Effects of Mental Fatigue Duration on Cortical Activity and Jump Performance

Inonu University12 enrolled

Overview

"This study investigates whether the length of time spent on a mentally demanding task affects brain activity and jumping performance in physically active young men. Twelve healthy male university students, all regularly engaged in sport, completed four separate testing sessions on different days, each at least 72 hours apart. In one session (the control condition), participants watched a calm nature documentary. In the other three sessions, mental fatigue was induced by having participants perform a demanding attention task (the Stroop color-word test) continuously for 10, 15, or 30 minutes. Before and after each session, brain activity was recorded using electroencephalography (EEG), a painless method that measures electrical activity through sensors placed on the scalp. Immediately afterward, participants performed a countermovement jump test, a standard measure of explosive leg power used in sports science. The study examines whether longer periods of mental fatigue produce progressively larger changes in brain activity and jump performance, and whether changes in brain activity are related to changes in jumping ability. The findings may help athletes, coaches, and students better understand how mentally tiring activities, such as studying or exams, could affect physical performance shortly afterward."

"Mental fatigue is a psychobiological state induced by prolonged demanding cognitive activity, characterized by subjective tiredness and measurable decrements in sustained attention and executive control. While mental fatigue has been linked to impairments in endurance, strength, and anaerobic performance, evidence regarding explosive, single-effort tasks such as the countermovement jump (CMJ) remains sparse and inconsistent, and it remains unclear whether the cortical and behavioral consequences of mental fatigue scale with the duration of the inducing cognitive task. This study used a single-group, repeated-measures crossover design in which the same twelve participants completed a non-fatiguing control condition and three graded mental-fatigue protocols (10, 15, and 30 minutes of continuous Stroop-task performance), with session order counterbalanced across participants and a minimum 72-hour washout between sessions. All sessions were conducted in the same laboratory within a consistent daily time window (10:00 ± 1 hour) to minimize circadian confounds. Resting-state EEG (spectral power in delta, theta, alpha, and beta bands; theta/alpha and theta/beta ratios; spectral and sample entropy; frontal theta and posterior alpha) and subjective fatigue (0-10 visual analogue scale) were assessed immediately before and after each condition. Countermovement-jump height and its kinetic/kinematic correlates were then measured to evaluate explosive lower-limb power, the study's primary outcome; EEG parameters were treated as secondary, mechanistic outcomes. Data were analyzed using repeated-measures ANOVA, Holm-Bonferroni-corrected Friedman/Wilcoxon tests where appropriate, and repeated-measures correlation to examine the relationship between post-intervention EEG parameters and CMJ performance. The study tested the hypothesis that increasing Stroop-task duration would produce progressively larger shifts in EEG-derived cortical activation and parallel reductions in CMJ performance, and that these neurophysiological and performance changes would be significantly associated with one another."

Interventions

Nature Documentary (Control)BEHAVIORAL

Viewing of a neutral, cognitively undemanding nature documentary matched in duration to the mental-fatigue protocols, serving as a non-fatiguing control condition.

10-Minute Stroop TaskBEHAVIORAL

Continuous performance of the Stroop color-word interference task for 10 minutes to induce mental fatigue.

15-Minute Stroop TaskBEHAVIORAL

Continuous performance of the Stroop color-word interference task for 15 minutes to induce mental fatigue.

30-Minute Stroop TaskBEHAVIORAL

Continuous performance of the Stroop color-word interference task for 30 minutes to induce mental fatigue.

Eligibility

Sex: MALEMin age: 18 YearsMax age: 30 YearsHealthy volunteers:

Medical Language ↔ Plain English

Inclusion Criteria: * Healthy male volunteers aged 18-30 years * Enrolled in the Faculty of Sport Sciences at İnönü University * Engaged in structured exercise at least three days per week * Free of any neurological, psychiatric, cardiovascular, or musculoskeletal disorder * Normal or corrected-to-normal vision * Physically capable of completing the experimental protocol safely Exclusion Criteria: * Diagnosed neurological, psychiatric, cardiovascular, or musculoskeletal disorder * Lower-limb injury within the preceding 6 months * Use of medication known to affect central nervous system function * Prior diagnosis of a sleep disorder * Uncorrectable visual impairment or any disturbance of color perception * Cognitive or sensory limitation likely to interfere with performance of the Stroop task * Failure to complete a session in full, non-compliance with investigator instructions during testing, inability to produce an EEG recording of analyzable quality for technical reasons, or discontinuation of the experimental procedure for any reason * Non-compliance with pre-session restrictions (vigorous physical exercise or alcohol consumption within 24 hours before each session; caffeine, energy drinks, or other stimulant substances within 12 hours before each session)

Outcomes

Primary Outcomes

Countermovement Jump (CMJ) Height

Countermovement jump (CMJ) height was assessed using the My Jump Lab application (version 5.2; C. Balsalobre-Fernández, Madrid, Spain) via video recorded at 240 frames/s on an iPad Air 11-inch (M3), positioned on a tripod approximately 2 m from the participant. Take-off and landing frames were identified manually by the same investigator using the application's frame-by-frame function, and jump height was calculated from flight time using the equation h = (g·t²)/8. Two jump attempts were performed in each experimental session, with 60 seconds of rest between trials, and the better performance was retained for analysis.

Time frame: Immediately after completion of each experimental protocol (control, and 10-, 15-, and 30-minute Stroop-task mental fatigue conditions); sessions were separated by a minimum 72-hour washout period.

Secondary Outcomes

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. Average velocity (m/s), take-off velocity (m/s), and impulse (N·s) were provided automatically by the application as derived sub-parameters, computed from jump height and body mass using the biomechanical model incorporated in My Jump Lab. Flight time (ms) was calculated from the same video recording using the application's frame-by-frame analysis. These parameters were analyzed as complementary derived measures of CMJ performance.

Time frame: Immediately after completion of each experimental protocol.

EEG Absolute Band Power (Delta, Theta, Alpha, Beta)

Resting-state EEG was recorded using a 10-electrode montage (Fp1, Fp2, Fz, FC1, FC2, Cz, Pz, O1, Oz, O2) following the international 10-20 system, via a wireless EEG system (Emotiv EPOC Flex) sampling at 256 Hz. Following preprocessing (0.5-45 Hz band-pass filtering, ICA-based artifact removal, and amplitude normalization), power spectral density was computed for each channel using Welch's method, and absolute power was calculated within the delta (1-4 Hz), theta (4-8 Hz), alpha (8-13 Hz), and beta (13-30 Hz) frequency bands, expressed in normalized (dimensionless) units.

Time frame: Recorded immediately before and immediately after each experimental protocol (control, and 10-, 15-, and 30-minute Stroop-task mental fatigue conditions); each recording lasted 3 minutes with eyes closed.

EEG Theta/Beta Ratio

The theta-to-beta power ratio was calculated from resting-state EEG recordings (10-electrode montage, international 10-20 system) by dividing theta-band power by beta-band power for each channel. The outcome was expressed as a unitless ratio.