Article

The Impact of Circadian Phenotype and Time since Awakening on Diurnal Performance in Athletes

Authors:
If you want to read the PDF, try requesting it from the authors.

Abstract

Circadian rhythms, among other factors, have been shown to regulate key physiological processes involved in athletic performance [1-7]. Personal best performance of athletes in the evening was confirmed across different sports [8-12]. Contrary to this view, we identified peak performance times in athletes to be different between human "larks" and "owls" (also called "morningness/eveningness types" [13] or "chronotypes" [14] and referred to as circadian phenotypes in this paper), i.e., individuals with well-documented genetic [15-20] and physiological [21-24] differences that result in disparities between their biological clocks and how they entrain to exogenous cues, such as the environmental light/dark cycle and social factors. We found time since entrained awakening to be the major predictor of peak performance times, rather than time of day, as well as significant individual performance variations as large as 26% in the course of a day. Our novel approach combining the use of an athlete-specific chronometric test, longitudinal circadian analysis, and physical performance tests to characterize relevant sleep/wake and performance parameters in athletes allows a comprehensive analysis of the link between the circadian system and diurnal performance variation. We establish that the evaluation of an athlete's personal best performance requires consideration of circadian phenotype, performance evaluation at different times of day, and analysis of performance as a function of time since entrained awakening. VIDEO ABSTRACT: Copyright © 2015 Elsevier Ltd. All rights reserved.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

... Broader literature has found that time of day impacts sporting performance and is influenced by factors such as habitual training time, 14,15 circadian rhythm, 11,[16][17][18] and various other factors. Because many components of sports performance fluctuate with time of day, examining circadian rhythms in performance parameters is a useful way of measuring when different performance components may peak. ...
... 12 One mediating factor that may play a role is chronotype which can result in interindividual differences in circadian rhythmicity and consequently performance. 9,14,16 Certain individuals present extreme chronotypes where their performance and behaviour show an inclination to morningness or eveningness. 16,27 They experience peaks and troughs in accordance with their own circadian physiological markers as opposed to environmental triggers, and so may experience peaks in performance at different times of the day. ...
... 9,14,16 Certain individuals present extreme chronotypes where their performance and behaviour show an inclination to morningness or eveningness. 16,27 They experience peaks and troughs in accordance with their own circadian physiological markers as opposed to environmental triggers, and so may experience peaks in performance at different times of the day. 16,27 Best performance times have been found to differ significantly between chronotypes. ...
Article
Full-text available
The game of cricket is played at various times of the day and no studies have investigated the time of day effects on perceptual, physical and performance measures of cricketers. Therefore, the purpose of this study was to focus on adolescent fast bowlers and their responses when bowling at different times of the day. First team, adolescent male fast bowlers (N = 5, Mean age 17.00 ± 0.55 years; stature 185.2 ± 6.5 cm and mass 86.06 ± 17.56 kg) were required to complete a fast-bowling simulation protocol whereby perceptual, physical and bowling-specific performance measures were tested at three different times of day (10:30, 14:30, 18:30). Over all the spells over one was significantly slower than all the other overs. There were no significant changes in bowling speed between the time intervals. However, there was a large increase in bowling speed at 14:30 compared to 10:30 (ES – 1.25) and a moderate increase in bowling speed (ES = 0.67) between 10:30 and 18:30. There was no significant change in accuracy at the different time intervals although it was best at 10:30 followed by 18:30 although the latter had a greater variance. In conclusion, this investigation found time of day did not significantly impact the responses, but the effects sizes show that bowling accuracy was worst at 14:30 despite the other parameters, such as speed of delivery, being best at this time, which may suggest a speed-accuracy trade-off. Additionally, both 10:30 and 18:30 were found to be times conducive to bowling performance with regards to accuracy.
... The test result indicated after analysis of chronotype and time interaction that the rowing speed of M-types slowed significantly by 4.8 s from AM to PM session and showed a larger decrement compared to E-types and N-types while rowing speed of E-types increased by an average 1.9 s from morning to evening. Childs et al. [32], in the study, evaluated the effect of chronotypes on the athlete's physical performance using the BLEEP test in hockey players. 20 hockey players with an average age of 20.4 years were classified as M-types, N-types and E-types using the MEQ test. ...
... The athletes were grouped as M-types, E-types, and N-types using the Horne and Ostberg Morningness and Eveningness Questionnaire in the majority of the studies, 11 out of 13 [14,[25][26][27][28][29][30][31][32][33][34][35] while the other 2 studies [24,32] used the RBUB chronometric test depending upon the scores then after the athletic tests were used to analyze the effect of chronotype over the performance. The RBUB chronometric test is better developed version of the chronometric test which takes into account both the Horne-Ostberg Morningness and Eveningness Questionnaire and the Munich Chronotype Questionnaire. ...
... The athletes were grouped as M-types, E-types, and N-types using the Horne and Ostberg Morningness and Eveningness Questionnaire in the majority of the studies, 11 out of 13 [14,[25][26][27][28][29][30][31][32][33][34][35] while the other 2 studies [24,32] used the RBUB chronometric test depending upon the scores then after the athletic tests were used to analyze the effect of chronotype over the performance. The RBUB chronometric test is better developed version of the chronometric test which takes into account both the Horne-Ostberg Morningness and Eveningness Questionnaire and the Munich Chronotype Questionnaire. ...
Article
Full-text available
IntroductionThe individual differences in exogenous and endogenous factors influence the various physiological and psychological processes related to athletic performance. The chronotypes reflect innate variation, which is essential to consider for obtaining significant outcomes in sports competitions and optimizing adequate recovery during rehabilitation following an injury. This systematic review aims to investigate the effect of chronotypes on athletic performance in the athletic population.Method The literature search for this review was carried out till 30th June 2021 from the following electronic databases—PubMed and Scopus about PRISMA guidelines. Randomized controlled trials and crossover studies consisting of the effect of chronotype on athletic performance in athletes irrespective of age and gender and having full text available in the English language were included while unpublished, Ph.D. thesis and duplicates were excluded.ResultInitially 936 articles were identified from electronic search and out of the 13 studies (PEDro score = 7.8) meet the inclusion criteria. Most of the studies (12 out of 13) demonstrated a significant influence of chronotype over athletic performance based on outcomes of the various physical performance test.Conclusion The present systematic review demonstrates that chronotypes affect the athletic performance. Twelve out of 13 were found to have a significant effect of chronotypes on athletic performance.
... cold vs. hot environments), and time-of-day effects on physical performance vary 8,13,14 . Additionally, variations in chronotype (which describes an individual's biological optimal timing for activity and sleep), relate to substantial variations in peak performance time 15,16 . ...
... Internal clock time also influences physical performance, causing early chronotypes to perform best around mid-day, intermediate chronotypes around mid-afternoon, and late chronotypes in the evening 16 . It is therefore possible that morning races benefit early types, while evening races benefit later types. ...
... Swim training times are often scheduled in the early morning, therefore a selection bias towards earlier chronotypes can exist, as has been determined in other sports 21 . Later chronotypes are also associated with more diurnal variation in performance, which might cause an additional selection pressure towards earlier chronotypes, particularly in Olympic athletes 16 . The optimal performance peak in finish times analyzed here occurs relatively early compared to the peak in CBT timing 1,22,23 , which may indicate an over-representation of early chronotypes (with earlier CBT peak times) among Olympic swimmers. ...
Article
Full-text available
Abstract The circadian system affects physiological, psychological, and molecular mechanisms in the body, resulting in varying physical performance over the day. The timing and relative size of these effects are important for optimizing sport performance. In this study, Olympic swim times (from 2004 to 2016) were used to determine time-of-day and circadian effects under maximal motivational conditions. Data of athletes who made it to the finals (N = 144, 72 female) were included and normalized on individual levels based on the average swim times over race types (heat, semifinal, and final) per individual for each stroke, distance and Olympic venue. Normalized swim times were analyzed with a linear mixed model and a sine fitted model. Swim performance was better during finals as compared to semi-finals and heats. Performance was strongly affected by time-of-day, showing fastest swim times in the late afternoon around 17:12 h, indicating 0.32% improved performance relative to 08:00 h. This study reveals clear effects of time-of-day on physical performance in Olympic athletes. The time-of-day effect is large, and exceeds the time difference between gold and silver medal in 40%, silver and bronze medal in 64%, and bronze or no medal in 61% of the finals.
... Kline et al. (2007) demonstrated that performance is associated with the time of the individual's lowest body temperature, which is an important marker of circadian phenotype. Similarly, other studies have shown individual internal time setting to be a predictor of peak time for cognitive and physical performance (Facer-Childs et al. 2018;Facer-Childs and Brandstaetter 2015). ...
... To assess the individual's performance capacity, we selected physiological variables that reflected the magnitude of physical effort expended to complete the task and might be affected by the time of day and season. Specifically, diurnal variations have been shown for VO 2 max (Hill et al. 1988), performance times (PT) of M-and E-type athletes (Brown et al. 2008;Facer-Childs and Brandstaetter 2015;Henst et al. 2015;Rae et al. 2015), peak power (POWERmax) in the Wingate test (Hill and Chtourou 2020), and heart rate recovery rate (HRR) (Sugawara et al. 2001). In addition to these variables, we measured maximal heart rate (HRmax), maximal carbon dioxide production (VCO 2 max), maximal ventilation (VEmax), anaerobic threshold (AT) onset, and maximal metabolic rate (MRmax) during maximal workload spiroergometry, which have either not been reported to show diurnal differences or not previously studied in this regard. ...
... Based on the data, we can conclude that E-types show significantly greater performance capacity in the evening compared to the morning. This corresponds to the results published previously (Brown et al. 2008;Facer-Childs et al. 2018;Facer-Childs and Brandstaetter 2015). The question arises whether the observed changes reflect the cardiovascular system's better capacity in the evening or higher motivation and lower subjective rating of physical exertion in the E-types as described before (Mulè et al. 2020;Vitale and Weydahl 2017). ...
Article
Circadian clocks regulate multiple physiological domains from molecular to behavioral levels and adjust bodily physiology to seasonal changes in day length. Circadian regulation of cellular bioenergy and immunity in the cardiovascular and muscle systems may underpin the individual diurnal differences in performance capacity during exercise. Several studies have shown diurnal differences in cardiopulmonary parameters at maximal and submaximal workloads in morning and evening circadian human phenotypes. However, the effect of seasons on these changes was not elucidated. In this study, we recruited subjects with Morningness–Eveningness Questionnaire scores corresponding to morning and evening types. Subjects underwent morning (7:00–9:00) and evening (20:00–22:00) maximal workload spiroergometry in both winter and summer seasons. We analyzed their performance time, anaerobic threshold, heart rate, and respiratory parameters. Our results suggest that evening types manifest diurnal variations in physical performance, particularly in winter. They also have slower heart rate recovery than morning types, irrespective of the time of day or season. Compared to winter, the chronotype effect on the magnitude of morning–evening differences in performance time, maximal heart rate, and anaerobic threshold onset was more significant in summer. Our data are in concordance with previous observations and confirm the difference between morning and evening types in the timing of maximum performance capacity.
... It has been suggested that chronotype influences sports performance, particularly amongst elite athletes (Vitale & Weydahl, 2017). Furthermore, there is potentially an interaction between chronotype and time of day that affects task performance meaning peak athletic performance occurs at different times of day between chronotypes (Facer-Childs & Brandstaetter, 2015). For example, ECTs have been shown to perform better at simple tasks (e.g., psychomotor vigilance, and grip strength) in the morning than LCTs (Facer-Childs et al., 2018). ...
... Researchers have suggested that the time of day when peak athletic performance occurs could be moderated by chronotype (Facer-Childs & Brandstaetter, 2015;Facer-Childs et al., 2018), and identifying inter-individual differences in circadian rhythmicity could prove valuable when planning training schedules (Vitale & Weydahl, 2017). However, 79% of practitioners in the present study had not attempted to determine their athletes' chronotype. ...
... However, 79% of practitioners in the present study had not attempted to determine their athletes' chronotype. Given that chronotype can be assessed using simple validated questionnaires, such as the Morningness-Eveningness Questionnaire (MEQ) and the Munich Chronotype Questionnaire (MCTQ), chronotype assessment could present an opportunity for practitioners to individualise schedules to minimise circadian disruption, enhance performance (Facer-Childs & Brandstaetter, 2015;Lastella et al., 2015), improve the reliability of performance/recovery assessments (Brown et al., 2008), and optimise sleep (Samuels, 2012). ...
Article
Full-text available
Achieving adequate sleep is considered important for athletic performance and recovery from exercise, yet the sleep monitoring methods applied amongst practitioners within high-performance sport are not well documented. This study aimed to identify the athlete sleep monitoring practices currently being implemented by practitioners working with full-time, junior (competing at the highest level), and semi-professional athletes. An online survey was developed and disseminated via email and social media to practitioners working with high-performance athletes. A sample of 145 practitioners completed the survey. Most (88%) practitioners rated sleep as 'extremely important' for recovery and performance (79%) and 84% of practitioners had advised athletes on improving sleep. The practitioners who reported monitoring sleep used several methods, including a questionnaire (37%), diary (26%) and actigraphy (19%). The most cited barrier to monitoring sleep was lack of time/resources. Most (79%) practitioners had not determined athletes' chronotypes. Over half (54%) of the practitioners suggested their athletes did not get enough sleep outside of competition periods; the highest ranked suggested reason for this was screen time (i.e., using electronic devices). Practitioners recognise the importance of sleep for athletes and sleep education/monitoring was common amongst the practitioners; however, chronotype analysis was not widely used. Most practitioners used questionnaires and diaries to monitor athletes' sleep and suggested that their athletes often experience insufficient sleep outside of competition periods.
... However, individual differences have been identified and are most readily observed in the predisposition for earlier or later sleep patterns. These differences are often termed as one's chronotype [14]. Misalignment between these rhythms and the external environment often occurs as a consequence of differences in sleep timing between workdays and free days, and has been termed "social jetlag" [15]. ...
... This could reflect early chronotypes having the ability to self-select when not constrained to fixed schedules. Since the timing of exercise has been shown to help facilitate circadian adaptation [29] and the time of peak performance is influenced by chronotype [14], these changes further support the need for taking into account individual (chronotype) factors when scheduling training and preparing for competition, especially within the elite sector. ...
