Posters 1

Background: Children’s independent mobility (CIM) represents their freedom to travel in their neighbourhood without adult supervision. It has been speculated that secular declines in CIM have coincided with a major increase in mental health problems such as anxiety and depression among children. Purpose: We investigated the relationships between two indicators of CIM and parent-perceived child distress in a national longitudinal study of Canadian parents. Methods: We recruited 2,291 parents of 7- to 12-year-olds across Canada and followed up with participants every 6 months until June 2022 (i.e., 4 assessments spanning 1.5 years). We assessed mobility licenses (i.e., children’s permission to do certain activities on their own) with 6 items (Hillman et al., 1990) and home range (i.e., how far [in minutes] children can roam with friends and/or siblings) with a 4-point item. Parents reported their child’s distress on a validated 11-point scale. We used generalized estimating equations to assess relationships between CIM measures and distress controlling for children’s age and gender, household income, study wave, school attendance and whether the household was in isolation in the week preceding the survey. Results: At each successive time point, the percentage of children experiencing clinically elevated distress was 51.8%, 44.0%, 43.2% and 42.4%, respectively. There was a graded association between home range and distress (p[trend] < 0.001). Compared to children allowed to roam 15-minutes (OR = 0.61; 95% CI: 0.51-0.72) had lower odds of elevated distress. CIM licenses were not associated with distress. Conclusions: Higher home range was associated with significantly lower parent-perceived child distress during the COVID-19 pandemic. Practical implications: Findings underscore the need for interventions to prevent child distress, including strategies to support children’s home range. Funding: Heart and Stroke Foundation of Canada.

Background: Child pedestrian/cyclist safety remains a concern, particularly in marginalized and underserved communities where access to resources is an issue. Traffic gardens (TG) offer purpose-built, authentic, and engaging informal learning environments. They are cost-effective, adaptable, and simple to implement, making them readily deployable in communities with greater disparities. Purpose: To examine the logistics of program delivery and reach among underserved populations for TG in North America. Methods: An online survey invitation was sent to TG representatives from across North America. Participants reported details on TG logistics, programming, curriculum, and reach with fixed and open-ended questions. Frequencies and descriptives summarized the sample and open-ended responses were coded using qualitative methods. Results: Participants represented TG (n=50) from across the USA and Canada. The majority (n= 38, 76%) were fixed/permanent facilities, established within the last 5 years (84%), with early elementary as the most commonly served age group (n=48, 96%). Non-profit organizations, schools and local governments were the most common partners for planning, installation and routine operations. Free play (n=41, 82%) was the most common type of activity at the TG, followed by rodeos (n=28, 56%), lessons (n=26, 54%), and physical education class (n=20, 40%). Most (n=30, 60%) reported having established curriculum for bicycle safety or bicycle skill-building (n=22, 44%) or promotion of bicycling (n=10, 20%). Most (n=44, 88%) respondents indicated there was some programming to reach specific groups: low income (n=27, 54%), Spanish speaking (n=5, 25%), specific racial/ethnic groups (n=3, 6%) and special needs (n=2, 4%). Conclusions: TG offer a range a programming and can serve as a resource to their communities and an asset to encourage the development and practice of bicycling skills and enjoyment for all. Practical implications: TG can serve as a partner for building children’s bicycling skills thereby encouraging lifelong participation in active transportation and address existing inequities.

Background: Childhood and adolescence are critical years for the formation of lifetime habits. Understanding how activity-related behaviours cluster and change in youth can help to time specific lifestyle interventions.

Purpose: We aimed to identify typologies of activity-related behaviours in children and adolescents and to explore transitions between them.

