Effects of Different Nap Durations on Volleyball Performance and EEG Activity Following Mental Fatigue (MFNAP)

Effects of Mental Fatigue and Different Nap Durations on Volleyball Performance and Brain Activity

Mental fatigue is known to impair cognitive and physical performance in athletes, but the effectiveness of different nap durations in counteracting these effects remains unclear. The purpose of this randomized crossover study is to investigate the effects of mental fatigue and different nap durations (20, 40, 60, and 90 minutes) on volleyball-specific performance and electroencephalographic (EEG) activity in trained male volleyball players. Mental fatigue is induced using a 15-minute Stroop task. Performance outcomes include the Volleyball Agility Test (VAT) and Countermovement Jump (CMJ), while cortical activity is assessed using resting-state EEG recordings. The findings are expected to improve understanding of the neurophysiological mechanisms underlying mental fatigue and recovery and to provide evidence-based recommendations regarding optimal nap duration for athletes.

Study Overview

• Status: Completed
• Conditions: Mental Fatigue; Recovery; Sport Performance; Volleyball
• Intervention / Treatment: Other: Control Condition; Behavioral: Mental Fatigue Induction; Behavioral: Daytime Nap 20 Minutes; Behavioral: Daytime Nap 40 Minutes; Behavioral: Daytime Nap 60 Minutes; Behavioral: Daytime Nap 90 Minutes

Detailed Description

Mental fatigue has emerged as an important factor influencing athletic performance by impairing attention, executive function, decision-making, and motor performance. Volleyball is a sport requiring rapid cognitive processing, agility, explosive power, and precise motor control, making athletes particularly vulnerable to the detrimental effects of mental fatigue. Although daytime napping has been proposed as an effective recovery strategy, the optimal nap duration for restoring sport performance and brain activity following mental fatigue remains uncertain.

This study employs a randomized crossover repeated-measures design in which each participant completes six experimental conditions: Control, Mental Fatigue, Mental Fatigue followed by a 20-minute nap, Mental Fatigue followed by a 40-minute nap, Mental Fatigue followed by a 60-minute nap, and Mental Fatigue followed by a 90-minute nap. Mental fatigue is induced using a standardized 15-minute computerized Stroop task. A 72-hour washout period is maintained between consecutive experimental sessions.

Primary assessments include volleyball-specific agility performance, countermovement jump performance, and resting-state electroencephalographic (EEG) recordings obtained before and after mental fatigue and following the nap intervention. EEG analyses focus on spectral power in the delta, theta, alpha, and beta frequency bands as well as Theta/Alpha and Theta/Beta ratios.

The study aims to determine whether different nap durations differentially improve volleyball-specific performance and cortical activity following mental fatigue. The results are expected to provide practical recommendations for coaches and athletes regarding evidence-based recovery strategies while contributing to a better understanding of the neurophysiological mechanisms underlying mental fatigue and post-nap recovery.

• Study Type: Interventional
• Enrollment (Actual): 10
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Turkey (Türkiye)
  • Malatya
    • Malatya, Malatya, Turkey (Türkiye), 44280
      • Inonu University, Faculty of Sport Sciences

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Male volleyball players aged 19 to 22 years.
• Minimum of 3 years of regular volleyball training and active participation in organized training.
• Apparently healthy and free from neurological, cardiovascular, musculoskeletal, or metabolic disorders.
• Normal or corrected-to-normal vision.
• Willing to provide written informed consent.
• Agreed to refrain from strenuous exercise, alcohol, and caffeine for at least 24 hours before each experimental session.