... Around 35% of the general population are evening types [32], who are particularly vulnerable to disruption of sleep and higher social jetlag. This is due to a chronic and recurrent mismatch between the internal circadian system, sleep-wake behavior, and social schedules, which impacts physical and cognitive performance, general health, and wellbeing [14,33]. Our results also show that all of these factors (later mid-sleep, higher social jetlag, and longer sleep latency) are associated with poorer mental health outcomes. ...
Article
Full-text available
The global coronavirus 19 (COVID-19) pandemic and associated lockdown restrictions resulted in the majority of sports competitions around the world being put on hold. This includes the National Basketball Association, the UEFA Champions League, Australian Football League, the Tokyo 2020 Olympic Games, and regional competitions. The mitigation strategies in place to control the pandemic have caused disruption to daily schedules, working environments, and lifestyle factors. Athletes rely on regular access to training facilities, practitioners, and coaches to maintain physical and mental health to achieve maximal performance and optimal recovery. Furthermore, participation in sport at any level increases social engagement and promotes better mental health. It is, therefore, critical to understanding how the COVID-19 pandemic and associated lockdown measures have affected the lives of athletes. We surveyed elite and sub-elite athletes (n = 565) across multiple sports. Significant disruptions were reported for all lifestyle factors including social interactions, physical activity, sleep patterns, and mental health. We found a significant increase in total sleep time and sleep latency, as well as a delay in mid-sleep times and a decrease in social jetlag. Training frequency and duration significantly decreased. Importantly, the changes to training and sleep-related factors were associated with mental health outcomes. With spikes in COVID-19 cases rising around the world and governments reinstituting lockdowns (e.g. United Kingdom; Melbourne, Australia; California, USA) these results will inform messaging and strategies to better manage sleep and mental health in a population for whom optimal performance is critical.
... Chronotype, also termed morningness-eveningness, is usually defined as a continuum between extreme morningness and extreme eveningness, with three chronotypes distinguished: the morning ('larks', M-type), the evening ('owls', E-type), and the neither type (N-type) in between them 5 . The M-type individuals, in contrast to the E-types, wake up and perform mentally and physically (including athletic performance) at their best in the earlier (morning) hours and they find it difficult to stay awake in the late-night hours 6,7 . Humans around the university students age are characterized by a tendency towards eveningness, which can cause decreased sleep duration if this clashes with the morning start of university activities 8 . ...
... Physical activity can help to recover after sleep disruption, but its effects depend on the timing of exercise 12 . Facer-Childs and Brandstaetter (2015) 7 indicated that chronotype and wake-up time are significant determinants of sport performance. In their study, E-types, compared to M-types, needed more time after waking up to prepare for a sports activity. ...
Article
Objective: The aim of this paper was to test how sport participation and chronotype affect objectively measured sleep timing parameters on workdays. Material and methods: The sample included 82 student athletes and 40 non-athletes who completed three-day wrist actigraphy monitoring and the Polish version of the Morningness-Eveningness Questionnaire. Results: Eveningness predicted later timing of falling asleep and mid-sleep, but not the wake-up time. Student athletes had earlier wake-up time and shorter sleep duration than non-athletes. Discussion: The results support the view that university students suffer insufficient sleep, especially those participating in extensive sport activity.
... Chronotype, also termed morningness-eveningness, is usually defined as a continuum between extreme morningness and extreme eveningness, with three chronotypes distinguished: the morning ('larks', M-type), the evening ('owls', E-type), and the neither type (N-type) in between them 5 . The M-type individuals, in contrast to the E-types, wake up and perform mentally and physically (including athletic performance) at their best in the earlier (morning) hours and they find it difficult to stay awake in the late-night hours 6,7 . Humans around the university students age are characterized by a tendency towards eveningness, which can cause decreased sleep duration if this clashes with the morning start of university activities 8 . ...
... Physical activity can help to recover after sleep disruption, but its effects depend on the timing of exercise 12 . Facer-Childs and Brandstaetter (2015) 7 indicated that chronotype and wake-up time are significant determinants of sport performance. In their study, E-types, compared to M-types, needed more time after waking up to prepare for a sports activity. ...
Article
Full-text available
Objective: The aim of this paper was to test how sport participation and chronotype affect objectively measured sleep timing parameters on workdays. Material and Methods: The sample included 82 student athletes and 40 non-athletes who completed three-day wrist actigraphy monitoring and the Polish version of the Morningness-Eveningness Questionnaire. Results: Eveningness predicted later timing of falling asleep and mid-sleep, but not the wake-up time. Student athletes had earlier wake-up time and shorter sleep duration than non-athletes. Discussion: The results support the view that university students suffer insufficient sleep, especially those participating in extensive sport activity.
... Daily circadian rhythmical oscillations occur in several physiological and behavioral functions that contribute to athletic performance (e.g., body temperature and cortisol concentration) [1][2][3]. Previous studies report a clear circadian rhythm in sports performance with oxygen uptake, peak power, and mean power during a 30 s Wingate test [4], isometric knee extensor strength [5], and aerobic endurance during a 20 m multistage shuttle run test [6] all being affected by the time of day. In this sense, the acrophase of body temperature has been identified to be concurrent with peaks in physical capacities such as muscular strength [5] and anaerobic power [4,7], which peak in the evening. ...
... In this sense, the physical movements performed during basketball games are dependent on players possessing adequate strength, power, anaerobic capacity, and aerobic capacity [18]. In turn, strength [5], power [1], anaerobic capacity [19], and aerobic capacity [6] have been shown to vary across the day which, in turn, may affect individual performance in basketball. However, these physical attributes are not indicative of game outcome or in-game performance in basketball and, therefore, other measures require consideration in chronotype studies. ...
Article
Full-text available
Sport-specific skills display diurnal variation across various team sports such as badminton and tennis serving accuracy and soccer dribbling, volleying, and chipping execution. However, the effects of athlete chronotype on in-game sport-specific skill performance according to time of day across team sports is not well understood. Therefore, the aim of this study was to identify the effect of player chronotype on in-game basketball performance during evening games. Professional male basketball players (n = 11) completed a morningness–eveningness questionnaire and were categorized according to chronotype (morning-type: n = 4; neither-type: n = 6; evening-type: n = 1). Box score data from the 2019/20 season were utilized to determine individual in-game performance during evening games played after 18:00 h. Composite metrics (i.e., effective field goal percentage, offensive rating, defensive rating, and player efficiency) were used as indicators of player performance. Non-significant (p ≥ 0.21) differences were evident between M-types and N-types for most performance measures. Small to very large effects were observed in the number of rebounds favoring M-types, and three-point shots attempted and made, assists, and steals favored N-types. In-game performance appeared to not be affected by chronotype (i.e., M-type vs. N-type) in evening games among professional male basketball players. The lack of observed effect between chronotype and in-game performance suggest coaching staff may not need to consider player chronotype when developing a match strategy or assigning player roles if largely dealing with M-types and N-types. However, to ensure the greatest specificity, coaching staff may endeavor to schedule habitual training times in line with that of competition in an effort to align player circadian rhythms to games.
... Evening types generally wake up and go to bed later than morning types. They will not reach maximum performance levels as quickly after wake-up as morning types (Facer-Childs et al. 2018;Facer-Childs and Brandstaetter 2015). Activity acrophases , nadirs of core temperatures (Baehr et al. 2000;Morgrain et al. 2004), dim light melatonin onset (Mongrain et al. 2004;Taillard et al. 2011), and melatonin peak (Taillard et al. 2011) are delayed 2-3 h in evening types compared to in morning types. ...
... They found the distribution of the chronotype of athletes was skewed toward morning type as compared to non-athlete controls. In another study, Facer-Childs et al. (2015) used the RB-UB chronometric test to demonstrate that the peak performance time of the bleep test varied with the chronotype of an athlete. Our research simply focused on the distribution of the chronotype of athletes evaluated by the rMEQ and MCTQ, and does not address which questionnaire fits best for elite athletes. ...
Article
This study aimed to test in elite athletes the correlation between the chronotype determined by the reduced version of the Morningness-Eveningness Questionnaire (rMEQ) and that determined by the Munich ChronoType Questionnaire (MCTQ). In total, 351 elite athletes filled out the rMEQ questionnaire, 59 athletes filled out the MCTQ questionnaire, and 39 athletes filled out both questionnaires. The rMEQ score and the corrected midpoint of sleep from the MCTQ correlated weakly (|r| = 0.360, p < .05); however, some cases were mismatched. The MSFsc also weakly correlated with age (|r| = 0.374, p < .05), while rMEQ did not. Our results may suggest that the choice of questionnaire to determine chronotype should depend on the purpose and the type of sport athlete.
... The time-of-day effect is generated by the interaction between the homeostatic process and the circadian rhythm, and further influences an individual's performance of different tasks to reach peak and low levels at different times of the day (Di Cagno et al. 2013;Facer-Childs et al. 2018;Hölzle et al. 2014;Ivanov et al. 2007). In general, human performance across various domains has been shown to be influenced by the time-of-day effect and may peak at different times of the day, such as better attention and short-term memory in the morning, higher mood and better eye-hand coordination in the afternoon, and better cardiopulmonary efficiency in the evening (Craig et al. 2003;Facer-Childs and Brandstaetter 2015). Of particular interest, previous studies have also identified a significant time-of-day effect on different movement parameters involving both cognitive and physiological performance (Carrier and Monk 2000;Di Cagno et al. 2013;Golombek et al. 2013). ...
... In order to address the issue regarding accurate motor assessment, it is critical to identify if overall motor coordination would be affected by the time-ofday effect and when the best or worst performance appears. Furthermore, as previous studies have demonstrated the potential impact of physical activity (Stodden et al. 2008), chronotype (Di Cagno et al. 2013;Facer-Childs and Brandstaetter 2015), and time-sinceawakening (Hines 2004) on motor performance, these factors should be also taken into account while interpreting the potential time-of-day effect on motor coordination. To the best of our knowledge, no study has employed a standardized test to explore this potential to inform the best time to administer a motor assessment. ...
Article
The evaluation of motor coordination is important for diagnosing children and adolescents with motor impairments. However, motor coordination may be affected by time-of-day effects, and thus, the intra-day variation could subsequently influence the assessment accuracy of the standardized test used in the diagnostic process. To the best of our knowledge, no study has been conducted to examine this possibility. Therefore, the purpose of this study was to investigate the time-of-day effect on motor coordination. A convenience sample of 25 youth (17-21 years) were recruited from local high schools and a local university. The Bruininks-Oseretsky Test of Motor Proficiency - Second Edition (Short Form) was administered at three different times (morning, noon, and afternoon) over three days to explore the potential time-of-day effect on motor coordination. The starting time of the test on the first day was counterbalanced. Other factors that could potentially impact motor performance were also measured, including physical activity, chronotype, and time-since-awakening. A statistically significant main effect of time-of-day was found on overall motor coordination (p< .01) and the domain of Manual Coordination (p< .01). The time-of-day effect on the domain of Strength & Agility (p = .055) was just above the threshold of statistical significance. Further analysis showed that overall motor coordination was better at noon (p< .01) and in the afternoon (p= .052) than in the morning, whereas manual coordination was the worst in the morning (p's < .01). Strength and agility were also significantly better at noon than in the morning (p< .01). In addition, poor motor coordination in the morning was also related to longer time-since-awakening. Overall, this study identifies the time-of-day effect on motor coordination that could lead to the inconsistent classification of motor performance. Therefore, in order to avoid the potential misclassification of motor coordination, health professionals should take into account the time-of-day effect on motor coordination and the possible impact of time-since-awakening while administering the assessment in the morning.
... Similarly, in metabolically compromised humans, training in the afternoon had greater benefits on metabolic parameters like peripheral insulin sensitivity, adipose tissue lipolysis, fasting plasma glucose levels, exercise performance and fat mass (Savikj et al., 2019;Mancilla et al., 2021). However, these circadian fluctuations in peak endurance and strength performance cannot be replicated in all human studies, alluding to a much more complicated and multifactorial relationship between circadian rhythmicity of central and peripheral clocks, environmental and lifestyle factors including sleep, nutrition, psychological aspects, ambient temperature and ultimately muscle function (Facer-Childs and Brandstaetter, 2015;Aoyama and Shibata, 2020). Individual variance in biological clocks and preference for either morning/ evening can be used to classify circadian phenotypes into early/intermediate/late chronotypes (ECT/ICT/LCT) (Duglan and Lamia, 2019). ...
... Individual variance in biological clocks and preference for either morning/ evening can be used to classify circadian phenotypes into early/intermediate/late chronotypes (ECT/ICT/LCT) (Duglan and Lamia, 2019). For example, peak performance depends not only on time-of-day but also on chronotype and time since entrained waking, with ECTs performing better in early-afternoon and LCTs in late-evening (Facer-Childs and Brandstaetter, 2015). Regular training at a particular time-ofday can entrain performance leading to greater adaptations at that time (Kusumoto et al., 2021). ...
Article
Full-text available
Circadian rhythms regulate a host of physiological processes in a time-dependent manner to maintain homeostasis in response to various environmental stimuli like day and night cycles, food intake, and physical activity. Disruptions in circadian rhythms due to genetic mutations, shift work, exposure to artificial light sources, aberrant eating habits, and abnormal sleep cycles can have dire consequences for health. Importantly, exercise training efficiently ameliorates many of these adverse effects and the role of skeletal muscle in mediating the benefits of exercise is a topic of great interest. However, the molecular and physiological interactions between the clock, skeletal muscle function and exercise are poorly understood, and are most likely a combination of molecular clock components directly acting in muscle as well as in concordance with other peripheral metabolic organ systems like the liver. This review aims to consolidate existing experimental evidence on the involvement of molecular clock factors in exercise adaptation of skeletal muscle and to highlight the existing gaps in knowledge that need to be investigated to develop therapeutic avenues for diseases that are associated with these systems.
... Endogenously driven, circadian rhythms govern a wide range of physiological processes involved in athletic recovery and performance (Facer-Childs and Brandstaetter, 2015;Simmons et al., 2022). These rhythms are synchronized to the 24-h environment via the light-dark cycle and behavioral cycles such as eating or drinking (Stephan, 2002;Roenneberg et al., 2013;Asher and Sassone-Corsi, 2015;Wehrens et al., 2017;Lewis et al., 2018). ...