Methods: The present study utilised data from the ELSPAC cohort. Data were collected at 11, 15 and 18 years of age. Activity-related behaviours included time spent outdoors, in organised physical activity (PA), sleeping, and watching TV and playing PC games. Latent transition analysis was employed to identify distinct typologies at each timepoint and transitions between them.
Results: Four distinct typologies were identified and labelled as Actives (high outdoor time and time in organised PA, low screen time; 12.8% of the sample at 11years; 23.6% at 15years; 20.4% at 18years), Active screeners (moderate outdoor time and high screen time; 21.0% at 11years; 24.3% at 15years; 10.4% at 18years), Poor sleepers (low proportion of meeting sleep recommendations; 1.1% at 11years; 8.1% at 15years, 50.8% at 18years), Averages (median levels of all activity-related behaviours; 65.1% at 11years; 44.0% at 15years; 18.4% at 18years). Most typologies remained relatively stable during the transition from 11 to 15 years, except Averages (53.2% stability). During the transition from 15 to 18 years, only Poor sleepers remained stable (99.5%), while other typologies had lower stability.

Conclusions: The most common typology, Averages, was the least stable from 11-15 years, suggesting that this period is one of change. Despite being relatively uncommon at earlier ages, the poor sleeper typology was the most common at age 18years.

Practical implications: Lifestyle interventions are required to be implemented throughout adolescence to stop the Averages from transitioning to Poor sleepers typology.

Funding: DJ was supported by the OP RDE project (DSGC-2021-0022, Reg. No.: CZ.02.2.69/0.0/0.0/19_073/0016713).

Background: Available evidence regarding activity behaviours and mental health among adolescents has focused primarily on physical activity (PA) and negative mental health outcomes such as anxiety, or more commonly, depression. An emerging field of research is determining associations between sedentary behaviours and screen-time, and worse mental health symptoms in adolescents. However, mixed results occur when type and context of the sedentary behaviour and screen-time is considered. Furthermore, the association between PA and sedentary behaviour and screen-time with positive mental health is relatively unknown. Establishing what is known on the synergistic or independent associations of sedentary behaviour, screen-time and PA with mental health is imperative for future research. Purpose: This review synthesised the available evidence on individual and joint associations between sedentary behaviours, screen-time, PA, and positive and negative mental health outcomes in adolescents. Methods: A systematic search of PubMed, Web of Science, CINAHL and PsychINFO, PsychARTICLES electronic databases was conducted in March to May 2021. Twelve independent researchers took part in the selection process using predefined inclusion criteria. Studies were included if they included either or both PA and sedentary behaviour or screen-time data and at least one mental health outcome (depression, anxiety, or positive mental health) in adolescents. A narrative synthesis of observational studies was conducted. Results: Thirty-six original articles met the eligibility criteria and were included in the review. There was a limited number of articles considering sedentary behaviour or screen-time in the context of PA levels (and vice-versa). Evidence on positive mental health was nearly non-existent. Conclusions: Ultimately, this review highlighted that a critical gap in the field is apparent. Practical implications: Considering the association of these exposures together may lead to a better understanding of the optimal ‘dose’ of PA, sedentary behaviour and screen-time to buffer negative mental health effects. Funding: N/A

Background: Coaches are a key influence of athletes’ body image but feel ill-equipped to address body image concerns and no tested body image intervention for coaches exists. Purpose: To evaluate a novel web-based intervention (Body Confident Coaching; BCC) aimed at upskilling coaches in improving athletes’ body image. Methods: A pilot randomised controlled trial with 97 coaches of adolescent girls (Mage=36.6, SD=10.4yrs; 70% female). Coaches were randomised into the intervention condition (five self-led 20-minute modules of BCC) or a waitlist control condition. Participants completed a survey pre- and post-intervention (coach self-efficacy body image scale, fat phobia scale, gender essentialism scale, feasibility and acceptability measures). Results: Coaches found the intervention easy to follow, appropriate, useful, and enjoyable. Preliminary efficacy analyses indicated that the intervention group reported higher levels of self-efficacy towards body image (η𝑝2=.19), and lower levels of fat phobia (η𝑝2=.39) and gender essentialism (η𝑝2=.20) at post-intervention, compared to the waitlist control group. However, these results need to be considered in light of the small sample size and high attrition rate (51%). Conclusions: BCC can increase coaches’ self-efficacy to identify and address athletes’ body image concerns, as well as reduce coaches’ fat phobia and gender essentialist beliefs. Practical implications: BCC is the first evidence-based and empirically tested intervention that targets coaches of adolescent girls and aims to increase their ability to identify and address body image concerns among their athletes and teams. Given many girls drop out of sports due to body image concerns, it is important for sport organisations to understand coaches’ influence on, and responsibility to address, body image concerns among their athletes. Funding: The study was funded by a research grant from the Dove Self-Esteem Project (Unilever; ref no. RHSS0180) and Nike (ref no. CON000000089960).

