Mediators of the association between physical activity and executive functions in primary school children

This is a self-archived version of an original article. This version may differ from the original in pagination and typographic details. Author(s): Title: Year: Version: Copyright: Rights: Rights url: Please cite the original version: CC BY-NC-ND 4.0 https://creativecommons.org/licenses/by-nc-nd/4.0/ Mediators of the association between physical activity and executive functions in primary school children © 2024 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group Published version Bao, Ran; Leahy, Angus A.; Lubans, David R.; Diallo, Thierno M.O.; Beauchamp, Mark R.; Smith, Jordan J.; Hillman, Charles H.; Wade, Levi Bao, R., Leahy, A. A., Lubans, D. R., Diallo, T. M., Beauchamp, M. R., Smith, J. J., Hillman, C. H., & Wade, L. (2024). Mediators of the association between physical activity and executive functions in primary school children. Journal of Sports Sciences, Early online. https://doi.org/10.1080/02640414.2024.2422203 2024 Journal of Sports Sciences ISSN: (Print) (Online) Journal homepage: www.tandfonline.com/journals/rjsp20 Mediators of the association between physical activity and executive functions in primary school children Ran Bao, Angus A. Leahy, David R. Lubans, Thierno M.O. Diallo, Mark R. Beauchamp, Jordan J. Smith, Charles H. Hillman & Levi Wade To cite this article: Ran Bao, Angus A. Leahy, David R. Lubans, Thierno M.O. Diallo, Mark R. Beauchamp, Jordan J. Smith, Charles H. Hillman & Levi Wade (28 Oct 2024): Mediators of the association between physical activity and executive functions in primary school children, Journal of Sports Sciences, DOI: 10.1080/02640414.2024.2422203 To link to this article: https://doi.org/10.1080/02640414.2024.2422203 © 2024 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group. Published online: 28 Oct 2024. Submit your article to this journal View related articles View Crossmark data Full Terms & Conditions of access and use can be found at https://www.tandfonline.com/action/journalInformation?journalCode=rjsp20 PHYSICAL ACTIVITY, HEALTH AND EXERCISE Mediators of the association between physical activity and executive functions in primary school children Ran Bao a,b , Angus A. Leahy a,b , David R. Lubans a,b,c , Thierno M.O. Diallo d , Mark R. Beauchamp e , Jordan J. Smith a,b , Charles H. Hillman f and Levi Wade a,b a Centre for Active Living and Learning, University of Newcastle, Callaghan, New South Wales, Australia; b Active Living Research Program, Hunter Medical Research Institute, New Lambton Heights, New South Wales, Australia; c Faculty of Sport and Health Sciences, University of Jyväskylä, Jyväskylä, Finland; d School of Social Sciences, Western Sydney University, Penrith, New South Wales, Australia; e School of Kinesiology, University of British Columbia, Vancouver, BC, Canada; f Center for Cognitive & Brain Health, Department of Psychology, Department of Physical Therapy, Movement & Rehabilitation Sciences, Center for Cognitive and Brain Health, Northeastern University, Boston, MA, USA ABSTRACT There is growing interest in identifying the mechanisms underpinning the effects of physical activity on executive functions (e.g. inhibitory control, cognitive flexibility) in children. Our study examined cardiorespiratory fitness, muscular fitness, and motor competence as potential mediators of this relationship. The study used baseline data from the Learning to Lead (L2L) cluster randomised controlled trial. In total, 675 children (7–11 years, 49.5% girls) completed measures of moderate-to-vigorous physical activity (MVPA), cardiorespiratory fitness, muscular fitness, motor competence, and executive functions. Structural equation modelling was used to examine the potential mediating roles of cardiorespiratory fitness, muscular fitness, and motor competence in the cross-sectional association between MVPA and executive functions. Cardiorespiratory fitness (β = 0.06, SE = 0.021, p = 0.004) partially mediated the association between MVPA and cognitive flexibility. Muscular fitness was a significant mediator of the association between MVPA and both inhibitory control (β = 0.03, SE = 0.014, p = 0.027) and cognitive flexibility (β = 0.06, SE = 0.021, p = 0.005). No significant mediated effects were found for motor competence. Our findings suggest cardiorespiratory and muscular fitness (but not motor competence) mediate the association between physical activity and executive functions in children. ARTICLE HISTORY Received 18 May 2024 Accepted 20 October 2024 KEYWORDS Moderate-to-vigorous physical