... For example, westward travel was negatively associated with winning percentages in the National Basketball Association (NBA) (McHill and Chinoy, 2020), National Hockey League (NHL), and National Football League (NFL) (Roy and Forest, 2018) and eastward travel was positively associated with winning percentages in MLB (Winter et al., 2009). However, individual variability in circadian phenotype has been shown to result in different diurnal physiological and performance profiles, which may skew results that do not account for these differences (Facer-Childs and Brandstaetter, 2015;Facer-Childs et al., 2018). ...
Article
Full-text available
Objectives: Elite athletes are often required to travel across time zones for national and international competitions, causing frequent jet lag. The aim of this study was to examine whether the direction of travel-related jet lag is associated with performance in the National Basketball Association (NBA), and if so, to explore potential mechanisms. Methods: Ten seasons comprising of 11,481 games of NBA data from the 2011/2012 to the 2020/2021 regular season were analyzed using multi-level mixed models with one fixed factor (three levels; jet lag direction: eastward vs westward vs no jet lag) and three random factors (team, opponent, game time). Predicted circadian resynchronization rate was accounted for, and home and away games were analysed separately. Mediation analyses were performed to examine potential mechanisms. Results: Among home teams, eastward (but not westward) jet lag was associated with reduced winning (Δ (i.e., change) = −6.03%, p = 0.051, marginal), points differential (Δ = −1.29 points, p = 0.015), rebound differential (Δ = −1.29 rebounds, p < 0.0001), and effective field goal percentage differential (Δ = −1.2%, p < 0.01). As the magnitude of eastward jet lag increased, home team points differential decreased (2 h Δ = −4.53 points, p < 0 . 05; 1 h Δ = −0.72 points, p = 0.07). No significant associations were found between jet lag and away team performance. Conclusion: Eastward jet lag was associated with impaired performance for home (but not away) teams. Sleep and circadian disruption associated with advancing phase following eastward travel may have significant adverse consequences on performance in the NBA, particularly when recovery time is limited. Sports organisations could consider chronobiology-informed scheduling and interventions to maximise recovery and performance of their athletes.
... The ASSQ evaluates both sleep and circadian factors related to sleep quantity, sleep quality, sleep timing, insomnia, sleep-disordered breathing, and sleep disturbance related to travel, during the recent past. Five items are used to calculate a 'sleep difficulty score' which classifies athletes into a category of clinical sleep problem; from no problem (score 0-4), to mild (score 5-7), to moderate (score 8-10) and severe (score [11][12][13][14][15][16][17]. Those categorized in the no and mild clinical sleep problem categories are deemed to not need further sleep assessment from a sleep professional but instead require education and monitoring [29]. ...
... The questions are multiple choice, framed in a preferential manner, with each answer providing a value from 0 to 6. The items are summed give a final score ranging between 16 ...
Article
Full-text available
Objectives: Limited research has been conducted on sleep problems in elite athletes at international competition, and how this relates to their general health and well-being. Methods: Sixty-five elite international athletes (37 males, 28 females, 21.8 ± 2.1 years) from different sports completed validated sleep (Athlete Sleep Screening Questionnaire), health (Subjective Health Complaints Inventory) and well-being (Sports Profile of Mood States) questionnaires; 1 month pre-competition, at the end of international competition, and 1 month post-competition. Results: Twenty-three percent of the elite athletes were identified as having a moderate or severe clinically significant sleep problem during competition, with 82% reporting less than 8 h of sleep per night. Athletes with a moderate or severe clinically significant sleep problem during competition had significantly greater general health complaints (p = 0.002), mood disturbance (p = 0.001) and poorer sleep hygiene (p = 0.002). Swimmers had more sleep difficulty pre and during competition compared to athletics and soccer (p = 0.009). Conclusion: Sleep disturbance during international competition is common and associated with poorer health and lower mood. Swimmers may be more at risk of sleep difficulty pre and during competition compared to those competing in athletics and soccer. Sleep services may be required to support elite athletes at international competition. ARTICLE HISTORY
... Could chronobiology make the difference between winning and losing for elite athletes? example, field data demonstrate a variation in performance (measured by cardiovascular endurance) of up to 26% depending on the time of day of tasks and an individual's circadian phenotype (Facer-Childs and Brandstaetter, 2015a). To put this data into perspective, a change in performance by 0.5% in the 2016 Olympics 100 m freestyle swimming event was the difference between fourth place and a gold medal, and a 2.5% increase in performance would have secured a gold medal, over Usain Bolt, for the last-placed runner in the 100 m sprint. ...
Article
Full-text available
Timing is everything. It allows us to anticipate the best time to conserve energy, identify the time of peak performance, recognise when attention may be sub-optimal, and find the most effective time for nutritional intake. The study of timing and cyclic phenomena in humans is termed human chronobiology (chrono= time) and has many implications for the elite athlete.
... Could chronobiology make the difference between winning and losing for elite athletes? example, field data demonstrate a variation in performance (measured by cardiovascular endurance) of up to 26% depending on the time of day of tasks and an individual's circadian phenotype (Facer-Childs and Brandstaetter, 2015a). To put this data into perspective, a change in performance by 0.5% in the 2016 Olympics 100 m freestyle swimming event was the difference between fourth place and a gold medal, and a 2.5% increase in performance would have secured a gold medal, over Usain Bolt, for the last-placed runner in the 100 m sprint. ...
Article
A popular science article about field-based ecophysiology and technological advances. https://www.physoc.org/magazine-articles/ecophysiology-and-climate-change/
... The chronotype can alternatively be determined from sleep parameters 6 . In the sports context, assessment of the circadian phenotype has covered runners of different levels 7,8 , professional rugby players 9 , cyclists 10 , swimmers 11 , collegiate rowers 12 and hockey and soccer players 13,14 . ...
Article
Full-text available
Abstract Aim: The aims of the present study were to verify the self-perception level of the chronotype of amateur street runners and to test the association between the chronotype, gender, age, and preferred training time. Methods: A total of 166 amateur street runners were included (♀ = 89, age 38.9 ± 11.2 years; ♂ = 77, age 38.0 ± 9.7 years). The Brazilian version of the Horne & östberg questionnaire was used to assess chronotypes and the preferred training time was determined through a multiple choice question. Based on chronotype definitions that suggest that when free to choose, morning-types (MT) would prefer training in the morning, evening-types (ET) in the evening and neither-types (NT) would not have a predilection for any specific time. The corroboration of this hypothesis was assumed as self-perception level of the chronotypes. Results: Women showed higher self-perception levels of their chronotype compared to men (58.4% vs. 41.6%; χ2 = 4.699; p = 0.030). By chronotypes, MT, NT, and ET self-perception levels were 73.9%, 15.9%, 88.9%, respectively (χ2 = 57.489; p < 0.001). The most observed women circadian typology was MT, while in men it was NT (χ2 = 8.951; p = 0.011). However, there was no significant association between gender and preferred training time (χ2 = 2.654; p = 0.265). Age, female gender and preference to exercise during the day are associated with MT. Conclusion: Women runners showed a greater perception of their circadian traits than men, despite there was no association between gender and preferred training time.
... In addition to physiological artefacts e.g., head motion, cardiac activity and respiratory rate, failing to consider individual differences in circadian timing and behaviour could lead to misinterpretation of results. This is especially important since there are clear diurnal differences in physiology and performance between ECPs and LCPs (Baehr et al., 2000;Burgess and Fogg, 2008;Facer-Childs and Brandstaetter, 2015;Facer-Childs et al., 2018;Facer-Childs et al., 2020). ...
Article
Full-text available
Background Functional connectivity (FC) of the motor network (MN) is often used to investigate how intrinsic properties of the brain are associated with motor abilities and performance. In addition, the MN is a key feature in clinical work to map the recovery after stroke and aid the understanding of neurodegenerative disorders. Time of day variation and individual differences in circadian timing, however, have not yet been considered collectively when looking at FC. Methods A total of 33 healthy, right handed individuals (13 male, 23.1 ± 4.2 years) took part in the study. Actigraphy, sleep diaries and circadian phase markers (dim light melatonin onset and cortisol awakening response) were used to determine early (ECP, n =13) and late (LCP, n = 20) circadian phenotype groups. Resting state functional MRI testing sessions were conducted at 14:00 h, 20:00 h and 08:00 h and preceded by a maximum voluntary contraction test for isometric grip strength to measure motor performance. Results Significant differences in FC of the MN between ECPs and LCPs were found, as well as significant variations between different times of day. A higher amplitude in diurnal variation of FC and performance was observed in LCPs compared to ECPs, with the morning being most significantly affected. Overall, lower FC was significantly associated with poorer motor performance. Discussion Our findings uncover intrinsic differences between times of day and circadian phenotype groups. This suggests that central mechanisms contribute to diurnal variation in motor performance and the functional integrity of the MN at rest influences the ability to perform in a motor task.
... Could chronobiology make the difference between winning and losing for elite athletes? example, field data demonstrate a variation in performance (measured by cardiovascular endurance) of up to 26% depending on the time of day of tasks and an individual's circadian phenotype (Facer-Childs and Brandstaetter, 2015a). To put this data into perspective, a change in performance by 0.5% in the 2016 Olympics 100 m freestyle swimming event was the difference between fourth place and a gold medal, and a 2.5% increase in performance would have secured a gold medal, over Usain Bolt, for the last-placed runner in the 100 m sprint. ...
... These results are consistent with previous studies, which found that athletic performance is higher later in the day. 15-19 26 32 72 Diurnal performance variations on the order of 10% were also observed in other studies, 18 reviewed by Drust et al. 15 The peak of performance correlates with the known peak time of CBT, and increased CBT due to warm environments seems to diminish diurnal variations in athletic performance. 16 In our study, we evaluated performance at two time points in the afternoon (15h and 18h). ...
Article
Full-text available
Objectives In this study, we investigated daily fluctuations in molecular (gene expression) and physiological (biomechanical muscle properties) features in human peripheral cells and their correlation with exercise performance. Methods 21 healthy participants (13 men and 8 women) took part in three test series: for the molecular analysis, 15 participants provided hair, blood or saliva time-course sampling for the rhythmicity analysis of core-clock gene expression via RT-PCR. For the exercise tests, 16 participants conducted strength and endurance exercises at different times of the day (9h, 12h, 15h and 18h). Myotonometry was carried out using a digital palpation device (MyotonPRO), five muscles were measured in 11 participants. A computational analysis was performed to relate core-clock gene expression, resting muscle tone and exercise performance. Results Core-clock genes show daily fluctuations in expression in all biological samples tested for all participants. Exercise performance peaks in the late afternoon (15–18 hours for both men and women) and shows variations in performance, depending on the type of exercise (eg, strength vs endurance). Muscle tone varies across the day and higher muscle tone correlates with better performance. Molecular daily profiles correlate with daily variation in exercise performance. Conclusion Training programmes can profit from these findings to increase efficiency and fine-tune timing of training sessions based on the individual molecular data. Our results can benefit both professional athletes, where a fraction of seconds may allow for a gold medal, and rehabilitation in clinical settings to increase therapy efficacy and reduce recovery times.
... Physical performance, dependent on muscle strength, power, contractibility and endurance, is also subject to diurnal variations, the lowest generally being in the morning and the most optimal in late afternoon [106]. However, these outcomes are also dependent on the individual's chronotype, meaning that for the "morning-type person" the optimal performance will be reached earlier in a day and vice versa [107]. In this context, the environmental temperature plays a role too; hot temperatures may blunt muscle performance at any time and for any chronotype [108]. ...
Article
Full-text available
As more insight is gained into personalized health care, the importance of personalized nutritional and behavioral approaches is even more relevant in the COVID-19 era, in addition to the need for further elucidation regarding several diseases/conditions. One of these concerning body composition (in this context; bone, lean and adipose tissue) is osteosarcopenic adiposity (OSA) syndrome. OSA occurs most often with aging, but also in cases of some chronic diseases and is exacerbated with the presence of low-grade chronic inflammation (LGCI). OSA has been associated with poor nutrition, metabolic disorders and diminished functional abilities. This paper addresses various influences on OSA and LGCI, as well as their mutual action on each other, and provides nutritional and behavioral approaches which could be personalized to help with either preventing or managing OSA and LGCI in general, and specifically in the time of the COVID-19 pandemic. Addressed in more detail are nutritional recommendations for and roles of macro- and micronutrients and bioactive food components; the microbiome; and optimal physical activity regimens. Other issues, such as food insecurity and nutritional inadequacy, circadian misalignment and shift workers are addressed as well. Since there is still a lack of longer-term primary studies in COVID-19 patients (either acute or recovered) and interventions for OSA improvement, this discussion is based on the existing knowledge, scientific hypotheses and observations derived from similar conditions or studies just being published at the time of this writing.
... This is in agreement with other studies [167][168][169]. However, recent results highlight that large variations in performance can be observed between morning and evening types [170][171][172]. Thomas et al. concluded that exercise in the evening could lead to misalignments in early chronotypes [173]. ...
Article
Full-text available
The circadian rhythmicity of endogenous metabolic and hormonal processes is controlled by a complex system of central and peripheral pacemakers, influenced by exogenous factors like light/dark-cycles, nutrition and exercise timing. There is evidence that alterations in this system may be involved in the pathogenesis of metabolic diseases. It has been shown that disruptions to normal diurnal rhythms lead to drastic changes in circadian processes, as often seen in modern society due to excessive exposure to unnatural light sources. Out of that, research has focused on time-restricted feeding and exercise, as both seem to be able to reset disruptions in circadian pacemakers. Based on these results and personal physical goals, optimal time periods for food intake and exercise have been identified. This review shows that appropriate nutrition and exercise timing are powerful tools to support, rather than not disturb, the circadian rhythm and potentially contribute to the prevention of metabolic diseases. Nevertheless, both lifestyle interventions are unable to address the real issue: the misalignment of our biological with our social time.
... The internal circadian clock dictates the daily timing of changes in physiology and behavior, and has been found to impact even high-level activities such as athletic performance 1,2 . However, in modern society with the ability to easily travel across time zones, humans often initiate athletic activities at times when the internal clock may not be promoting optimal performance and thus could provide a benefit to the team that does not travel [3][4][5] . ...
