The Restorative Role of Daytime Naps in Mentally Fatigued Endurance Athletes (Nap&Run)

The Restorative Role of Daytime Naps in Mentally Fatigued Endurance Athletes: a Randomized Controlled Trial

This randomized, counterbalanced crossover study investigated whether a 30-minute daytime nap can mitigate the effects of experimentally induced mental fatigue in amateur master endurance athletes. Male athletes completed two home-based experimental sessions separated by one week: a mental fatigue condition, in which a 30-minute cognitively demanding task battery preceded the nap, and a control condition, in which participants took only the nap. Sleep parameters during the nap were monitored by wrist actigraphy, and perceived sleep quality was assessed after awakening. Subjective sleepiness, perceived mental fatigue, and cognitive performance were evaluated before the nap, immediately after the nap, and/or 30 minutes after the nap.

The study examined whether mental fatigue influenced nap characteristics and whether the nap improved recovery-related outcomes. The main outcomes included actigraphy-derived nap parameters, perceived sleep quality, sleepiness assessed with the Karolinska Sleepiness Scale, perceived mental fatigue assessed using a visual analogue scale, and cognitive performance assessed with a Flanker task.

Study Overview

• Status: Completed
• Conditions: Sleep; Mental Fatigue; Endurance Exercise; Daytime Napping
• Intervention / Treatment: Behavioral: Mental Fatigue Induction Protocol; Behavioral: Daytime Nap

• Study Type: Interventional
• Enrollment (Actual): 11
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Italy
  • Milan, Italy
    • University of Milan

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Male amateur master endurance athletes
• Age between 28 and 50 years
• Peak oxygen uptake (VO₂peak) ≥55 mL·kg-¹·min-¹
• Habitual nocturnal sleep duration of at least 7 hours
• Able and willing to complete both experimental sessions and daytime nap procedures

Exclusion Criteria:

• Diagnosed medical condition or injury
• Diagnosed sleep disorder
• Use of medications or supplements affecting sleep or cognition, including melatonin
• Habitual sleep duration of less than 7 hours per night
• Inability to nap during the experimental sessions

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: Single

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Mental Fatigue + Daytime Nap; Participants completed a 30-minute mental fatigue induction protocol consisting of cognitively demanding tasks, followed by a 30-minute daytime nap performed at home between 14:00 and 15:00. Subjective sleepiness, perceived mental fatigue, nap characteristics, perceived sleep quality, and cognitive performance were assessed before and/or after the nap.	Behavioral: Mental Fatigue Induction Protocol; Participants completed a 30-minute computerized cognitive task battery designed to induce mental fatigue before the daytime nap. The protocol consisted of three consecutive 10-minute cognitively demanding tasks: a Flanker task, a memory task, and a Stroop task.; Behavioral: Daytime Nap; Participants took a 30-minute daytime nap at home between 14:00 and 15:00, at least one hour after lunch, in a quiet and dimly lit room. Nap characteristics were monitored using wrist actigraphy, and perceived sleep quality was assessed after awakening.
Active Comparator: Daytime Nap Control; Participants completed the control condition consisting of a 30-minute daytime nap performed at home between 14:00 and 15:00, without the preceding mental fatigue induction protocol. Subjective sleepiness, perceived mental fatigue, nap characteristics, perceived sleep quality, and cognitive performance were assessed before and/or after the nap.	Behavioral: Daytime Nap; Participants took a 30-minute daytime nap at home between 14:00 and 15:00, at least one hour after lunch, in a quiet and dimly lit room. Nap characteristics were monitored using wrist actigraphy, and perceived sleep quality was assessed after awakening.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Perceived mental fatigue	Perceived mental fatigue was assessed using a 100-mm visual analogue scale for mental fatigue (VAS-MF), anchored from 0-mm "No mental fatigue" to 100-mm "Maximum mental fatigue." Participants marked the point that best represented their perceived level of mental fatigue.	Before the nap, immediately after the nap, and 30 minutes after the nap in each experimental condition.

