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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.

With digitalization and virtual entertainment being the megatrends of the 21st century, there is reasonable concern about the role of physical activity (PA) in the daily life of children and adolescents. To identify risk-groups with insufficient PA and to guide interventions, continuous and representative tracking of PA is crucial. In this paper, representative PA data of children and adolescents from the Motorik-Modul (MoMo) baseline study (2003-2006, N = 4,528) is compared to those of Wave 2 (2014-2017, N = 3,708). Participants aged 4-17 were drawn out of 167 sample points in Germany and the data was weighted to ensure representativeness for Germany. Organized (sports clubs and schools) and unorganized (unorganized sports and playing outside) PA was measured by questionnaire and stratified by sex, age, and socioeconomic status. Contrary to common expectation, overall PA remained stable among youths in the past ten years, however, there is an ongoing trend towards organized forms of PA at the expense of unorganized sports and playing outside. Besides different trends in settings, there is inequality in PA distribution among socioeconomic status and gender, unequally pronounced in different settings. (Autor).

Physical activity (PA) as a precondition of child development is related with social environmental correlates. However, domain-specific PA and gender issues have been neglected in studies on social support and modelling and PA in school-aged children. The aim of this study was to assess the relationships of parental and peer modelling and social support with domain-specific PA participation in a large sample of school-aged children, taking gender into account. 3,505 school children aged 6 to 17 years old participated in the German nationwide 'MoMo' cohort-study. By using the MoMo-PAQ the participants and their parents provided self-report data on perceived social support and social modelling and domain-specific PA participation. Relationships of social environmental variables and the physical outcomes were analysed by logistic regression analyses. At secondary school level, girls were less likely than boys to participate in physical activity in and outside of sports clubs, extra-curricular physical activity and in outdoor play (p < 0.05), but at primary school level this pattern only applied to club sport (p < 0.01). Girls also received less social support than boys (p < 0.01). Physical activity participation in all domains was associated with any of the social support and modelling variables and differences between physical activity domains and between boys and girls occurred. Most consistently physical activity in sports clubs was related with the social environmental correlates in boys (primary school: R2 = 0.60; secondary school: R2 = 0.45) and girls (primary school: R2 = 0.53; secondary school: R2 = 0.47). In future, reciprocal relationships of social environmental variables and PA should be considered in longitudinal studies to obtain insights into the direction of the associations. Furthermore, interventions encompassing the social environment and focussed particularly on the promotion of domain-specific PA in girls in secondary school-age are warranted.

[This corrects the article DOI: 10.1371/journal.pone.0293555.].

Body composition (BC) changes with age and is associated with morbidity and mortality. A physically active lifestyle influences BC and represents an important predictor of successful aging. To emphasize this, the World Health Organization established activity recommendations for all age groups. We describe BC during adulthood using a cross-sectional sample from a German community and investigate the associations between physical activity (PA), physical fitness (PF), and BC. Data from 329 men and women aged 35 to 86 years were analyzed. PA was measured by questionnaire and classified into sport activity and habitual activity. PF was measured through physical performance tests and BC by bioelectrical impedance analysis. Fat mass index (FMI) and fat-free mass index (FFMI) were calculated to represent height-adjusted BC. Associations between PA, PF, and BC were analyzed using linear regression models. For both sexes, strength was positively associated with FFMI (♂: ß = 0.313; ♀: ß = 0.213) and phase angle (♂: ß = 0.357; ♀: ß = 0.409). For FMI, a significant negative association with strength was found only in women (ß = -0.189). Cardiorespiratory fitness showed a negative association with FMI (ß = -0.312) and FFMI (ß = -0.201) for men, while in women a positive association was found for FFMI (ß = 0.186). For coordination, a significant association with FMI was observed only in women (ß = -0.190). Regarding PA only one significant relationship between sport activity and FMI among women (ß = -0.170) was found. In our sample, PF was closer related to BC than PA. Strength and cardiorespiratory fitness were the strongest predictors for BC. This supports the World Health Organization's activity recommendations to include both resistance and endurance training in the weekly sports program to maintain a healthy BC.

Background The bias caused by drop-out is an important factor in large population-based epidemiological studies. Many studies account for it by weighting their longitudinal data, but to date there is no detailed final approach for how to conduct these weights. Methods In this study we describe the observed longitudinal bias and a three-step longitudinal weighting approach used for the longitudinal data in the MoMo baseline ( N  = 4528, 4–17 years) and wave 1 study with 2807 (62%) participants between 2003 and 2012. Results The most meaningful drop-out predictors were socioeconomic status of the household, socioeconomic characteristics of the mother and daily TV usage. Weighting reduced the bias between the longitudinal participants and the baseline sample, and also increased variance by 5% to 35% with a final weighting efficiency of 41.67%. Conclusions We conclude that a weighting procedure is important to reduce longitudinal bias in health-oriented epidemiological studies and suggest identifying the most influencing variables in the first step, then use logistic regression modeling to calculate the inverse of the probability of participation in the second step, and finally trim and standardize the weights in the third step.

