Comparison of statistical models for characterizing continuous differences between two biomechanical measurement systems.

Most biomechanical processes are continuous in nature. Measurement systems record this continuous behavior as curve data, which is often treated inappropriately in validation studies. The current paper compares different statistical models for analyzing the agreement of curves from two measurement systems. All models were evaluated in various error scenarios (simulated and real-world data). Excellent results were obtained using a functional method, with coverage probabilities close to the desired level in all data sets. Pointwise constructed bands had a lower coverage probability, but still contained most of the curve points and may thus be an option in scenarios where assumptions of functional models are violated (e.g., when curves are much noisier than those presented here, or in the presence of drift). Models that account for within-subject variation showed a higher coverage probability and less uncertainty about the variation of band limits. We hope this study, along with the provided research code, will inspire researchers to use methods for curve data more frequently and appropriately.

Urban-Rural Differences in Children's and Adolescent's Physical Activity and Screen-Time Trends Across 15 Years.

BACKGROUND: Urban and rural areas have been experiencing major demographic and structural changes, characterized by an aging population in rural areas and a growth of cities in number and size. However, it is poorly researched how children's physical activity and screen time developed in urban and rural areas. To address this deficit, we investigated physical activity and screen-time trends in Germany's pediatric population across four urbanicity levels (rural, small town, medium-sized town, city). METHOD: We obtained weighted data at three cross-sectional timepoints between 2003 and 2017, representative for Germany's child and adolescent population. Physical activity and screen time were self-reported. We analyzed trends using a structural equation modeling framework for the overall sample and calculated interactions between the trends and age and gender, respectively. RESULTS: In total, 12,161 children and adolescents between 4 and 17 years participated in the study. Children and adolescents in rural areas experienced a downward trend in total physical activity. Outdoor play and leisure-time physical activity decreased across all areas, with the strongest decline in rural areas. Computer and gaming time increased across all areas except for cities, with the sharpest increase in rural areas. The decline in outdoor play and the incline in computer and gaming time were driven by adolescents. Females showed stronger increases in computer and gaming time than males. CONCLUSION: Our findings suggest that in a representative sample of children and adolescents in Germany, detrimental trends in children's physical activity and screen time occur at a higher rate in rural areas compared with urban environments. This provides critical information for health policy: While all children and adolescents should be targeted for physical activity promotion, a special focus should be on tailoring interventions for rural areas to prevent and mitigate inequalities in physical activity across urban and rural areas.

Changes of Self-Rated Health Status, Overweight and Physical Activity During Childhood and Adolescence-The Ratchet Effect of High Parental Socioeconomic Status.

Childhood and adolescence are important life periods for the development of health status and physical activity (PA) behaviours. This study analyses the stability and potential changes of self-rated health status, overweight and PA behaviour over time, specifically focusing on the age and the socioeconomic status of children and adolescents. We employ representative longitudinal data for German children and adolescents from the Motorik-Modul Study and the German Health Interview and Examination Survey. Using four different dichotomous health status and PA indicators (self-rated health status [SRHS]; overweight; moderate-to-vigorous PA; and leisure sports engagement), we report within-person transition rates across the panel waves when the survey was taken (2003-2006, 2009-2012, and 2014-2017). Additionally, we report results of logistic regressions estimating the impact of children's age, gender, migration background, and their parents' socioeconomic status on these transition rates. The transition rates show mixed results. While children and adolescents from highly problematic states reporting bad SRHS and no leisure sports engagement at an early stage tend to improve later on, overweight children mostly stay overweight. Age and social inequality indicators correlate with some of the chances of improving or worsening the health and PA states. Most clearly, high parental status prevents the health status and PA from worsening over all transitions, particularly becoming overweight, representing a ratchet effect. The results of the present study underline that health policy needs to target specific groups to reduce social inequality in the health status and PA of children and adolescents.

Development of coordination and muscular fitness in children and adolescents with parent-reported ADHD in the German longitudinal MoMo Study.

This study examined the development of muscular fitness and coordination in children and adolescents with and without attention deficit hyperactivity disorder (ADHD) over a period of 11 years. Data was collected in three measurement waves as part of the longitudinal, representative Motorik-Modul (MoMo) study in Germany (2003-2006, 2009-2012, 2014-2017). The overall sample comprised 2988 participants (253 with ADHD, 65% males; 2735 non-ADHD, 47% males; mean age 9 years). Structural equation modeling was conducted, and the estimated models had a good fit. No differences in muscular fitness were observed between participants with and without ADHD. Participants with ADHD had a lower coordinative performance at first measurement than those without ADHD. The difference in coordinative performance persisted throughout the study period.