Background: Compensatory behavior of physical activity (PA) in adolescents based on the ActivityStat hypothesis is scarcely investigated, and existing studies show inconclusive results. Especially, little is known about influencing factors of compensatory behavior. Purpose: The aim of the present study is to investigate the occurrence, direction, and timeframe of compensation in adolescents. Furthermore, we want to identify the awareness and influencing factors of compensatory behavior. Methods: A mixed methods crossover analysis design with 15 adolescents (8 boys,7 girls) aged 11–15 (mean 13.04 ± 1.28) years was conducted. Participants provided a habitual weekly schedule with regular activities, then kept an activity diary to capture their actual behavior for one week. Data between the weekly schedule and activity diary were compared. Deviations in the diary > ±20% were considered as possible compensation opportunities. Compensation opportunities were assessed to determine if compensation had occurred (or not) within-day and/or between-day, and in which ‘direction’ (i.e., positive or negative). Additionally, interviews were conducted to explore awareness and influencing factors. Results: Overall, 198 compensation opportunities were identified. Compensation occurred in 109 of these opportunities (69 within-day, 40 between-day). Negative compensation occurred in 57 opportunities and 52 opportunities were compensated positively. Approximately half of the adolescents were unaware of their compensatory behavior, and only one participant was aware of all compensatory behavior. The most mentioned influences for positive compensation were social support and good weather. For negative compensation, tiredness as well as no need for movement were predominantly mentioned. No negative compensation occurred because adolescents wanted to stick to their routines or participate in hedonistic activities (i.e., activities they enjoy). Conclusion: New insights into adolescent compensatory behavior were gained, but consistency in occurrence, direction, and timeframe was lacking. Practical Implications: Supporting hedonistic activities and routines may aid individuals in managing compensatory behaviors. Funding: No funding.

Background: Research indicates 21% of primary schoolchildren and 16% of post-primary schoolchildren in Northern Ireland (NI) currently meet the daily recommended minimum of 60 minutes of moderate-to-vigorous PA. Whole-of-school approaches have been identified as one of 7 key investments for PA promotion, including active classrooms and high-quality physical education. Purpose: This research involves adapting and feasibility testing two successful interventions: TransformUs (primary schools, Australia) and the Youth – Physical Activity Towards Health (Y-PATH) intervention (post-primary schools, Ireland) for the NI context. Methods: As part of the adaptability, the interventions were rebranded as Children – Sit Less, Move More (C-SLAMM) intervention (formerly TransformUs) and Y-PATH NI. Within both studies, we conducted focus groups with pupils, and interviews with stakeholders (ranging from parents to school senior leadership), to understand current views and perceptions of opportunities for PA within the classroom and wider school environment. In addition, we conducted an online survey with n1500 post-primary schoolchildren to better understand their preferences for PA provision. Results: Findings from the Y-PATH NI study have highlighted a preference for PA to be provided with friends, during schooltime. Findings from our qualitive work highlighted several important factors that should be closely considered within school-based PA promotion, including incorporating an element of choice, adaptability, and flexibility within approaches. Based on findings from the qualitative work, we feasibility tested the C-SLAMM intervention in 8 primary schools in Northern Ireland, over an 8-week period. Conclusions and practical implications: Evaluation of the C-SLAMM intervention highlighted the importance of stakeholder buy-in from teachers, parents, and pupils if school-based PA promotion is to be successful. This feasibility work developed methods to assess implementation and adherence, which will be utilised within our feasibility testing of the Y-PATH NI intervention, commencing in early 2024. Funding: Northern Ireland Chest Heart and Stroke.

