Objective Assessments of Mental Fatigue During a Continuous Long-Term Stress Condition

Figures

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  FIGURE 1. Experimental procedures. (A) The experiment included two phases, i.e., phase 1 with each assessment session for the first three consecutive competition days, and phase 2 with three assessment sessions with a 24-h period of sleep deprivation during the last two competition days. (B) The assessment included four sessions, which were 1 min self-rating, 5 min resting-state EEG, 4 min audio stimulation oddball task, and 4 min visual simulation oddball task; there were short breaks between each session. EEG = electroencephalography.

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  FIGURE 2. EEG processing flow diagram.

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  FIGURE 3. The analyzed results of PFC EEG. (A) 10 s filtered EEG data from Day 1 and 5. (B) The average power spectral density (PSD) of Day 1 (blue) and Day 5 (orange), the shade indicates the standard deviation of the PSD. The PSD value on Day 5 in the 13–18 Hz band is lower than that of Day 1. (C) The Rényi entropy of EEG over six assessment sessions. The Rényi entropy significantly increased over six sessions (p < 0.05, ANOVA), and it was significantly higher in the last session than in the first day. Day 4-A was the first assessment in day four, day 4-B was the second assessment in day four.

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  FIGURE 4. The reaction time for the oddball task and self-rated fatigue for the SSS over six assessment sessions. Error bars indicate the standard deviation. (A) The reaction time for the audio stimulation (blue) and visual stimulation (orange) increased as the competition progressed, and the bars indicate the standard deviation. (B) The self-rated fatigue increased as the competition progressed, and Day 5 is significantly different from the first three assessments. Day 4-A was the first assessment in day four, day 4-B was the second assessment in day four.

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  FIGURE 5. Sleep time changes during the competition. (A) The total sleep time before each assessment. Error bars represent standard deviation. Day 4-A was the first assessment in day four, day 4-B was the second assessment in day four. (B) The EEG Rényi entropy and sleep time correlation analysis.