Diurnal variation of psycho-cognitive performances: effects of mental fatigue in young active men with a moderately morning chronotype

Abstract

The aim of this study was to evaluate the effects of mental fatigue on the daily variation of psycho-cognitive performances in young men with normal sleep quality and a moderately morning chronotype. Fourteen non-smoking active male students (age: 20.51 ± 0.92 years; height: 175 ± 5.27cm and weight: 73.19 ± 4.24 kg), voluntarily participated to this study. After giving consent and familiarization with all experimental procedures, subjects performed six test sessions at three times of the day (07:00, 12:00, and 18:00) to assess mood, reaction time, short-term memory, and vigilance. At each time point, testing was conducted under two randomized conditions : without mental fatigue and following mental fatigue. Results showed that psycho-cognitive performances present a circadian rhythm, and that fatigue induces alterations in psychological and cognitive functions at any time of the day and especially in the afternoon at 18:00 when cognitive performance normally reaches its highest level (p <0.05). In conclusion, the psycho-cognitive performances in young active men with a moderately morning chronotype were time-of-day dependent and alterations caused by mental fatigue are more remarkable when they reach its maximum values.