Background: Although adolescent physical activity (PA) tracks into adulthood, it is unclear if adolescent participation in different types of PA predicts adult PA. Purposes: 1) Identify adolescent profiles of PA participation. 2) Assess associations between these profiles and levels of PA in emerging adulthood. Methods: We used data from 893 participants in the Monitoring Activities of Teenagers to Comprehend Their Habits (MATCH) longitudinal study. Participants self-reported their involvement in 36 different PAs three times per year for eight years during adolescence (11-18 years). They also reported their PA level (IPAQ) 2.5, 3.5 and 4.5 years later when they were emerging adults (20, 21 and 22 years). We used group-based multi-trajectory models to identify longitudinal joint-trajectories of adolescent PA participation. We included these adolescent profiles in a mixed-distribution two parts model as predictors of i) the probability of reporting any PA during emerging adulthood, and ii) the PA level of emerging adults reporting PA. Results: We identified five adolescent PA profiles: “non-participants” (9% of the sample), “dropouts” (30%), “active in unorganized PA” (19%), “active in organized PA” (27%), and “highly active through a variety of PA” (15%). Being categorized as “non-participant” or “dropout” during adolescence was associated with similar likelihoods of reporting PA and PA level during emerging adulthood. In contrast with “non-participants”, those in the “active-unorganized” (OR, 95% CI: 2.9, 2.1-3.8), “active-organized” (2.4, 1.7-3.2), and “highly active-variety” (4.2, 3.3-5.1) were considerably more likely to report any PA during emerging adulthood. Among emerging adults who reported PA, those with an adolescent profile of “active-unorganized”, “active-organized” and “highly active-variety” had higher PA levels than “non-participants” (all p<0.001). Conclusions: Patterns of PA participation during adolescence represent strong predictors of PA in emerging adulthood. Practical implications: Promoting maintenance of any type of PA during adolescence is key to preventing low PA among emerging adults.

Background: There is an urgent need to tackle low physical activity (PA) levels in Australia and the Pacific Islands. This necessitates innovative solutions to address insufficient daily moderate-to-vigorous PA (MVPA) in adolescents. The iEngage program, co-designed with a digital health industry partner, is a modular and technology-based health educational program that was designed to enhance MVPA among adolescents. It was tested in distinct school contexts, specifically in Australia and New Caledonia. Methods: iEngage was implemented a) in urban area with two Sydney schools over 5 weeks, engaging 10–12-year-olds (n = 57), and b) in remote area with 24 adolescents from New Caledonia aged 12 to 14 years. The program incorporated technology, integrating Misfit Ray© activity trackers and mobile apps, while providing goal-setting guidance, self-monitoring, and experiential learning. Results: In the urban iEngage study, adolescents exhibited a 30% increase in daily steps (+2647 steps/day, P < .001) at completion of the program, with boys outpacing girls in goal attainment. Proportion of days exceeding 11,000 steps increased from 35% to 48%, indicating sustained improvement. In the trial implemented in a remote area, adolescents showed a consistency rate of reaching 11,000 steps per day peaking at 59% toward the end of the program, demonstrating progressive adherence to international recommendations. Daily behaviour clustering indicated a 27% increase in adherence, which was particularly noticeable in less active adolescents. Conclusion: These trials collectively affirm the efficacy of technology-supported educational programs in enhancing adolescents' PA levels in both urban and remote contexts. The iEngage program, with its comprehensive approach, successfully empowered adolescents to set and achieve PA goals. These findings underscore the potential of technology-driven interventions to bridge the gap between global health recommendations and the specific needs of Pacific adolescents, providing valuable insights for future health promotion initiatives. Funding: Pacific Fund, Diabetes Australia.

