Tan et al.
Journal of Physiological Anthropology(2023) 42:26
https://doi.org/10.1186/s40101-023-00343-2

ORIGINAL ARTICLE

Journal of
Physiological Anthropology

Open Access

Chronotype characteristics of professional
athletes in China: a comprehensive descriptive
study
Chenhao Tan1, Jiaojiao Lu1, Jinhao Wang1, Yan An1, Guohuan Cao1, Defeng Zhao1 and Jun Qiu1*   

Abstract
Background Chronotype has gained recognition as a significant factor in enhancing athletic performance. This
study aimed to deepen our understanding of athletes’ sleep chronotypes and provide a foundation for developing
evidence-based training and competition programs. By comprehensively describing and analyzing the chronotype
characteristics of Chinese professional athletes, considering individual and sports factors, sleep quality and habits,
and mental energy, this research aimed to contribute valuable insights to the field.
Methods A sample of 1069 professional athletes from sports teams in Shanghai completed the Athlete Sleep Screening Questionnaire and the Athlete Mental Energy Scale to assess chronotype, sleep quality, sleep-influencing habits,
and mental energy.
Results Among athletes, sleep typology fell within the intermediate range, slightly leaning toward morningness.
Male athletes and those who engaged in static sports displayed a greater propensity for morningness. Age correlatedwith a preference for eveningness. High-level athletes exhibited a stronger inclination toward eveningness. Sleep
quality issues were associated with an inclination toward eveningness. Daily caffeine intake and the habit of using
electronic devices before bedtime are also linked to eveningness. Chronotype demonstrated the ability to predictvarious dimensions of athletes’ mental energy. It was the strongest predictor of vigor, but the loadings were smaller
than those of sleep quality.
Conclusion Chinese athletes’ chronotypes primarily exhibit distinct characteristics related to individual factors suchas gender, sports discipline, and ranking, as well as habits like caffeine consumption and electronic device use. Moreover, these sleep patterns demonstrate predictive capabilities across all dimensions of athletes’ mental energy. This
study sheds light on Chinese athletes’ unique sleep chronotype attributes, enriching our understanding of sleep patterns among professional athletes under various systems. These insights offer an initial basis for enhancing the effectiveness of athlete scheduling and training management.
Keywords Chronotype, Athlete, Professional, ASSQ, Mental energy*Correspondence:
Jun Qiu
qiujun@shriss.cn
1
Shanghai Research Institute of Sports Science (Shanghai Anti-Doping
Agency), Shanghai 200030, China

Background
Sleep plays a crucial role in ensuring athletes’ health andsignificantly impacts their athletic performance [1]. Adequate sleep can enhance athletes’ physiological and psychological functions, improve fatigue recovery, and evenreduce the risk of sports injuries [1–5]. Athletes’ sleep, asa natural means of achieving optimal competitive states,
has garnered increasing attention.

© The Author(s) 2023. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which
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Tan et al. Journal of Physiological Anthropology(2023) 42:26

Chronotype refers to an individual’s preference forbeing an early riser or a night owl, reflecting their inclination toward specific circadian rhythms [6, 7]. Similar
to the extensive research on sleep quality, studies investigating chronotype have consistently unveiled significant
correlations with various facets of athletic performance,
encompassing physiological, psychological, and sportspecific skill sets [8–10]. In light of these discoveries,
researchers have proposed chronotype-related strategies
to enhance training and competition outcomes [7, 11–13]. Indeed, chronotype has emerged as an innovative
approach to elevate training and competitive performance [14].
However, this pioneering approach has garnered insufficient attention, particularly among Chinese athletes,
where research remains notably scarce. Investigations
into athlete chronotypes are predominantly confined toathletes hailing from European, American, and Oceanic
nations [15–19]. These studies bear significant potential in elucidating the characteristics and implications ofchronotype within the professional athlete community.
Nevertheless, it is imperative to acknowledge that whilechronotype indeed harbors intrinsic stability and biological underpinnings [20, 21], social factors such as dietary
habits, living conditions, and social interactions also
influence the formation of chronotype [22]. The impactof these social determinants is indeed discernible among
athletes.
In East Asia, researchers in Japan and Korea havedelved into the chronotype of their elite athletes, revealing that most surveyed Japanese athletes manifest intermediate chronotypes, while most Korean athletes tend
toward eveningness [8, 23]. This contrasts with findings
from some studies suggesting a higher prevalence ofmorningness among elite athletes [15, 17], underscoring
the potential sway of social factors.
Thus, can the attributes of chronotype among Chinese
professional athletes, who share similar ethnic, regional,
and cultural backgrounds with these studies, be directly
extrapolated to delineate and inform practice? In reality,
such an assertion oversimplifies the matter. Due to the
distinctive facets of China’s athletic training and management system [24], Chinese professional athletes are
ensconced within a unique institutional and environmental framework that markedly diverges from numerous
other nations. The peculiarities of this system encompass
regulatory aspects and environmental conditions, which
may wield a specific influence on their chronotype.
In competitive sports, athletes in China’s highly centralized whole-nation system (nationwide system) grapple
with a distinct training and living milieu [24–26]. Within
the nationwide system, sports training receives financial
backing from governmental bodies, with exceptionally

