(2023) 9:58
Cunha et al. Sports Medicine - Openhttps://doi.org/10.1186/s40798-023-00599-z

SYSTEMATIC REVIEWSports Medicine - Open

Open Access

The Impact of Sleep Interventions
on Athletic Performance: A Systematic Review
Lúcio A. Cunha1 , Júlio A. Costa2 , Elisa A. Marques1,3 , João Brito2 , Michele Lastella4    andPedro Figueiredo5,6*   

Abstract
Background Sleep is essential for maximal performance in the athletic population. Despite that, the sport context
has many factors that can negatively influence athletes’ sleep and subsequent recovery.
Objectives The purpose of this systematic review was to synthesize the most recent literature regarding sleep interventions aimed at improving sleep and subsequent performance in athletes.
Methods The present systematic review was conducted based on the PRISMA guidelines and the PICOS approach.
The search was conducted in May 2022 using the electronic database PubMed, SPORTDiscus via EBSCOhost, and Web
of Science. Once extracted, studies were included if they met the following criteria: (1) participants were athletes
of individual or team sports; (2) implemented an intervention aimed at improving sleep; (3) measured at least one
objective performance/recovery outcome; and (4) reported the relationship between sleep and performance.
Results The search returned 1584 records. Following the screening, a total of 25 studies met our inclusion criteria. All
the included articles were intervention studies published between 2011 and 2021. The included studies implemented
various sleep interventions, such as sleep hygiene, naps, sleep extension, light manipulation, cold water immersion,
mindfulness, or a combination of two or more strategies. Sleep extension and naps were the most representativeand most effective strategies to improve sleep and performance. Mindfulness and light manipulation demonstrated
promising results, but more studies are needed to confirm these findings. Sleep hygiene, removing electronic devices
at night, and cold water immersion had no effects on sleep and subsequent performance/recovery, but these results
are based on a few studies only.
Conclusion While acknowledging the limited amount of high-quality evidence reviewed, it appears that increasing
sleep duration at night or through napping was the most effective interventions to improve physical and/or cognitive
performance.
Protocol Registration This protocol was registered in the International Platform of Registered Systematic Review
and Meta-Analysis Protocols (INPLASY) on May 11, 2022, with the registration number INPLASY202250069.
Keywords Sleep interventions, Athletes, Performance*Correspondence:
Pedro Figueiredo
pfigueiredo@uaeu.ac.ae
Full list of author information is available at the end of the article© The Author(s) 2023. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which
permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to theoriginal author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images orother third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line
to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory
regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of thislicence, visit http://​creat​iveco​mmons.​org/​licen​ses/​by/4.​0/.

Cunha et al. Sports Medicine - Open(2023) 9:58

Key Points• Increasing sleep duration through naps or night-time
sleep may positively impact physical and/or cognitive
performance.
• Extending sleep duration by 46–113 min in athletes
that habitually sleep ~ 7 h per night may be a general recommendation for future sleep extension programs.
• Supplementing sleep during the day with a 20–90min nap can improve performance outcomes after aregular night and restore performance decrements tobaseline levels after a night with partial sleep restriction.

Introduction
Sleep is a biological need crucial for human health andwell-being [1]. During periods of sleep restriction or deprivation, general health is negatively affected, particularly
the immune system, endocrine, physical, or cognitive
functions [2–4]. While the general sleep recommendations advocate that adults obtain 7–9 h of sleep per nightto maintain optimal health and functioning [5], many
adults do not comply with these recommendations. For
athletes, often exposed to high-intensity training, it isrecognized that sleep is the most important method forpsychological and physiological recovery [6, 7]. Elite athletes report needing approximately 8 h of sleep per nightto feel rested [8]. However, elite athletes often sleep lessthan 7 h [8, 9] due to several potential sport and nonsport-related factors, which may vary across sports.
Several sport-specific factors are associated with sleep
inadequacy, including transmeridian travel (disrupting
the circadian rhythm and exposing the athletes to an
unfamiliar sleeping environment), cognitive arousal on
the night before a competition, evening competitions,high training loads, and early morning training [10, 11].
In addition, various non-sport factors, such as social
demands, work/study commitments (e.g., sponsorships),
lifestyle choices (e.g., diet), individual characteristics(e.g., age), attitudes and beliefs (e.g., societal influence),
and family commitments, have been linked with inadequate sleep in athletes [10]. Despite some mixed results, adecline in physical and cognitive performance can occur
after a night of sleep restriction [4, 12, 13]. For example,
two studies with runners and judo athletes showed thatafter a night with partial sleep restriction (4 h of sleep),endurance performance, muscle strength, and power
were negatively affected [14, 15]. A night with partial
sleep restriction can also affect the execution of motor
skills that require a high cognitive dimension, such as

Page 2 of 18

reported for handball goalkeepers [16], dart players [17],and tennis players [18].
Given the growing concern about athletes’ sleep, studies
examining sleep interventions have grown exponentiallyover the recent years [19]. To date, studies examining thesleep/wake behavior of athletes have focused on nutrition[13, 20], sleep hygiene [21], and sleep extension/napping[22, 23]. In a systematic literature review evaluating theeffectiveness of sleep interventions for athletes specifically aimed at improving performance outcomes, Bonnar et al. [24] showed that sleep extension was the mostbeneficial intervention, while napping, sleep hygiene, andpost-exercise recovery strategies provided mixed results.
However, this review was conducted over 5 years ago.
Since then, many studies have been published, and ourunderstanding of the impact of sleep interventions onathletic performance has improved. More recently, in anexpert consensus about athletes’ sleep, Walsh et al. [10]narratively reviewed the studies of the general phenomena of athlete’s sleep. Despite being very comprehensive,
the study included only a few reports regarding sleep
interventions that explored the effect of sleep extension,
sleep hygiene and naps on athletic performance. In thisregard, a more comprehensive review of the literature on
the entire spectrum of sleep interventions is needed.
Therefore, this systematic review aimed to update andexpand the findings of Bonnar et al. [24] and synthesize themost recent literature regarding sleep interventions aimed
at improving sleep and subsequent performance in athletes.