Exclusion Criteria:

• History of neurological, psychiatric, cardiovascular, or musculoskeletal disorders.
• Current injury affecting sports performance.
• Use of medications known to influence cognitive function, sleep, or central nervous system activity.
• Diagnosed sleep disorders.
• Failure to comply with study procedures or pre-test instructions.
• Inability to complete all experimental sessions.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: None (Open Label)

Number of Arms

6

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: Control; Participants completed the control condition without mental fatigue induction or daytime nap intervention. A neutral documentary was viewed for 15 minutes. Resting-state EEG recordings, volleyball-specific agility performance, and countermovement jump performance were assessed according to the study protocol.	Other: Control Condition; Participants watched a neutral documentary for 15 minutes without mental fatigue induction or daytime nap intervention before EEG and performance assessments.
Experimental: Mental Fatigue; Participants completed a 15-minute computerized Stroop task to induce mental fatigue. Following the mental fatigue protocol, resting-state EEG recordings, volleyball-specific agility performance, and countermovement jump performance were assessed.	Behavioral: Mental Fatigue Induction; Mental fatigue was induced using a standardized 15-minute computerized Stroop Color-Word Task designed to increase cognitive load and induce mental fatigue before performance and EEG assessments.
Experimental: Nap20; Participants completed a 15-minute computerized Stroop task followed by a supervised 20-minute daytime nap. Resting-state EEG recordings, volleyball-specific agility performance, and countermovement jump performance were assessed after the nap intervention.	Behavioral: Mental Fatigue Induction; Mental fatigue was induced using a standardized 15-minute computerized Stroop Color-Word Task designed to increase cognitive load and induce mental fatigue before performance and EEG assessments.; Behavioral: Daytime Nap 20 Minutes; Participants underwent a supervised 20-minute daytime nap following mental fatigue induction in a quiet, darkened room before post-intervention EEG and performance assessments.
Experimental: Nap40; Participants completed a 15-minute computerized Stroop task followed by a supervised 40-minute daytime nap. Resting-state EEG recordings, volleyball-specific agility performance, and countermovement jump performance were assessed after the nap intervention.	Behavioral: Mental Fatigue Induction; Mental fatigue was induced using a standardized 15-minute computerized Stroop Color-Word Task designed to increase cognitive load and induce mental fatigue before performance and EEG assessments.; Behavioral: Daytime Nap 40 Minutes; Participants underwent a supervised 40-minute daytime nap following mental fatigue induction in a quiet, darkened room before post-intervention EEG and performance assessments.
Experimental: Nap60; Participants completed a 15-minute computerized Stroop task followed by a supervised 60-minute daytime nap. Resting-state EEG recordings, volleyball-specific agility performance, and countermovement jump performance were assessed after the nap intervention.	Behavioral: Mental Fatigue Induction; Mental fatigue was induced using a standardized 15-minute computerized Stroop Color-Word Task designed to increase cognitive load and induce mental fatigue before performance and EEG assessments.; Behavioral: Daytime Nap 60 Minutes; Participants underwent a supervised 60-minute daytime nap following mental fatigue induction in a quiet, darkened room before post-intervention EEG and performance assessments.
Experimental: Nap90; Participants completed a 15-minute computerized Stroop task followed by a supervised 90-minute daytime nap. Resting-state EEG recordings, volleyball-specific agility performance, and countermovement jump performance were assessed after the nap intervention.	Behavioral: Mental Fatigue Induction; Mental fatigue was induced using a standardized 15-minute computerized Stroop Color-Word Task designed to increase cognitive load and induce mental fatigue before performance and EEG assessments.; Behavioral: Daytime Nap 90 Minutes; Participants underwent a supervised 90-minute daytime nap following mental fatigue induction in a quiet, darkened room before post-intervention EEG and performance assessments.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
EEG Spectral Power	Resting-state electroencephalographic (EEG) activity was recorded from the Fz, Cz, Pz, O1, and O2 electrode sites. Power spectral density was analyzed for the delta (1-4 Hz), theta (4-8 Hz), alpha (8-13 Hz), and beta (13-30 Hz) frequency bands. All frequency-band power values were expressed in microvolts squared per hertz (µV²/Hz).	At baseline, immediately after the mental fatigue task, and immediately after completion of the assigned intervention during each experimental session.
EEG Theta/Alpha Ratio	The theta-to-alpha power ratio was calculated from resting-state EEG recordings obtained from the Fz, Cz, Pz, O1, and O2 electrode sites by dividing theta-band power by alpha-band power. The outcome was expressed as a unitless ratio.	At baseline, immediately after the mental fatigue task, and immediately after completion of the assigned intervention during each experimental session.
EEG Theta/Beta Ratio	The theta-to-beta power ratio was calculated from resting-state EEG recordings obtained from the Fz, Cz, Pz, O1, and O2 electrode sites by dividing theta-band power by beta-band power. The outcome was expressed as a unitless ratio.	At baseline, immediately after the mental fatigue task, and immediately after completion of the assigned intervention during each experimental session.
Volleyball-Specific Agility Performance	Volleyball-specific agility performance was assessed using the Volleyball Agility Test (VAT). Performance was quantified as test completion time (seconds), with lower values indicating better agility performance.	Immediately after completion of each experimental protocol.
Countermovement Jump Height	Countermovement jump (CMJ) performance was assessed using the My Jump Lab application by measuring jump height in centimeters (cm), with higher values indicating better jump performance.	Immediately after completion of each experimental protocol.