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gifted athletes embarking on rigorous collective training
as early as middle school, progressing into professional
athletes within a structured team-oriented environment.
Some athletes may commence this journey even during
their elementary school years. While these athletes relish economic security through government sponsorship,covering their daily livelihood, training expenses, andmedical needs, they encounter stringent institutional
regulations, often contending with selection pressures[26, 27]. Even for athletes still of school age, training
takes precedence over their daily routines [26]. This system markedly deviates from the more prevalent focus on
student-athletes in many studies [28]. The specific characteristics stemming from this institutional frameworkand cultural context have yet to be explored concerning
the chronotype among athletes.
This study centers on professional athletes in China,
utilizing specialized measurement tools developed
explicitly for athletes to delineate and assess their chronotypes. The primary objective is to offer a comprehensive
overview of chronotype characteristics among Chinese
professional athletes, enriching existing research andadvancing our comprehension of athlete chronotypes.
Moreover, in conjunction with previous studies, conducting cross-cultural and cross-institutional comparisons ofchronotypes can facilitate a more profound analysis of
the potential impact of the management systems within
which Chinese athletes operate. This research is expected
to be a valuable reference for subsequent investigations
and practical implementations in athlete sleep research
and management.
Specifically, this study will sequentially focus on three
aspects of chronotype among Chinese athletes. Firstly, it
examined athletes’ demographic and sports factors commonly explored in previous research, including demographic variables, sports types, and levels of expertise.
To capture the impact of sleep on cognitive abilities,
this study categorized sports based on their cognitive
demands [29], going beyond the traditional dichotomy ofindividual versus team sports. This approach facilitateda more in-depth analysis of the relationships between
sleep and sport-specific characteristics. Secondly, thestudy investigated sleep symptoms and habits of athletes, employing a specialized sleep scale for athletes thatencompassed dimensions related to athlete sleep quality,
specific sleep disorders, and lifestyle habits that influence
sleep. Finally, the study examined factors influencing
athletic performance. As the study encompassed various sports, the physiological responses and other performance-related factors differed [9]. Therefore, the focus
was on psychological factors that are relevant acrossdifferent sports. Specifically, the study analyzed the relationship between chronotype and mental energy from aTan et al. Journal of Physiological Anthropology(2023) 42:26

training needs perspective. Mental energy is the ability
to sustain prolonged thinking, maintain attention, andblock distractions to achieve success [30]. Unlike specificphysiological functions or performance metrics that varyacross sports, mental energy can support performance inall sports without being influenced by inconsistencies in
performance indicators.
Furthermore, as a specialized sleep questionnaire
designed for athletes was utilized, this study also conducted an additional assessment of the tool’s convergent
validity. This step was undertaken to augment the reliability of the obtained results.

Methods
Participants

One-hundred four Chinese professional athletes (sample
1) were recruited to conduct a supplementary assessmentof the validity of the chronotype subscale of the ASSQ
among athletes. This group consisted of 49 males and 55
females, with an average age of 18.63 years (SD = 3.39).
The formal sample used to analyze chronotype comprised 1069 athletes from various professional sports
teams in Shanghai (sample 2). All athletes participatedin this study voluntarily. This research constituted a partof an extensive psychological assessment encompassing all professional athletes under the management of
the Shanghai sports administrative system. With only
a few exceptions attributable to competitions or off-sitetraining, most professional athletes engaged in longterm training at training centers or specialized institutions took part in this study. Consequently, the athletes
included in this research are highly representative.
Among them, 136 athletes were excluded due to thefollowing criteria: not undergoing long-term training atathletic training bases, having coaching duties, training
with their current team for less than one year, or being
under 14 years old. The final sample consisted of 933 athletes, comprising 470 males and 463 females. The mean
age of the participants was 19.47 years (SD = 3.96), andtheir average training experience in their current sport
was 8.33 years (SD = 4.05). The age distribution reflected
the typical range among Chinese professional athletes,
encompassing various career stages, from emerging talents to seasoned performers. Among the participants,
383 athletes held the title of “national athlete” or higher,
314 were classified as “first-class athletes,” and 236
were categorized as “second-class athletes” or lower.
These three designations were used to categorize theathletes into high (highly nationally/moderately internationally competitive), middle (highly provincially/
moderately nationally competitive), and low (provinciallycompetitive) levels of professional athletes. The data usedin this study were collected through a large-scale survey

