Linking physical fitness to perceived mental fatigue in school-aged adolescents: the moderator role of age and sex

Mental fatigue is an increasing concern among school-aged adolescents and may negatively affect academic performance and well-being. Identifying modifiable factors that can mitigate this condition is therefore critical. Accordingly, this study aimed to examine the relationships between physical fitness and perceived mental fatigue in school-aged adolescents, while also investigating the moderator role of age and sex in these associations. Four hundred and twenty-five school-aged adolescents (13.8 ± 1.4 years) participated in the present study, of whom 222 were boys and 203 were girls. Participants completed the Visual Analogue Scale using computers in the classroom to report their subjective feeling of mental fatigue. Also, participants completed the EUROFIT battery on two different days during the school period. Results revealed significant associations between age and mental fatigue, as well as with sit-and-reach, agility performance and cardiorespiratory fitness (course navette). In addition, regression analyses showed that, in Model 1, only agility was significantly associated with mental fatigue, whereas in Model 2, mental fatigue was positively associated with both sit-and-reach and agility performance, and in Model 3 was related only with age y sex. Finally, a moderating effect of age was observed in the relationships between mental fatigue and handgrip, horizontal jump and agility performance, without significant moderator effects for sex in any physical fitness variable. These findings indicate that interventions targeting agility and flexibility could be particularly effective in reducing mental fatigue among adolescents, being school-based programmes, considering age- differences, a key strategy to attenuate the perceived mental fatigue in scholars.