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Countermovement Jump-Derived Mechanical and Kinematic Parameters	Countermovement jump (CMJ)-derived mechanical and kinematic parameters were obtained using the My Jump Lab application from the CMJ assessment performed at the end of each experimental protocol. Participant jump height and body mass were entered into the application's manual data-entry module, which provided flight time (ms), average velocity (m/s), take-off velocity (m/s), and impulse (kg·m/s). These parameters were analyzed as complementary derived measures of CMJ performance.	Immediately after completion of each experimental protocol.
Pittsburgh Sleep Quality Index (PSQI) Score	Sleep quality was assessed using the Pittsburgh Sleep Quality Index (PSQI), a validated self-reported questionnaire that evaluates sleep quality over the previous month. The PSQI consists of 19 self-rated items yielding a global score ranging from 0 to 21, with higher scores indicating poorer subjective sleep quality.	Baseline (before the first experimental session).
Visual Analog Scale (VAS) Score for Perceived Nap Quality	Perceived nap quality was assessed using a 100-mm Visual Analog Scale (VAS). Participants rated the overall quality of their daytime nap on a horizontal line ranging from 0 mm (very poor nap quality) to 100 mm (excellent nap quality). Higher scores indicate better perceived nap quality.	Immediately after each daytime nap intervention (20-, 40-, 60-, and 90-minute nap conditions).

Collaborators and Investigators

• Sponsor: Inonu University
• Investigators: Study Chair: Ozgur EKEN, Associate Professor, Inonu University

Study record dates

Study Major Dates

• Study Start (Actual): October 1, 2025
• Primary Completion (Actual): December 1, 2025
• Study Completion (Actual): December 1, 2025

Study Registration Dates

• First Submitted: June 30, 2026
• First Submitted That Met QC Criteria: July 11, 2026
• First Posted (Actual): July 14, 2026

Study Record Updates

• Last Update Posted (Actual): July 14, 2026
• Last Update Submitted That Met QC Criteria: July 11, 2026
• Last Verified: July 1, 2026

More Information

Terms related to this study

• Keywords: Recovery; EEG; Electroencephalography; Brain Activity; Athletes; Volleyball; Agility; Cognitive Performance; Nap; Mental Fatigue; Countermovement Jump
• Additional Relevant MeSH Terms: Behavioral Symptoms; Fatigue; Pathological Conditions, Signs and Symptoms; Behavior; Signs and Symptoms; Mental Fatigue
• Other Study ID Numbers: OB-MFNAP-2026-01; TDK-2025-4002 (Other Grant/Funding Number: Inonu University Scientific Research Projects Coordination (BAP))

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: Individual participant data will not be shared because the study includes a small sample size, and no data-sharing plan was included in the approved study protocol or informed consent. Aggregate study results will be reported in scientific publications.

Drug and device information, study documents

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