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conducted among athletes from Shanghai’s provincelevel sports teams. Some athletes had national teamexperience.
All participants underwent long-term training at athletic training bases managed by Shanghai’s sports administration. Their sports disciplines included football,basketball, volleyball, track and field, handball, waterpolo, swimming, modern pentathlon, fencing, table tennis, badminton, boxing, judo, taekwondo, martial arts,
gymnastics, and field hockey. Based on previous categorizations of cognitive demands [29], the athletes wereclassified into static sports (n = 340), interceptive sports(n = 180), and strategic sports (n = 380). Thirty-three athletes could not be clearly classified and were excluded
from analyses involving sports types. Static sports
referred to individual sports such as athletics and swimming, interceptive sports involved individual opponents
like fencing, table tennis, and badminton, while strategic
sports encompassed team sports.
The study was approved by the Ethics Committee of the
Shanghai Research Institute of Sports Science (Shanghai
Anti-Doping Agency), no. LLSC20220005. Participants
provided written informed consent before participatingin the study, and permission was obtained in advancefrom their respective sports teams (for minors, consent
was provided by their guardians).
ScalesAthlete Sleep Screening Questionnaire (ASSQ)

The Athlete Sleep Screening Questionnaire (ASSQ) isa specialized tool designed for screening sleep quality
among athletes, with athletes responding based on theirrecent sleep conditions [31]. These responses guide subsequent assessments and intervention recommendations
for their sleep.
Initially, the ASSQ comprised 15 items, primarilysourced from various self-report sleep scales. Experts
categorized these items into sections related to total sleep
time, insomnia, sleep quality, chronotype, travel disturbance, and sleep disordered breathing, guided by clinicalsignificance [31]. Subsequent studies assessing the reliability and validity of the ASSQ led to the development ofa 16-item version. This revised version includes sections
on sleep difficulty score, modifiers, and other items ofinterest and has been incorporated into the Sport Mental
Health Assessment Tool 1 [32, 33]. For this study, we utilized this validated version of the ASSQ [32].
The sleep difficulty score (SDS) consists of 5 questions (items 1, 3–6), with higher scores indicating amore pronounced degree of sleep difficulty. The ASSQ’s
modifiers encompass indicators for sleep breathing disorders, travel-related issues, and chronotype [31, 32].
The sleep breathing disorders indicator comprises twoTan et al. Journal of Physiological Anthropology(2023) 42:26

questions (items 13 & 14), with an affirmative response
to either indicating the presence of this problem. The
travel-related indicator contains two questions: a positive
response to one (item 11) suggests the need for targeted
sleep education, while a positive response to the other(item 12) suggests the need for medical or sleep sciencediagnosis and intervention. The chronotype section of
the ASSQ comprises four questions (items 7–10). The
Athlete Morningness/Eveningness Scale was used in theinitial item pool. However, it was subsequently replacedby the composite scale of morningness during the compilation process, which continued to the final version.
Higher scores in the chronotype dimension indicate
more pronounced “morningness” characteristics (conversely, “eveningness”), allowing for interventions suchas light therapy or melatonin supplementation based on
the scores [32]. Other items of interest pertain to issues
related to napping, caffeine intake, and pre-sleep electronic device usage, with higher scores indicating greater
frequency of these behaviors.
This scale has been applied in studies involving athlete
populations and has been introduced in China with thedevelopment of a Chinese version [33–36]. The Chineseversion of the ASSQ’s SDS comprises four items (withthe sleep medication item removed) with scores ranging
from 0 to 17, while the chronotype section includes three
items with scores ranging from 0 to 11. Among the otheritems of interest, “napping” has been explicitly defined as“afternoon nap” to align with the habits of Chinese athletes. It should be noted that in the Chinese version, thevalidity result of the chronotype subscale was provided
based on the Pittsburgh Sleep Quality Index [36]. However, the validity between the chronotype subscale andother chronotype scales was not provided. Therefore, weused the Reduced Morningness-Eveningness Questionnaire in this study to provide additional convergent validation information.
This study employed the ASSQ’s chronotype subscale
to assess athletes’ chronotypes. Continuous scores were
included in the analysis to better describe the degree ofmorningness or eveningness, following a precedent fromprior research [10]. The SDS was used to represent overall sleep quality. Responses on sleep breathing disorders,travel sleep issues, afternoon napping, caffeine intake,and pre-sleep electronic device usage were used todescribe athletes’ sleep disorders and habits. Responses
to these questions were recorded. Specifically, (1) sleep
breathing disorder results were categorized into “present” or “absent,” with an affirmative response to either
item coded as “present”; (2) travel-related sleep issues
were categorized into “absent” or “present,” with anaffirmative response to either item coded as “present”;(3) afternoon napping was recoded into “almost every

