempenho esportivo de atletas. Diversas funções biológicas apresentam variação circadiana (para saber mais, leia https://condorinst.com/o-que-ritmo-circadiano/) e, dentre elas, o desempenho físico. Já foi demonstrado que a força, flexibilidade, percepção subjetiva de esforço, e desempenho cognitivo apresentam oscilações circadianas (DRUST; WATERHOUSE; ATKINSON; EDWARDS et al., 2005Not only, impaired sleep during jet lag jet lag can lead to problems with hormones important to sports performance, such as testosterone and growth hormone. For these reasons, it is important that the coaching staff and athletes adopt specific strategies to accelerate the process of resynchronization to the new destination, thus avoiding a reduction in sports performance at the time of competition.
Ways to assess sleep in athletes
Athletes' sleep can be evaluated through subjective measures such as questionnaires and sleep diaries, and objective measures through actigraphy and polysomnography.
Diários de sono são ferramentas úteis e funcionais ao permitir a avaliação da qualidade de sono de maneira prática e com baixo custo. Para saber mais, leia https://condorinst.com/o-que-e-diario-do-sono/.
Questionnaires are also extremely valid tools to assess athletes, mainly because they allow the assessment of numerous people in a short period of time, and this point is especially useful for large teams. A widely used questionnaire is the Pittsburgh Sleep Quality Index, which aims to assess self-reported sleep over the past 30 days. At the end, it classifies the respondent's sleep as good, bad, or bad with the possible presence of sleep disorder, as well as classifying the respondent's sleep efficiency as adequate or inadequate. In addition, a questionnaire developed specifically for athletes, the Athlete Sleep Behavior Questionnaire Athlete Sleep Behavior Questionnaire) is extremely useful when applied in conjunction with the Pittsburgh questionnaire. The ASBQ assesses and classifies the athlete's sleep behavior through the frequency of occurrence of everyday situations, such as ingesting stimulants before night training, sleeping in different rooms and using electronic devices before bed. Thus, it classifies sleep behavior as good, intermediate and bad, and with these results in hand, it is possible to design effective strategies to improve the athlete's behavior and, consequently, the quality of their sleep.
Actigraphy is a technique designed to assess sleep and biological rhythms through the actigraph. The actigraph is a device similar to a wristwatch and contains a light sensor and a movement sensor, and through these sensors it is possible to extract information about sleep, such as total sleep time, latency to sleep onset, sleep efficiency, awakenings after sleep onset and wakefulness, as well as sleep start and end times. In addition, the actogram, a graphic generated from the reading of the actigraph data, allows the identification of the moments of beginning and end of sleep more clearly, thus making it possible to trace strategies regarding the movement and regularity of that athlete's sleep-wake cycle. In addition, Condor offers in our software the possibility to analyze specific variables related to the biological rhythm, such as the periodogram, consinor and spectrogram.
Conclusion
Sleep plays a key role in the physical and cognitive recovery of athletes, and restricting it or not achieving a satisfactory quality of sleep leads to worse reaction time, mood and cognitive performance, as well as a higher probability of injury. However, athletes often have poor sleep and insufficient quantity, and the causes that lead to this unwanted sleep are diverse. Therefore, it is important that the technical committee adopt preventive strategies related to the sleep of athletes, with the aim of educating, raising awareness and evaluating them, so that aspects that can be improved both in the routine and in the health of these athletes are identified.