Article
Full-text available
On March 11th, 2020, the National Basketball Association (NBA) paused its season after ~ 64 games due to the Coronavirus 2019 (COVID-19) outbreak, only to resume ~ 5 months later with the top 22 teams isolated together (known as the “bubble”) in Orlando, Florida to play eight games each as an end to the regular season. This restart, with no new travel by teams, provided a natural experiment whereby the impact of travel and home-court advantage could be systematically examined. We show here that in the pre-COVID-19 regular season, traveling across time zones reduces winning percentage, team shooting accuracy, and turnover percentage, whereas traveling in general reduces offensive rebounding and increases the number of points the opposing (home) team scores. Moreover, we demonstrate that competition in a scenario where no teams travel (restart bubble) reduces the typical effects of travel and home-court advantage on winning percentage, shooting accuracy, and rebounding. Thus, home-court advantage in professional basketball appears to be linked with the away team’s impaired shooting accuracy (i.e., movement precision) and rebounding, which may be separately influenced by either circadian disruption or the general effect of travel, as these differences manifest differently when teams travel within or across multiple time zones.
... One possible aid is the "setting" of wake-up times to synchronize chronotype and performance. Facer-Childs and Brandstaetter (2015) reported that wake-up time is a predictor of optimal performance times. ...
Article
Chronotype refer to individuals’ time-of-day preferences for activities, which can be classified as “morning types = (M-types)”, “evening types = (E-types)”, and “neither types (N-types)”. The primary aim of this study was to compare the chronotype distribution of Czech First League (1L) and Czech National Football League (2L) male elite football players, which was divided into two secondary aims: (i) statistically identify and compare the number (presence) of particular chronotypes in 1L, and (ii) statistically identify and compare the number (presence) of particular chronotypes in 2L. The present cross-sectional study employed a self-reported standardized questionnaire, the Composite Scale of Morningness, to study the chronotype distribution among the male elite football players. The chronotype distribution of 139 (85 from 1L with mean age ± S.D. = 25.5 ± 3.7 years and 54 from 2L age = 24.4 ± 4.5 years) players was assessed. Overall, 61 (71.8%) of the participants from 1L were mainly N-types, followed by M- and E-types. Similarly, 40 (74.1%) participants from 2L were mainly N-types, followed by M- and E-types. The statistical analysis of the 1L players showed a significantly higher presence of N-types compared to M- and E-types (χ2 (2) = 57.62, p < .05, V = .58). The same results were detected in 2L, where the N-type was identified in the majority of football players (χ2 (2) = 57.62, p < .05, V = .58). The statistical comparison of the number of presented chronotypes did not show a significant difference (F = 3.29, p > .05, V = .16) between players of the 1L and 2L. Thus, N-types are dominant among Czech elite football players, and the chronotype distribution of male elite football players from the Czech First League and the Czech National Football League does not �vary.
... However, glycaemic control and postprandial responses were In contrast to previous short-term training studies reporting no increase in cardiorespiratory fitness [32][33][34], we observed significant improvements inVO 2peak in both exercise groups after only 5 days of training, suggesting that the time of day of exercise did not influence gains in aerobic fitness. Human skeletal muscle mitochondrial oxidative capacity is highest towards the end of the day [35], coinciding with the timing of peak physical performance [36], with afternoon exercise being more efficacious than morning exercise at improving glucose profiles in both the current study and previous reports [8,9]. Synchrony between skeletal muscle and other insulinsensitive tissues is critical to maintain whole-body glucose homeostasis, with insulin secretion and sensitivity under circadian regulation, peaking early in the day and declining in the late afternoon/evening in healthy individuals [37]. ...
Article
Full-text available
Aims/hypothesis We determined whether the time of day of exercise training (morning vs evening) would modulate the effects of consumption of a high-fat diet (HFD) on glycaemic control, whole-body health markers and serum metabolomics. Methods In this three-armed parallel-group randomised trial undertaken at a university in Melbourne, Australia, overweight/obese men consumed an HFD (65% of energy from fat) for 11 consecutive days. Participants were recruited via social media and community advertisements. Eligibility criteria for participation were male sex, age 30–45 years, BMI 27.0–35.0 kg/m ² and sedentary lifestyle. The main exclusion criteria were known CVD or type 2 diabetes, taking prescription medications, and shift-work. After 5 days, participants were allocated using a computer random generator to either exercise in the morning (06:30 hours), exercise in the evening (18:30 hours) or no exercise for the subsequent 5 days. Participants and researchers were not blinded to group assignment. Changes in serum metabolites, circulating lipids, cardiorespiratory fitness, BP, and glycaemic control (from continuous glucose monitoring) were compared between groups. Results Twenty-five participants were randomised (morning exercise n = 9; evening exercise n = 8; no exercise n = 8) and 24 participants completed the study and were included in analyses ( n = 8 per group). Five days of HFD induced marked perturbations in serum metabolites related to lipid and amino acid metabolism. Exercise training had a smaller impact than the HFD on changes in circulating metabolites, and only exercise undertaken in the evening was able to partly reverse some of the HFD-induced changes in metabolomic profiles. Twenty-four-hour glucose concentrations were lower after 5 days of HFD compared with the participants’ habitual diet (5.3 ± 0.4 vs 5.6 ± 0.4 mmol/l, p = 0.001). There were no significant changes in 24 h glucose concentrations for either exercise group but lower nocturnal glucose levels were observed in participants who trained in the evening, compared with when they consumed the HFD alone (4.9 ± 0.4 vs 5.3 ± 0.3 mmol/l, p = 0.04). Compared with the no-exercise group, peak oxygen uptake improved after both morning (estimated effect 1.3 ml min ⁻¹ kg ⁻¹ [95% CI 0.5, 2.0], p = 0.003) and evening exercise (estimated effect 1.4 ml min ⁻¹ kg ⁻¹ [95% CI 0.6, 2.2], p = 0.001). Fasting blood glucose, insulin, cholesterol, triacylglycerol and LDL-cholesterol concentrations decreased only in participants allocated to evening exercise training. There were no unintended or adverse effects. Conclusions/interpretation A short-term HFD in overweight/obese men induced substantial alterations in lipid- and amino acid-related serum metabolites. Improvements in cardiorespiratory fitness were similar regardless of the time of day of exercise training. However, improvements in glycaemic control and partial reversal of HFD-induced changes in metabolic profiles were only observed when participants exercise trained in the evening. Trial registration anzctr.org.au registration no. ACTRN12617000304336. Funding This study was funded by the Novo Nordisk Foundation (NNF14OC0011493). Graphical abstract
... In line with this, daily variations in resistance and endurance exercise peak performance have been reported during the normal active phase in humans (Mirizio et al. 2020) and rodents (Ezagouri et al. 2019) in most, but not all (Knaier et al. 2019;Mirizio et al. 2020) trials. The robustness and timing of such performance peaks seem highly variable, depending on a multitude of parameters including chronotype, time from awakening, muscle and liver glycogen levels, nutritional status, and temperature (Facer-Childs & Brandstaetter, 2015;Hearris et al. 2018). It thus is unknown whether and how the intrinsic muscle clock machinery influences the physiological and molecular responses of skeletal muscle to exercise and ultimately physical performance. ...
Article
Full-text available
Key points: Maximal endurance performance is greater in the early daytime. Timed exercise differentially alters the muscle transcriptome and (phospho)-proteome. Early daytime exercise triggers energy provisioning and tissue regeneration. Early night-time exercise activates stress-related and catabolic pathways. Scheduled training has limited effects on the muscle and liver circadian clocks. Abstract: Timed physical activity might potentiate the health benefits of training. The underlying signalling events triggered by exercise at different times of day are, however, poorly understood. Here, we found that time-dependent variations in maximal treadmill exercise capacity of naïve mice were associated with energy stores, mostly hepatic glycogen levels. Importantly, running at different times of day resulted in a vastly different activation of signalling pathways, e.g. related to stress response, vesicular trafficking, repair and regeneration. Second, voluntary wheel running at the opposite phase of the dark, feeding period surprisingly revealed a minimal zeitgeber (i.e. phase-shifting) effect of training on the muscle clock. This integrated study provides important insights into the circadian regulation of endurance performance and the control of the circadian clock by exercise. In future studies, these results could contribute to better understanding circadian aspects of training design in athletes and the application of chrono-exercise-based interventions in patients.
... Training programme design (exercise selection, frequency, duration, intensity, recovery times, repetition and set ranges, etc.) can also influence the magnitude of adaptation to training (Campos et al., 2002;Contreras et al., 2016;Fry 2004;Rossi et al., 2016;Schoenfeld et al., 2016a, Schoenfeld et al., 2016bWilson et al., 1993), as can time of day of training (Ammar et al., 2016;Facer-Childs & Brandstaetter, 2015), such that two people with an identical genotype doing different training programmes would see a difference in phenotype. Indeed, Sisson and colleagues (2009) found that total exercise volume was a factor in the number of non-responders to exercise; by increasing volume threefold, the number of non-responders to an aerobic training intervention was reduced from 45% to 19% 19%, suggesting that environmental influences can perhaps over-ride the genetic pre-disposition to exercise non-response. ...
Thesis
Full-text available
Variation between individuals in response to a stimulus is a well-established phenomenon. This thesis discusses the drivers of this inter-individual response, identifying three major determinants; genetic, environmental, and epigenetic variation between individuals. Focusing on genetic variation, the thesis explores how this information may be useful in elite sport, aiming to answer the question “Is there utility to genetic information in elite sport?” The current literature was critically analysed, with a finding that the majority of exercise genomics research explains what has happened previously, as opposed to assisting practitioners in modifying athlete preparation and enhancing performance. An exploration of the potential ways in which genetic information may be useful in elite sport then follows, including that of inter- individual variation in response to caffeine supplementation, the use of genetic information to assist in reducing hamstring injuries, and whether genetic information may help identify future elite athletes. These themes are then explored via empirical work. In the first study, an internet-based questionnaire assessed the frequency of genetic testing in elite athletes, finding that around 10% had undertaken such a test. The second study determined that a panel of five genetic variants could predict the magnitude of improvements in Yo-Yo test improvements following a standardised training programme in youth soccer players. The third study demonstrated the effectiveness of a panel of seven genetic variants in predicting the magnitude of neuromuscular fatigue in youth soccer players. The fourth and final study recruited five current or former elite athletes, including an Olympic Champion, and created the most comprehensive Total Genotype Score in the published literature to date, to determine whether their scores deviated significantly from a control population of over 500 non-athletes. The genetic panels were unable to adequately discriminate the elite performers from non-athletes, suggesting that, at this time, genetic testing holds no utility in the identification of future elite performers. The wider utilisation of genetic information as a public health tool is discussed, and a framework for the implementation of genetic information in sport is also proposed. In summary, this thesis suggests that there is great potential for the use of genetic information to assist practitioners in the athlete management process in elite sport, and demonstrates the efficacy of some commercially available panels, whilst cautioning against the use of such information as a talent identification tool. The major limitation of the current thesis is the low sample sizes of many of the experimental chapters, a common issue in exercise genetics research. Future work should aim to further explore the implementation of genetic information in elite sporting environments.
... In both of the abovementioned studies, we expect the effect of chronotype to be an effect of time-shift of a few hours [77]. However, our model suggests something different, namely an interaction similar to the so-called synchrony effects of chronotype reported in the context of cognitive performance in education [78,79], or of physical performance in athletes [80]. Goldstein et al. [79] define chronotype synchrony as the state in which the time of optimal performance is equal to the time of preference of the chronotype, e.g. ...
Article
Full-text available
Non-visual photoreceptors (ipRGCs) and rods both exert a strong influence on the human pupil, yet pupil models regularly use cone-derived sensitivity as their basis. This inconsistency is further exacerbated by the fact that circadian effects can modulate the wavelength sensitivity. We assessed the pupillary reaction to narrowband light stimuli in the mesopic range. Pupil size for eighty-three healthy participants with normal color vision was measured in nine experimental protocols with varying series of continuous or discontinuous light stimuli under Ganzfeld conditions, presented after 90 seconds of dark adaptation. One hundred and fifty series of stimulation were conducted across three experiments, and were analyzed for wavelength-dependency on the normalized pupillary constriction (nPC), conditional on experimental settings and individual traits. Traits were surveyed by questionnaire; color vision was tested by Ishihara plates or the Lanthony D15 test. Data were analyzed with generalized additive mixed models (GAMM). The normalized pupillary constriction response is consistent with L+M-cone derived sensitivity when the series of light stimuli is continuous, i.e., is not interrupted by periods of darkness, but not otherwise. The results also show that a mesopic illuminance weighing led to an overall best prediction of pupillary constriction compared to other types of illuminance measures. IpRGC influence on nPC is not readily apparent from the results. When we explored the interaction of chronotype and time of day on the wavelength dependency, differences consistent with ipRGC influence became apparent. The models indicate that subjects of differing chronotype show a heightened or lowered sensitivity to short wavelengths, depending on their time of preference. IpRGC influence is also seen in the post-illumination pupil reflex if the prior light-stimulus duration is one second. However, shorter wavelengths than expected become more important if the light-stimulus duration is fifteen or thirty seconds. The influence of sex on nPC was present, but showed no interaction with wavelength. Our results help to define the conditions, under which the different wavelength sensitivities in the literature hold up for narrowband light settings. The chronotype effect might signify a mechanism for strengthening the individual´s chronotype. It could also be the result of the participant’s prior exposure to light ( light history ). Our explorative findings for this effect demand replication in a controlled study.
... The relationship between poor sleep quality and evening chronotype is in line with established knowledge about delayed phase syndrome in adolescents and young adults and its adverse consequences on sleep duration, physical and mental health [45]. Moreover, this emphasizes the importance of considering circadian phenotypes in collegiate athletes because of their relationship with sleep and performance [46,47]. ...
Article
Full-text available
The COVID-19 pandemic has changed our lifestyle, sleep and physical activity habits. This study evaluated the prevalence of poor sleep quality, its disrupters, and the impact of the pandemic in collegiate athletes. We performed a cross-sectional study of collegiate athletes (N = 339, median age: 20 (IQR,19–21) years old, 48.5% female, 47% individual sports) who received a web-based questionnaire in April 2021. This survey included subject characteristics, chronotype, sleep disrupters, the changes due to the pandemic and sleep quality (Pittsburg Sleep Quality Index [PSQI]). A multivariate linear regression was performed to assess the relationship between sleep quality, gender, chronotype, sleep disrupters and the changes to training volume or sleep. Results showed a disrupted sleep quality in 63.7%. One in five students had a total sleep time under 6.5 h per night. Poor sleep quality was significantly correlated with nocturnal concerns related to the pandemic, evening chronotype, female gender, third year of study, caffeine consumption and lack of sleep routine (all p < 0.05). To conclude, poor sleep quality is common in collegiate athletes. Sleep disrupters remain prevalent in the lifestyle habits of this population and may have been exacerbated by changes related to the COVID-19 pandemic. Sleep hygiene should become a major aspect of sports education during the return to post-covid normality.