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training day” (5–7 days per week) and “not every trainingday” (other options); (4) caffeine intake was recoded into
“almost none” (less than one can per day) and “intake”(other options); and (5) pre-sleep electronic device usage
was recoded into “every training day” (daily) and “notevery training day” (other options).
Athlete Mental Energy Scale (AMES)The AMES measures the intensity of motivation, confidence, attention, and emotions in athletes using 18 items
rated on a 1–6 scale. It comprises six subscales: vigor,
confidence, motivation, tireless, concentration, and calm[37]. Each dimension of the AMES consists of three
items, with scores ranging from 3 to 18. The Chinese version of the AMES has demonstrated strong reliability andvalidity, with adapted versions in other Asian languages
also displaying good cross-cultural validity [38]. The simplified Chinese version provided by the original authors
maintains the same structure and exhibits good psychometric properties. The AMES has been effectively utilized in athlete research [39–41].
Reduced Morningness‑Eveningness Questionnaire (rMEQ)

The convergent validity of the chronotype subscale of
ASSQ was assessed using the rMEQ. The rMEQ consistsof five items that evaluate morningness and eveningness
tendencies, with scores ranging from 4 to 25. Higherscores indicate a stronger morningness tendency. The
Chinese version of the rMEQ has demonstrated good
reliability and validity [42].
Procedure

All measures were completed individually using mobile
phones, with scheduling based on competition and training demands. Specifically, the 1-month period before
and after testing avoided significant domestic and international competitions and off-site training, allowing
athletes to maintain their regular lifestyle and training
routines. In validating the chronotype subscale, athletes
completed the paper-based questionnaire or an online
survey at the laboratory site.
Statistical analysis

Statistical analysis was conducted using SPSS 26.0. At
first, the normality of the two variables in sample 1 was
examined. The normality of rMEQ was confirmed (Shapiro–Wilk = 0.978, p = 0.079), while the chronotype
variable of ASSQ did not pass a strict normality test
(Shapiro–Wilk = 0.919, p < 0.001). Therefore, Spearman’s correlation analysis was used to analyze validity.
For sample 2, recoding was performed for factors suchas sleep breathing disorder, travel sleep issues, napping,
caffeine intake, and pre-sleep electronic device usage.

Tan et al. Journal of Physiological Anthropology(2023) 42:26

Since the chronotype score did not pass a strict normality
test (Shapiro–Wilk = 0.946, p < 0.001), even though they
exhibited approximate normality in distribution, nonparametric tests, specifically Wilcoxon signed-rank tests,
Mann–Whitney U-tests, and Kruskal–Wallis ANOVA,
were used to ensure the robustness of the results. Cliff ’s
δ was used as the effect size in pairwise comparisons,and Bonferroni correction was applied for multiple comparisons. Additionally, Spearman’s correlation analysis
examined the relationship between athlete age and sleep
difficulty.
Considering that the level of Chinese professional athletes is not only related to their athletic skills but also
highly related to their age (as higher-level rankings often
require accumulated athletic achievements), a mediation
model with age as a mediator variable was constructedusing PROCESS v4.2 to control for the potential influence of athlete age [43]. Model 4 was employed in theanalysis, with the level as the ordinal independent variable, age as the mediator variable, and chronotype as thedependent variable. A 95% confidence interval was set,and Bootstrap was set to 10,000.
Finally, a multiple linear regression was used to predict the dimensions of psychological energy with athlete
chronotype as the independent variable. In this regression model, alongside chronotype, several potentiallyinfluential factors, including age, gender, and sleep quality, were incorporated using the enter method. Gender,
sport type, and athletic level were set as dummy variables

Fig. 1 Distribution of chronotype scores among all athletes

Page 5 of 13(with male, static type, and low-level athletes as references). VIF > 5 was used as the criterion for detecting
significant multicollinearity. Since the regression analysis
does not strictly require a specific data distribution, anddata distribution has minimal impact with larger sample sizes, additional transformations or processing of thedata may be overly aggressive [44, 45]. Therefore, in thisstudy, no additional data transformation was performed
based on data distribution for the statistical analysis processes involving regression analysis.

Results
Validation of the chronotype subscale

The analysis revealed a significant and positive correlation between the scores on the chronotype subscale of
the ASSQ and the total scores on the rMEQ (ρ = 0.663,
p < 0.001). This finding confirmed the convergent validityof the chronotype subscale of the ASSQ again.
Demographic and sport factors

The overall mean and distribution of scores indicate that
athletes, on average, tend to exhibit a central but slightly
morning-oriented chronotype (see Fig. 1, Table 1). Athletes scored significantly higher than the midpoint of
the score range (0–11 points, midpoint at 5 points) on
the chronotype subscale, W = 271,548.500 and p < 0.001.
However, there was no significant difference between
those scoring and 6 points, W = 119,225.00 and p = 0.126.