Methods
Protocol and Registration

This protocol was registered in the International Platformof Registered Systematic Review and Meta-Analysis Protocols (INPLASY) on May 11, 2022, with the registration
number INPLASY202250069.
Eligibility Criteria

This systematic review was conducted based on the
PRISMA guidelines [25, 26] and the PICO approach [27].
The PICO approach was established as follows: Population: individual or team sports athletes; Intervention:
strategies to improve or extend sleep; Comparators: control group or a baseline phase without sleep intervention;
Outcomes: subjective and/or objective measurement of
sleep and physical and/or cognitive performance. No sex
or age restriction was applied. To be considered for the
first screening, the studies had to be published or in-pressin peer-reviewed journals (i.e., abstracts published inconference proceedings, books, theses, and dissertations

Cunha et al. Sports Medicine - Open(2023) 9:58

were not considered), published in English, and have an
abstract available for screening.
Search Strategy

The articles were searched in May 2022, and three electronic databases were used: PubMed, SPORTDiscus via
EBSCOhost, and Web of Science. In each database, thefollowing descriptors covering the characteristic of participants, intervention, and outcomes were used: (athlet* OR sport*) AND (sleep AND (education OR hygiene
OR Duration OR extension OR therapy OR strateg*)
OR nap*) AND (performance OR competiti* OR recovery OR fatigue OR outcome*). Searches were conductedusing ‘‘title and abstract’’ (PubMed), ‘‘topic’’ (Web of Science), and “abstract” (SPORTDiscus via EBSCOhost).
Discrepancies in the search fields are due to differencesin the options available in the databases. Filters for “English” and “articles” were applied. A reference management software (EndNote 20, Clarivate Analytics, USA)was used to import and analyze all references.
Study Selection

Studies were included if they met the following criteria: (1) participants were athletes of individual or teamsports, from trained to world-class athletes [28]; (2)implemented an intervention aimed at improving sleep;(3) measured at least one objective performance/recovery outcome; and (4) reported the relationship between
sleep and performance.
Studies on referees or military tactical athletes, studies reporting only subjective performance measures,and interventions that included sleep medication were
excluded.
Data Collection Process

Before starting the article selection process, duplicate
citations obtained from the different databases were
eliminated. Then, two evaluators (LC and JC) independently examined the article title, abstract, and keywords
in the first screening stage according to the establishedinclusion and exclusion criteria. Subsequently, fulltext articles of those citations were read and selected if
suitable for inclusion. In cases of disagreement, a third
reviewer (PF) was consulted. The detailed data collection process is shown in a flowchart (Fig. 1).

Page 3 of 18

polysomnography; (7) performance/recovery assessment
test and related physiological outcomes (e.g., psychomotor vigilance task, countermovement jump, or Wingate
test; creatine kinase, heart rate variability (HRV), or lactate); and (8) main results.
Risk‑of‑Bias Assessment

We applied the revised Cochrane risk-of-bias tool for randomized trials (RoB2) [29, 30] to assess the potential riskof bias. RoB2 is an outcome-focused, domain-based toolthat evaluates the risk of bias in outcomes in individuallyrandomized, parallel-group trials, randomized crossover trials (RCT), and cluster RCTs [29, 30]. RoB2 has fiverisk-of-bias domains covering the different aspects of thetrial design, conduct, and reporting. These include: (1)bias arising from the randomization process; (2) bias due
to deviations from intended interventions; (3) bias due
to missing outcome data; (4) bias in the measurement of
the outcome; and (5) bias in the selection of the reported
results. We also applied the RoB2 version for crossover
trials, which considers the within-participants design notaddressed by the RoB2 for randomized trials and includes
an additional domain: bias arising from period and carryover effects and an additional question on domain“bias in the selection of the reported results.” In both
RoB2 and RoB2 for crossover trials, responses to signaling questions are mapped using a decision algorithm todetermine each risk-of-bias domain judgment [30]. Basedon the domain-level assessment, the overall risk-of-bias
judgment was made for each assessed outcome in eachtrial.
The risk-of-bias assessment tool for non-randomized
studies (RoBANS) [31] was applied to analyze non-randomized studies included. The RoBANS is a domainbased evaluation tool, compatible with the Cochranerisk-of-bias tool [31], that has six risk-of-bias domains:(1) selection of participants; (2) confounding variables;(3) measurement of exposure; (4) blinding of outcome
assessments; (5) incomplete outcome data; and (6) selective outcome reporting. Two researchers (LC and JC)
independently applied both tools (RoB2 and RoBANS).
After completion, the three tables were compared, and all
disagreements were discussed and reanalyzed until consensus was achieved.

Results

Data Items

Study Selection

For the papers included in the analysis, we consideredinformation about: (1) geographical location where
the study was conducted; (2) study design; (3) sport;(4) sample (size, age, and sex); (5) type of intervention (e.g., sleep hygiene, napping, or sleep extension);(6) sleep assessment (e.g., questionnaires, actigraphy, or

The search strategy returned 1584 records. Of the 61
studies retained for full-text screening, we excluded 37
studies that did not meet the inclusion criteria (Fig. 1).
An additional article identified through the included
studies’ reference lists was included. Twenty-five studies
were therefore eligible for review.

Cunha et al. Sports Medicine - Open(2023) 9:58

Page 4 of 18

Fig. 1 Flowchart of the systematic review following the PRISMA statement

Characteristics of Included Studies

The characteristics of the included studies are presented
in Table 1.
All the included articles were intervention studies published between 2011 and 2021 (60% crossover trials, 8%
RCT, and 32% non-RCT). The number of participantsin the included studies ranged from 9 to 31 athletes,with an age range from 13 to 33 years. Studies covered
17 different sports (11 studies included team sports, 13
included individual sports, and 1 was unreported). Of
the 25 studies analyzed, 17 included only male athletes,
3 had only female athletes, and 5 included both male andfemale athletes. Finally, the level/category of the athletes
was highly heterogeneous and represented mainly by justone or two studies, except for trained athletes that were
included in nine studies [32–40], highly trained athletes

in four studies [41–44], and elite athletes in three studies[45–47].
Risk of Bias

The risk-of-bias analysis is summarized in Fig. 2. Figure 2A describes the analysis of crossover studies. Fivestudies were judged to be at a high risk of bias, and ten
studies were considered with some concerns. Some possible biases were related to the carryover effects andoutcome measurement (particularly the use of subjective tools), but the lack of pre-registration of intentions/
methodology (which avoids the possibility of selecting the reported result) was particularly relevant for theoverall results. Figure 2B describes the analysis of RCT.
Two studies were judged to be at a high risk of bias due

Randomized crossover Soccer, rugby,
trial
and handball
No. of groups: three

Randomized crossover Soccer, rugby,
trial
and handball
No. of groups: two

Randomized crossover Karate
trial
No. of groups: two

Boukhris et al. [35]Tunisia

Boukhris et al. [39]Tunisia

Daaloul et al. [49]Tunisia

Napping

Australian football

Pre–post-trial
No. of groups: one

Van Ryswyk et al. [48]AustraliaSport

Randomized crossover Soccer
trial
No. of groups: two

Study design

Fullagar et al. [54]Germany

Sleep hygiene

Study, country

Table 1 Study characteristics of included articles

13, 23.0 ± 2.0 y, 100%male

14, 20.3 ± 3.0 y, 100%male

14, 20.3 ± 3.0 y, 100%
male

25, 23.7 ± 2.0 y, 100%
male

20, NR, 100% male

Sample (size, age*,sex)

