Physical Activity or Inactivity and Fatigue in Children and Adolescents: A Cross-Sectional Study

<b>Background/Objectives</b>: Physical inactivity needs to be strategically addressed throughout adolescence because it is often accompanied by an alteration in the quality of life. Fatigue is one of the most common symptoms encountered in medical practice. However, little is known about the causal relationship between lifestyle and fatigue. The purpose of this study was to describe the prevalence of fatigue among children and adolescents and to investigate whether various sport types and training volume/week are related to increased fatigue over time while considering gender and age. <b>Methods</b>: A total of 1617 participants (mean age = 13.3 ± 1.9 years, 8.2 to 16.1) completed a questionnaire assessing their perception of fatigue and including questions regarding weekly physical practices and attitudes toward sports and health. The participants were secondary school students, whether or not they practiced sports, leisure activities, or music. Analyses of variance and Newman-Keul post-hoc tests were applied to assess differences between groups. A mediation model was used to determine the relationship between physical activity and fatigue score with the relevant role of mediating factors (physical activity level or physical activity type). <b>Results</b>: Older adolescents had significantly higher scores of fatigue than younger ones (28.9 ± 17.5 vs. 25.6 ± 16.6; <i>p</i> < 0.01). Girls had significantly higher scores of fatigue than boys (30.7 ± 17.5 vs. 23.8 ± 15.8; <i>p</i> < 0.001). Additionally, 10.7% of participants were sedentary and presented significantly higher scores of fatigue than participants in the Leisure (35.1 ± 18.2 vs. 29.4 ± 17.3; <i>p</i> < 0.001) and Sport groups (35.1 ± 18.2 vs. 25.3 ± 16.2; <i>p</i> < 0.0001). In the sedentary group, low physical activity was associated with a high score of fatigue; but in the Sport group, high physical activity was associated with a low score of fatigue. <b>Conclusions</b>: Fatigue is closely related to health, physical activity volume, gender, and age. Fatigue symptoms obtained through a questionnaire assessment can serve as an important index for health evaluation.