Tan et al. Journal of Physiological Anthropology(2023) 42:26

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Table 1 Descriptive results of chronotype scores among
athletes by different demographic and sports factorsnSexSports

Level

Total

M

SD

Male

470

6.24

1.86

Female

463

5.85

1.81

Static

340

6.28

1.91

Interceptive

180

5.67

1.91

Strategic

380

6.02

1.74

Low

236

6.40

1.69

Middle

314

6.33

1.69

High

383

5.59

1.95

933

6.04

1.84

Regarding gender differences, female athletes demonstrated a greater inclination toward an evening chronotype than their male counterparts. Mann–Whitney
U-test results revealed a significant gender difference,
U = 95,299.000, p < 0.001, and Cliff ’s δ = 0.124.
In terms of age, there was a significant but weak negative correlation between athlete age and chronotype
scores, ρ =  − 0.218 and p < 0.001 (see Fig. 2 A–B anddescriptive statistics in Table 1 for details).
Significant differences were observed among athletes from different sports, as indicated by the results of
Kruskal–Wallis ANOVA, H = 14.215 and p = 0.001. Multiple comparisons revealed that athletes in static sports
tended to have a more morning-oriented chronotype
than those in interceptive sports, p = 0.001 and Cliff ’s
δ = 0.188. However, no significant differences were foundbetween athletes in static sports and strategic sports,
p = 0.057 and Cliff ’s δ = 0.101. Similarly, there were noFig. 2 Chronotype characteristics of athletes across different demographic and sport-related factors (including differences in gender (A),age-related correlations (B), distinctions between different sports (C), and variations among different sports levels (D). *p < .050, **p < .010,***p < .001. Dotted lines in the scatter plots represent the 95% confidence intervals for linear trends)

Tan et al. Journal of Physiological Anthropology(2023) 42:26

significant differences between interceptive and strategic
sports athletes, p = 0.214 and Cliff ’s δ = 0.096. Differenceswere also observed among athletes at different levels,
H = 35.731 and p < 0.001. Multiple comparisons showedthat high-level athletes were more evening oriented than
low-level athletes, p < 0.001 and Cliff ’s δ = 0.242. Highlevel athletes also exhibited a more evening-oriented
chronotype than middle-level athletes, p < 0.001 andCliff ’s δ = 0.210. There were no differences between middle- and low-level athletes, p > 0.999 and Cliff ’s δ = 0.039(see Fig. 2 C–D).
In the analysis of mediation effects, the three levels
were transformed into dummy variables, with middleand high-level athletes serving as reference categories
for low-level athletes. The results revealed an omnibus
total effect of level on chronotype, with nonzero relative
total effects for both levels, F(2, 930) = 16.463, p < 0.001.
An omnibus direct effect was observed, with nonzero
relative direct effects for both levels, F(2, 929) = 7.218,
p = 0.008. Regarding relative mediation effects, when
middle-level athletes were compared to low-level athletes, the relative total effect was not significant, 95%
CI = [− 0.376, 0.234]. However, when high-level athletes
were compared to low-level athletes, the relative total
effect was significant, 95% CI = [− 1.108, − 0.522], with adirect effect of − 0.530 (95% CI = [− 0.888, − 0.172]) andan indirect effect of − 0.285 (95% CI = [− 0.501, − 0.074]),
accounting for 34.98% of the total effect.
Further mediation analysis was conducted based on the
differences found among sports levels, using middle-levelathletes as the reference category for high-level athletes.
The results indicated that in terms of relative mediation effects, when high-level athletes were compared to
middle-level athletes, the relative total effect was significant, 95% CI = [− 1.013, − 0.474], with a direct effectof − 0.560 (95% CI = [− 0.860, − 0.259]) and an indirect
effect of − 0.184 (95% CI = [− 0.327, − 0.047]), accountingfor 24.77% of the total effect.
Sleep symptoms and habits

There was a relatively low negative correlation between
sleep difficulties and chronotype, ρ =  − 0.196, p < 0.001.
Athletes with apparent sleep breathing disorders showedno significant differences in chronotype (U = 0.115,
p = 0.735, Cliff ’s δ =  − 0.015). Similarly, athletes experiencing travel-related sleep issues exhibited no significant
differences in chronotype (U = 101,044.500, p = 0.057,
Cliff ’s δ = 0.070) (see Table 2 and Fig. 3A–C).
Regarding sleep habits, athletes who napped daily
showed no significant differences in sleep type
(U = 86,793.000, p = 0.545, Cliff ’s δ =  − 0.019). Athletes
who consumed caffeine-containing foods daily exhibited differences in sleep type (U = 75,481.000, p < 0.001,

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Table 2 Descriptive results of chronotype scores among
athletes by different sleep symptoms and habitsnSleep breathing disorders

M

SD

Absent721 6.03 1.82

Present

212 6.10 1.92

Travel-related sleep issues Absent

481 6.16 1.79

Present

452 5.92 1.89

Nap frequency

Almost every training day 620 6.02 1.83
Not every training ­daya

Caffeine intake
Electronic device use

313 6.09 1.87

Essentially no intake

619 6.27 1.84

Intakeb

314 5.60 1.76

Every training day

604 5.69 1.82

Not every training ­dayc

329 6.70 1.69

Note: aIncluding “three or four times per week” (n = 236), “once or twice perweek” (n = 51), and “none” (n = 26). bIncluding “1–2 cans per day” (n = 269),“3 cans per day”(n = 35), “ 4 cans per day” (n = 7), and “5 cans per day” (n = 3).
cIncluding “not at all (n = 78),” “1 − 3 times per week” (n = 150), and “4 − 6 times
per week” (n = 101)