30-min nap
versus no nap,
after a reference night
and after a nightwith sleep restriction

40-min nap versus no nap

40-min nap versus 90-min nap
versus no nap

Sleep hygiene

Sleep hygiene
after friendly matchwith a kick-off timeof 20:45 versus no sleep hygieneIntervention

Actigraphy and sleep
diaries

Nap: questionnaire(nap quality usinga scale ranging from 0
to 10)
Night prior experiment: actigraphy

Nap: questionnaire(nap quality usinga scale ranging from 0
to 10)
Night prior experiment: actigraphy

Actigraphy, questionnaire (Pittsburgh
Sleep Quality Index),
and sleep diaries

Actigraphy and sleep
diaries

Sleep assessment

CP: SRT, MRT, and LRT
PP: SJ, CMJ,
and karate-specifictest

REC: CK, LDH, ASAT,
ALAT, and CRP
PP: 5-m SRT

CP: DCT
PP: knee extensors
maximal voluntaryisometric contraction
and 5-m SRT

CP: psychomotor
vigilance task

After reference night:
Nap ↑ SRT, MRT, and LRT;no differences in physical performance
After a PSD night: ↓MRT, LRT, CMJ, and KST,
no differences in SRTand SJ; Nap restored
performance decreases
in SRT, MRT, and LRT

Nap ↑ recovery and 5-m
SRT performance (total
and highest distance)

40- and 90-min nap: ↑attention (DCT), KEMIVC,
and 5mSRT; 40-min nap
versus 90-min nap:↑
DCT, KEMIVC, and ↑ total
distance in 5-m SRT(favoring 90-min nap)

No differences in CP
or objective sleep
parameters

REC: The Yo–Yo
No differencesintermittent recovery in recovery of exercise
test—level 2 and CMJ performance or blood
12 h and 36 h postmarkers; sleep hygienematch, submaximal↑ total sleep timeinterval-based running and number waketest 18 and 42 h post- episodes comparedmatch with a heartwith no sleep hygiene;
rate interval monitoring system; c-reactive
protein, creatine
kinase, and urea 10,
20, 34, and 44 h postmatch

Performance/
Main results
recovery assessment
test

Cunha et al. Sports Medicine - Open(2023) 9:58
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Study design

Studies 1 and 2: randomized crossover trial
No. of groups: two

Counterbalanced
and randomized
crossover trial
No. of groups: two

Counterbalanced
and randomized
crossover trial
No. of groups: one

Non-RCT​
No. of groups: two

Counterbalanced
crossover trial
No. of groups: two

Study, country

Suppiah et al. [52]Singapore

Petit et al. [36]FranceRomdhani et al. [45]Tunisia

Morita et al. [42]Japan

Hsouna et al. [40]Non-reported

Table 1 (continued)
Sample (size, age*,sex)

Intervention

SoccerSoftballJudo

From different sports

Nap: wireless dry electroencephalographic
sensorNight prior experiment: actigraphy

Sleep assessment

2-h nap versus no nap

Nap: sleepiness (Stanford Sleepiness Scale)upon waking
Night prior experiment: actigraphy

Actigraphy, sleep
diaries, and polysomnography

20-min nap verNap subjective quality
sus 90-min nap
versus no nap
after a night with sleep
restriction

20-min nap verPolysomnography
sus no nap in normal
conditions and at 5-hadvanced sleep schedules (simulated jet lag)12, 23 ± 3 y, 100% male 40-min nap versus no nap after a simulated soccer matchon previous night(kick-off at 21:00)

16, IG = 22.1 ± 0.8 y,
CG = 22.0 ± 0.9 y, 100%
female9, 18.5 ± 0.9 y, 100%male

16, 22.2 ± 1.7 y, 100%
femaleStudy 1: shooters
Study 1: 12, 13.8 ± 1.0 y, 30-min nap verStudy 2: track and field 100% malesus no nap
Study 2: 19, 14.8 ± 1.1 y,
100% maleSport

PP: 5-m SRT

CP: three-ball cascadejuggling

CP: multiple-choice
reaction time and simple reaction time
(using a specialized
software)
PP: RAST

PP: Wingate test
and plasma lactate

Study 1: PP: shooting assessment (20competition shots)and HRV
Study 2: PP: 20-m
sprint↑ total and best distanceafter nap; no differencesin fatigue index

IG: ↑ Three-ball cascadejuggling performance
CG: = Three-ball cascadejuggling performanceN20 versus no nap: ↑in MCRT, ↑ maximum
power in RAST; no difference in SRT performanceN90 versus no nap:
no differences in MCRTor SRT performance; ↑maximum, minimum,and mean power
and fatigue index
in RAST

No differencesin physical performanceand plasma lactate
under normal conditions or simulated jet lag

Study 1: no differences in shooting
performance or HRV
after a nap
Study 2: ↓ 20-m sprint
performance

Performance/
Main results
recovery assessment
test

Cunha et al. Sports Medicine - Open(2023) 9:58
Page 6 of 18

Pre–post-trial
No. of groups: one

Pre–post-trial
No. of groups: one

Swinbourne et al. [50]New Zealand

Mah et al. [41]USA

Jones et al. [34]Australia

RCT​
No. of groups: two

Pre–post-trial
No. of groups: one

Schwartz and Simon
[43]
USA

Remove electronic devices

Counterbalanced
crossover trial
No. of groups: one

Roberts et al. [37]Australia

Sleep extension

Study 1: water polo
Study 2: Triathlon

Basketball

Rugby

TennisCycling and triathlon

Randomized crossover Handball
trial
No. of groups: three

Nishida et al. [44]
Japan

Sport

Study design

Study, country

Table 1 (continued)

Study 1: 13, 17 ± 1 y,
46% male
Study 2: 12, 17 ± 1 y,
67% male11, 19.4 ± 1.4 y, 100%
male

25, 25 ± 2.7 y, 100%male

12, 20.2 y (18–22),42%
male

9, 30 ± 6 y, 100% male11, 20.7 ± 1.2 y, 100%male

Sample (size, age*,sex)
Nap: subjective quality(visual analog scale,0–10) and sleepinessbefore and after (Karolinska Sleepiness Scale)Night prior experiment: wearable device(Fitbit charge 3)
Sleep quality: questionnaire (Pittsburgh
Sleep Quality Index)

Sleep assessment

Remove electronic
devices in the evening
versus unrestricted
electronic device use