activity; cardiorespiratory fitness; muscular fitness; motor competence; executive functions; children Introduction The health benefits of physical activity for young people are well documented and include a range of physical (e.g., enhanced physical fitness) and psychological (e.g., decreased depressive symptoms) benefits (Biddle et al., 2019; Chaput et al., 2020). There is also evidence that physical activity is beneficial for child and adolescent executive functioning (Biddle et al., 2019). Executive functions encompass the ability to select, schedule, coordinate, and monitor complex, goal-directed cognitive activities (Diamond, 2013). They include inhibitory control, which is the ability to maintain focus and suppress prepotent or automatised responses (such as avoiding distractions in the classroom), working memory, which is the ability to retain and update information when performing tasks (for instance, remembering multiple steps in solving a maths problem), and cognitive flexibility, which is the ability to shift mental resources between tasks (like when we need to adjust strategies in response to new rules in a game). Executive functions support higher-order processes such as problem solving, reasoning, and planning (Diamond, 2013; Willoughby & Hudson, 2023). In children, better executive functions are related to positive physical, psychological, and social-emotional health (Diamond, 2013; Riggs et al., 2006; Yang et al., 2022), whereas impaired executive functions may have detrimental effects on physical (e.g., a risk of obesity (Mamrot & Hanć, 2019)) and mental (e.g., depression (Gardiner & Iarocci, 2018; Hollocks et al., 2014)) health. Deficiencies in executive functions are also associated with suboptimal academic performance (Cortés Pascual et al., 2019; Jacob & Parkinson, 2015) and increased social-emotional challenges (e.g., poor social adaptation (Gardiner & Iarocci, 2018; Riggs et al., 2006)). Previous studies have shown that, although the effects are typically small, physical activity interventions are generally beneficial to children and adolescents’ executive functions (Ciria et al., 2023; García-Hermoso et al., 2021; Singh et al., 2019; Xue et al., 2019). Given that children spend a substantial amount of time at school, it is important to explore how physical activity during school hours contributes to these cognitive benefits. There is also growing acknowledgement of the importance of identifying the mechanisms responsible for the effect of physical activity on executive functions. A deeper understanding of these mechanisms may help to inform the design and implementation of future physical activity programmes. The existing evidence suggests that this relationship is likely influenced by both the qualitative (e.g., type, level of CONTACT Levi Wade [email protected] Centre for Active Living and Learning, University of Newcastle, University Drive, Callaghan, New South Wale 2308, Australia JOURNAL OF SPORTS SCIENCES https://doi.org/10.1080/02640414.2024.2422203 © 2024 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group. This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives License (http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited, and is not altered, transformed, or built upon in any way. The terms on which this article has been published allow the posting of the Accepted Manuscript in a repository by the author(s) or with their consent. cognitive demand) and quantitative (e.g., intensity) characteristics of the physical activity (Best, 2010; Hill et al., 2023; D. R. Lubans et al., 2021; Willoughby & Hudson, 2023). However, there is no consensus on the relative contributions of these characteristics (Diamond & Ling, 2019; Hillman et al., 2019). Work in this area has resulted in the proposition of two related hypotheses: the “fitness” and the “skill acquisition” hypotheses (Petruzzello et al., 1997; Tomporowski & Pesce, 2019). The “fitness” hypothesis suggests that participation in physical activity of sufficient duration and intensity to improve fitness (e.g., cardiorespiratory fitness, muscular fitness) may enhance cognition via changes in the structure and function of the brain (Petruzzello et al., 1997; Tomporowski & Pesce, 2019). The “skill acquisition” hypothesis suggests that physical activity provides opportunities for skill acquisition, and subsequent improvements in cognition are driven by the influence of skill acquisition on changes to related neural pathways (Tomporowski & Pesce, 2019). More specifically, it is engagement in cognitive complex and/or novel movements that likely lead to improvements