... Similarly, another study determined that MT collegiate rowers performed significantly better in the morning than the evening, while ET rowers performed the same at either time of day [6]. Other research has demonstrated that performance during a cardiovascular endurance test may differ up to 26% for each chronotype based on time of day [7]. Further investigations revealed significant differences in maximal voluntary contractions performed at different times of day based on chronotypes, where MT performed best in the afternoon (14:00 h) and ET performed best in the evening (20:00 h) [8]. ...
Article
Full-text available
Circadian chronotype is dependent on many factors including age, physical activity participation, eating and sleeping patterns, and typical schedule. Recently, the COVID-19 pandemic resulted in schedule changes for most individuals. Therefore, the purpose of this study is to examine whether sport participation influences circadian chronotype and physical activity and whether COVID-19 restrictions have impacted chronotype scores. Briefly, 128 physically active males (n = 62) and females (n = 66) between 18 and 55 years old (24.7 ± 7.1) completed a survey consisting of demographics information, the Morningness–Eveningness Questionnaire (MEQ), and the Godin Leisure Time Physical Activity Scale (LTPA). Participants were asked to answer relevant questions about their habits/preferences before and after COVID-19-related restrictions were implemented. MEQ scores categorized individuals into morning (MT), intermediate (IT), and evening (ET) chronotypes. Three-way (pre-COVID-19 chronotype x sport participation x time) repeated measures ANOVA was conducted to evaluate differences in MEQ and LTPA. A significant main effect of time was found for MEQ (p = 0.018) and LTPA (p = 0.002), indicating changes following COVID-19. A significant time x chronotype interaction was shown for MEQ (p < 0.001) with MT (p < 0.001), IT (p = 0.044), and ET (p = 0.044) individuals indicating chronotype-specific changes following COVID-19. LTPA was decreased and MEQ scores changed following COVID-19, with shifts toward IT scores.
... A chronotype -a biologically driven circadian typology -refers to individual differences in sleep-wake cycles, diurnal preferences, and alertness throughout the day ( Roenneberg et al., 2003 ;Susman et al., 2007 ). Questionnaires have reliably confirmed the differences in chronotypes ( Adan and Almirall, 1991 ;Horne and Östberg, 1976 ), which have been shown to be strongly correlated with the physiological properties of circadian rhythms, including melatonin levels, core body temperature, rest/activity cycles, midsleep point, heart rate, blood pressure, and physical activity ( Adan et al., 2012 ;Anderson et al., 2017 ;Facer-Childs and Brandstaetter, 2015 ;Roeser et al., 2012 ). Genetic factors have been shown to associate with diurnal preference and homeostatic regulation of sleep. ...
Preprint
Full-text available
Circadian rhythms synchronize a variety of physiological processes ranging from neural activity and hormone secretion to sleep cycles and feeding habits. Despite significant diurnal variation, time-of-day (TOD) is rarely recorded or analyzed in human brain research. Moreover, sleep-wake patterns, diurnal preferences, and daytime alertness vary across individuals, known as sleep chronotypes. Here, we performed graph-theory network analysis on resting-state functional MRI (rs-fMRI) data to explore topological differences in whole-brain functional networks between morning and evening sessions (TOD effect), and between extreme morning-type and evening-type chronotypes. To that end, 62 individuals (31 extreme morning, 31 evening-type) underwent two fMRI sessions: about 1 hour after the wake-up time (morning), and 10 hours thereafter, scheduled in accord with their declared habitual sleep-wake pattern. TOD significantly altered functional connectivity (FC) patterns, but there was no significant difference in chronotypic categories. Compared to the morning session, we found relatively increased small-worldness, modularity, assortativity, and synchronization in the evening session, indicating more efficient functional topology. Local measures were changed during the day predominantly across the areas involved in somatomotor, ventral attention, as well as default mode networks. Also, connectivity and hub analyses showed that the somatomotor, ventral attention, and visual networks are the most densely-connected brain areas in both sessions, respectively, with the first being more active in the evening session and the two latter in the morning session. Collectively, these findings suggest TOD can impact classic analyses used in human neuroimaging such as functional connectivity, and should be recorded and included in the analysis of functional neuroimaging data.
... 7 Among them, differences in behavioral, physiological, and neurological performance between morningness chronotype (MCPs) and eveningness chronotype participants (ECPs) have been found. [8][9][10][11][12][13][14] Previous studies have found that chronotype is closely related to sleep homeostatic. The accumulation and dissipation of HSP in MCPs and ECPs are different, the former is faster in accumulation and dissipation than the latter. ...
Article
Full-text available
Background: Chronotype is an appropriate variable to investigate sleep homeostatic and circadian rhythm. Based on functional MRI, the resting-state functional connectivity (rsFC) of insula-angular decrease with the increase in homeostatic sleep pressure (HSP). However, the distinct neural response of different chronotype remained to be clarified. Therefore, we investigated how HSP influenced insular-angular neural interaction of different chronotype. Methods: 64 morningness-chronotype (MCPs) and 128 eveningness-chronotype participants (ECPs) received resting-state functional MRI (rsfMRI) scan. HSP was divided into three levels (Low, Medium, and High) based on the elapsed time awake. Insular-angular rsFC was calculated for MCPs and ECPs on each HSP. Results: As the levels of HSP increased, the negative rsFC between right insular and bilateral angular increased in MCPs while decreased in ECPs. Specifically, ECPs compared with MCPs showed lower rsFC at medium levels of HSP, but higher rsFC at high levels of HSP. In addition, ECPs compared with MCPs exhibited lower rsFC between right insular and right angular at low levels of HSP. Conclusion: The distinct modes of rsFC was found in different chronotype in response to HSP. The results provided the foundation and evidence for investigating the processes of circadian rhythm and sleep homeostatic.
... A chronotype -a biologically driven circadian typology -refers to individual differences in sleep-wake cycles, diurnal preferences, and alertness throughout the day ( Roenneberg et al., 2003 ;Susman et al., 2007 ). Questionnaires have reliably confirmed the differences in chronotypes ( Adan and Almirall, 1991 ;Horne and Östberg, 1976 ), which have been shown to be strongly correlated with the physiological properties of circadian rhythms, including melatonin levels, core body temperature, rest/activity cycles, midsleep point, heart rate, blood pressure, and physical activity ( Adan et al., 2012 ;Anderson et al., 2017 ;Facer-Childs and Brandstaetter, 2015 ;Roeser et al., 2012 ). Genetic factors have been shown to associate with diurnal preference and homeostatic regulation of sleep. ...
Article
Full-text available
Circadian rhythms (lasting approximately 24 hours) control and entrain various physiological processes, ranging from neural activity and hormone secretion to sleep cycles and eating habits. Several studies have shown that time of day (TOD) is associated with human cognition and brain functions. In this study, utilizing a chronotype-based paradigm, we applied a graph theory approach on resting-state functional MRI (rs-fMRI) data to compare whole-brain functional network topology between morning and evening sessions and between morning-type (MT) and evening-type (ET) participants. Sixty-two individuals (31 MT and 31 ET) underwent two fMRI sessions, approximately 1 hour (morning) and 10 hours (evening) after their wake-up time, according to their declared habitual sleep-wake pattern on a regular working day. In the global analysis, the findings revealed the effect of TOD on functional connectivity (FC) patterns, including increased small-worldness, assortativity, and synchronization across the day. However, we identified no significant differences based on chronotype categories. The study of the modular structure of the brain at mesoscale showed that functional networks tended to be more integrated with one another in the evening session than in the morning session. Local/regional changes were affected by both factors (i.e., TOD and chronotype), mostly in areas associated with somatomotor, attention, frontoparietal, and default networks. Furthermore, connectivity and hub analyses revealed that the somatomotor, ventral attention, and visual networks covered the most highly connected areas in the morning and evening sessions: the latter two were more active in the morning sessions, and the first was identified as being more active in the evening. Finally, we performed a correlation analysis to determine whether global and nodal measures were associated with subjective assessments across participants. Collectively, these findings contribute to an increased understanding of diurnal fluctuations in resting brain activity and highlight the role of TOD in future studies on brain function and the design of fMRI experiments.
... The adjustments of circadian rhythmicity produced by exercise have been shown to occur, even for low-intensity endurance exercise [111], and seem to be independent of the time of day the individual performs the exercise [125], although optimal diurnal exercise periods can be adjusted according to the individual chronotype [126]. According to previous research, individuals can be categorized into three distinct chronotype groups: early circadian chronotype, intermediate circadian chronotype, and late circadian chronotype [127]. Individuals in the early circadian chronotype group appear to have a greater disposition to early (morning) physical exercise, while those in the late circadian chronotype prefer to exercise during the late evening. ...
Article
Full-text available
Aging is characterized by several progressive physiological changes, including changes in the circadian rhythm. Circadian rhythms influence behavior, physiology, and metabolic processes in order to maintain homeostasis; they also influence the function of endothelial cells, smooth muscle cells, and immune cells in the vessel wall. A clock misalignment could favor vascular damage and indirectly also affect skeletal muscle function. In this review, we focus on the dysregulation of circadian rhythm due to aging and its relationship with skeletal muscle changes and vascular health as possible risk factors for the development of sarcopenia, as well as the role of physical exercise as a potential modulator of these processes.
... The physical performance was studied using the BLEEP (20m multistage fitness test) test for athletes and found that the earlier circadian phenotype had their highest performance at noon, the intermediate circadian phenotypes had their highest performance 16:00 hours, while the late circadian phenotypes had their highest performance at 19:30 hours. 19 If the residents chronotype is well known before the schedule of the work is done, we can benefit in many aspects: In the ED, the morning chronotype will perform better in day shifts and may prefer to take more day shifts and less night shifts, while the evening chronotype may prefer to get more evening shifts. Also, on inpatient rotations if there are two teams, it is possible to have two residents with two different chronotypes, morning and evening. ...
Article
Background Medical trainees’ work schedule is designed to cover duties without consideration of differences in circadian rhythms during a 24-hour period (chronotype). Objective To explore chronotype variation among medical trainees and understand its association with burn-out and schedule satisfaction. Methods In a multicentre observational study, we conducted two surveys between 1 October 2018 and 1 April 2019. Trainees from nine centres across the USA participated. We measured burn-out using Maslach Burnout Inventory (MBI), and trainee chronotype using the Morningness-Eveningness Questionnaire (MEQ). Results 324 (32%) out of 1012 responded to our survey. Participants were 51% female and had a mean age of 30.8 years. Most participants had an intermediate MEQ type (65%). A large proportion of participants had burn-out on at least one of three tested MBI scales (62%); 5% of participants had burn-out on all three MBI scales. More participants with evening MEQ type had burn-out (66%) compared with morning MEQ type (55%), however, the results were not statically significant (p=0.294). Overall satisfaction with work shifts was 6.5 (95% CI 6.3 to 6.7), with higher satisfaction with day shift 7.7 (95% CI 7.5 to 7.9) and lowest satisfaction with overnight 24-hour call 3.5 (95% CI 3.2 to 3.9). Satisfaction was lower in trainees with burn-out 6.0 (95% CI 5.7 to 6.4), (p<0.001). In the follow-up survey, burn-out was present in at least one scale in 64% compared with 60% of respondents in the initial survey. Conclusion Burn-out is prevalent among medical trainees. Improving alignment between trainee preferences may improve performance, reduce human errors and burn-out.
... Both, animal (Yamanaka et al., 2008;Wolff and Esser, 2012) and human studies (Yamanaka et al., 2006;Okamoto et al., 2013;Basti et al., 2021) have also found that exercise can alter circadian rhythms in behaviour and gene expression. In addition, the circadian clock seems to also have an influence on the benefits of exercise interventions pertaining to cognitive and physical performance (Atkinson and Reilly, 1996;Drust et al., 2005;Waterhouse et al., 2005;Facer-Childs and Brandstaetter, 2015b;a;Facer-Childs et al., 2018). ...
Article
Full-text available
A variety of organisms including mammals have evolved a 24h, self-sustained timekeeping machinery known as the circadian clock (biological clock), which enables to anticipate, respond, and adapt to environmental influences such as the daily light and dark cycles. Proper functioning of the clock plays a pivotal role in the temporal regulation of a wide range of cellular, physiological, and behavioural processes. The disruption of circadian rhythms was found to be associated with the onset and progression of several pathologies including sleep and mental disorders, cancer, and neurodegeneration. Thus, the role of the circadian clock in health and disease, and its clinical applications, have gained increasing attention, but the exact mechanisms underlying temporal regulation require further work and the integration of evidence from different research fields. In this review, we address the current knowledge regarding the functioning of molecular circuits as generators of circadian rhythms and the essential role of circadian synchrony in a healthy organism. In particular, we discuss the role of circadian regulation in the context of behaviour and cognitive functioning, delineating how the loss of this tight interplay is linked to pathological development with a focus on mental disorders and neurodegeneration. We further describe emerging new aspects on the link between the circadian clock and physical exercise-induced cognitive functioning, and its current usage as circadian activator with a positive impact in delaying the progression of certain pathologies including neurodegeneration and brain-related disorders. Finally, we discuss recent epidemiological evidence pointing to an important role of the circadian clock in mental health.