Indicators to Assess Physical Health of Children and Adolescents in Activity Research-A Scoping Review.

Sufficient physical activity can help promote and maintain health, while its lack can jeopardize it. Since health and physical activity lay their foundation for later life in childhood and adolescence, it is important to examine this relationship from the beginning. Therefore, this scoping review aims to provide an overview of physical health indicators in children and adolescents in research on the effects of physical activity and sedentary behavior. We identified the indicators used to quantify or assess physical health and summarized the methods used to measure these indicators. We systematically searched Scopus, Pubmed, and Web of Science databases for systematic reviews. The search yielded 4595 records from which 32 records were included in the review. The measurements for physical health reported in the reviews contained measures of body composition, cardiometabolic biomarkers, physical fitness, harm/injury, or bone health. Body composition was the most used indicator to assess and evaluate physical health in children, whereas information on harm and injury was barely available. In future research longitudinal studies are mandatory to focus on the prospective relationships between physical activity or sedentary behavior, and physical health.

Physical fitness of children and youth with asthma in comparison to the reference population : Cross-sectional results of the population-based MoMo study in Germany.

BACKGROUND: Physical fitness is an essential marker of health. The literature regarding the question of whether individuals with asthma have reduced physical fitness compared to their non-asthmatic peers is inconsistent and focuses on the cardiorespiratory endurance dimension. This study provides a comparison of different dimensions of physical fitness in individuals with and without asthma on the basis of the German population-based study "KiGGS" (German Health Interview and Examination Survey for Children and Adolescents) and its in-depth study "MoMo" (2009-2012: wave 1 and 2014-2017: wave 2). METHODS: In total, 7731 individuals aged 6-30 years were included in this cross-sectional analysis at two measurement waves, including 353 individuals with and 7378 without asthma. The 12-month prevalence of physician-diagnosed asthma was assessed by interview. Physical fitness was measured by six test items of the MoMo test profile. "Cardiorespiratory endurance" was measured by an ergometric test, "muscular strength" by standing long jump, push-ups and sit-ups and "coordination" by jumping sideways and balancing backwards. Because of the broad age range of the sample, age- and sex-specific percentiles were used. Physical activity, age, gender and general state of health were assessed by questionnaire. RESULTS: The individuals with asthma reported a poorer general state of health at both measurement waves. However, the results of the fitness tests indicated that they were as physically fit as their peers without asthma in relation to cardiorespiratory endurance and muscular strength. The mean percentiles were all within the same range. The results of the comparisons of coordination performance were inconsistent. At wave 1 they were within the same range, at wave 2 individuals with asthma showed a poorer coordination performance (p = 0.041; HL = 4.125, CI of HL 0.155-8.125). CONCLUSIONS: To the best of our knowledge, this is the first study to compare the physical fitness of individuals with and without asthma by considering several dimensions of physical fitness. The study demonstrates that cardiorespiratory endurance and muscular strength are not reduced in individuals with asthma. The results of the comparisons at the two measurement waves were remarkably stable.

Relating outdoor play to sedentary behavior and physical activity in youth - results from a cohort study.

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.

Reply to Kersting et al. Comment on "Wunsch et al. The Impact of COVID-19 on the Interrelation of Physical Activity, Screen Time and Health-Related Quality of Life in Children and Adolescents in Germany: Results of the Motorik-Modul Study. Children 2021, 8, 98".

In reply to the comment of Kersting et al [...].

Population density predicts youth's physical activity changes during Covid-19 - Results from the MoMo study.

Children in Germany showed positive physical activity changes during the first Covid-19 lockdown in April 2020, but it is unclear how the changes relate to population density, which we investigated in a longitudinal sample of 1711 youth (4-17 years). For each ten citizens more per km2, less positive physical activity changes were observed. For example, a child living in an area with 100 citizens/km2 increased daily life physical activity by 44.50 min/day, whereas a child living in an area with 3000 citizens/km2 only engaged in an additional 9.70 min/day. Policymakers should ensure that youth in densely populated areas have access to physical activity opportunities during the pandemic.

Sports participation of children and adolescents in Germany: disentangling the influence of parental socioeconomic status.