Sleep extension (atleast 10 h in bed
per night, with a regular sleep–wakeschedule and napping
encouraged)

Sleep extension (atleast 10 h of sleep)
via sleep scheduling advice, strategic
napping, and sleep
hygiene versus control

7 days of sleep extension (at least 9 h),including naps

Actigraphy and sleep
quality diaries

Actigraphy and sleep
diaries

Actigraphy, questionnaire (Pittsburgh
Sleep Quality Index),
and sleep diaries

Sleep diaries

Actigraphy and sleep
Three consecudiaries
tive days of sleep
extension (30% morethan a normal night)
versus sleep restriction(30% less than a normal night) versus normal night

60-min nap versus 20-min nap
versus no nap

Intervention

Study 1: none
Study 2: CP: psychomotor vigilance test

CP: psychomotor
vigilance task
PP: specific to basketball (timed 282 feetsprint, free throw,and three-pointshooting accuracy)

CP: the five-minutepsychomotor vigilance test

PP: serving accuracy

CP: psychomotor
vigilance task
PP: ETT

REC: HRV during nap
PP: Handballperformance (20-mturnaround run, 10-m
load run, and ballshooting)

Study 2: no differencesin cognitive performance or sleep↑ Psychomotor vigilance
performance, timed 282
feet sprint, free throw,
three-point shooting
accuracy, and TST↑ reaction time
performance, ↑ total
sleep time, and ↑ sleep
efficiency compared
to control↑ Serving accuracy
and TST

Sleep extension compared with NN: ↑ PVT
and ETT performance;
SR compared with NN: ↓PVT and ETT performance

No differences in handball performanceor HRV; 60-min nap↑ shooting accuracy
in individuals with poor
sleep quality; HRV
correlated negatively
with 10-m load run
in 60-min nap

Performance/
Main results
recovery assessment
test

Cunha et al. Sports Medicine - Open(2023) 9:58
Page 7 of 18

Non-RCT​No. of groups: two

Dunican et al. [32]Australia

Chauvineau et al. [55]FranceCold water immersion

Jones et al. [33]USACounterbalanced
and randomized
crossover trial
No. of groups: three

Non-RCT​
No. of groups: two

Pre–post-trial
No. of groups: one

Rosa et al. [51]BrazilMindfulness

RCT​
No. of groups: two

Zhao et al. [38]ChinaLight interventions

Study design

Study, country

Table 1 (continued)

Running

RowingSwimming

Basketball

Judo

Sport

12, 28 ± 5.8 y, 100%
male

27, 18–23 y, 100%
female22, 24.8 ± 3.4 y, 50%
male20, 18.6 ± 3.6 y, 100%
male

18, 18 ± 2 y, 56% male

Sample (size, age*,sex)

Whole CWI versus partial CWI versus control(sitting for 10 min)Mindfulness-based
stress reduction versus no intervention

Bright-light therapy(with portable glasses)
and sleep hygiene

30-min red-lighttherapy every night
versus no lightintervention (placebogroup) with the samedevice (device off )Electronic devices
removed for a 48-h
period versus unrestricted electronic
device use

Intervention

Actigraphy, questionnaire (the Spiegel
Sleep Inventory),polysomnography,
and core body temperature

Actigraphy and questionnaire (Pittsburgh
Sleep Quality Indexand Epworth Sleepiness Scale)

Actigraphy and sleep
diaries

Questionnaire (Pittsburgh Sleep Quality
Index) and serum
melatonin

Actigraphy and sleep
diaries

Sleep assessment

REC: Hooper Indexand creatine kinasepre- and post-simulated trial, postCWI, 24 h and 48 h;
the Total of Recovery
Scale post-CWI,
24 h and 48 h; CMJ
and KEMIVC preand post-simulated
trial, 24 h and 48 h;
Nocturnal HRV
in simulated trial day

PP: rowing performance (6000 m
ergometer test)

CP: psychomotor
vigilance test

PP: Cooper 12-minuterun

CP: The Cogstate
research tool
PP: The single leg
three hop test

No differences in fatigue
or muscle damage,core temperature, TST,
SE, WASO, and latency;
CWI ↓ arousals; whole
CWI ↓ parasympathetic
modulation↑ in rowing performance and subjective
sleep quality, and ↓in sleepiness, comparedwith control group↑ reaction time performance, delayed sleep/
wake cycles, and ↓ total
sleep time

Red-light therapy
group: ↑ distancein Cooper 12-min run
performances, ↑ serum
melatonin, and ↑ sleep
quality
Placebo group: no differences in Cooper 12-min
run test performance,
serum melatonin,or sleep

No differences
between groups
in cognitive or athletic
performance and sleep
quality and quantity

Performance/
Main results
recovery assessment
test

Cunha et al. Sports Medicine - Open(2023) 9:58
Page 8 of 18

Study design

Randomized crossover Tennis
trial
No. of groups: two

Counterbalanced
and randomized
crossover trial
No. of groups: fourCounterbalanced
and randomized
crossover trial
No. of groups: five

Lever et al. [53]Australia

Romdhani et al. [47]Tunisia

Romdhani et al. [46]Tunisia

9, 18.78 ± 1.09 y, 100%male

Sleep assessment

Sleep hygiene
and mindfulness versus no intervention

CP: simple and twochoice reaction time
(using a specialized
software)Nap subjective quality (100-mm analog
scale) and sleepinessbefore and after(Epworth sleepinessscale)

Normal sleep night
Nap subjective quality PP: RAST and plasma
without nap (NSN)(100-mm analog scale) lactate
versus NNP versus NNC versus 20-min
NP versus 20-min NC,
after a night with sleep
restriction

PP: match performance (games won
or lost)REC: fatigue, vigor (theBrunel Mood Scale),muscle and joint
soreness (1–10 Likert
scale)

20-min NC ↑ RAST
performance, compared with NNP, NNC,
and 20-min NP; ↓ RAST
performance in NNP
and NNC, comparedwith NSN; NC and NP
restored RAST performance comparedwith NSN; 20-min NP↑ Pmax comparedwith NNP; lactate ↑with 20-min NC and NP,
compared with NNP

Study 1: ↑ SRT performance in NNC; ↑ TCRT
performance in NP
and NC; ↓ sleepiness
in NNC, NP, and NC
Study 2: ↑ SRT performance in NNC; ↑ TCRT
performance in NP
and NC; ↓ sleepinessin NP

No differences in match
performance; ↑ TST,no change in SE, SL,
WASO, WE, and WED↓ muscle and joint
soreness, no differencesin vigor; large effectsizes though non-significant results for ↓ fatigue,and ↑ TST; no differencesin SE or SL