Preprint
Full-text available
Timed physical activity might potentiate the health benefits of training. The underlying signaling events triggered by exercise at different times of the day are, however, poorly understood. Here, we found that time-dependent variations in maximal treadmill exercise capacity of naïve mice were associated with energy stores, mostly hepatic glycogen levels. Importantly, running at different times of the day resulted in a vastly different activation of signaling pathways, e.g., related to stress response, vesicular trafficking, repair, and regeneration. Second, voluntary wheel running at the opposite phase of the dark, feeding period surprisingly revealed minimal Zeitgeber (i.e., synchronizing) activity of training. This integrated study provides important insights into the circadian regulation of endurance performance and the control of the circadian clock by exercise. These results are of high importance to understand circadian aspects of training design in athletes and the application of chrono-exercise-based interventions in patients. Highlights Maximal endurance performance is greater in the early morning Timed exercise differentially alters the muscle transcriptome and (phospho)-proteome Morning exercise triggers energy provisioning and tissue regeneration Evening exercise activates stress-related and catabolic pathways Training exerts poor Zeitgeber activity on the muscle and liver clocks
Preprint
Full-text available
Research on biological rhythms has revealed widespread variation in timing within populations. Repeatable individual chronotypes have been linked to performance in humans but, in free-living species, benefits of chronotype are poorly understood. To address this gap, we investigated fitness correlates of incubation patterns in female songbirds (great tit, Parus major) at urban and forest sites. We confirm repeatable chronotypes (r ≥ 0.31) and show novel links between chronotype and reproductive fitness. In both habitats, females that started activity earlier in the day raised more fledglings. We also observed that forest females started their day at similar times throughout the breeding season, whereas urban females tied their onset of activity closely to sunrise. Our study points to possible mechanisms that underlie chronotype variation and provides sought-after evidence for its relevance to fitness.
Article
The aim of the present study was to explore whether caffeine (CAF) intake counteracts the morning reduction in cognitive and short-term maximal physical performances related to the daily variation pattern in young female handball players. In a randomized order, 15 active young female handball players [mean (SD) age:16.3 ± 0.8 y, height: 166.1 ± 5.3 cm; body mass: 58.7 ± 9.1 kg; BMI: 21.3 ± 3.1 kg/m²] performed the simple reaction time (SRT), the attention (AT), the squat jump (SJ), the Illinois agility (IAT) and the 5 m run shuttles (to determine total (TD) and peak (PD) distances) tests at 08:00 h and 18:00 h, 60 min after a placebo (cellulose) or CAF (6 mg·kg⁻¹) intake. The results revealed a significant diurnal variation during both the placebo and the CAF conditions, with improvement of cognitive and physical performances from 08:00 h to 18:00 h (P < .05). Moreover, the improvement of SRT and AT after CAF was better in the morning compared to the afternoon (e.g., 5.3% vs. 2.8% for SRT and 4.2% vs. 0.9% for AT). At 08:00 h and 18:00 h, SJ, IAT, TD, and PD were higher after CAF intake than Placebo (p < .05). This improvement was greater at 08:00 h than 18:00 h (e.g., 4.2% vs 1% for SJ, 1.6% vs 0.2% for IAT, 2.4% vs. 0.3% for TD, and 6% vs. 0.9% for PD). In conclusion, the dose of 6 mg·kg⁻¹ CAF intake improves the cognitive and physical performances in young female handball players and reduces the intraday variation of these parameters. Abbreviations: CAF: Caffeine PLC: Placebo SRT: Simple Reaction Time AT: Attention Test SJ: Squat Jump IAT: Illinois Agility Test OT: Oral Temperature QUEST: Questionnaire RPE: Rating of Perceived Exertion PD: Peak Distance TD: Total Distance.
Article
Circadian rhythms evolved through adaptation to daily light/dark changes in the environment; they are believed to be regulated by the core circadian clock interlocking feedback loop. Recent studies indicate that each core component executes general and specific functions in metabolism. Here, we review the current understanding of the role of these core circadian clock genes in the regulation of metabolism using various genetically modified animal models. Additionally, emerging evidence shows that exposure to environmental stimuli, such as artificial light, unbalanced diet, mistimed eating, and exercise, remodels the circadian physiological processes and causes metabolic disorders. This Review summarizes the reciprocal regulation between the circadian clock and metabolism, highlights remaining gaps in knowledge about the regulation of circadian rhythms and metabolism, and examines potential applications to human health and disease.
Article
Introduction Chronic sleep restriction has been linked to occupational errors and motor vehicle crashes. Enhancing slow wave sleep may alleviate some of the cognitive deficits associated with chronic sleep restriction. However, the extent to which acoustic stimulation of slow wave activity (SWA) may improve alertness and attention is not well established, particularly with respect to consecutive nights of exposure. Methods Twenty-five healthy adults (32.9±8.2 years; 16 female) who self-restricted their sleep during workdays participated in a randomized, double-blind, cross-over study. Participants wore an automated acoustic stimulation device for two consecutive nights. Acoustic tones (50ms long) were delivered on the up-phase of the slow wave first and then at a constant 1-second inter-tone-intervals once N3 was identified (STIM) until an arousal or shift to another sleep stage occurred, or at inaudible decibels during equivalent stimulation periods (SHAM). Subjective alertness (KSS, Samn-Perelli) was assessed across both days, and objective measures of alertness (MSLT) and attention (PVT) were assessed after two nights of stimulation. Results After one night of acoustic stimulation, increased slow wave energy was observed in 68% of participants, with an average significant increase of 17.7% (p = 0.01), while Night 2 was associated with a 22.2% increase in SWA (p = 0.08). SWE was highly stable across the two nights of STIM (ICC 0.93, p < 0.001), and around half (56%) of participants were consistently classified as a responder (11/25) or non-responders (3/25). Daytime testing showed that participants felt more alert and awake following each night of acoustic stimulation (p < 0.05), with improved objective attention across the day following two nights of acoustic stimulation. Discussion Consecutive nights of acoustic stimulation enhanced SWA on both nights, and improved next day alertness and attention. Given large individual differences, we highlight the need to examine both the long-term effects of stimulation, and to identify inter-individual differences in acoustic stimulation response. Our findings suggest that the use of an acoustic device to enhance slow wave sleep may alleviate some of the deficits in alertness and attention typically associated with sleep restriction.
Thesis
Full-text available
This PhD investigated the importance of sleep in the recovery processes of rugby union players. Study 1 found students and student-athletes presented low sleep quality assessed with the Pittsburgh Sleep Quality (65% ≤5 indicating poor sleep quality). Moreover, student-athletes presented a higher intra-individual variability (small to moderate). In study 2, different age groups of rugby union players presented low total sleep time (≤7 hours) and efficiency (≤85%). However, only small differences in sleep schedule were observed between age groups. Study 2 investigated the validity of self-reported sleep parameters and found a large mean bias (87 min) when compared with actigraphy for sleep duration. Additionally, unclear relationships with subjective sleep quality were found. Study 3 investigated the validity, reliability and sensitivity of a standardised run (i.e. Running Load Index). The results demonstrated a large relationship with leg stiffness (r=0.62) and with a coefficient of variation of 11.5%. Moreover, a large increase in Running Load Index was found after a week of training highlighting its sensitivity. Study 4 highlighted a later fall asleep and wake up time, shorter total sleep time and lower subjective sleep quality post-match. Moreover, collisions, travel time and kick-off time explained most of the changes in sleep compared with match load. Despite, a decrease in perceived wellness (small to very large) and neuromuscular function (small) were observed, sleep had marginal effect on their respective changes. The effect of acute sleep extension on recovery was investigated in Study 5. The results suggested that such as strategy has beneficial effects on cognitive function (i.e. Stroop task). Altogether the results from this PhD suggest that acute changes in sleep post-match affect mainly perceptual and cognitive measures rather than neuromuscular function. Nevertheless, more work is necessary to consider the effect of chronic lack of sleep on post-match recovery.
Article
The current study examined the possible relationships between one-off single night sleep metrics and subsequent kicking performance in a youth soccer context. Twenty-eight under-17 academy players (15.9±0.8 years-old) completed a kick testing protocol consisting in 20 attempts, 18 m from the goal and against a goalkeeper. Four digital video cameras (240 Hz) allowed to determine 3-D approach run, lower limb and ball velocities. Two additional cameras (60 Hz) were used to calculate 2-D mean radial error, bivariate variable error and accuracy. Over 24 h prior to testing, players were monitored by wrist actigraphy to determine their sleep indices. Self-reported sleep quality, sleepiness and chronotype scale scores (Horne and Östberg morningness-eveningness questionnaire) were also collected immediately before kicking experiment. Multiple linear regressions indicated that wake up time and chronotype contributed to 40% of mean radial error. Self-reported sleep quality influenced respectively on 19% and 24% of accuracy and bivariate variable error variances. Taken together self-reported sleep quality and wake up time explained 33% of accuracy (all p<0.05). Indicators of kicking velocity were non-significantly correlated with sleep (r = -0.30–0.29; p>0.05). One-off sleep measures showed some sensitivity to acutely detect inter-individual oscillations in kicking performance. Low perceived sleep quality, later wake up time and a chronotype toward evening preference seems either related to immediately subsequent worst ability of ball placement when kicking. Monitoring sleep-wake transition and perceived sleep quality may be important to help prevent acute performance declines in targeting the goal during kick attempts from the edge of penalty area. Keywords: recovery, chronotype, skill-related performance, human movement, kinematics, team sports.
Article
Full-text available
The primary aims of the present study were to examine the impact of chronotype on sleep/wake behaviour, perceived exertion, and training load among professional footballers. Thirty-six elite female professional football player’s (mean ± SD: age, 25 ± 4 y; weight, 68 ± 7 kg) sleep and training behaviours were examined for 10 consecutive nights during a pre-season period using a self-report online player-management system and wrist activity monitors. All athletes completed the Morningness-Eveningness Questionnaire (rMEQ) on the first day of data collection. Eleven participants were morning types, seventeen participants were intermediate types, and three participants were evening types. Separate linear mixed models were conducted to assess differences in sleep, perceived exertion, and training behaviours between chronotype groups. Morning types woke up earlier (wake time: 07:19 ± 01:16 vs. 07:53 ± 01:01, p = 0.04) and reported higher ratings of perceived exertion compared to intermediate types (6.7 ± 1.1 vs. 5.9 ± 1.2, p = 0.01). No differences were observed between chronotype groups for bedtime, time in bed, total sleep time, sleep efficiency, training duration, or training load. In circumstances where professional female football players are required to train at a time opposing their natural circadian preference (e.g., morning type training in the evening), their perceived exertion during training may be higher than that of players that are training at a time that aligns with their natural circadian preference (e.g., evening type training in the evening). It is important for practitioners to monitor individual trends in training variables (e.g., rating of perceived exertion, training load) with relation to athlete chronotype and training time. Future research should examine the relationship between chronotype, training time, and rating of perceived exertion across different training durations.
Article
Chronobiology is the scientific discipline of study of biological rhythms, a term that has gained ground in the sports world. Recently numerous studies have indicated that the time of day in which sports are practiced influences the achievement of good physical performance. The aim of this review was to study the relationship between circadian rhythms and physical performance, according to the latest published data. In addition, the physiological processes involved in the physical response and the differences according to the type of sport and athletes’ characteristics were studied. A bibliographic search was carried out through five databases (Pubmed, Scopus, Researcher Gate, Google Scholar, UOC Library), focusing on articles published in the last ten years and written in English and Spanish. 36 papers met the inclusion criteria. Body temperature is a factor that shows a circadian pattern with a marked peak in the later afternoon, time of the day at which physical performance is at its highest, i.e. speed, agility, distance covered, jumping power. The perception of effort is also higher in the afternoon. Regarding the chronotype, evening types seem to be the most affected to do sports out of their optimal time-of-day. The tendency shows more morning types as age increases. Training sessions should be planned according to the optimal time of day for each athlete. It’s essential to take into account individual chronotype. The desynchronization of circadian rhythms can cause a decrease in physical performance.
Article
Full-text available
The article is devoted to the analysis of the current state of regenerative and rehabilitative treatments of skeletal muscles, the possibilities of restoring the functioning of tissue lost due to aging, injuries or diseases. The study of the molecular genetic basis of mechanotransduction and mechanotherapy will allow the identification of genes and molecules, the expression levels of which can serve as biomarkers of the effectiveness of regenerative-rehabilitation measures. These mechanisms are potential therapeutic targets for stimulating of regeneration of skeletal muscles. The focus of the article is on the choice of an individual approach, both when conducting basic scientific research and developing rehabilitation programs. All this will significantly improve patient outcomes.
Conference Paper
Full-text available
Erörterung über die Relevanz des Biorhythmus für die sportliche Leistungsfähigkeit (insbesondere im Schwimmsport)
Article
Introduction: Diurnal variations in physical performance can affect athletes' success in competitive sports depending on whether the time of peak performance concurs with the time of competition. The purpose of this systematic review was to investigate the diurnal variation in maximum endurance and strength performance. Methods: The databases PubMed, EMBASE, and Web-of-Science were searched from inception to November 2020. The search string was externally reviewed according to PRESS guidelines, the review was conducted in accordance to PRISMA guidelines, and registered beforehand on PROSPERO. Eligibility criteria were that [1] the studies included humans, [2] any kind of maximum endurance or maximum strength test was performed at [3] a minimum of three different times of the day. There were no restrictions regarding study design, participants' sex, age or fitness levels. Results: From 10,460 screened articles 63 articles met all three inclusion criteria. Meta-analysis on the harmonizable 29 studies provided evidence for diurnal variations in physical performance. In detail, the overall effect sizes (95% confidence intervals) were 0.23 (0.05; 0.40), 0.73 (0.37; 1.09), 0.39 (0.18; 0.60), and 0.79 (0.28, 1.30) for endurance exercise tests, maximum power output in Wingate-test, handgrip strength, and jump height all in favor of higher performance in the evening. The overall risk of bias in individual studies was moderately high. Conclusions: There is strong evidence that anaerobic power as well as jump height are maximal between 13:00 and 19:00. There is some evidence that handgrip strength peaks between 13:00 and 21:00, but only little evidence that there is a time of peak performance in maximum endurance.
Article
Full-text available
We hypothesized that professional football teams would perform better than anticipated during games occurring close to their circadian peak in performance. We reviewed the past 40 years of evening and daytime professional football games between west coast and east coast United States teams. In order to account for known factors influencing football game outcomes we compared the results to the point spread which addresses all significant differences between opposing teams for sports betting purposes. One sample t-tests, Wilcoxon signed ranked tests, and linear regression were performed. Comparison to day game data was included as a control. Academic medical center. N/A. N/A. The results were strongly in favor of the west coast teams during evening games against east coast teams, with the west coast teams beating the point spread about twice as often (t = 3.95, P < 0.0001) as east coast teams. For similar daytime game match-ups, we observed no such advantage. Sleep and circadian physiology have profound effects on human function including the performance of elite athletes. Professional football players playing close to the circadian peak in performance demonstrate a significant athletic advantage over those who are playing at other times. Application of this knowledge is likely to enhance human performance. Smith RS; Efron B; Mah CD; Malhotra A. The impact of circadian misalignment on athletic performance in professional football players. SLEEP 2013;36(12):1999-2001.