in executive functions. There is evidence from cross-sectional and experimental studies in support of the “fitness” hypothesis. Reviews of the literature suggest that cardiorespiratory fitness is positively associated with executive functions in children and adolescents (Best, 2010; De Greeff et al., 2018; Hillman et al., 2008). Changes in executive functions may be attributable, at least in part, to exercise-induced increases in neurotrophins (including brainderived neurotrophic factor and insulin-like growth factor) that subsequently influence brain structure and function (Khan & Hillman, 2014; Stillman et al., 2016). There is also evidence that changes in muscular fitness (i.e., muscle strength, endurance, and power) may provide some explanation for the relationship between physical activity and executive functions (Robinson et al., 2023; Soga et al., 2018). A recent meta-analysis found that muscular fitness was positively associated with cognitive flexibility (Cohen’s d = 0.18) and working memory (Cohen’s d = 0.14) in children and adolescents (Robinson et al., 2023). Similar to cardiorespiratory fitness, the association between muscular fitness and executive functions may be explained by changes in brain structure and function (e.g., white matter volume, brain-derived neurotrophic factor) (Esteban-Cornejo et al., 2019; Isaac et al., 2021). Muscular fitness is associated with notable health improvements in children and adolescents, including reductions in metabolic risk factors and improvements in psychological outcomes (J. Smith et al., 2014), each of which may improve executive functions (Kamijo et al., 2012; D. Lubans et al., 2016). While promising, limited studies have examined the mediating effects of fitness (particularly muscular fitness) in the relationship with executive functions in children. The “skill acquisition” hypothesis suggests that the process of learning new skills might explain the benefits of physical activity for cognition. In support of this idea, reviews from the past few years note a positive association between motor skill competency and executive functions in children and adolescents (Gandotra et al., 2022; Hill et al., 2023; Willoughby & Hudson, 2023), with a recent meta-analysis indicating a small consistent association (r = 0.18) (Bao et al., 2024). The theory is that cognitively complex activity (including the acquisition of new skills) relies on shared functional regions within the brain, notably the prefrontal cortex, the cerebellum, and the basal ganglia, which are believed to underpin the association between physical activity and executive functions (Diamond, 2000; Leisman et al., 2016; Pangelinan et al., 2011). Despite few experimental studies, the existing evidence suggests that physical activity programmes may benefit the development of executive functions in children by improving their motor competence (MC) (Mulvey et al., 2018; Vazou et al., 2020). As outlined, emerging evidence suggests cardiorespiratory fitness, muscular fitness and motor competence may mediate the relationship between physical activity and executive functions in children. However, only a few studies have formally tested the fitness and skill acquisition hypotheses via mediation analyses (Muntaner-Mas et al., 2022; Spanou et al., 2022). While these studies have provided valuable findings, they did not test the relative contributions of cardiorespiratory fitness, muscular fitness, and motor competence to executive functions. To Figure 1. Hypothesized associations between moderate-to-vigorous physical activity, cardiorespiratory fitness, muscular fitness, motor competence and executive functions. 2R. BAO ET AL. address these research gaps, our study aimed to explore the mediating roles of these three components in the association between school-hour moderate-to-vigorous physical activity (MVPA) and executive functions in children (Figure 1). Our research questions were as follows: (1) Is physical activity positively associated with cardiorespiratory fitness, muscular fitness, and motor competence (a pathway)? (2) Is cardiorespiratory fitness, muscular fitness, and motor competence positively associated with executive functions (b pathway)? (3) Is physical activity positively associated with executive functions (c`pathway)? (4) Will cardiorespiratory fitness, muscular fitness, and motor competence mediate the cross-sectional associations between physical activity and executive functions? We hypothesized that cardiorespiratory fitness, muscular fitness, and motor competence would be positively associated with physical activity and mediate the