Cliff ’s δ =  − 0.223). Athletes who did not consume caffeine tended to be more morning oriented. Athletes who
used electronic devices daily before sleep showed differences in sleep type (U = 66,589.000, p < 0.001, Cliff ’s
δ =  − 0.330). Athletes with a daily pre-sleep electronic
device usage tendency leaned toward eveningness (seeTable 2 and Fig. 3D–F).
Mental energy

Chronotype predicted dimensions of mental energy,
although the model fit was not optimal enough. After
controlling for age, gender, and sleep quality, chronotype still predicted all dimensions, with stronger effects
on vigor. However, sleep difficulties may have been astronger predictor than chronotype, and the model fit
remained suboptimal (see descriptive results, standardized coefficients, and fit indices in Tables 3 and 4).

Discussion
Chinese professional athletes’ chronotypes were concentrated in the middle range but slightly skewed towardmorningness. This characteristic differed from researchon professional athletes in other East Asian countries.
Specifically, the distribution of chronotype scores among
Chinese athletes in this study was similar to that foundin a study of international and national elite athletes inJapan [23], except that the latter exhibited a normal distribution. In contrast, another study of elite athletes in
Korea found a higher prevalence of eveningness [8].
These differences may have reflected the overall impactof China’s administrative management of athletes’ daily
lives and training schedules on chronotypes.

Tan et al. Journal of Physiological Anthropology(2023) 42:26

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Fig. 3 Chronotype characteristics of athletes across different sleep symptoms and habits (including correlations with the severity of sleep disorders(A), differences in the presence of sleep breathing disorders (B), differences in the presence of travel-related sleep issues (C), differences in napping
habits (D), differences in daily caffeine intake (E), and differences in daily pre-sleep electronic device usage (F). *p < .050, **p < .010, ***p < .001.
Dotted lines in the scatter plots represent the 95% confidence intervals for linear trends)

Table 3 Descriptive results of mental energy
M

SD

Vigor

12.26

2.86

Confidence

11.71

2.96

Motivation

13.60

3.04

Concentration

12.28

3.38

Tireless

9.13

3.28

Calm

11.30

3.28

Chinese male athletes tended to be more morning oriented than their female counterparts. This gender-based
preference contradicted the results of several large-sample surveys and meta-analyses conducted in the general
population [46–48]. The differences among them may

exhibit unique characteristics of professional athletes.
Although no direct comparison was made, a study ofSouth Korean athletes found a higher proportion of evening-oriented female athletes among those with a preference for eveningness [8].
Athletes’ age was correlated with an inclination towardeveningness. This phenomenon aligned with the averageage results for different chronotypes among Korean athletes and conformed to the typical age-related changes inchronotype preferences [8, 49, 50]. Eveningness strengthened with age, peaking around the early 20 s [49, 50].
Since the average age of athletes in this study was around20, representing the typical age range for Chinese administrative athletes, this age range may have coincided withincreasing eveningness tendencies.
Athletes in static sports tended to be more inclined
toward morningness than interceptive sports, with only

Tan et al. Journal of Physiological Anthropology(2023) 42:26

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Table 4 Standardized regression coefficients and model fit of linear regression for chronotype and other factors on mental energy
Sex

