## 4 Discussion
This finding is in line with one study by [PERSON] et al. [23] who found higher performance in four different physical fitness tests in those schoolchildren who were physically active during PE classes and school recesses. Furthermore, [PERSON] et al. [24] found a higher cardiorespiratory fitness in young people who were sedentary for more than 15 min during recess time. Likewise, [PERSON] et al. [45] found that higher physical fitness (e.g., cardiorespiratory fitness, muscular strength) was associated with being active during PE classes among Brazilian schoolchildren. Conversely, [PERSON] et al. [46] found that physical fitness was not related to during-school PA in Georgian schoolchildren. This discrepancy could be explained by the different methodology applied (i.e., FitnessGram test) or by the fact that the information was reported by the teachers and not by the schoolchildren. There are some potential reasons justifying our results. First, children who spend less time on PA during both PE classes and school recesses spend more time in sedentary behaviors (characterized by a low energy expenditure), which are associated with undesirable health outcomes (e.g., excess weight, low physical fitness) [8]. Moreover, replacing MVPA with any other movement behavior (e.g., sedentary behavior) predicted higher adiposity and lower physical fitness (e.g., cardiorespiratory fitness) in children [47]. Second, a higher PA intensity demands a greater energy expenditure [48], and, consequently, schoolchildren who engage in higher PA intensity expend more energy expenditure than their counterparts [49]. In this sense, [PERSON] et al. [50] found that PE classes and recesses are the school settings that generate the highest energy expenditure. Third, higher PA intensity is also associated with health benefits in the young population (e.g., normal weight, higher physical fitness) [8,51], which could also be applicable in the school context. Fourth, another possible explanation could lie in the relationship between the PA intensity and a healthier diet. Eating healthy foods is associated with higher odds of being physically active (i.e., more MVPA) and less sedentary in children, compared to their counterparts consuming less healthy meals [52]. Supporting this, a healthy diet is associated with a more adequate weight status [53] and high physical fitness [54]. This study is not without limitations. First, the cross-sectional precludes establishing cause-effect relationships, and reverse causality may occur if children with excess weight or low GFS engage in lower PA intensity during PE classes or school recesses (or both), and vice versa. Second, although we used validated PA questionnaires, we did not use more objective measure (e.g., accelerometers), which would have provided a more accurate estimation of PA level. Third, BMI is a limited measure of the extent and distribution of body fat, but it has the great advantage of having consistent and comparable data in many population-based surveys, especially compared with other methods, such as dual-energy x-ray absorptiometry (DEXA), which more complex and expensive [35]. Moreover, a systematic review concluded that DEXA and BMI were highly correlated [55] for determining body fat. Fourth, the failure to consider the developmental status of the participants could have introduced a confusing effect. Finally, we have not taken into account if children had access to equipment in the school recess, since those can help increase PA [56] and provide opportunities for children to select physical activities of their choice. Despite these limitations, this study includes some strengths. For instance, we used objective measures to determine excess weight and physical fitness (e.g., BMI, ALPHA fitness test battery [26]) in the sample of schoolchildren analyzed. Furthermore, since only a few studies have analyzed the association between PA at school setting and excess weight or physical fitness, we contribute to increase the scientific knowledge of this understudied topic.