Performance/
Main results
recovery assessment
test

Actigraphy and sleep
diaries

Sleep hygiene, CWI,
Actigraphy
and full-body compression versus control(passive stretching)Intervention

23, 19.78 ± 1.41 y
Study 1: after a night
Study 1: 9, 100% male with sleep restriction,
Study 2: 14, 100% male no nap with placebo(NNP) versus no nap
with caffeine (NNC)
versus 20-min nap
with placebo (NP)versus 20-min nap
with caffeine (NC)Study 2: after a normalnight, NNP versus NNC
versus NP versus NC

17, 15.7 ± 1.1 y, 58%
male

8, 20.9 ± 3.6 y, 100%male

Sample (size, age*,sex)*Age is presented as mean ± standard deviation or range(2023) 9:58

CG Control group, CP Cognitive performance, PP Physical performance, REC Recovery, IG Intervention group, NR Not reported, RCT​Randomized controlled trial, CK Creatine kinase, LDH Lactate dehydrogenase, ASAT
Aspartate aminotransferase, ALAT Alanine aminotransferase, CRP C-reactive protein, DCT Digit cancelation test, 5-m SRT 5-m shuttle run test, KEMIVC Knee extensors maximal isometric voluntary contraction, SRT Simple
reaction time, MRT Mental rotation test, LRT Lower reaction test, SJ Squat jump, TST Total sleep time, SE Sleep efficiency, SL Sleep latency, WASO Wake after sleep onset, WE Wake episodes, WED Wake-episode duration, SE
Sleep efficiency, SR Sleep restriction, NN Normal night, PSR Partial sleep restriction, ETT Endurance time trial, PVT Psychomotor vigilance task, HRV Heart rate variability, HR Heart rate, RAST Running-based anaerobic sprint
test, CWI Cold water immersion

Judo

Judo

Randomized crossover Tennis
trial
No. of groups: twoSport

Duffield et al. [56]Australia

Combination of two or more strategies

Study, country

Table 1 (continued)

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Cunha et al. Sports Medicine - Open(2023) 9:58

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Fig. 2 Risk-of-bias judgments by A RoB2 for crossover trials, B RoB2 for randomized controlled trials, and C RoBANS for non-randomized trials

Cunha et al. Sports Medicine - Open(2023) 9:58

Page 11 of 18

Fig. 2 continued

to the possible bias in all domains, except in domain 3(missing outcome data). Figure 2C describes the analysis
of non-RCT. Some potential biases were the lack of control over confounding variables and the lack of pre-registration of intentions/methodology.
Effects of Sleep Interventions on Cognitive Performance

Twelve studies investigated the effect of sleep interventions on sleep and cognitive performance, of which one
study explored sleep hygiene [48], four investigatednaps [35, 42, 45, 49], one investigated naps combinedwith caffeine consumption [47], three investigated sleep
extension [37, 41, 50], two investigated the removal ofelectronic devices [32, 34], and one investigated an artificial light intervention [51]. Only one study [48] examined
the impact of sleep hygiene for six weeks and did not findany improvement on vigilance and attention, as measured by the Psychomotor Vigilance Task.
Regarding napping, despite differences in study design,
a positive effect was found for short (20–40 min) andlong naps (90–120 min) on attention, simple reaction
time, multiple choice reaction time, juggling performance, mental rotation test, and lower reaction test [35,42, 45, 49]. After a night of partial sleep deprivation anda typical night, Romdhani et al. [47] examined the effectof napping and caffeine or placebo and found that twochoice reaction time was improved, regardless of caffeine

ingestion or sleep deprivation. For simple reaction time,
performance was only enhanced after caffeine ingestion,
regardless of sleep deprivation or napping.
Regarding sleep extension interventions, the results
showed that increasing sleep duration positively impacts
psychomotor vigilance task and reaction time [37, 41,
50].
Following the removal of electronics, Dunican et al.
[32] and Jones et al. [34] did not observe any effects on
sleep or cognitive performance (the Cogstate researchtool and 5-min psychomotor vigilance task). Rosa et al.
[51] examined the effect of artificial bright light on thesleep/wake cycle and psychomotor vigilance task performance. They observed an improvement in mean reaction
time and a delay in the sleep/wake cycle, although sleep
duration was significantly reduced.
In summary, naps, sleep extension, and light therapy
demonstrated positive results on cognitive performance[35, 37, 41, 42, 45, 47, 49–51]. In contrast, removing
electronic devices and sleep hygiene revealed no effects[32, 34, 48]. Data from these studies are summarized inTable 1.
Effects of Sleep Interventions on Physical Performance

Sixteen studies investigated the effect of sleep interventions on sleep and physical performance, of which eight
investigated the effect of napping [35, 36, 39, 40, 44, 45,Cunha et al. Sports Medicine - Open(2023) 9:58

49, 52], one investigated naps combined with caffeine[46], three examined the impact of sleep extension [37,41, 43], one investigated the effect of removing electronic
devices [32], one investigated the effect of light intervention [38], one investigated the effect of mindfulness[33], and one investigated the effect of combining sleep
hygiene and mindfulness [53].
Boukhris et al. [35], Romdhani et al. [45], and Nishida
et al. [44] investigated the effects of short (20–40 min) andlong naps (60–90 min) on maximal strength (knee extensors maximal voluntary isometric contraction), anaerobic capacity (running-based anaerobic sprint test and5-min shuttle run test), and handball performance. The
results showed a positive effect of naps, although Boukhris et al. [35] observed greater effects with a longer nap,
and Nishida et al. [44] found positive effects following a
60-min nap in individuals with poor sleep quality. Boukhris et al. [39] and Hsouna et al. [40] examined the effectof a 40-min nap compared with no nap on the 5-min shuttle run test. They found a positive impact in total and best
distance, despite no differences in fatigue index.
Despite the different contexts, Petit el al. [36] and Daaloul et al. [49] found no effects of napping when examining the impact of a short nap (20–30 min) on the Wingate
test, squat jump, countermovement jump (CMJ), andkarate-specific test. In a study divided into two experiments, Suppiah et al. [52] showed that napping negatively
impacted sprint performance in track and field athletes.
However, no effect was observed on shooting performance in shooters. Romdhani et al. [46] showed that a
20-min nap combined with caffeine improved runningbased anaerobic sprint test (RAST) performance. In
addition, caffeine without nap and a 20-min nap with aplacebo improved maximum power.
Regarding sleep extension, increasing sleep duration
improved basketball and tennis performance (timed 282
feet sprint, free throw, three-point shooting accuracy,
and serving accuracy) and endurance capacity [37, 41,43]. With respect to removing electronic devices andlight intervention studies, Dunican et al. [32] did notshow any effect of removing the electronic devices on the
single leg three hop test, while Zhao et al. [38] found that
14 days of red-light treatment at night increased sleep
quality and endurance performance (Cooper 12-minuterun test). Jones et al. [33] showed that an 8-week mindfulness-based stress reduction program improved rowing
performance (6000-m ergometer test). In contrast, Leveret al. [53] showed no improvement in tennis match performance (games won or lost) after combining mindfulness and sleep hygiene education.
In summary, napping interventions had conflicting
results since five studies showed a positive effect [35, 39,
40, 44, 45], one showed positive results but was combined