Vigor
Confidence
Motivation
Concentration
Tireless
Calm
VIF

Age

Sport type

Level

Interceptive

Strategic

MiddleSDS

Chorontype

Radj2

0.193

High

β

− 0.131

.089

.059

0.135

− .001.027− 0.3340.176

p< .001.019.086< .001

0.982

0.563

< .001< .001β− 0.179

0.166

.037

0.126

− .007− .003− 0.260

0.104

p< .001< .001

0.288< .001

0.873

0.958

< .001.001

β− 0.109− .021

.008

0.158

.026

.016

− 0.250.088

p< .001

0.604

0.814

< .001

0.530

0.744

< .001.008

β− 0.101− .028

.058

0.146

.042

.003

− 0.303

0.127

p

.002

0.475

.096

< .001

0.305

0.942

< .001< .001β− 0.133

.034

0.110

0.126

− .072− .088− 0.2240.146

p< .001

0.395

.002

.001

.083

.072

< .001< .001β− 0.133

0.219− .044.044.029− .028− 0.2250.115

p< .001< .001

0.220

0.232

0.488

0.562

< .001< .001

1.095

1.625

1.305

1.382

1.744

2.419

1.110

1.111

a slight and nonsignificant difference from strategic
sports. This result expanded upon existing research findings. Previous studies often found that individual athletes tended to be morning oriented, especially those inphysically demanding sports [16, 17, 51, 52]. Static andinterceptive sports in this study broadly corresponded
to individual sports in previous research, while strategic
sports corresponded to team sports [29]. Notably, significant differences existed among individual sports in Chinese professional athletes, while differences compared
to team sports were less pronounced. The characteristicsof training in each sport may have been a critical factor
in this phenomenon. Different sports were believed toaffect chronotype preferences due to variations in training schedules [7, 17, 53]. Under administrative oversight,
Chinese professional athletes’ training times and daily
routines were strictly managed [26, 27], including minimum and maximum training times. This uniform scheduling may have weakened the distinctions among sports.
Differences among individual sports could have been
related to physical demands and additional training time,
warranting further research with training data tracking.
High-level Chinese athletes tended to be more evening oriented than lower-level athletes. This result contradicted findings from previous research [54]. More
importantly, the same pattern persisted even when
including age as a mediating variable. Whether this pattern had cultural factors was currently unclear. Japaneseinternational- and national-level athletes did not exhibita pronounced preference for eveningness [23]. However, there was no data on athletes of different levels todetermine whether they were less evening oriented.
Although the Korean elite athlete population exhibited

0.144
0.116
0.157
0.121
0.125

clear eveningness [8], the study did not define athletic
levels and lacked comparisons between different levels.
Management factors might have provided an alternative explanation. Opportunities related to education andemployment were associated with athletes’ achievements
in China [26, 27]. High-level athletes had opportunities for further education and employment due to theirachievements, which required additional efforts and may
have led to a relaxation of daily management previously
imposed under strict regulations. The current study did
not investigate athletes’ daily activities, necessitating further research to validate this possibility.
In the realm of sleep symptoms, poor sleep quality has
shown an association with a propensity toward eveningness. This discovery aligns with previous research that
has illuminated the detrimental effects of chronotype
on sleep quality [18]. When schedules are meticulously
regulated, deviations in sleep–wake times, such as latebedtimes, can exacerbate shifts in sleep quality [55]. For
Chinese athletes, personalized schedules are often unattainable, posing challenges for evening-oriented athletes.
Notably, there were no discernible differences in chronotype concerning sleep breathing disorders or travelrelated sleep issues. These specific sleep symptoms might
involve alternative physiological mechanisms.
Regarding sleep-related habits, daily napping exhibited no correlation with chronotype. Napping is increasingly recognized as a means of enhancing training quality[56]. However, owing to the traditional Chinese cultural
esteem for midday naps [57], afternoon naps have long
been integrated into the daily routines of Chinese athletes under management. This study showed that mostathletes habitually napped daily or on most training

Tan et al. Journal of Physiological Anthropology(2023) 42:26

days, with very few athletes seldom napping. Since thisstudy employed the ASSQ, primarily focusing on nap frequency [31], without delving into finer details like timing
and duration, it may not have sufficed to elucidate therelationship between the nap characteristics of frequently
napping athletes and their chronotypes. Further, in-depth
research is imperative to scrutinize this relationship.
Caffeine intake was associated with a proclivity towardeveningness, notwithstanding previous studies failingto establish such a connection [58]. In this study, themajority of athletes consumed minimal caffeine. Foods
with high caffeine content are not conventionally part of
the Chinese diet, and dietary and anti-doping management requirements on training days might have contributed to the limited adoption of this habit. Athletes withhigher caffeine consumption might do so out of functional necessity, aligning with the traits of eveningness.
Coupled with the napping pattern, this might suggest
the necessity for further examining lifestyles and habits
across different regions and systems. This also necessitates an analysis of factors such as timing and motivation
for caffeine intake [59].
The utilization of electronic devices before bedtime
correlated with a predisposition toward eveningness.
This discovery concurs with the prerequisites of sleep
hygiene management [60]. Furthermore, it aligns withprior research findings that athletes who engage withelectronic devices before bedtime typically exhibit later
sleep onset [61]. The daily management of Chinese athletes seemingly had no notable impact on electronic
device use, warranting the attention of management
personnel.
Sleep chronotype displayed a significant but relatively
weak association with various mental energy dimensions.
This implies that sleep chronotype can indeed influence
the athletic performance of Chinese athletes throughmental energy, complementing findings related to otherfacets of physical performance [8, 17, 62]. However, it isimperative to note that while sleep chronotype can forecast mental energy, the role of sleep quality appears to be
more paramount. This might be attributed to the influence of sleep chronotype through synchronization withdaily schedules, while sleep quality directly correlateswith fatigue recovery. Hence, the emphasis on chronotype should likely underscore strategies for training andcompetition timings [62], while sleep quality should beseamlessly integrated into routine management practices.
This study represents the first attempt to describeand preliminarily analyze the characteristics of sleep
chronotype among Chinese professional athletes who
operate under a nationwide system, emphasizing training and adhering to tightly regulated daily routines.
Based on these findings, we can provide preliminary

