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

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.

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.

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.