Page 12 of 18

with caffeine [46], three showed no effect [36, 49, 52],and one a negative effect [52]. All sleep extension studies demonstrated improvements in physical performance[37, 41, 43], as did light [38] and mindfulness interventions [33]. Lastly, removing electronic devices [32] or
combining mindfulness with sleep hygiene [53] did notaffect physical performance measures. The main effects
are summarized in Table 1.
Effects of Sleep Interventions on Recovery

Five studies investigated the effect of sleep interventions
on sleep quality, sleep duration, and recovery, of which
one study investigated the effect of an acute sleep hygieneintervention [54], two investigated the effect of naps [39,44], one investigated the effect of cold water immersion[55], and one investigated the impact of combining threestrategies [56].
Concerning naps, Boukhris et al. [39] studied the effectof a 40-min nap on levels of muscle damage and inflammatory responses and found positive effects. On theother hand, Nishida et al. [44] compared the effect ofshort (20 min) and long naps (60 min) compared withno naps on HRV and did not find any difference between
experiments. Chauvineau et al. [55] compared the effectof whole-body and partial-body cold water immersion
with the control condition (i.e., sitting 10 min in a controlled environment) on HRV, wellness (Hooper index),
creatine kinase, CMJ, and maximal isometric strength
24 h and 48 h post-intervention and found no differences
between conditions. In regard to sleep hygiene, Fullagar
et al. [54] demonstrated that a sleep hygiene intervention following a late-night soccer match had no effect on
physical recovery (Yo–Yo intermittent recovery test—level 2 and CMJ 12 h and 36 h post-match, submaximal
interval-based running test 18 h and 42 h post-match)or in blood markers of muscle damage and inflammation (C-reactive protein, creatine kinase, and urea 10 h,
20 h, 34 h, and 44 h post-match). Duffield et al. [56] combined sleep hygiene, full-body compression, and cold
water immersion after and between two sessions of oncourt tennis on the same day. They found a reduction inmuscle and joint soreness the next morning, and large
effect sizes, despite no significant differences, in reducing
fatigue and increasing total sleep time, but no differencesin vigor or sleep efficiency.
In summary, cold water immersion [55] and sleep
hygiene [54] had no impact on performance recovery, muscle damage, or inflammation. Naps positively
impacted muscle damage and inflammation [39], despite
no effect on HRV [44]. Combining sleep hygiene, cold
water immersion, and full-body compression positively
affected muscle and joint soreness [56].

Cunha et al. Sports Medicine - Open(2023) 9:58

Discussion
Sleep is widely recognized as one of the foundations for
optimal health, well-being, and performance for athletes[10, 13, 57]. This systematic review synthesized the evidence regarding sleep interventions aimed at improving
sleep, and whether this improvement would influence
performance and/or recovery. Twenty-five studies withdifferent sports and sleep interventions were analyzed.
The findings reinforced that napping and sleep extension were the most promising sleep interventions for
improved sleep and subsequent physical and/or cognitive
performance.
All the included studies that implemented sleep extension showed a positive impact on performance outcomes (e.g., reaction time or sport-specific performance).
The results showed that extending sleep duration by
46–113 min (e.g., increase of 11–27%) over 3–49 nights
in athletes that habitually slept ~ 7 h per night may be alogical recommendation for future sleep extension programs [37, 41, 43, 50]. To achieve such sleep duration,
studies have reported that athletes needed to extend theirusual time in bed to 9–10 h [37, 41, 43, 50]. In addition,
the individual characteristics of the athlete’s sleep habits should be considered before implementing any sleep
intervention, as it is important to adapt to individual
needs [24]. Lastella et al. [9] demonstrated, in a sample of 124 participants, that elite athletes obtained well
below 8 h of sleep per night (6.8 ± 1.1 h), which may not
be enough to maximize performance. For example, Sargent et al. [8] revealed that elite athletes reported needing
approximately 8.3 h of sleep to feel rested. Despite thisself-reported sleep need, only 3% of athletes obtained
their required sleep amount. It is plausible that athletes
who fall short of their sleep requirements are likely tobenefit from a sleep extension intervention.
Napping was the most representative sleep intervention of the included studies [35, 36, 39, 40, 42, 44, 45,
49, 52]. Napping is a strategy that provides an opportunity to supplement the night-time sleep period, offering
an alternative for athletes to increase sleep duration. In
most of the studies analyzed, the results revealed a positive impact of napping on cognitive performance [35, 42,
45, 49]. However, some mixed results were reported forphysical performance [35, 36, 45, 49, 52] and recovery[39, 44] outcomes. During nights of partial sleep restriction (e.g., 4 h of sleep), decreases in general performanceoutcomes such as muscle power or psychomotor vigilance were observed [4]. The included studies showedthat napping could restore performance to baseline levels[45, 49]. With regard to nap duration, the improvements
in physical and cognitive performance were greater innaps of longer duration (e.g., 90 min) compared withshorter durations (e.g., 40 min) after a normal night

