Mental fatigue (MF) has been shown to negatively impact subjective and behavioral outcomes, but its effects on physical performance may vary among individuals. This exploratory analysis aimed to determine whether sleep quality and chronotype influence responses to mental fatigue.
The study involved a randomized controlled trial where mental fatigue was induced through a 45-minute Stroop task, while a control group watched a documentary for the same duration. Participants were assessed on various dependent variables including subjective levels of mental fatigue, cognitive performance via a GoNoGo task, physical performance through a time trial, and the Rating of Perceived Exertion during the trial.
Sleep quality was measured using the Pittsburgh Sleep Quality Index, and chronotype was assessed with the Single Item Chronotype scale. The researchers included weekly caffeine consumption as a covariate in their analyses.
Results indicated that most analyses showed no significant differences in mental fatigue responses between different chronotype or sleep quality groups. However, there were notable findings regarding subjective measures. Specifically, sleep quality and chronotype had a significant influence on the general feeling of mental fatigue (p = 0.028 and p = 0.002, respectively) and a marked difference in sleepiness levels among chronotype groups (p < 0.001).
The authors concluded that while sleep quality and chronotype may affect subjective experiences of mental fatigue, they do not significantly modulate cognitive or physical performance outcomes. The study suggests that future research should incorporate a broader range of subjective and objective sleep measures and focus on athlete-specific populations to further explore the relationship between mental fatigue and sleep quality.