Background: Screen time is often used as an indicator of sedentary behaviour and has been linked to many poor health outcomes including cardiovascular disease, mental health and musculoskeletal disorders. However, there is limited evidence on how screen time by infants and their mothers could impact infant development. Purpose: This study aimed to investigate the influence of infant and maternal screen time (i.e. mobile touchscreen devices [MTSD] and television) and other family factors on infant development. Methods: This analysis used data from 1157 participants from The ORIGINS Project, collected when the infant was 12 months of age. Data on maternal and infant screen time (Technology Use Questionnaire, TechU-Q), sociodemographic factors (e.g. infant sex, household income), maternal mental health (Depression Anxiety Stress Scales, DASS-21), and child development (Ages and Stages Questionnaire, version 3, ASQ-3) were used. Multivariable linear regression with parametric bootstrap sampling was used for analyses. Results: When considering family factors, infants with higher MTSD use had poorer infant development. However, there were no associations between infant television use or maternal screen time, and infant development. Associations were also found between some family factors and infant development, including maternal mental health and parental education, with maternal mental health being the most consistent predictor of infant development. Conclusion: Overall, screen time by infant or their mothers may not be that important for infant development and rather should be best considered as part of the family system in which many behaviours and factors are interrelated. Practical implications: To improve infant development outcomes, less emphasis should be on screen time, and more on supporting the family as a whole, with a focus on supporting maternal mental health in particular. Funding: The Australian Research Council Centre of Excellence for the Digital Child and core funding was received for ORIGINS project.

Background: TransformUs program has improved physical activity (PA) and reduced sedentary time (SED) in primary schools through active pedagogy and supportive classroom and school ground environments. Purpose: This pilot study aims to trial TransformUs to determine the effect on PA and SED in secondary schools. Methods: This study involved adolescents (n=129) from three Australian schools. Each school selected a different combination of TransformUs strategies (active classrooms, active recreation, and supportive school environments) to increase PA and reduce SED, which included active academic breaks/lessons, standing desks, teacher’s professional development, sport/fitness equipment, and organised activities. Interventions spanned 12, 11, and 6 weeks for schools 1, 2, and 3, respectively. Garmin Vivosmart 4 heart rate monitoring tracked SED and PA (light [LPA], moderate [MPA], and vigorous [VPA]) at baseline, every 2 weeks during the interventions, and at follow-up. Mixed model analysis separately assessed intervention effects on each school’s SED and PA during school, class, and recess. Results: School 1 showed no significant intervention effect. School 2 exhibited increased MPA during class time in the first 2 weeks, with significant variations during recess. School 3 displayed decreased LPA during the second 2 weeks of intervention compared to baseline, particularly during class time. Secondary analysis revealed significant differences within the intervention period, including increased SED and decreased LPA during recess in the first 2 weeks. Conclusion: Overall, no movement behaviours were significantly changed before and after the intervention in any of the three schools during school time. Significant changes in SED, LPA and MPA within the intervention period indicate variability in the response to the implemented strategies. Practical implications: The variability in response to the implemented strategies among the three schools highlights the importance of carefully tailoring interventions to each school’s specific context and needs. The study was funded through the Victorian Department of Education.