Page 10 of 13

recommendations for Chinese athletes and those undersimilar management structures. First and foremost,
sports organizations should pay heightened attention
to the performance of female athletes, athletes engaged
in interceptive sports, and high-level athletes participating in morning training or competitions. Simultaneously,
they should consider other athletes’ performance whenparticipating in nighttime competitions. In addressing
sleep-related issues, medical support services should
concentrate on evaluating the sleep quality of eveningoriented athletes and contemplate incorporating sleep
chronotype screening when dealing with sleep-related
concerns. Additionally, there is a pressing need forenhanced education on sleep hygiene, particularly concerning caffeine intake and the use of electronic devices
in daily routines. Concerning athletic capabilities, it isessential to recognize the mental energy levels of evening-oriented athletes. However, it is equally vital not tooversimplify this relationship by solely attributing it tosleep chronotype and enforcing strict control over athletes’ sleep habits. Instead, it is advisable to prioritize anuanced understanding of the distinctive features of
sleep quality over time.
However, this study harbors limitations that may haveconstrained the research outcomes. Firstly, the study
exclusively relied on self-report questionnaires tailored
for athletes, thus lacking objective measures of chronotype, sleep patterns, daily routines, and athletic performance. Secondly, data collection regarding athletes’
habits and training particulars was somewhat limited,particularly concerning factors such as nap duration, timing, dietary habits, electronic device usage, and strategies
for managing training fatigue and recovery. These limitations hindered a more in-depth analysis of these influential factors. Lastly, the study lacked comparative analyses
across various management systems and cultures, which
complicates the ability to distinguish between the effects
of management systems and cultural influences.
Future research endeavors should strive to employ
more objective measurement methods to validate thephenomena unearthed in this study. This includes further
exploration of sleep chronotype recognition, comprehensive assessments of sleep quality, and the quantificationof athletic capabilities. Additionally, future studies shouldseek to elucidate the underlying mechanisms driving theobserved phenomena. This could be achieved by considering various factors such as daily training regimens,routines, and lifestyle habits, with particular attention toathletes’ dietary preferences and nap behaviors. Lastly,
it is imperative to emphasize conducting cross-systemand cross-cultural comparisons. These comparisons will
facilitate a more effective delineation of the relationshipbetween the sleep chronotype characteristics of ChineseTan et al. Journal of Physiological Anthropology(2023) 42:26

athletes and the specific management strategies in place.
This examination should encompass characteristics
intrinsic to age groups, scheduling regulations, ranking
systems, and habit formation. Only through such comprehensive efforts can we gain a more nuanced understanding of the intricate dynamics at play.

Conclusion
Under China’s comprehensive sports management system, the sleep chronotype of professional athletes reveals
distinctiveness primarily influenced by individual characteristics such as gender, sport types, and ranking, as wellas lifestyle habits, including daytime napping and caffeine
consumption. Importantly, it demonstrates the capability
to predict all dimensions of athletes’ mental energy. This
study provides an initial description of the manifestationand characteristics of sleep chronotype among professional athletes, operating within the unique social context of China’s competitive sports management system.
These findings lay the foundation for the development of
preliminary strategies to address these unique aspects.
Moreover, this study underscores the necessity of considering the influence of management systems wheninvestigating athletes’ sleep chronotypes, emphasizing
the need for more in-depth research into the impact ofmanagement systems akin to that experienced by Chinese athletes.
Abbreviations
ASSQ	Athlete Sleep Screening Questionnaire
AMES	Athlete Mental Energy Scale
SDS	Sleep Difficulty Score
ANOVA	Analysis of varianceAcknowledgements
We would like to thank participants who devoted their time and efforts.
Authors’ contributions
CT, JL, DZ, and JQ conceptualized the study. CT, JL, JW, YA, and GC organized
the data collection. CT wrote the first draft of the manuscript. CT and JW
revised the manuscript. CT and JL run the analyses and wrote the results section. JQ supervised the project. All authors contributed to revision of the final
version of the manuscript.
Funding
This research was supported by the Shanghai “Science and Technology
Innovation Action Plan” social development science and technology research
projects (22dz1204601) by the Science and Technology Commission of Shanghai Municipality. The funders had no role in study design, data collection andanalysis, decision to publish, or preparation of the manuscript.
Availability of data and materials
The datasets used and/or analyzed during the current study are available fromthe corresponding author on reasonable request.

Declarations
Ethics approval and consent to participate
The research protocol was approved by the Ethics Committee of the Shanghai Research Institute of Sports Science (Shanghai Anti-Doping Center):Page 11 of 13

LLSC20220005. Prior to participating in the study, athletes provided informed
consent.
Consent for publication
Not applicable.
Competing interests
The authors declare that they have no competing interests.
Received: 23 July 2023 Accepted: 22 October 2023

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