The study published in the European Journal of Sport Science explores the relationship between sleep quality, chronotype, and mental fatigue (MF) on various performance outcomes. Mental fatigue is known to negatively impact subjective and behavioral outcomes, but its effects on physical performance have been less clear.
In this randomized controlled trial, the researchers induced mental fatigue using a 45-minute Stroop task. Participants were divided into groups based on their sleep quality, assessed via the Pittsburgh Sleep Quality Index, and their chronotype, determined using the Single Item Chronotype scale. The control condition involved watching a documentary of equal duration.
The dependent variables measured included subjective MF levels using a visual analogue scale, cognitive performance assessed through a GoNoGo task, physical performance evaluated via a time trial, and the Rating of Perceived Exertion during the time trial. Weekly caffeine consumption was also included as a covariate in the analyses.
Results indicated that most analyses showed no significant differences in MF responses between the chronotype or sleep-quality groups. However, some subjective measures did reveal significant findings. Specifically, sleep quality and chronotype significantly influenced the general subjective feeling of MF (p = 0.028 and p = 0.002, respectively) and there was a notable difference in sleepiness feelings between chronotype groups (p < 0.001).
The authors suggest that future research should incorporate a broader range of subjective and objective measures of sleep and focus on athlete-specific populations to further delineate 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 the effects of mental fatigue on physical performance outcomes.
Evidence scorecard
- Analytic validity: established
- Clinical validity: established
- Clinical utility: not established