The article presents results of research, where mental fatigue was caused by solving mathematical problems. Significant instability of work pace was found, but there was no general reduction of speed of task solving or increase of number of mistakes. Also variations of average span of eye sight were noticed. Day sleep during the work break helped to stabilize these parameters and evaluate subjective state of health and energy.
Keywords: day sleep, eye movement, mental fatigue, span of eye sight, working efficiencyAll articles can be accessed under Creative Commons Attribution 4.0 International Public License (CC BY 4.0).