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| ID | Type | Description | Link |
|---|---|---|---|
| TDK-2025-4002 | Other Grant/Funding Number | Inonu University Scientific Research Projects Coordination (BAP) |
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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.
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.
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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| Control | Active Comparator | 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. |
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| Mental Fatigue | Experimental | 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. |
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| Nap20 | Experimental | 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. |
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| Nap40 | Experimental | 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. |
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| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| Mental Fatigue Induction | Behavioral | 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. |
| 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. |
| 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. |
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Inclusion Criteria:
Exclusion Criteria:
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| Name | Affiliation | Role |
|---|---|---|
| Ozgur EKEN, Associate Professor | Inonu University | Study Chair |
| Facility | Status | City | State | ZIP | Country | Contacts |
|---|---|---|---|---|---|---|
| Inonu University, Faculty of Sport Sciences | Malatya | Malatya | 44280 | Turkey (Türkiye) |
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.
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Randomized crossover repeated-measures design. Each participant completed all six experimental conditions in a randomized order with a 72-hour washout period between sessions.
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| Nap60 | Experimental | 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. |
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| Nap90 | Experimental | 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. |
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| Control Condition | Other | Participants watched a neutral documentary for 15 minutes without mental fatigue induction or daytime nap intervention before EEG and performance assessments. |
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| Daytime Nap 20 Minutes | Behavioral | Participants underwent a supervised 20-minute daytime nap following mental fatigue induction in a quiet, darkened room before post-intervention EEG and performance assessments. |
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| Daytime Nap 40 Minutes | Behavioral | Participants underwent a supervised 40-minute daytime nap following mental fatigue induction in a quiet, darkened room before post-intervention EEG and performance assessments. |
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| Daytime Nap 60 Minutes | Behavioral | Participants underwent a supervised 60-minute daytime nap following mental fatigue induction in a quiet, darkened room before post-intervention EEG and performance assessments. |
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| Daytime Nap 90 Minutes | Behavioral | Participants underwent a supervised 90-minute daytime nap following mental fatigue induction in a quiet, darkened room before post-intervention EEG and performance assessments. |
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| Immediately after completion of each experimental protocol. |
| 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). |
| ID | Term |
|---|---|
| D005222 | Mental Fatigue |
| ID | Term |
|---|---|
| D005221 | Fatigue |
| D012816 | Signs and Symptoms |
| D013568 | Pathological Conditions, Signs and Symptoms |
| D001526 | Behavioral Symptoms |
| D001519 | Behavior |
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