cross-sectional relationship with executive functions. Methods Study design and participants We used baseline data from the Learning to Lead (L2L) cluster randomised controlled trial. Detailed information about this programme is available in our published protocol paper (Wade et al., 2023). Data were collected by trained researchers between 2022 (cohort 1) and 2023 (cohort 2) across 20 primary schools in the state of New South Wales (NSW), Australia. In total, 675 children (7–11 years, 49.5% girls) who were in Grades 3 and 4 were eligible and included in the current cross-sectional study. We obtained written informed assent from students and written consent from their parents or legal guardians. The study was approved by the human research ethics committee of the University of Newcastle (approval number: H-2020–0109) and the NSW Department of Education (reference number: 2020143). The L2L trial was prospectively registered with the Australian New Zealand Clinical Trials Registry (reference number: ACTRN12621000376842). Measurement Baseline data regarding participants’ demographic information (e.g., age, socioeconomic status) were collected via an online survey using electronic tablets. Physical activity Children’s physical activity levels were assessed by wristworn accelerometers (ActiGraph GT9X). Participants wore the device on their non-dominant wrist and were asked to wear them during the school day for five school days (approximately between the hours of 9:00 am and 3:00 pm). Physical activity intensity was categorised as light, moderate, and vigorous using validated cut points (Chandler et al., 2016). Physical fitness Cardiorespiratory fitness was evaluated using the 20 m Multistage Fitness Test. This test has shown moderate-to-high validity to estimate maximum oxygen uptake in children (Mayorga-Vega et al., 2015). The children were required to run between two lines set up 20 m apart. The total score was the number of completed laps. Muscular fitness was assessed by the standing long jump, which has shown good validity and reliability to assess muscular fitness in children and adolescents (Castro-Piñero et al., 2010; Ruiz et al., 2011). Participants performed two jumps, with the furthest jump recorded in centimetres as their final score. Motor competence Motor competence was assessed using a subset of object control skills (throwing, catching, and kicking) from the Test of Gross Motor Development 3 (TGMD-3) (Webster & Ulrich, 2017). Children were filmed performing three trials of each of the three skills (including an initial practice trial that was not assessed). These skills were selected based on their transferability into a variety of different sports that are popular among Australian children. Each skill in the recording was assessed according to skill-specific performance criteria by trained research assistants. Each skill component was scored a “1” if performed correctly, or “0” if performed incorrectly. This procedure was completed for each of the two primary trials, and trial scores were summed to calculate a total score for each skill. An overall object control movement skills score was calculated by summing the scores from all three skills. Executive functions Inhibitory control and cognitive flexibility were measured using two assessments from the National Institute of Health Toolbox for the Assessment of Neurological and Behavioural Function. Participants completed both tests on an iPad app in a quiet room alongside a maximum of 20 other students completing the tests at the same time. Instructions for both tests were explained by a member of the research team and were also shown on the screen. All participants wore headphones for the duration of the test battery, which took approximately 10 min to complete. Inhibitory control was assessed using the “Flanker Inhibitory Control and Attention Test” (version for children between 8 and 11 years). In this population, scores derived from this test have shown convergent validity and good test– retest reliability (ICC = 0.95, 95% CI = 0.92–0.97) (Weintraub et al., 2013). Inhibition performance was calculated as a combination of speed and accuracy and produced a score between 0 and 10, with a higher score indicating greater performance. Cognitive flexibility was assessed by the Dimensional Change Card Sort Test (version for children between 8 and 11 years). Scores derived from this test have also shown good test– retest reliability (ICC = 0.94, 95% CI = 0.92–0.96), and validity when used with children and adolescents (Weintraub et al., 2013). Based on a combination of test accuracy and speed, JOURNAL