Page 13 of 18[35]. However, following a night of partial sleep restriction, a short nap (20 min) was as effective as a long nap(90 min) in restoring performance to baseline levels(normal sleep night) [45]. There are still questions about
the effects of daytime naps on night-time sleep variables(e.g., latency), especially naps of longer durations [36, 58].
Further, the notion of sleep inertia (e.g., feeling of grogginess upon wakening) needs to be considered when napping is implemented. For example, the longer the nap thehigher the chance of experiencing sleep inertia [59]. A
period of at least 30 min should be allowed after a nap
to avoid the detrimental effects of sleep inertia on physical or cognitive performance [60], particularly for naps
longer than 90 min. Based on the results of the included
studies, it is unlikely that naps negatively affect performance outcomes in athletes. For all included studies, only
one showed that napping decreased sprint performancein track-and-field athletes. However, the study did notreveal any effects on other sprint variables or shooting
performance in pistol and rifle shooters [52].
The results of sleep hygiene interventions showed noeffect on performance recovery, blood markers of damage (creatine kinase) and inflammation (C-reactive protein), or cognitive performance [48, 54]. Sleep hygiene
currently refers to a list of behaviors, environmental conditions, and other sleep-related factors believed to promote improvements in sleep duration and quality [61].
Van Ryswyk et al. [48], contrasting with other studies thatapplied sleep hygiene with success [62, 63], concluded
that a sleep hygiene protocol did not improve sleep quality and/or duration. Fullagar et al. [54] found that a sleep
hygiene protocol resulted in a significant improvement
in sleep duration after a late night soccer match compared to no sleep hygiene (6:09 ± 0:43 h vs 4:30 ± 0:27 h;
P < 0.05), but no differences in recovery were observed
between conditions. A possible explanation could bethat even with an improvement in sleep duration, thisimprovement may not be enough, as it was still far fromthe 7 h of the minimum recommended sleep duration [5].
In studies that investigated the removal of electronic
devices, the results showed no impact on sleep and/or
athletic/cognitive performance [32, 34]. The main objective of this strategy is to reduce the exposure to the artificial light emitted by screens, especially before bedtime,
reducing the decline in sleep quality and disturbance inthe biorhythms [64]. Biorhythms are explained by theoscillation levels of endogenous hormones, like melatonin or cortisol, that regulate the sleep–wake cycle[65]. Despite this rationale, the results showed that theremoval of electronic devices did not result in any change
in sleep [32, 34]. Based on these results, it is unlikelythat the removal of electronic devices should be on the“first line” of sleep interventions, because the difficultyCunha et al. Sports Medicine - Open(2023) 9:58

of adherence by the athletes should also be considered.
In addition, using electronic devices up to one hour
before bedtime with the “night shift” mode (short-wavelength light limitation) significantly reduced melatonin
suppression when compared with blue-light exposure(10 ± 2.7% vs 41 ± 4.1%) [66]. Furthermore, if devices wereused with low light levels, the suppression of 10% may
have been even smaller. It appears that using electronic
devices in these circumstances, within reasonable limits,
may not be problematic for athletes’ sleep. Moreover, it
is still unclear whether ~ 10% of melatonin suppression
induces circadian disruption and whether the type ofactivities (e.g., social media or gaming) can promote cognitive arousal.
Concerning light interventions, two studies investigated the effect of phototherapy but with different objectives. Zhao et al. [38] studied the effect of whole-body
red-light phototherapy on sleep quality and endurance
performance. At the same time, Rosa et al. [51] investigated the effect of bright-light therapy on sleep/wakecycle and reaction time. It is known that light is the mostpowerful circadian synchronizer for humans, which
begins with its reception in the eyes and finishes in thepineal gland, which produces melatonin, a neurohormone essential for the functioning of the body-clock[67]. Zhao et al. [38] applied red-light therapy, which,unlike bright light, appears to have no impact on melatonin suppression [68] and may improve recovery [69,70]. Despite increased sleep quality and melatonin levels after red-light therapy, it is important to interpretthese results cautiously. The study used an inappropriate tool (the Pittsburgh Sleep Quality Index) to examine sleep quality over a short period and only analyzed
melatonin levels upon waking. The authors also found ahigher increase in running distance (Cooper 12-min runtest) in the red-light treatment group (12.8%) comparedto the control group (5.5%; P < 0.05). As the method used
to examine sleep over a short period was unreliable anddid not measure any exercise recovery outcome, these
conclusions must be interpreted cautiously. In contrast,
Rosa et al. [51] showed that bright-light therapy in theevening delayed the sleep/wake cycle and improved reaction time, promoting higher levels of alertness in a period
when the athletes would usually be preparing for sleep.
Further studies are needed to confirm these findings,
considering that bright-light therapy can manipulate thebody-clock to compete at night when alertness is usually
already starting to drop.
The rationale for the possible positive effects of cold
water immersion on sleep is that cold water immersion
could accelerate the declining core body temperatureand the reactivation of parasympathetic activity after
exercise [71, 72]. Despite this, Chavineau et al. [55] did

Page 14 of 18

not find any impact on sleep architecture, muscle damage, core temperature, or fatigue, while Duffield et al.
[56], combining cold water immersion with sleep hygieneand full-body compression, showed a positive effect onmuscle/joint soreness and sleep duration (large effectsizes though non-significant results). However, Duffield
et al.’s study [56] applied sleep hygiene and compression
garments in addition to cold water immersion, and this
could explain the differences between the results of thestudies.
Finally, the studies that investigated the effect of mindfulness combined with sleep hygiene or mindfulness
alone showed promising results. For example, Leveret al. [53] showed that combining sleep hygiene withmindfulness during a tennis tournament improved sleep
duration, compared with a control group without any
intervention (7.1 h vs 7.7 h). Despite an increase in sleep
duration, no performance or sleep quality improvements
were observed. Since this study only examined general
performance that may be influenced by several factors(games won or lost), the impact of this type of intervention needs to be examined in detail in future studies.
Jones et al. [33] tested a mindfulness intervention andshowed no effect on sleep duration but did find improvements in sleep quality, mindfulness tendency (Five Facet
Mindfulness Questionnaire) and rowing performance(6000-m ergometer test). It is plausible that mindfulness
can improve sleep quality and/or duration; it could also
positively impact physical/cognitive performance, as seenin sleep extension studies. However, it remains to be clarified whether the increase in mindfulness directly benefits athletic performance via attentional strategy, because
mindfulness training appears to improve performance inprecision sports such as shooting and dart throwing. Still,
few controlled experimental studies have investigated theeffects in non-precision sports [73].
In summary, this systematic review updated the knowledge about several sleep interventions’ effects on improving sleep and subsequent performance in athletes. In
2017, Bonnar et al. [24] conducted a systematic review
with a similar aim to the present review. Since then, manystudies have been published and our understanding about
the phenomena has improved. In the present review, wewere able to include 15 more studies that brought newinterventions, supporting some of the conclusions andshowing different directions in other topics, comparedto those of Bonnar et al. [24]. The effectiveness of sleep
extension programs was reinforced with two new studies
that showed, once again, the positive effects on sleep andsubsequent performance. Napping was the most studiedintervention since Bonnar et al.’s [24] study. The present
review includes eight new studies that gave a different perspective, identifying positive effects on cognitiveCunha et al. Sports Medicine - Open(2023) 9:58

performance, despite mixed results on physical performance and recovery, while Bonnar et al. [24] only had
two studies included with very different protocols, which
did not allow for an in-depth discussion. The amountof studies examining sleep hygiene remained the same,considering that Duffield et al.’s study [56] also included
compression and cold water immersion and Lever et al.
[53] included mindfulness, suggesting that more researchis warranted. New interventions, such as mindfulness,removing electronic devices at night or sleep/wake cycle
manipulation through bright-light exposure are includedin this review. Bonnar et al.’s review pointed out the lackof studies that evaluated cognitive techniques to improve
sleep and subsequent performance. The negative impact
of increasing arousal on the pre-competition night due tostress and anxiety, a common situation in the sports field,
is known [74]. Although we are far from a definitive conclusion about the effect of cognitive interventions, suchas mindfulness, researchers are beginning to be aware of
the importance of studying this topic. Our review reinforces the importance of this line of research that could
attenuate the detrimental effects of cognitive arousal on
pre-competition night and improve sleep.
Before implementing any strategy to improve sleep in
athletes, there is some information that should be considered (Fig. 3). The first step should to provide a sleep
education session, conducted by a specialist. The goal

