The impact of COVID-19 on social life has been drastic and global. However, the different numbers of cases and different actions in different countries have been leading to various interesting yet unexplored effects on human behavior. In the present study, we compare the physical activity and recreational screen time of a representative sample of 1711 4- to 17-year-olds before and during the strictest time of the first COVID-19 lockdown in Germany. We found that sports activity declined whereas recreational screen time increased. However, a substantial increase in habitual physical activities leads to an overall increase in physical activity among children and adolescents in Germany. The effects differ in size but not in their direction between age groups and are stable for boys and girls. We conclude from this natural experiment that physical activity among children and adolescents is highly context-driven and mutual and does not act as a functional opposite to recreational screen time.

Reduced physical activity (PA) and prolonged screen time (ST) negatively influence health-related quality of life (HRQoL), a protective factor against illness and mortality. Studies addressing the relationship between PA, ST, and mental health in youth are scarce, especially in times with high mental health burdens like the COVID-19 pandemic. The purpose of this examination was to investigate whether PA, ST, and HRQoL before COVID-19 predict PA, ST, and HRQoL during the COVID-19 pandemic. Participants from the Motorik-Modul Study (MoMo; N = 1711; Mage = 10.36 (SD = 4.04) years, female = 49.8%; healthy weight = 76.8%) self-reported their PA and ST as well as HRQoL both before and during COVID-19. Relationships of all variables, from before to during COVID-19, were investigated through a path prediction model. Results showed all variables during COVID-19 were predicted by the respective levels before COVID-19, independent of gender and age. Cross-lags revealed a negative influence of before COVID-19 ST on during COVID-19 PA. HRQoL before COVID-19 was positively associated with during COVID-19 PA in children younger than 10 years and females, but not in adolescents and boys. As age- and gender-independent negative influence of before COVID-19 ST on during COVID-19 PA has been detected, health policy may be advised to focus on a general reduction in ST instead of PA enhancement to ensure high PA levels.

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Mental health (MH) and behavioural health are fundamental to a good quality of life. Only few studies investigated the influence between behavioural health (e.g., physical activity (PA), screen-time (ST)) and MH from childhood to adolescence. Therefore, this study investigated the relationship between PA and ST with MH by sex in a 11-year longitudinal cohort of German school children during 2003-2017. A German Motorik-Modul Cohort-Study subsample (N=686; 55.2% female; MageT1=5.57 years, SDageT1=1.00; MageT2=11.85 years, SDageT2=1.03; MageT3=16.86 years, SDageT3=1.04) who participated in all three measurements were analysed regarding PA, ST and MH (emotional symptoms, conduct problems, hyperactivity/inattention, peer relationship problems, prosocial behaviour, and overall strengths and difficulties). Path panel prediction models were run with T1, T2, and T3 PA, ST and MH indicators. PA predicted less television (TV)/video watching in females, and TV/video watching predicted personal computer (PC)/internet use in both sexes. Behaviour and MH results suggest for females higher TV/video and PC/internet use was related to higher MH challenges over maturation. Some preadolescent males MH challenges increased ST (TV/video watching and PC/internet use) in adolescence. Innovative and effective methods should be explored to reduce childhood ST especially among females with early signs of MH issues, and address preadolescent males MH challenges.