OF SPORTS SCIENCES 3 the test provides a score between 0 and 10, with higher scores indicating superior performance. Statistical analysis To maximise the number of students in the current study whilst preserving the validity of the measurement, we conducted ICC analyses comparing two or more and three or more days of valid accelerometry. The values were as follows: two or more, ICC = 0.75, and three or more, ICC = 0.83. According to previous studies, an ICC of 0.75, calculated from two or more days, is considered acceptable for accelerometry (Antczak et al., 2021; Barboza et al., 2021; Ridley et al., 2009), accordingly, we used data with two or more days of valid wear time. Descriptive analyses (the Chi-square and independent t-test) and bivariate correlations between physical activity, motor competence, cardiorespiratory fitness, muscular fitness, and executive functions (alpha levels set at p < 0.05) were conducted in IBM SPSS Statistics for Windows, V.28.0 (IBM, Armonk, New York, USA) and are presented in Table 1. We used multi-level structural equation modelling in Mplus version 8.10 to investigate whether cardiorespiratory fitness, muscular fitness, or motor competence mediate the crosssectional associations between MVPA and executive functions (indirect effect). These questions were investigated using the models shown in Figures 2 and 3. To address missing data and Table 1. Characteristics of the study sample. Overall (n = 675 a ) Boys (n = 336, 50.5%) Girls (n = 329, 49.5%) Statistic (χ 2 /t) P valuen (%) Mean (SD) n (%) Mean (SD) n (%) Mean (SD) Cultural background, n (%) Australian 606 (90.2%) 300 (89.3%) 302 (91.8%) 1.22 0.270 Other 66 (9.8%) 36 (10.7%) 27 (8.2%) Socioeconomic status, n (%) Low 66 (9.9%) 32 (9.6%) 33 (10.1%) 0.83 0.659 Medium 512 (76.4%) 253 (75.5%) 254 (77.4%) High 92 (13.7%) 50 (14.9%) 41 (12.5%) Age 672 8.7 (0.7) 336 8.7 (0.7) 329 8.6 (0.7) 1.87 0.062 MVPA (minutes) 675 34.3 (14.1) 336 39.6 (14.8) 329 29.0 (10.8) 10.52 <0.001 MC (scores) 643 14.4 (3.5) 316 15.9 (3.2) 320 12.9 (3.2) 11.74 <0.001 Cardiorespiratory fitness (laps) 653 26.2 (15.4) 327 29.6 (17.6) 318 22.7 (12.0) 5.80 <0.001 Muscular fitness (cm) 662 119.7 (22. 6) 329 125.6 (23.5) 325 114.0 (19.9) 6.78 <0.001 Inhibitory control (scores) 666 7.4 (1.1) 331 7.5 (1.1) 327 7.4 (1.0) 1.28 0.202 Cognitive flexibility (scores) 666 6.9 (1.1) 331 6.9 (1.1) 327 6.8 (1.1) 0.63 0.532 a = there was missing data for the sex of 10 participants. Figure 2. The mediating association between MVPA and inhibitory control in overall sample (n = 664). (Note: adjusted for socioeconomic status and sex, the numbers in the brackets refer to SE, solid lines represent significant β coefficients and dashed lines indicate non-significant β coefficients) 4R. BAO ET AL. the non-independence of students clustering within schools, we applied robust maximum likelihood estimation by adjusting standard errors using a sandwich estimator. Each outcome was standardised by converting them into z-scores before analysis. Two multiple mediator models were used to estimate the indirect effects of physical activity on inhibitory control and cognitive flexibility. The goodness of model fits were evaluated using χ 2 (Chi-square statistics), the Comparative Fit Index (CFI) (Bentler, 1990), the Tucker-Lewis Index (TLI) (Tucker & Lewis, 1973), the Root Mean Square Error of Approximation (RMSEA) (Browne & Cudeck, 1992) and their 90% confidence interval (90% CI). A value of TLI and CFI greater than 0.95 and an RMSEA less than 0.05 indicate an adequate model fit to the observed data (Hu & Bentler, 1999). Each model adjusted for socioeconomic status and sex. Each model tested the relationship between the independent variable and the hypothesised mediators (a path); the mediators and the dependent variables (b path). Then, a series of product of coefficients (a path × b path) were tested to calculate the mediated estimates for each hypothesised mediator (cardiorespiratory fitness, muscular fitness, and motor competence). The indirect estimates were considered significant where p < 0.05. The magnitude of the associations can be described as small (0.10–0.29), moderate (0.30–0.49), and strong (≥0.50) (Cohen, 2013). Results The sample characteristics are displayed in Table 1. Among 675 children (with a mean of 8.67 ± 0.67 years), 49.5% were female, and 90.2% of them were born in Australia. Table 2 outlines the bivariate correlations among all measures. Figure 2 presents the results of direct estimates of MVPA and mediators on inhibitory control in children. The mediation model for inhibitory control provided an adequate