Mental fatigue (MF) has been shown to negatively impact subjective and behavioral outcomes in various performance contexts. However, the effects on physical performance outcomes have been less pronounced than previously reported. This discrepancy may be attributed to individual differences among participants. To further explore these differences, the authors of this study examined whether sleep quality and chronotype could modulate subjective and behavioral responses to MF.
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 of equal duration. Participants were assessed at approximately the same time of day to control for circadian influences. The dependent variables measured included subjective levels of MF using a visual analogue scale, cognitive performance through a GoNoGo task, physical performance via a time trial, and the Rating of Perceived Exertion during the time trial.
To evaluate the influence of sleep quality and chronotype, the Pittsburgh Sleep Quality Index and the Single Item Chronotype scale were utilized as between-subject variables in exploratory moderation analyses. Additionally, weekly caffeine consumption was included as a covariate in the analyses.
Most analyses revealed no meaningful differences in MF responses between groups categorized by chronotype or sleep quality. However, some significant findings were noted: sleep quality (p = 0.028) and chronotype (p = 0.002) had a significant influence on the general subjective feeling of MF, while differences in sleepiness levels were observed between chronotype groups (p < 0.001).
The authors suggest that future research should incorporate multidimensional subjective and objective measures of sleep and focus on athlete-specific populations to further clarify the relationship between MF and impaired sleep quality.
What this study does not show
This study does not establish a direct causal relationship between sleep quality or chronotype and physical performance outcomes in the context of mental fatigue.
Evidence scorecard
- Analytic validity: established
- Clinical validity: established
- Clinical utility: not established
The evidence is based on a human randomized controlled trial.