Conference Paper
Full-text available
Aims: The aims of the present study were to identify the chronotype of Australia’s elite triathletes and to determine whether morning-types (M-types) compared to neither-types (N-types) and evening-types (E-types) are better able to cope with the demands of early morning training. Methods: Twenty-three elite triathletes (7 female and 16 male) from the Australian Institute of Sport were surveyed at the start of a training camp. Participants completed the Morningness-Eveningness Questionnaire (MEQ), Epworth Sleepiness Scale, and two questions concerning sleep satisfaction and sleep quality. Participants were assigned to a chronotype group on the basis of MEQ scores using the Horne and Ostberg classification system. Independent samples t-tests were used to compare subjective sleep variables (i.e. daytime sleepiness, sleep satisfaction, sleep quality) between chronotype groups. Results: Twelve participants were N-types, 11 were M-types and nil participants were E-types. There was no difference in daytime sleepiness, sleep satisfaction, sleep quality between M-types and N-types. There was no difference in the gender distribution between chronotype groups. Discussion: The results from the present study revealed that triathletes at the elite level tend to show either a morning or neither preference. There were no E-types within this sample of elite triathletes. This finding supports the notion that E-types do not select sports which require early morning training. Further, no differences were found for daytime sleepiness, sleep satisfaction, and sleep quality between Mtypes and N-types.
Article
Full-text available
Almost all physiological and biochemical processes within the human body follow a circadian rhythm (CR). In humans, the suprachiasmatic nucleus regulates sleep- wake cycle and other daily biorhythms in line with solar time. Due to such daily physiological fluctuations, several investigations on neuromuscular performance have reported a distinct CR during exercise. Generally, peak performances have been found to occur in the early evening, at approximately the peak of core body temperature. The increase in core body temperature has been found to increase energy metabolism, improve muscle compliance and facilitate actin-myosin crossbridging. In addition, steroidal hormones such as testosterone (T) and cortisol (C) also display a clear CR. The role of T within the body is to maintain anabolism through the process of protein synthesis. By contrast, C plays a catabolic function and is involved in the response of stress. Due to the anabolic and catabolic nature of both T and C, it has been postulated that a causal relationship may exist between the CR of T and C and muscular performance. This review will therefore discuss the effects of CR on physical performance and its implications for training. Furthermore, this review will examine the impact of muscular performance on CR in hormonal responses and whether could variations in T and C be potentially beneficial for muscular adaptation. Key pointsA distinct CR can be observed in physical performance.CR of exercise performance is highly associated with CR in core body temperatureBoth T and C display a clear CR, however, the current evidence does not show a clear relationship with neuromuscular adaptations.TST is able to induce changes in physical performance variables at the particular time point, but not for the circadian profile of T and C.
Article
Full-text available
The aim of this review is to highlight two emerging concepts for the elite athlete using the resistance-training model: (i) the short-term effects of testosterone (T) and cortisol (C) on the neuromuscular system; and (ii) the dose-response training role of these endogenous hormones. Exogenous evidence confirms that T and C can regulate long-term changes in muscle growth and performance, especially with resistance training. This evidence also confirms that changes in T or C concentrations can moderate or support neuromuscular performance through various short-term mechanisms (e.g. second messengers, lipid/protein pathways, neuronal activity, behaviour, cognition, motor-system function, muscle properties and energy metabolism). The possibility of dual T and C effects on the neuromuscular system offers a new paradigm for understanding resistance-training performance and adaptations. Endogenous evidence supports the short-term T and C effects on human performance. Several factors (e.g. workout design, nutrition, genetics, training status and type) can acutely modify T and/or C concentrations and thereby potentially influence resistance-training performance and the adaptive outcomes. This novel short-term pathway appears to be more prominent in athletes (vs non-athletes), possibly due to the training of the neuromuscular and endocrine systems. However, the exact contribution of these endogenous hormones to the training process is still unclear. Research also confirms a dose-response training role for basal changes in endogenous T and C, again, especially for elite athletes. Although full proof within the physiological range is lacking, this athlete model reconciles a proposed permissive role for endogenous hormones in untrained individuals. It is also clear that the steroid receptors (cell bound) mediate target tissue effects by adapting to exercise and training, but the response patterns of the membrane-bound receptors remain highly speculative. This information provides a new perspective for examining, interpreting and utilizing T and C within the elite sporting environment. For example, individual hormonal data may be used to better prescribe resistance exercise and training programmes or to assess the trainability of elite athletes. Possible strategies for acutely modifying the hormonal milieu and, thereafter, the performance/training outcomes were also identified (see above). The limitations and challenges associated with the analysis and interpretation of hormonal research in sport (e.g. procedural issues, analytical methods, research design) were another discussion point. Finally, this review highlights the need for more experimental research on humans, in particular athletes, to specifically address the concept of dual steroid effects on the neuromuscular system.
Article
Full-text available
The present study developed and tested a theoretical model examining the inter-relationships among sleep duration, sleep quality, and circadian chronotype and their effect on alertness, depression, and academic performance. Participants were 385 adolescents aged 13–18 years (M = 15.6, SD = 1.0; 60% male) were recruited from eight socioeconomically diverse high schools in South Australia. Participants completed a battery of questionnaires during class time and recorded their sleep patterns in a sleep diary for 8 days. A good fit was found between the model and the data (χ2/df = 1.78, CFI = .99, RMSEA = .04). Circadian chronotype showed the largest association with on adolescent functioning, with more evening-typed students reporting worse sleep quality (β = .50, p < .001) and diminished alertness (β = .59, p < .001). Sleep quality was significantly associated with poor outcomes: adolescents with poorer sleep quality reported less sleep on school nights (β = −.28, p < .001), diminished daytime alertness (β = .33, p < .001), and more depressed mood (β = .47, p < .001). Adolescents with poor sleep quality and/or more evening chronotype were also more likely to report worse grades, through the association with depression. Sleep duration showed no direct effect on adolescent functioning. These results identified the importance of two lesser-studied aspects of sleep: circadian chronotype and sleep quality. Easy-to-implement strategies to optimize sleep quality and maintain an adaptive circadian body clock may help to increase daytime alertness, elevate mood, and improve academic performance.
Article
Full-text available
Evening chronotypes typically have sleep patterns timed 2-3 hours later than morning chronotypes. Ambulatory studies have suggested that differences in the timing of underlying circadian rhythms as a cause of the sleep period differences. However, differences in endogenous circadian rhythms are best explored in laboratory protocols such as the constant routine. We used a 27-hour modified constant routine to measure the endogenous core temperature and melatonin circadian rhythms as well as subjective and objective sleepiness from hourly 15-minute sleep opportunities. Ten (8f) morning type individuals were compared with 12 (8f) evening types. All were young, healthy, good sleepers. The typical sleep onset, arising times, circadian phase markers for temperature and melatonin and objective sleepiness were all 2-3 hours later for the evening types than morning types. However, consistent with past studies the differences for the subjective sleepiness rhythms were much greater (5-9 hours). Therefore, the present study supports the important role of subjective alertness/sleepiness in determining the sleep period differences between morning and evening types and the possible vulnerability of evening types to delayed sleep phase disorder.
Article
Full-text available
The circadian clock can only reliably fulfil its function if it is stably entrained. Most clocks use the light–dark cycle as environmental signal (zeitgeber) for this active synchronisation. How we think about clock function and entrainment has been strongly influenced by the early concepts of the field’s pioneers, and the astonishing finding that circadian rhythms continue a self-sustained oscillation in constant conditions has become central to our understanding of entrainment. Here, we argue that we have to rethink these initial circadian dogmas to fully understand the circadian programme and how it entrains. Light is also the prominent zeitgeber for the human clock, as has been shown experimentally in the laboratory and in large-scale epidemiological studies in real life, and we hypothesise that social zeitgebers act through light entrainment via behavioural feedback loops (zeitnehmer). We show that human entrainment can be investigated in detail outside of the laboratory, by using the many ‘experimental’ conditions provided by the real world, such as daylight savings time, the ‘forced synchrony’ imposed by the introduction of time zones, or the fact that humans increasingly create their own light environment. The conditions of human entrainment have changed drastically over the past 100 years and have led to an increasing discrepancy between biological and social time (social jetlag). The increasing evidence that social jetlag has detrimental consequences for health suggests that shift-work is only an extreme form of circadian misalignment, and that the majority of the population in the industrialised world suffers from a similarly ‘forced synchrony’.
Article
Full-text available
Individuals differ in their preferred timing of sleep and activity, which is referred to as a chronotype. The timing shows a wide distribution; extremely early chronotypes may wake up when the extremely late chronotypes fall asleep. The chronotype is supposed to be determined by the central circadian clock located in the suprachiasmatic nuclei (SCN) of the hypothalamus because the phasing of the pineal melatonin rhythm, which is driven by the SCN, correlates with the sleep timing preference. In addition to the SCN, circadian oscillators are also present in most if not all bodily cells. These peripheral clocks are synchronized by the central SCN clock and by other tissue-specific entraining cues. At the molecular level, the circadian oscillations are based on a complex, self-sustaining mechanism that drives the rhythmical expression of clock genes and their proteins. The aim of the present field study was to elucidate whether the changes in the internal timing of early and late chronotypes, as expressed by changes in the phases of their mid-sleep and melatonin secretion, can also be detected at the molecular clockwork level in subjects examined under real-life conditions. Ninety-five adult volunteers were chronotyped using an adapted Munich chronotype questionnaire to assess their mid-sleep phase, and 6 subjects with early chronotypes and 6 with late chronotypes were chosen for the study. For the assessment of the circadian phase, the subjects provided samples of saliva for the melatonin assay and samples of oral mucosa for the determination of clock gene Per1, Per2, and Rev-erbα mRNA levels every 4 h during a 24-h period. The significant correlation between the phase of the melatonin profile and timing of mid-sleep confirmed the classification of the subjects according to their chronotype. The circadian phases of the Per1, Per2, and Rev-erbα expression profiles in the oral mucosa were advanced in the early chronotypes compared with those in the late chronotypes (p < .001) and correlated significantly with the mid-sleep phase of the individual subjects. Moreover, the circadian phases of the Per1 expression profiles of individual subjects correlated significantly with the phases of their melatonin profiles (p < .05), whereas the correlation for the Per2 and Rev-erbα phases was nonsignificant, although the trend was the same. Our results demonstrate that the individual chronotype in humans living in real-life conditions affects not only the phasing of the daily melatonin rhythm in saliva but also the phasing of Per1, Per2, and Rev-erbα clock gene expression profiles in buccal mucosa cells. This report represents the first demonstration that the human peripheral circadian clock may sense the individual's chronotype under field study conditions. The data contribute to our understanding of the mechanisms underlying human chronotypes in real life. (Author correspondence: sumova@biomed.cas.cz ).
Article
Full-text available
A link between diurnal preference and a variable number tandem-repeat (VNTR) polymorphism in the PERIOD3 gene (PER3) has been demonstrated: the longer PER3 and shorter PER3 alleles with preferences for mornings and evenings, respectively. As many competitive events in South Africa for individual athletes are scheduled for the early mornings, we hypothesized that this might favor those athletes with a preference for morning activities. Self-selected white, male cyclists (CYC, n 125), runners (RUN, n 120) and Ironman triathletes (IM, n 287) of European descent were compared with a control population of active, non-competitive individuals (CON, n 96). The chronotypes of all CYC, RUN and CON participants and a sub-sample of the IM group (n 49) were assessed using the HorneÖstberg MorningnessEveningness Questionnaire, and the PER3 VNTR genotype for each participant was determined. The athlete groups contained more morning-type individuals than the CON group (CYC: 72, n 90; RUN: 67, n 80; IM: 59, n 29; CON: 41, n 39; p < .001). The prevalence of the PER3 allele was greater in the athlete groups (CYC: 61, n 152; RUN: 58, n 132; IM: 56, n 324; CON: 38, n 76; p < .001), and more athletes were genotyped as PER355 than CON individuals (CYC: 41, n 51; RUN: 23, n 26; IM: 28, n 81, CON: 9, n 8; p < .001). A strong relationship between chronotype and PER3 VNTR genotype was observed (p < .001). Finally, the time of day at which the athletes preferred to train was related to their chronotype (p < .001). This is the first study of its kind in a South African sporting population, and the results have not yet been replicated. These data suggest that white males of European descent participating in individual endurance sports in South Africa are more likely to be morning types. Furthermore, the PER3 VNTR may be one of the factors contributing to this observation.
Article
Full-text available
Several studies have shown that mutations and polymorphisms in clock genes are associated with abnormal circadian parameters in humans and also with more subtle non-pathological phenotypes like chronotypes. However, there have been conflicting results, and none of these studies analyzed the combined effects of more than one clock gene. Up to date, association studies in humans have focused on the analysis of only one clock gene per study. Since these genes encode proteins that physically interact with each other, combinations of polymorphisms in different clock genes could have a synergistic or an inhibitory effect upon circadian phenotypes. In the present study, we analyzed the combined effects of four polymorphisms in four clock genes (Per2, Per3, Clock and Bmal1) in people with extreme diurnal preferences (morning or evening). We found that a specific combination of polymorphisms in these genes is more frequent in people who have a morning preference for activity and there is a different combination in individuals with an evening preference for activity. Taken together, these results show that it is possible to detect clock gene interactions associated with human circadian phenotypes and bring an innovative idea of building a clock gene variation map that may be applied to human circadian biology.