fit to the data with χ 2 (18) = 8.126, CFI = 0.994, TLI = 0.979, RMSEA = 0.031 and 90% CI = 0.000–- 0.067. Figure 3 shows the results of direct estimates of MVPA and mediators on cognitive flexibility in children. The mediation Figure 3. The mediating association between MVPA and cognitive flexibility in overall sample (n = 664). (Note: adjusted for socioeconomic status and sex, the numbers in the brackets refer to SE, solid lines represent significant β coefficients and dashed lines indicate non-significant β coefficients) Table 2. Pearson’s bivariate correlations among variables in children. Coefficients (sample size) 1 2 3 4 5 6 1. MVPA 1 2. CRF 0.462** (653) 1 3. MF 0.387** (662) 0.590** (649) 1 4. MC 0.389** (643) 0.363** (627) 0.413** (636) 1 5. Inhibitory control 0.012 (666) 0.093* (647) 0.122** (656) 0.084* (637) 1 6. Cognitive flexibility 0.039 (666) 0.197** (647) 0.218** (656) 0.109** (637) 0.332** (666) 1 MVPA = moderate-to-vigorous physical activity; CRF = cardiorespiratory fitness; MF = muscular fitness; MC = motor competence. *. Correlation is significant at the 0.05 level (2-tailed); **. Correlation is significant at the 0.01 level (2-tailed). JOURNAL OF SPORTS SCIENCES 5 model for cognitive flexibility also provided an adequate fit to the data, χ 2 (18) = 605.754, CFI = 0.994, TLI = 0.979, RMSEA = 0.032 and 90% CI = 0.000–0.069. MVPA on hypothesised mediators (a pathway – action theory tests) MVPA was associated with cardiorespiratory fitness (β = 0.46, SE = 0.049, p < 0.001), muscular fitness (β = 0.35, SE = 0.055, p < 0.001) and motor competence (β = 0.27, SE = 0.049, p < 0.001). Hypothesised mediators on executive functions (b pathway – conceptual theory tests) Muscular fitness was associated with inhibitory control (β = 0.09, SE = 0.043, p = 0.045) and cognitive flexibility (β = 0.16, SE = 0.053, p = 0.002), while cardiorespiratory fitness was only associated with cognitive flexibility (β = 0.13, SE = 0.044, p = 0.003). No significant associations were observed between motor competence and measures of executive function. MVPA on executive functions (c` pathway – including mediators) MVPA was negatively associated with cognitive flexibility (β = −0.10, SE = 0.043, p = 0.016), while no association was observed between MVPA and inhibitory control. Significance of the indirect effects (ab pathway – mediation tests) Table 3 displays the indirect estimates of MVPA on inhibitory control and cognitive flexibility. Cardiorespiratory fitness mediated the association between MVPA and cognitive flexibility in the overall sample (β = 0.06, SE = 0.021, p = 0.004). Muscular fitness mediated the relationship between MVPA and inhibitory control in the overall sample (β = 0.03, SE = 0.014, p = 0.027). Muscular fitness was also a significant mediator of the effect of MVPA on cognitive flexibility (β = 0.06, SE = 0.021, p = 0.005) in the overall sample. We did not observe indirect effects of motor competence in the relationship between MVPA and executive functions in children. Discussion The aim of our study was to examine whether cardiorespiratory fitness, muscular fitness, or motor competence mediated the cross-sectional association between MVPA and executive functions in children. The findings indicated that cardiorespiratory fitness mediated the association between MVPA and cognitive flexibility, while muscular fitness mediated the relationship between MVPA and both inhibitory control and cognitive flexibility. Conversely, we did not find a mediating role of motor competence on either outcome. The “fitness” hypothesis postulates that participation in physical activity of sufficient duration and intensity can produce cardiorespiratory fitness gains, which may subsequently enhance cognition (Petruzzello et al., 1997; Tomporowski & Pesce, 2019). In line with this hypothesis, our findings suggested that cardiorespiratory fitness was positively associated with executive functions in children, which is consistent with reviews on the topic (De Greeff et al., 2018; Hillman et al., 2008; Van Waelvelde et al., 2020). Notably, few studies have formally examined the mediation of cardiorespiratory fitness in children (Visier-Alfonso et al., 2021; Yangüez et al., 2021). Specifically, we found that cardiorespiratory fitness mediated the relationship between MVPA and cognitive flexibility but not for inhibitory control. Research on the mediating effects of cardiorespiratory fitness, as assessed by the 20-m shuttle run test, has yielded mixed results. Some studies have reported similar findings to the current study (Yangüez et al., 2021), while others have found