Dr Levi Wade

Objectives: Late adolescence (15¿19 years) is a period of heightened susceptibility to stress, but regular physical activity may attenuate reactivity to stressors. We aimed to explore the effects of physical activity intensity on older adolescents' stress-reactivity and self-reported mental health. Design and Methods: Three-arm randomised controlled trial in New South Wales, Australia (April¿June 2021). Thirty-seven older adolescents (16.1 ± 0.2 years, 59.5 % female) were randomised to: i) non-active control (CON), ii) light-intensity physical activity (LPA), or iii) moderate-to-vigorous-intensity physical activity (MVPA). Physical activity groups participated in 2 x 20-min sessions/week for 6 weeks. Salivary cortisol (sCort) reactivity to induced stress was assessed using the Trier Social Stress Test for Groups and quantified as area under the curve (sCortAUC; Primary outcome). Secondary outcomes included peak cortisol (sCortPeak), subjective-reactivity, perceived stress, and non-specific psychological distress. Group differences were assessed using multiple linear regression and quantified using Cohen's d. Results: No statistically significant effects were observed for sCortAUC or sCortPeak and the pattern of effects for subjective-reactivity was inconsistent. Effects for self-reported mental health were also non-significant (p >.05 for all) but of meaningful magnitude, favouring LPA and MVPA over CON (d's = -0.38 to -0.54). Delivery fidelity was high, satisfaction was moderate-to-high, and there was no evidence of harm. However, recruitment, retention for sCort measures, and adherence were lower than expected. Conclusion: Suboptimal recruitment, retention, and adherence limited our ability to conclude on the effect of physical activity intensity on older adolescents' sCort-reactivity to induced stress. We observed potentially meaningful effects on self-reported mental health for both physical activity conditions, which could be confirmed in a future powered trial.

Background: Motor competence and executive functions co-develop throughout childhood and adolescence, and there is emerging evidence that improvements in motor competence may have cognitive benefits in these populations. There is a need to provide a quantitative synthesis of the cross-sectional, longitudinal and experimental studies that have examined the association between motor competence and executive functions in school-aged youth. Objectives: The primary aim of our systematic review was to synthesise evidence of the association between motor competence and executive functions in school-aged children and adolescents (5¿18¿years). Our secondary aim was to examine key moderators of this association. Methods: We searched the PubMed, PsycINFO, Scopus, Ovid MEDLINE, SPORTDiscus and EMBASE databases from inception up to 27 June 2023. We included cross-sectional, longitudinal and experimental studies that assessed the association between motor competence (e.g., general motor competence, locomotor skills, object control skills and stability skills) and executive functions (e.g., general executive functions, inhibition, working memory and cognitive flexibility) in children and adolescents aged 5¿18¿years. Results: In total, 12,117 records were screened for eligibility, and 44 studies were included. From the 44 included studies, we meta-analysed 37 studies with 251 effect sizes using a structural equation modelling approach in the statistical program R. We found a small positive association (r = 0.18, [95% confidence interval (CI) 0.13¿0.22]) between motor competence and executive functions. The positive associations were observed in cross-sectional (r = 0.17, [95% CI 0.13¿0.22]), longitudinal (r = 0.15, [95% CI 0.03¿0.28]) and experimental studies (r = 0.25, [95% CI 0.01¿0.45]). We also found that general motor competence (r = 0.25, [95% CI 0.18¿0.33]), locomotor (r = 0.15, [95% CI 0.09¿0.21]), object control (r = 0.14, [95% CI 0.08¿0.20]) and stability (r = 0.14, [95% CI 0.08¿0.20]) skills were associated with executive functions. We did not find any moderating effects for participants' age on the associations between motor competence and executive functions. Conclusions: Our findings suggest a small-to-moderate positive association between motor competence and executive functions in children and adolescents. The small number of experimental studies included in this review support the assertion that interventions targeting children's motor competence may be a promising strategy to improve their executive functions; however, more research is needed to confirm these findings. Future studies should explore the underlying mechanisms linking motor competence and executive functions as their comprehension may be used to optimise future intervention design and delivery. PROSPERO Registration: CRD42021285134.

The aim of our systematic review and meta-analysis was to quantitatively synthesise the effects of school-based peer-led interventions on leaders' academic, psychosocial, behavioural, and physical outcomes. Eligible studies were those that: (i) evaluated a school-based peer-led intervention using an experimental or quasi-experimental study design, (ii) included an age-matched control or comparison group, and (iii) evaluated the impact of the intervention on one or more leader outcomes. Medline, Sportdiscus, Psychinfo, Embase, and Scopus online databases were searched on the 24th of October, 2022 which yielded 13,572 results, with 31 included in the narrative synthesis and 12 in the meta-analysis. We found large positive effects for leaders' attitudes toward bullying (d = 1.02), small-to-medium positive effects for leaders' literacy (d = 0.39), and small positive effects for leaders' self-esteem (d = 0.18). There were mixed findings for behavioural outcomes and null effects for physical outcomes. Notable limitations of this research are the inclusion of a relatively small number of studies, and high heterogeneity in those included. Our findings have the potential to inform educational practice, but also highlight the need for further research examining the mechanisms that might account for the observed effects. Our systematic review was prospectively registered with PROSPERO (CRD42021273129).

Objective The present study examined the effect of a school-based multicomponent physical activity intervention on aggression in adolescent males from low-income areas, and explored potential mediators of change in aggression. Methods Participants were adolescent males (N = 361; 12.7 ± 0.5 years) enrolled in the 'Active Teen Leaders Avoiding Screen-time' cluster RCT. Self-report measures for aggression, perceived strength and recreational screen-time were collected at baseline and 8-months. The effect of the intervention on aggression was tested using multi-level linear regression and potential mediators (i.e., screen-time and perceived strength) were explored using a product-of-coefficients test. Results There was no significant intervention effects for aggression (C [SE] = -0.038 [0.044], p =.384) or perceived strength (A [SE] = -0.0 [0.0], p =.884). However, a statistically significant effect was found for screen-time (A [SE] = -0.160 [0.04], p= <0.01). Changes in screen-time significantly mediated changes in aggression at post-test (AB [SE] = -0.021 [0.009], 95% CI = -0.042 to -0.005). Conclusion Limiting recreational screen-time may help to reduce aggression in adolescent boys. Interventions targeting adolescents' recreational screen-time should examine their 'flow-on' effects on externalising behaviours in adolescent populations.