Page 15 of 18

will be to raise awareness among athletes and coaches
about the importance of sleep for optimal performance/
recovery and explain the different strategies that could be
used [10, 24]. After that, the habitual sleep/wake patterns
should be identified [10]. This should be done with reliable and validated tools (e.g., actigraphy) for 7 to 14 days
and apply validated questionnaires in athletes (e.g.,
Athlete Sleep Behaviour Questionnaire) [74]. This will
facilitate an individualized approach to meet individual
needs and identify the athletes with clinical sleep issues(e.g., insomnia) who should be referred to a sleep physician. Some caution should be taken with sleep monitors,
as some athletes may be concerned about sleep monitor data, which may increase anxiety and result in worse
sleep [10, 74].
To implement a sleep extension program, it is necessary to consider whether the athlete is obtaining adequate
sleep for their needs [22]. If the athlete feels the need tosleep more, the recommendations based on included
articles could be applied, although with some caution, as
none of the included studies showed a low risk of bias.
Furthermore, it is important to consider that to increase
sleep duration based on the recommendations of thisreview, athletes may need to extend their usual time in
bed to 9–10 h [37, 41, 43, 50]. In cases of athletes who aresatisfied with the amount of sleep that they usually get,the possibility of increasing wakefulness in bed should be

Fig. 3 An example of how to implement a sleep intervention aimed at improving sleep and subsequent performance/recovery

Cunha et al. Sports Medicine - Open(2023) 9:58

considered before trying to extend sleep duration. Napping is an alternative strategy to supplement insufficientnight-time sleep, but can also be beneficial for those who
only want a boost in alertness during the day [10, 60].
Sleep hygiene is a set of behaviors that should be implemented, although its effectiveness may be limited whenused alone [48, 53, 56]. Implementing mindfulness is along-term strategy because it needs to be learned. Preliminary evidence showed the long-term effect of mindfulness (5 to 12 months) on sleep [75], although Joneset al. [33] showed positive results on sleep quality within
a 9-week period (one session per week). More researchis needed to allow more solid recommendations. Motivation is also an important variable when a behavioral
change is necessary, as in the case of sleep hygiene andmindfulness, and should be considered. Future researchshould investigate the impact of this variable on the effectiveness of behavioral interventions.
Long-term sleep monitoring should be conducted(sleep logs or validated devices) to assess whether interventions resulted in better sleep [10].
Limitations

The current systematic review has limitations whichshould be acknowledged. First, the strengths of our conclusions are limited, since none of the included studies
presented a low risk of bias. This is in line with a recent
expert consensus statement about athletes’ sleep studies,
warning about the poor quality of the evidence, and theneed to use more consistent, reliable, and valid researchmethods in athletes’ sleep studies [10]. To reduce therisk of bias, future studies should: design randomized
controlled or crossover trials; identify the chronotype,
due to possible bias in performance measures; explainin detail the randomization process; monitor a baseline
sleep period (1–2 weeks) without any intervention; consider the carry over effect of the interventions, in thecase of crossover trials; use objective and/or subjective
validated tools for monitoring sleep; use objective performance measures; report missing data; and register the
protocol before conducting the study. Second, there washigh heterogeneity between the type of sleep interventions, type of sport, performance tests used, and levelof the athletes. Lastly, there is a risk of language bias
because we only considered studies written in English.

Conclusion
Based on the results of this systematic review, increasing sleep duration through naps or night-time sleep may
positively impact physical and/or cognitive performance.
If athletes habitually obtain ~ 7 h of sleep per night, a general recommendation may be to increase sleep duration

Page 16 of 18

up to 2 h over 3–49 nights. Also, supplementing sleep
during the day with a nap (20–90 min) can be implemented when necessary. In addition to improving thesleep duration, naps can improve performance outcomes
after a regular night and restore performance decrements
to baseline levels after a night with partial sleep restriction. For strategies such as sleep hygiene, mindfulness, or
limiting the use of electronic devices before bedtime, itis plausible that such interventions can positively impact
performance outcomes if they can improve sleep quality
and/or duration. Strategies with light exposure may be an
option to manipulate the biological clock and increase thealertness of the athletes in the moments when this starts
to fall (e.g., at night). However, more studies are needed
to confirm these findings. Future research on this topic
should use more reliable and valid research methods toincrease the quality of evidence so that more solid conclusions can be drawn. In addition, studies that explore theeffect of 1–3 h of sleep restriction on physical and cognitive performance may be interesting, as this is the mostcommon situation detected in the athletes’ context.
Author Contributions
LC and PF devised the study. LC, EM, and PF developed the methodology
and interpreted the data. LC performed database searches and wrote theinitial draft of the manuscript. LC and JC executed the screening process,data extraction, and risk-of-bias assessment. The manuscript was criticallyrevised by JC, EM, JB, ML, and PF. PF supervised the study. All authors read andapproved the final manuscript.
Funding
Lúcio Cunha was supported by the Portuguese Foundation for Science andTechnology [UI/BD/151482/2021]. No other sources of funding were used
toassist in the preparation of this manuscript.
Availability of Data and Materials
Not applicable.
Code Availability
Not applicable.

Declarations
Ethics Approval and Consent to Participate
Not applicable.
Consent for Publication
Not applicable.
Competing interests
The authors declare that they have no competing interests.
Author details
1
Research Center in Sports Sciences, Health Sciences and Human Development, CIDESD, University of Maia, Maia, Portugal. 2 Portugal Football School,
Portuguese Football Federation, Cruz Quebrada, Portugal. 3 School of Sport,
Exercise and Health Sciences, Loughborough University, Loughborough, UK.
4Appleton Institute for Behavioural Science, Central Queensland University,
Adelaide, Australia. 5 Physical Education Department, College of Education,
United Arab Emirates University, Al Ain, Abu Dhabi, UAE. 6 Research Centerin Sports Sciences, Health Sciences and Human Development, CIDESD, Vila
Real, Portugal.

Cunha et al. Sports Medicine - Open(2023) 9:58

Received: 6 October 2022 Accepted: 18 June 2023

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