that cardiorespiratory fitness mediates inhibitory control but not cognitive flexibility (Visier-Alfonso et al., 2021). These discrepancies may be partly due to methodological differences in how cardiorespiratory fitness is measured. For instance, while some studies have used direct measures of maximal oxygen consumption, in the current study, cardiorespiratory fitness was assessed based on the number of completed laps in the shuttle run. The finding that cardiorespiratory fitness mediated the relationship between MVPA and cognitive flexibility may be explained by several hypotheses. Cardiorespiratory fitness can contribute to greater cerebral circulation, and an upregulation of neurotrophins (e.g., brainderived neurotrophic factor) that contribute to executive function performance (Stimpson et al., 2018). Alternatively, there is a behavioural explanation for cardiorespiratory fitness as a mediator of executive functions. Aerobic exercises demand varying levels of cognitive engagement, which may pose challenges to children’s executive functions (Best, 2010; Tomporowski & Pesce, 2019). In particular, contextual interference arises during participation in aerobic exercises, compelling children’s need to create, monitor and modify their actions to accomplish diverse and complex exercise tasks (Best, 2010; Tomporowski & Pesce, 2019). This process necessitates the involvement of executive processes, and the cognitive skills essential for engaging in aerobic exercises may transfer to performance on executive function tasks (Best, 2010). We found that muscular fitness was a mediator between MVPA and both of our executive functioning outcomes. The Table 3. The indirect estimates of MVPA on executive functions through mediators. Pathways Overall (n = 675) βSE p MVPA to inhibitory control via CRF 0.02 0.027 0.404 MVPA to inhibitory control via MF 0.03 0.014 0.027 MVPA to inhibitory control via MC 0.02 0.012 0.185 MVPA to cognitive flexibility via CRF 0.06 0.021 0.004 MVPA to cognitive flexibility via MF 0.06 0.021 0.005 MVPA to cognitive flexibility via MC 0.01 0.010 0.435 MVPA, moderate-to-vigorous physical activity; CRF, cardiorespiratory fitness; MF, muscular fitness; MC, motor competence; β, standardised coefficients; SE, standard error. 6R. BAO ET AL. relationship between muscular fitness and executive functions in children is still an emerging field of research, but our findings are consistent with the existing literature (Robinson et al., 2023; J. J. Smith et al., 2014). A recent review found that muscular fitness is positively associated with cognitive flexibility (Cohen’s d = 0.18) and working memory (Cohen’s d = 0.14) in children and adolescents (Robinson et al., 2023). Further, there is evidence that higher levels of muscular fitness are associated with greater inhibitory control and cognitive flexibility (Solis‐Urra et al., 2021; Zeng et al., 2023). There is also evidence of a positive association between muscular fitness and white matter volume in children (Esteban-Cornejo et al., 2019). However, it is important to acknowledge the differences in how muscular fitness was assessed across studies. For example, several studies have used composite measures, such as the combination of handgrip strength and the standing long jump (Esteban-Cornejo et al., 2019; Solis‐Urra et al., 2021), or a broader battery of tests, including the assessment of grip strength, pull ups (boys), sit-ups (girls) and standing long jump (Zeng et al., 2023). In contrast, our study assessed muscular fitness solely using the standing long jump test. These methodological differences in how muscular fitness is assessed must be considered when comparing our results with those of other studies. Interestingly, our study has shown that muscular fitness was a predictor of executive functioning, independently of cardiorespiratory fitness. This relationship may be explained, at least in part, by the relationship of muscular fitness to brain structure and functions. The activation of skeletal muscle may stimulate the release of neurotrophins (such as irisin and brain-derived neurotrophic factor), which may facilitate executive functions (Isaac et al., 2021). Therefore, it may be the case that activities that are particularly taxing on skeletal muscle (e.g., resistance exercise), and thus contribute to muscular fitness, may be especially effective on executive functions. Clearly, there is a need for further research on the relationship between muscular fitness and executive functions. The “skill” hypothesis proposed that physical activity participation can facilitate the acquisition of motor skill