BACKGROUND: Participation in sports and physical activity (PA) is a critical resource for children's health and social development. This study analyzes how the parental socioeconomic status (SES) of children and adolescents affects their PA in sports clubs (organized sports) and outside of sports clubs (unorganized sports) and tests whether the potential impact of parental SES is mediated by the opportunity structure of their residential area (walkability, infrastructure, etc.) and by family and peer support for PA. Furthermore, PA is analyzed respecting differences by gender and migration background. METHODS: Using representative data from the MoMo/KiGGS study (2009-2012 and 2014-2017), we take into account about 8000 measurements from about 7000 subjects. We estimate hurdle regression models to analyze the minutes per week spent on sports activities. RESULTS: Results show that children with a higher parental SES, children living in areas with many opportunities for PA, and children receiving family and peer support are more physically active than children without these features. Controlled for opportunities and support, status effects are small but visible. The differences regarding parental SES are much more apparent for organized sports than for unorganized sports, indicating the relevance of economic resources. Boys are more active than girls, whereas there is no clear effect of migration background. CONCLUSIONS: The coefficient of parental SES on organized sports most probably relates to the resources needed to participate in sports clubs, including fees and equipment. Lower membership fees might potentially help to integrate children with low parental SES into sports clubs and thereby make organized sports more accessible to all social classes.

Comparison of self-reported & device-based, measured physical activity among children in Germany.

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%) (meanPAQ = 3.82 days; meanACC = 2.34 days; Fmethod = 915.85; p = <.001; fCohen = .64). The differences between the methods are significantly smaller in younger children than in the older age groups (Fage = 264.2, p < .001; fCohen = .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.

The Impact of COVID-19 on the Interrelation of Physical Activity, Screen Time and Health-Related Quality of Life in Children and Adolescents in Germany: Results of the Motorik-Modul Study.

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.

Population-based trends in physical fitness of children and adolescents in Germany, 2003-2017.

Physical fitness is an important health resource. From 2003 onwards, the MoMo study, a part of the German Health Interview and Examination Survey for Children and Adolescents (KiGGS), has investigated physical fitness on the basis of nationally representative data. The objective of this paper was to analyse trends in physical fitness of three cohorts at the ages of 4-17 years. Changes within 10 test items of the MoMo-test profile are reported. The mean values of physical fitness and the relevant influencing factors were directly compared across cohorts (in the total group and in age-and sex-subgroups). Statistical significance of differences was examined by calculating the confidence intervals (95% CI) for complex samples; effect sizes were determined using Cohen's d. The results indicated that physical fitness levels of German children and adolescents initially slightly increased between MoMo baseline (2003-2006) and wave 1 (2009-2012). This could partly be attributed to increased physical activity in sports clubs and in extracurricular sports at school. Then, between MoMo wave 1 and MoMo wave 2 (2014-2017) the physical fitness of children and adolescents in Germany remained the same, as did all influencing factors with the exception of extracurricular sport. From a public health perspective, programmes and measures that can increase the chances for all children and adolescents to strive for greater physical fitness should be of the highest priority.

Trends in active commuting to school from 2003 to 2017 among children and adolescents from Germany: the MoMo Study.

BACKGROUND: Inactivity in children and adolescents is a global issue requiring interventions that target different domains of physical activity, such as active transport. The aim of this study was to assess the prevalence, historical trends and socio-demographic correlates of active commuting to school (ACS) in a nationwide sample of girls and boys from Germany. METHODS: Data of commuting behaviour and socio-demographic factors were collected, covering three measurement points from 2003 to 2017. The MoMo Study derived its data from a representative sample of children and adolescents aged 4-17 years who answered a questionnaire (N = 11 387). Statistically significant differences between Baseline, Wave 1 and Wave 2 were determined via 95% confidence intervals (CIs) for complex samples. RESULTS: Overall, ACS decreased from 84.4% at the first measurement point to 78.3% in the third measurement point. The proportion of cases in which children opted for passive modes of commuting increased predominantly in those aged 4-5 years, in children with a low-to-medium socio-economic status, and in children residing in small- or medium-sized towns. No gender differences were found in active commuting. The results of multinomial logistic regression identified age, migration background and residential area as correlates of walking for boys. For girls, the likelihood of walking, cycling and taking public transport instead of opting for motorized transport increased with age. CONCLUSIONS: Intervention programmes to increase active transport in children and adolescents should target different age groups and also consider parental influence in determining the child's choice of transport mode.

Predictive value of physical fitness on self-rated health: A longitudinal study.

