*4.2. Explanation Approaches*

Overall, our results show no evidence for a negative effect of the COVID-19 pandemic on physical fitness in children between the ages of 7 and 9 years, but changes varied for the different test items and dimensions. Especially, performances of the COVID cohorts in test items for strength increased. It seems that alternative options of exercising physical fitness like online and indoor workouts mitigate some effects of COVID-19 pandemic. However, due to the restrictions and closures of organized forms in sports clubs or schools, we conclude that dimensions where high intensities and stimuli are needed could not benefit. This could suggest the relevant role of physical activity with peers and within an institution to maintain a global and comprehensive development in all dimensions of physical fitness.

When classifying the data into gender and age-specific percentiles of a nationwide reference sample, the children in this specific community represent a very high level of physical fitness above the average [33,34]. The community has various specific initiatives and commitments to promote physical activity. For example, the primary school curriculum emphasizes the importance of physical fitness and appropriate promotion is determined in the preamble. The community is also a part of the project "Bewegte Kommune-Kinder" which aims to enable a sufficient and adequate development of physical fitness for all children in the community. It seems that children who had higher levels of physical fitness before COVID-19 are more resilient with regard to restrictions and limitations affecting physical activity. Similary, Jarnig et al. [23] reported that children who were members of sports clubs had better cardiorespiratory fitness measures at all time points. However, a higher level in the beginning leads to a higher level after the pandemic [23]. Adequate levels of physical fitness appear to increase resilience to limited physical activity due to external circumstances, such as the lockdowns during the COVID-19 pandemic.

Furthermore, there is evidence that total physical activity did not decline globally during the COVID-19 pandemic but that the form of being physically active changed [19–21,35]. While organized physical activity decreased, time spent in habitual physical activity and unstructured forms such as playing outside increased [20,22,35]. Schmidt et al. [22] found an increase from 75 min per day before the COVID-19 pandemic to 105 min per day playing outside during lockdown in spring 2020 for 6-to-10-year-old children in Germany. Most notably, socioeconomic background and place of residence are influencing determinants of levels of physical activity and physical fitness [19,20,32,35]. We also analyzed physical activity changes in our sample and can confirm these findings. Children indicated that they spent less minutes for physical activity in sports clubs, while time for physical activity in leisure time increased during the COVID-19 pandemic [36].

Wessely et al. [32] reported decreasing results for measurements of physical fitness during the COVID-19 pandemic, whereby children with a high social burden showed lower performance levels. Children with low socioeconomic status also showed lower levels of physical activity, but the home and living environment had a particular influence [19,20]. In our study, we have no data on socioeconomic status of the study subjects, but we

consider community structure data. The community has less than 5000 inhabitants and is located in the north-east of Baden-Württemberg in Germany. The environment is known as rural with access to green areas and playgrounds. For the children in this community, the environment might have provided easy opportunities to be physically active during the COVID-19 pandemic and thus possibly prevented a negative effect on physical fitness. For rural children, the impact of COVID-19 policies and restrictions was limited, but results may differ in urban children. Asked with whom they were physically active, more children in this community named their parents, when restrictions were issued [36].