competency, which subsequently improves cognitive function. Engagement in cognitively complex and/or novel motor skill tasks may lead to improvements in executive functions. There is evidence that motor competence is positively associated with executive functions in children and adolescents (Gandotra et al., 2022; Hill et al., 2023; Willoughby & Hudson, 2023). Recently, findings from a meta-analysis suggest that motor competence (r = 0.18) is associated with executive functions in children and adolescents (Bao et al., 2024). Further, emerging evidence suggests that motor competence may influence the relationship between physical activity and executive functions (Hill et al., 2023; Willoughby & Hudson, 2023). The underlying mechanisms may be related to the use of functional regions within the brain, such as prefrontal cortex, the cerebellum, and the basal ganglia that are common to both motor and cognitive activities (Diamond, 2000; Leisman et al., 2016). Contrary to our hypothesis, we did not find that motor competence mediated the association between MVPA and executive functions. Notably, few studies have formally investigated the potential mediating role of motor competence in this relationship. Among them, Spanou et al. (2022), found that motor competence, assessed using the Bruininks – Oseretsky Test of Motor Proficiency-Second Edition (BOT-2), mediated the association between physical activity and executive functions in children. Given the limited research on the potentially mediating role of motor competence, future longitudinal and experimental research is needed to better understand the temporality of this relationship and the causal pathways linking motor competence, physical activity, and executive functions. To date, much of the existing research has focused on the relationship between cardiorespiratory fitness and executive functioning, with substantially less attention given to the potential contributions of muscular fitness and motor competence (De Greeff et al., 2018; Xue et al., 2019). This imbalance leaves a gap in our understanding of the specific aspects of physical activity that may influence cognitive development in children. The current study addresses this gap by testing the relative contributions of cardiorespiratory fitness, muscular fitness, and motor competence to children’s executive functions. Our findings lend support to the “fitness hypothesis”, suggesting that physical activity-induced improvements in both cardiorespiratory and muscular fitness are significantly associated with enhanced executive functioning performance. Importantly, this is one of the few studies to formally test and compare the relative impact of these distinct aspects of physical fitness and competence on executive functions, thereby providing a more comprehensive understanding of the intricate relationships between physical activity and cognitive development. Strengths and limitations To our knowledge, this is the first study to formally test cardiorespiratory fitness, motor competence, and muscular fitness as mediators in the relationship between device-assessed physical activity and executive functions in children. We used a multilevel modelling approach, which is considered best practice for analysing clustered data. However, several limitations should be considered. First, our findings are based on a cross-sectional study design, preventing the analysis of a causal relationship between MVPA and executive functions in children. There are potential bi-directional associations between physical activity and motor competence, as well as cardiorespiratory and muscular fitness in children and adolescents (Barnett et al., 2022). For example, improvements in motor competence may lead to increased physical activity among youth. Conversely, increasing physical activity could also enhance motor competence. Future experimental research is needed to establish the temporal order of these relationships. Second, although inhibition, cognitive flexibility, and working memory are considered the three core executive functions (Zelazo, 2020), we did not measure working memory due to logistical constraints. We used the NIH toolbox that includes a measure of working memory that requires oneon-one administration. This was not feasible, as we needed to test several students simultaneously. Future research should include working memory to provide a more comprehensive account of the relationship between physical activity and executive functions. Third, our assessment of motor competence was limited to three object control skills. It is possible JOURNAL OF SPORTS SCIENCES 7