BACKGROUND: The self-rated health of adolescents and young adults is important for estimating future morbidities and mortality. Little is known about how physical fitness in younger populations predicts self-rated health. This longitudinal study (2003-2017) aims to explore the effects of physical fitness on self-rated health on the basis of the German population-based study KiGGS and its in-depth study, MoMo. METHODS: Self-rated health was assessed using a one-item scale, and physical fitness was measured with seven test items covering the dimensions of coordination, muscular fitness, and cardiorespiratory fitness. Longitudinal analyses were conducted using the structural equation modeling approach in Mplus 8.0 using the maximum likelihood estimator. RESULTS: The longitudinal samples of the KiGGS/MoMo study (T1, n = 2376; T2, n = 2821; and T3, n = 2047) had a mean age of 8.5, 14.8, and 20.0 years at T1, T2, and T3, respectively. All measurement and structural models had excellent model fits. While the results of the latent regression analysis indicated moderate-to-high stability for the coordination and muscular fitness dimensions, only low-to-moderate stability coefficients were found for cardiorespiratory fitness and self-rated health. Furthermore, small significant cross-lagged regression coefficients revealed that coordination and muscular fitness predicted self-rated health at later measurement points. CONCLUSION: To the best of our knowledge, this is the first longitudinal study to demonstrate the positive predictive value of two dimensions of physical fitness, coordination and muscular fitness, on self-rated health at a later stage. The public health implications are highlighted.

Physical activity and screen time of children and adolescents before and during the COVID-19 lockdown in Germany: a natural experiment.

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.

Measurement properties of the German version of the Physical Activity Enjoyment Scale for adults.

The physical activity enjoyment scale (PACES) is a measurement instrument that is commonly used in monitoring and intervention research to assess how much people enjoy being physically active, as this has been related to physical activity adherence. However, while the measurement properties of PACES are well-researched in the English language, there is a gap of research in the German language, especially when looking at adults. Thus, the purpose of this work was to examine reliability, factorial validity, criterion-related validity, and measurement invariance across sex, age groups and time of the PACES for German-speaking adults. Data was obtained from the Motorik-Modul-Study (MoMo) in which 863 adults (53.5% female; mean age = 20.9 years) were examined. To investigate measurement invariance across age groups, data from 2,274 adolescents (50.5% female; mean age = 14.4 years) was obtained additionally. The study provided a nationwide representative sample for Germany. Results showed high internal consistency of PACES in adults (Cronbach's α = .94). Confirmatory factor analyses confirmed the invariance of the measure across age groups, time, and sex. Criterion-related validity could be shown as the global factor significantly correlated with overall physical activity, physical activity in sports clubs, and leisure-time physical activity. The analyses of factorial structure indicated a method effect for positively and negatively worded items. Correlated uniqueness, latent method factor and a hybrid model were applied to analyze the method effect and results indicated that the method effect of positively worded items was predictive of physical activity independently of the global factor. Overall, it can be concluded that PACES is reliable, valid and invariant measure of physical activity enjoyment to be used in German-speaking adults. Further studies are warranted to examine the factorial structure of the PACES and the consequences of the method effect.

Representative Percentile Curves of Physical Fitness From Early Childhood to Early Adulthood: The MoMo Study.

Introduction: Monitoring of physical fitness in youth is important because physical fitness is a summative indicator of health. From a developmental and preventive perspective, physical fitness levels are relatively stable from childhood to early adulthood. Thus, it is important to monitor physical fitness on a population based level being able to intervene at early stages (1). In order to reliably assess and evaluate the physical fitness of youth, a reliable system of standard values based on representative data is required. The aim of this analysis is to report sex- and age-specific physical fitness percentile curves from childhood to early adulthood in a nationwide sample in Germany. Methods: We use data from the nationwide representative Motorik Modul (MoMo) Study in Germany (data collection wave 1: 2009-2012; age: 4-23 years; n = 3,742; 50.1% female). Physical fitness was assessed by means of the MoMo test profile covering four dimensions of physical fitness (strength, endurance, coordination, and flexibility) and including eight physical fitness items. Percentile curves were fitted using the LMS transformation method of Cole and Green. Results: Standardized age- and sex-specific physical fitness percentiles were calculated for eight items: ergometric endurance testing, standing long jump, push-ups, sit-ups, jumping side-ways, balancing backwards, static stand, and stand and reach test. The physical fitness curves differ according to gender and the fitness dimension. Physical fitness improvements with age are linear (e.g., max. strength) or curvilinear (e.g., coordination) and have their stagnation points at different times over the course of adolescence. Discussion: Our results provide for the first time sex- and age-specific physical fitness percentile curves for Germany from 4 to 17 years. Differences in curve-shapes indicating a timed and capacity-specific physical fitness development. Nationwide German physical fitness percentiles can be useful in comparing different populations (e.g., cross-country), reporting secular trends, comparing special groups, and to evaluate physical fitness interventions.