Article
Full-text available
The aim of this review is to highlight two emerging concepts for the elite athlete using the resistance-training model: (i) the short-term effects of testosterone (T) and cortisol (C) on the neuromuscular system; and (ii) the dose-response training role of these endogenous hormones. Exogenous evidence confirms that T and C can regulate long-term changes in muscle growth and performance, especially with resistance training. This evidence also confirms that changes in T or C concentrations can moderate or support neuromuscular performance through various short-term mechanisms (e.g. second messengers, lipid/protein pathways, neuronal activity, behaviour, cognition, motor-system function, muscle properties and energy metabolism). The possibility of dual T and C effects on the neuromuscular system offers a new paradigm for understanding resistance-training performance and adaptations. Endogenous evidence supports the short-term T and C effects on human performance. Several factors (e.g. workout design, nutrition, genetics, training status and type) can acutely modify T and/or C concentrations and thereby potentially influence resistance-training performance and the adaptive outcomes. This novel short-term pathway appears to be more prominent in athletes (vs non-athletes), possibly due to the training of the neuromuscular and endocrine systems. However, the exact contribution of these endogenous hormones to the training process is still unclear. Research also confirms a dose-response training role for basal changes in endogenous T and C, again, especially for elite athletes. Although full proof within the physiological range is lacking, this athlete model reconciles a proposed permissive role for endogenous hormones in untrained individuals. It is also clear that the steroid receptors (cell bound) mediate target tissue effects by adapting to exercise and training, but the response patterns of the membrane-bound receptors remain highly speculative. This information provides a new perspective for examining, interpreting and utilizing T and C within the elite sporting environment. For example, individual hormonal data may be used to better prescribe resistance exercise and training programmes or to assess the trainability of elite athletes. Possible strategies for acutely modifying the hormonal milieu and, thereafter, the performance/training outcomes were also identified (see above). The limitations and challenges associated with the analysis and interpretation of hormonal research in sport (e.g. procedural issues, analytical methods, research design) were another discussion point. Finally, this review highlights the need for more experimental research on humans, in particular athletes, to specifically address the concept of dual steroid effects on the neuromuscular system.
Article
Full-text available
The objective of this study was to evaluate the sleep quality, sleepiness, chronotype and the anxiety level of Brazilian Paralympics athletes before the 2008 Beijing Paralympic Games. Cross-sectional study. Setting Exercise and Psychobiology Studies Center (CEPE) and Universidade Federal de São Paulo, an urban city in Brazil. A total of 27 Paralympics athletes of both genders (16 men and 11 women) with an average age of 28±6 years who practised athletics (track and field events) were evaluated. Sleep quality was evaluated using the Pittsburgh Scale and the Epworth Sleepiness Scale to evaluate sleepiness. Chronotype was determined by the Horne and Östberg questionnaire and anxiety through the State-Trait Anxiety Inventory. The evaluations were performed in Brazil 10 days before the competition. The study's results demonstrate that 83.3% of the athletes that presented excessive daytime sleepiness also had poor sleep quality. The authors noted that 71.4% were classified into the morning type and 72% of the athletes who presented a medium anxiety level also presented poor sleep quality. Athletes with poor sleep quality showed significantly lower sleep efficiency (p=0.0119) and greater sleep latency (p=0.0068) than athletes with good sleep quality. Athletes who presented excessive daytime sleepiness presented lower sleep efficiency compared to non-sleepy athletes (p=0.0241). The authors conclude that the majority of athletes presented poor sleep quality before the competition. This information should be taken into consideration whenever possible when scheduling rest, training and competition times.
Article
Full-text available
The study focused on chronotype-related differences in subjective load assessment, sleepiness, and salivary cortisol pattern in subjects performing daylong simulated driving. Individual differences in work stress appraisal and psychobiological cost of prolonged load seem to be of importance in view of expanding compressed working time schedules. Twenty-one healthy, male volunteers (mean +/- SD: 27.9 +/- 4.9 yrs) were required to stay in semiconstant routine conditions. They performed four sessions (each lasting approximately 2.5 h) of simulated driving, i.e., completed chosen tasks from computer driving games. Saliva samples were collected after each driving session, i.e., at 10:00-11:00, 14:00-15:00, 18:00-19:00, and 22:00-23:00 h as well as 10-30 min after waking (between 05:00 and 06:00 h) and at bedtime (after 00:00 h). Two subgroups of subjects were distinguished on the basis of the Chronotype Questionnaire: morning (M)- and evening (E)-oriented types. Subjective data on sleep need, sleeping time preferences, sleeping problems, and the details of the preceding night were investigated by questionnaire. Subjective measures of task load (NASA Task Load Index [NASA-TLX]), activation (Thayer's Activation-Deactivation Adjective Check List [AD ACL]), and sleepiness (Karolinska Sleepiness Scale [KSS]) were applied at times of saliva samples collection. M- and E-oriented types differed significantly as to their ideal sleep length (6 h 54 min +/- 44 versus 8 h 13 min +/- 50 min), preferred sleep timing (midpoint at 03:19 versus 04:26), and sleep index, i.e., 'real-to-ideal' sleep ratio, before the experimental day (0.88 versus 0.67). Sleep deficit proved to be integrated with eveningness. M and E types exhibited similar diurnal profiles of energy, tiredness, tension, and calmness assessed by AD ACL, but E types estimated higher their workload (NASA-TLX) and sleepiness (KSS). M types exhibited a trend of higher mean cortisol levels than E types (F = 4.192, p < .056) and distinct diurnal variation (F = 2.950, p < .019), whereas E types showed a flattened diurnal curve. Cortisol values did not correlate with subjective assessments of workload, arousal, or sleepiness at any time-of-day. Diurnal cortisol pattern parameters (i.e., morning level, mean level, and range of diurnal changes) showed significant positive correlations with sleep length before the experiment (r = .48, .54, and .53, respectively) and with sleep index (r = .63, .64, and .56, respectively). The conclusions of this study are: (i) E-oriented types showed lower salivary cortisol levels and a flattened diurnal curve in comparison with M types; (ii) sleep loss was associated with lower morning cortisol and mean diurnal level, whereas higher cortisol levels were observed in rested individuals. In the context of stress theory, it may be hypothesized that rested subjects perceived the driving task as a challenge, whereas those with reduced sleep were not challenged, but bored/exhausted with the experimental situation.
Article
Full-text available
The aim of this study was to evaluate time-of-day effects on fatigue during a sustained anaerobic cycling exercise. Sixteen healthy male competitive cyclists were asked to perform a 60 s Wingate test against a braking load of 0.087 kg.kg body mass(-1) during two experimental sessions, which were set up either at 06:00 or 18:00 h in counterbalanced order. There was only one session per day with a recovery period of at least 36 h between the two sessions. Each subject was trained to perform the test. The body mass used to determine the braking load was that of the first test session for each subject and remained constant throughout the two test periods. During the test, peak power (PP), mean power during the first 30 s (MP30 s) and the full 60 s of the test (MP60 s), and fatigue (i.e., the decrease in power output values throughout the exercise) were analyzed. Results confirmed the existence of diurnal variation in anaerobic power output. PP, MP30 s, and MP60 s were significantly higher at 18:00 than 06:00 h, with gains equal to 8.2, 7.8, and 7.8%, respectively. Moreover, all the power output values recorded in the evening were higher than those recorded in the morning, indicating that fatigue induced by this exercise is not affected by time-of-day in male competitive cyclists. It is hypothesized that the freedom and complexity of pedalling could allow adaptations in movement patterns, as a function of time-of-day, in order to maintain higher performance in the evening. For practical considerations, the more complex the movements required to perform a sport, the more the time-of-day effect can be taken into account and adapted to by the trained athlete, particularly in cyclic sporting disciplines such as swimming, running, rowing, and kayaking.
Article
Full-text available
Sudden cardiac and cerebral events are most common in the morning. A fundamental question is whether these events are triggered by the increase in physical activity after waking, and/or a result of circadian variation in the responses of circulatory function to exercise. Although signaling pathways from the master circadian clock in the suprachiasmatic nuclei to sites of circulatory control are not yet understood, it is known that cerebral blood flow, autoregulation and cerebrovascular reactivity to changes in CO(2) are impaired in the morning and, therefore, could explain the increased risk of cerebrovascular events. Blood pressure (BP) and the rate pressure product (RPP) show marked 'morning surges' when people are studied in free-living conditions, making the rupture of a fragile atherosclerotic plaque and sudden cardiac event more likely. Since cerebral autoregulation is reduced in the morning, this surge in BP may also exacerbate the risk of hemorrhagic and ischemic strokes in the presence of other acute and chronic risk factors. Increased sympathetic activity, decreased endothelial function, and increased platelet aggregability could also be important in explaining the morning peak in cardiac and cerebral events but how these factors respond to exercise at different times of day is unclear. Evidence is emerging that the exercise-related responses of BP and RPP are increased in the morning when prior sleep is controlled. We recommend that such 'semi-constant routine' protocols are employed to examine the relative influence of the body clock and exogenous factors on the 24-h variation in other circulatory factors.
Article
Full-text available
Cognition is regulated across the 24 h sleep-wake cycle by circadian rhythmicity and sleep homeostasis through unknown brain mechanisms. We investigated these mechanisms in a functional magnetic resonance imaging study of executive function using a working memory 3-back task during a normal sleep-wake cycle and during sleep loss. The study population was stratified according to homozygosity for a variable-number (4 or 5) tandem-repeat polymorphism in the coding region of the clock gene PERIOD3. This polymorphism confers vulnerability to sleep loss and circadian misalignment through its effects on sleep homeostasis. In the less-vulnerable genotype, no changes were observed in brain responses during the normal-sleep wake cycle. During sleep loss, these individuals recruited supplemental anterior frontal, temporal and subcortical regions, while executive function was maintained. In contrast, in the vulnerable genotype, activation in a posterior prefrontal area was already reduced when comparing the evening to the morning during a normal sleep-wake cycle. Furthermore, in the morning after a night of sleep loss, widespread reductions in activation in prefrontal, temporal, parietal and occipital areas were observed in this genotype. These differences occurred in the absence of genotype-dependent differences in circadian phase. The data show that dynamic changes in brain responses to an executive task evolve across the sleep-wake and circadian cycles in a regionally specific manner that is determined by a polymorphism which affects sleep homeostasis. The findings support a model of individual differences in executive control, in which the allocation of prefrontal resources is constrained by sleep pressure and circadian phase.
Article
Full-text available
Diurnal variation in both core body temperature and indicators of physical performance are usually observed when measures are taken at 06:00 and 18:00 h. However, differences have been reported between findings in the literature; this may be in some part due to methodological reasons, such as if the experimenter allowed subjects to eat breakfast before the morning 06:00 h session, or even the waking time of subjects. Eleven diurnally active male subjects participated in four test sessions to examine if the time of morning wakening (04:00 or 05:00 h) and eating or not eating breakfast influence body temperature, flexibility, force production, and aerobic performance at 06:00 h. All four sessions were separated by > or = 36 h and were completed in a counterbalanced order. Each test session comprised a sit-and-reach test, an arm maximal voluntary torque evaluation (isometric, concentric at 1.05 rad.s(-1) and at 4.19 rad.s(-1)), and a 10 min all-out cycle ergometer test. Our results indicate the effects of waking time or food intake depend on the parameter tested. Consequently, we advise researchers to take care in experimental design and to at least standardize the time of awakening and consumption of breakfast.
Article
Full-text available
An English language self-assessment Morningness-Eveningness questionnaire is presented and evaluated against individual differences in the circadian vatiation of oral temperature. 48 subjects falling into Morning, Evening and Intermediate type categories regularly took their temperature. Circadian peak time were identified from the smoothed temperature curves of each subject. Results showed that Morning types and a significantly earlier peak time than Evening types and tended to have a higher daytime temperature and lower post peak temperature. The Intermediate type had temperatures between those of the other groups. Although no significant differences in sleep lengths were found between the three types, Morning types retired and arose significantly earlier than Evening types. Whilst these time significatly correlated with peak time, the questionnaire showed a higher peak time correlation. Although sleep habits are an important déterminant of peak time there are other contibutory factors, and these appear to be partly covered by the questionnaire. Although the questionnaire appears to be valid, further evaluation using a wider subject population is required.
Article
Full-text available
The purpose of this study was to assess the validity of the 1 min stage version of the 20 m shuttle run multistage test to predict VO2max in adults (53 males and 24 females, 19 to 47 years old). The maximal shuttle run speed (S-MAS) was thus compared to the VO2max attained during a multistage treadmill test (TE-VO2max), the retroextrapolated VO2max at time zero of the O2 recovery curve of the shuttle run (SR-VO2max) and the VO2max predicted from a previously developed regression equation with children (Mercier et al., 1983) and putting 18 year olds in the regression equation for all adults which yielded (SP-VO2max = -27.4 + 6.0 S-MAS). The latter regression equation was very similar to the ones obtained with the two other criteria and was thus retained to ensure a smooth transition between children and adults in predicting VO2max. Correlations and standard errors of the estimate between S-MAS and TE-VO2max (r = 0.90 and Syx = 4.4) or SR-VO2max (r = 0.87 and Syx = 4.7) were quite good. TE-, SR- and SP-VO2max were also similar (mean +/- SD = 49.4 +/- 10.1, 48.8 +/- 9.3 and 47.1 +/- 8.3 mL.kg-1.min-1, respectively, p greater than 0.05). It was concluded that the 20 m shuttle run is a valid test to predict VO2max in adults.
Article
Full-text available
A maximal multistage 20 m shuttle run test was designed to determine the maximal aerobic power of schoolchildren, healthy adults attending fitness class and athletes performing in sports with frequent stops and starts (e.g. basketball, fencing and so on). Subjects run back and forth on a 20 m course and must touch the 20 m line; at the same time a sound signal is emitted from a prerecorded tape. Frequency of the sound signals is increased 0.5 km h-1 each minute from a starting speed of 8.5 km h-1. When the subject can no longer follow the pace, the last stage number announced is used to predict maximal oxygen uptake (VO2max) (Y, ml kg-1 min-1) from the speed (X, km h-1) corresponding to that stage (speed = 8 + 0.5 stage no.) and age (A, year): Y = 31.025 + 3.238 X - 3.248A + 0.1536AX, r = 0.71 with 188 boys and girls aged 8-19 years. To obtain this regression, the test was performed individually. Right upon termination VO2 was measured with four 20 s samples and VO2max was estimated by retroextrapolating the O2 recovery curve at time zero of recovery. For adults, similar measurements indicated that the same equation could be used keeping age constant at 18 (r = 0.90, n = 77 men and women 18-50 years old). Test-retest reliability coefficients were 0.89 for children (139 boys and girls 6-16 years old) and 0.95 for adults (81 men and women, 20-45 years old).(ABSTRACT TRUNCATED AT 250 WORDS)