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Subjective sleepiness	Subjective sleepiness was assessed using the Karolinska Sleepiness Scale (KSS), a 9-point scale ranging from 1, "not sleepy at all," to 9, "extremely sleepy."	Before the nap, immediately after the nap, and 30 minutes after the nap
Flanker Task Reaction Time	Accuracy during the computerized Flanker task was calculated as the percentage of correct responses and used as an indicator of executive function performance. Accuracy ranges from 0 to 100%.	30 minutes after the nap in each experimental condition.
Perceived Nap Sleep Quality	Perceived sleep quality after the nap was assessed using a 10-point Likert scale, from 0 to 10, with higher scores indicating better perceived sleep quality.	Immediately after the nap in each experimental condition.
Actigraphy-Derived nap start time	Clock time at which the nap period begins, usually identified from the rest interval or sleep diary. Nap start time is expressed as clock time, using the 24-hour format.	During the 30-minute daytime nap in each experimental condition.
Actigraphy-Derived nap time in bed	Total time spent in bed or within the defined nap/rest interval, from nap start time to nap end time. Values are expressed in minutes.	During the 30-minute daytime nap in each experimental condition.
Actigraphy-Derived nap total sleep time	Total duration of epochs scored as sleep during the nap/rest interval. Values are expressed in minutes.	During the 30-minute daytime nap in each experimental condition.
Actigraphy-Derived nap sleep onset latency	Time elapsed between nap start time and the first epoch scored as sleep. Values are expressed in minutes.	During the 30-minute daytime nap in each experimental condition.
Actigraphy-Derived nap sleep efficiency	Sleep efficiency is expressed as a percentage, ranging from 0% to 100%, and is calculated as the ratio between total sleep time and time in bed multiplied by 100	During the 30-minute daytime nap in each experimental condition.
Actigraphy-Derived nap fragmentation index	An index reflecting sleep disruption or restlessness, based on movement and short immobility bouts during the sleep period. Higher values indicate more fragmented sleep. Fragmentation index is expressed as a percentage from 0% to 100%	During the 30-minute daytime nap in each experimental condition.

Collaborators and Investigators

• Sponsor: L.U.de.S. Sagl
• Collaborators: University of Rennes; Universty of Milan; University of Physical Culture in Cracow; Universita Telematica E-Campus

Publications and helpful links

General Publications

• Kaida K, Takahashi M, Akerstedt T, Nakata A, Otsuka Y, Haratani T, Fukasawa K. Validation of the Karolinska sleepiness scale against performance and EEG variables. Clin Neurophysiol. 2006 Jul;117(7):1574-81. doi: 10.1016/j.clinph.2006.03.011. Epub 2006 May 6.
• Van Cutsem J, Marcora S, De Pauw K, Bailey S, Meeusen R, Roelands B. The Effects of Mental Fatigue on Physical Performance: A Systematic Review. Sports Med. 2017 Aug;47(8):1569-1588. doi: 10.1007/s40279-016-0672-0.
• Marcora SM, Staiano W, Manning V. Mental fatigue impairs physical performance in humans. J Appl Physiol (1985). 2009 Mar;106(3):857-64. doi: 10.1152/japplphysiol.91324.2008. Epub 2009 Jan 8.
• Macari M, Pela IR, Silva CA, Viana RS. Fever response induced by intravenous and intracerebroventricular injection of pyrogen in thyroidectomised and protein-calorie malnourished rabbits. Pflugers Arch. 1990 Jan;415(4):440-3. doi: 10.1007/BF00373621.
• Mesas AE, Nunez de Arenas-Arroyo S, Martinez-Vizcaino V, Garrido-Miguel M, Fernandez-Rodriguez R, Bizzozero-Peroni B, Torres-Costoso AI. Is daytime napping an effective strategy to improve sport-related cognitive and physical performance and reduce fatigue? A systematic review and meta-analysis of randomised controlled trials. Br J Sports Med. 2023 Apr;57(7):417-426. doi: 10.1136/bjsports-2022-106355. Epub 2023 Jan 23.
• Lastella M, Halson SL, Vitale JA, Memon AR, Vincent GE. To Nap or Not to Nap? A Systematic Review Evaluating Napping Behavior in Athletes and the Impact on Various Measures of Athletic Performance. Nat Sci Sleep. 2021 Jun 24;13:841-862. doi: 10.2147/NSS.S315556. eCollection 2021.

Study record dates

Study Major Dates

• Study Start (Actual): January 11, 2021
• Primary Completion (Actual): May 15, 2021
• Study Completion (Actual): May 15, 2021

Study Registration Dates

• First Submitted: April 28, 2026
• First Submitted That Met QC Criteria: May 5, 2026
• First Posted (Actual): May 12, 2026

Study Record Updates

• Last Update Posted (Actual): May 12, 2026
• Last Update Submitted That Met QC Criteria: May 5, 2026
• Last Verified: May 1, 2026

More Information

Terms related to this study

• Keywords: Recovery; Sleep; Running; Actigraphy; Napping
• Additional Relevant MeSH Terms: Behavioral Symptoms; Fatigue; Pathological Conditions, Signs and Symptoms; Behavior; Signs and Symptoms; Mental Fatigue
• Other Study ID Numbers: Nap&Run01

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: Individual participant data will not be made publicly available. Data supporting the findings of this study may be available from the corresponding author upon reasonable request.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No