Background: Sleep is crucial for people’s whole life cycle health. Sleep is affected by many factors, and physical activity is one of the important factors. Recreational physical activity (RPA) is a type of physical activity that refers to physical activity during leisure time, including sports, fitness, and other recreational activities. Moderate-vigorous recreational physical activity (MVRPA) plays an important role in adolescent physical and mental health.
Objective: Investigate the association between MVRPA and sleep duration in adolescents aged 16-17 years.
Methods: This study included five cycles of data from the National Health and Nutrition Examination Survey (NHANES) from 2007 through 2016 and included 532 participants, and the weighted participants were 14,289,45. RPA was collected by a physical activity questionnaire. Sleep duration was collected from responses to sleep duration questions. Participants were classified into three groups: short sleep (< 7 hours/day), adequate sleep (7-9 hours/day), and excessive sleep (> 9 hours/day). Chi-square analysis and the Kruskal-Wallis H test were used to analyze the correlation between MVRRA and sleep duration.
Results: The proportion of participants with short sleep, adequate sleep, and excessive sleep was 16.73%, 76.69%, and 6%, respectively. Different MVRRA time (H = 0.07, P = 0.967), age ((c²= 1.097, P = 0.578), education level ((c² = 1.289, P = 0.525) and the sleep time is not statistically significant; Gender ((c²=11.064,P=0.04) and sleep duration were statistically significant .
Conclusion: There was no significant association between MVRPA time and sleep duration, which might be explained by: The age span of the subjects was small and the representativeness was insufficient; Sleep duration is influenced by multiple factors.
Practical implications: In the future, intervention studies on physical activity and sleep can be considered in children and adolescents at different levels. Multivariate analysis was also performed to include obesity, diet, and other factors in the study.

Background: Parental technoference (PT), defined as parental technology use during parent-child interactions, may impact children’s health and development due to a lack of attention and responsiveness. However, no study has explored associations between PT and the World Health Organization’s guidelines on physical activity (PA), sedentary screen time (ST), and sleep for children under five years (24-hour movement guidelines; 24HMBG). Purpose: To explore the association between PT and adherence to the 24HMBG among children aged 1-4y in Chile. Methods: This is a secondary analysis of a cross-sectional study conducted in Chile from May to September 2022. Caregivers of children aged 1-5y completed an online questionnaire about their weekly use of screen devices during playtime, bedtime, travel time, and walks with the child (as proxies for PT), and their child’s PA, ST and sleep. Data for children aged 1-4y were included in this analysis. PT was defined as frequent if it occurred at least more than half of the week. Logistic regression was employed to assess the association. Results: 1214 caregivers (mean age 33y) provided complete data for this analysis. Fifteen percent of the children (mean age 2.5y) met the overall 24HMBG. Higher adherence was observed for sleep (68%) and PA (64%) compared to ST (35%). Ten percent of the children were frequently exposed to PT. Frequent PT was negatively associated with meeting the overall 24HMBG (OR=0.486; p=0.034) after adjusting for sociodemographic factors. Conclusions: Toddlers and preschoolers with higher exposure to PT were less likely to meet the 24HMBG. Further research is needed to explore the impact of parent’s screen device use on children’s health and development. Practical implications: Given the widespread use of technological devices in families, parents should prioritise engagement and responsiveness with their children to mitigate potential negative effects. Funding: National Fund for the Promotion of Sports (FONDEPORTE, Chile).

Background: Rising concerns that leisure time physical activity (PA) is being replaced by video gaming, yet there is a lack of evidence that the displacement hypothesis is true among adolescents. Purpose: To examine the associations between video gaming and PA among Finnish 11y –20y olds, and how associations may change by school type. Methods: The self-reported Finnish School-aged Physical Activity (F-SPA) studies for 2020 (high school students) and 2022 (upper general secondary students) were pooled together. Two genres of video games, 1. sport simulations, and 2. esports, were categorized into “a lot” and “not a lot” of gaming. Single item moderate to vigorous PA for at least 60 minutes per day was converted into four categories (0–2; 3–4; 5–6, 7 days). Odds ratios via multinominal logistic regressions with reference = 0-2 days were performed. Results: More of the sample were from high school (n=2406) than upper general secondary School (n=946). Of these, 17% (n =552) of students reported playing a lot of sport simulation games, and 43% (n=1431) reported playing a lot of esports. Playing a lot of esports (5-6 days, OR = .7, CI=.57–.97; 7 days OR=.5, CI=.37–.70) was negatively, and playing a lot of sports simulation games (7 days, OR=1.6, CI=1.11–2.30) was positively associated with PA compared to the reference category. Conclusions: The displacement hypothesis was partly supported, depending on the genre of video games, namely playing esports. Contrary to the hypothesis, playing a lot of sport games was associated with more PA, suggesting the importance of sport simulations as part of a physical activity relationship. Practical implications: Not all gaming is bad for health. Sports simulation gaming is part of a PA culture. Funding: The study was funded by the Finnish Ministry of Education and Culture.