Background As children show a more complex but less structured movement behavior than adults, assessment of their many spontaneous and impulsive movements is a challenge for physical activity (PA) assessment. Since neither questionnaires nor accelerometers enable optimal detection of all facets of PA, a multimodal, combined approach of self-reported and device-based methods is recommended. Based on the number of days on which the participants reached the physical activity (PA) values given in the WHO guideline, this study examines 1) the difference between self-reported and device-based, measured PA and 2) whether PA differences between age and gender groups obtained by two methods are comparable. Methods Participants aged 6–17 years were randomly chosen and data were collected representatively at 167 sample points throughout Germany within the Motorik-Modul Study. PA of n  = 2694 participants (52.3% female) was measured using the ActiGraph accelerometer (ACC) and a physical activity questionnaire (PAQ). The sample was divided into three age groups (6–10 yrs. n  = 788, 11–13 yrs. n  = 823, 14–17 yrs. n  = 1083). Numbers of days per week with at least 60 min moderate to vigorous PA (MVPA) were analyzed for both methods. Results Only every 25th respondent (4%) reaches the WHO standard of 60 min MVPA every day if measured with ACC. Self-reported PA was slightly higher (9%) (mean PAQ  = 3.82 days; mean ACC  = 2.34 days; F method  = 915.85; p =  <.001; f Cohen  = .64). The differences between the methods are significantly smaller in younger children than in the older age groups ( F age  = 264.2, p  < .001; f Cohen  = .48). The older the subjects are, the lower is the proportion of those who meet the WHO guideline on each day, with girls meeting the guideline less frequently than boys in all age groups. Conclusion Children and adolescents living in Germany show a very low adherence to the WHO guideline on PA. While younger children are much more active with their free play, especially children over 10 years of age and especially girls should be the target of programs to increase PA.

Background and Objectives. Most performance theories were tested under controlled laboratory settings and offer therefore only limited transferability to real-life situations. E-sport competitions offer a relatively controllable while at the same time competitive setting, and our aim was to examine different influencing factors on competitive performance. Design and Methods. Salivary cortisol was measured immediately before, after, and 30 minutes after a game of 23 computer players during e-sport tournaments. The players answered the Flow Short Scale, which consists of the two subdimensions “flow experience” and “anxiety” subsequent to their game. The performance was assessed by the result of each player’s game (win or loss). Results. Mean cortisol levels increased significantly during the game but response patterns were inconsistent. Winners and losers differed significantly in anxiety with winners showing higher anxiety levels. After dividing the sample into three groups of different cortisol response patterns, significant differences in performance and anxiety were found, with low to moderate levels of cortisol being associated with the highest performance and anxiety. Conclusions. A low to moderate physiological arousal and a simultaneously high level of anxiety represent a favorable state for achieving optimal performance during e-sports. Anxiety seems to exert a stronger influence on performance than physiological arousal.

We examined the longitudinal association between physical activity (PA) and the risk of incident metabolic syndrome (MetS) among middle-aged, community-dwelling adults, including 591 individuals (314 females; mean (SD) age, 43.8 (8.5) years) who were free of MetS at baseline. Habitual and sports-related PA was assessed by a self-reported questionnaire. MetS was defined based on HDL-cholesterols, triglycerides, glucose or HbA1c, blood pressure, and waist circumference. We calculated Cox proportional hazard ratios (HR) and 95% confidence intervals (CI) using regression analyses. Over a mean follow-up of 12.5 years, 205 participants developed incident MetS. Four different sports-related PA measures were associated with a decreased risk of incident MetS: (1) Engaging in ≥ 75 min/week (HR 0.71, 95% CI 0.53–0.94), (2) maintaining a continuously high amount from baseline to follow-up of ≥ 75 min/week (HR 0.66, 95% CI 0.46–0.94), (3) starting from < 150 min/week at baseline to ≥ 150 min/week at follow-up (HR 0.65, 95% CI 0.45–0.94), and (4) increasing from < 16.6 MET-hours/week at baseline to ≥ 16.6 MET-hours/week at follow-up (HR 0.47, 95% CI 0.31–0.71). Thus, maintaining, starting or increasing sports-related PA is associated with a lower risk of incident MetS.

Background Outdoor play, sedentary behavior (SB), and moderate-to-vigorous physical activity (MVPA) are related to youth’s health, however, there are research gaps regarding 1) associations between outdoor play, SB, and MVPA across a broad pediatric age range (6–17 years), and 2) longitudinal associations between outdoor play, SB, and MVPA across childhood and adolescence. Two studies were conducted to address those research gaps: Study 1 aimed to investigate relationships between outdoor play and accelerometer-assessed SB and MVPA in a cross-sectional nationwide sample of children and adolescents in Germany. Study 2 aimed to investigate prospective associations between outdoor play and self-reported screen-time SB and MVPA and in a sample of children with three measurement timepoints across 11 years. Methods Data were obtained of the German national representative Motorik-Modul (MoMo) Study and the German Health Interview and Examination Survey for Children and Adolescents (KiGGS). In Study 1, N  = 2278 participants (6–17 years) were included with self-reported outdoor play and accelerometer-assessed SB and MVPA. Associations were examined via multiple linear regressions. In Study 2, N  = 570 participants (baseline: 4–7 years) were included in the longitudinal analysis with follow-ups six and 11 years later. Screen-time SB (TV watching and PC/Gaming), MVPA, and outdoor play were self-reported. Associations were investigated through a path prediction model. Results Study 1 showed that compared to <1 h outdoor play, higher engagement in daily outdoor play was related to lower SB (1-2 h: − 9.75 min/day, P  = 0.017; ≥2 h: − 17.78 min/day, P  < 0.001) and higher MVPA (≥2 h: + 3.87 min/day, P  = 0.001). The cross-sectional relationship between MVPA and outdoor play was moderated by sex (in favor of males) and age (in favor of younger children). Study 2 showed that outdoor play in early childhood negatively predicted PC use/Gaming in later childhood, but was unrelated to MVPA. Conclusion In Study 1, outdoor play was negatively related to SB cross-sectionally. In Study 2, outdoor play in early childhood was negatively related to PC and Gaming time in later childhood. Thus, providing outdoor play opportunities, especially during early childhood, has potential to prevent SB. Future research should investigate longitudinal relationships using device-based assessments for SB and MVPA.