Background: Digital screen technology use by children has been traditionally used as a surrogate measure of sedentary behaviour exposure. However, poor health outcomes in children are more strongly associated with screen use than with device measured sedentary behaviour. This suggests other aspects of screen use may be important. Better evidence on which aspects of screen use are critical to child health requires measurement methods that can capture the complex interactions between children, technology, the tasks they perform and the context of the interactions, to compare contemporaneously with device measured sedentary behaviour. Such methods can provide clearer and more relevant evidence to guide families and those working with children. Purpose: The purpose of this study was to evaluate the range of screen use measurement methods available and support researcher selection of the most appropriate method(s). Methods: A narrative review was conducted, built on recent systematic reviews and literature searches of methods used with children, or with the potential to be used with children, to identify measurement challenges and methods along with aspects researchers should consider in method selection. Results: Evolution of technology has increased the complexity of child-technology interactions and thus increased the challenge of adequately capturing sufficiently important aspects of this interaction. Self-/proxy- reporting via questionnaire/diary/electronic sampling, direct observation, visual/audio recording devices, screen device onboard capture, network traffic and content capture, proximity sensors and specialised systems were identified as ways to capture particular aspects of children’s screen use, along with examples of use, and advantages and disadvantages. Conclusions: The complex child-technology interactions may require a combination of methods to provide stronger practical evidence on health implications. Practical implications: Researchers need to look beyond simple measures of screen time to provide evidence with practical detail of relevance for families. Funding: The Australian Research Council Centre of Excellence for the Digital Child.

Background: Evidence regarding associations between physical activity (PA), fundamental motor skills (FMS), and physical fitness (FIT) in younger children is scarce and result are mixed. Purpose: This study aimed to investigate bidirectional associations between intensity-specific PA with FMS and FIT in 3–4-year-old preschool children. Methods: We included 821 children (3.8 yr, 53.5% boys) from the Active Learning Norwegian Preschool(er)s (ACTNOW) study who were measured at baseline and 18 months later. PA was measured with ActiGraph GT3X+ accelerometers, FMS were evaluated using 9 skills used as indicators of locomotor skills, object control skills, and balance skills, and FIT was measured through upper- and lower-body muscular strength (handgrip and standing long jump) and motor fitness (4×10 shuttle-run test). Structural equation modeling with latent growth models adjusted for covariates was used to investigate the bi-directional associations for PA with FMS and FIT. Results: All PA intensities positively predicted future locomotor skills (p=≤0.001-0.019) and motor fitness (p=≤0.001-0.007). All intensities except light PA (LPA) positively predicted object control skills (p=0.001-0.033), handgrip strength (p=0.007-0.033), and standing long jump (p=≤0.001). Moderate PA (MPA) and moderate-to-vigorous PA (MVPA) positively predicted balance skills (p=0.001-0.010). SED negatively predicted locomotor skills, object control skills, and all fitness measures (p=≤0.001-0.034). For the opposite pathway, locomotor skills positively predicted total PA (TPA), vigorous PA (VPA), and MVPA (p=0.013-0.046), and negatively predicted SED (p=0.032). Motor fitness positively predicted TPA and VPA (p=0.003-0.018). Conclusion: Our findings suggest that promoting locomotor skills and motor fitness in preschool children is beneficial for future participation in high-intensity PA. Furthermore, promoting MVPA in early childhood can have a positive impact on the development of a broad range of FMS and FIT measures. Funding: Supported by The Research Council of Norway (grant.nr 287903); County Governor of Sogn og Fjordane; Sparebanken Sogn og Fjordane Foundation; Western Norway University of Applied Sciences.