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Introduction:The relationship between physical activity (PA) intensity and executive functions in older adolescents remains poorly understood. This study aimed to examine the associations between PA intensity, volume, attentional control, and working memory and the moderating effects of sex in older adolescents. Method:We analyzed baseline data from 418 participants (211 females, M age = 16.5 ± 0.40 years) from the Burn 2 Learn trial. Adolescents wore GT9X Link accelerometers on a non-dominant wrist for 7 days, 24-h•d −1 . PA intensity was expressed as intensity gradient (IG) and moderate-to-vigorous PA (MVPA, Hildebrand cut-points); PA volume was expressed as average acceleration (AvACC). Attentional control was measured with a standard deviation (SDRT) and a coefficient of variation (CVRT) of the reaction time on the incongruent trials of a flanker task. Working memory was expressed as a d prime (a signal discrimination index) on the 2-back task. The moderating effects of sex on the PA-executive functions associations, adjusting for age, BMI z-score, and cardiorespiratory fitness, were tested using multilevel random intercept models.Results: After controlling for AvACC, sex moderated the relationships between IG and incongruent SDRT (B = 0.53, 95% CI: 0.12, 0.94) and CVRT (B = 0.63, 95% CI: 0.22, 1.05; ps ≤ 0.002). Only girls with higher IG showed smaller incongruent SDRT and CVRT (Bs ≤ −0.26, ps ≤ 0.01). IG was not related to working memory. AvACC and MVPA were not associated with attentional control or working memory.

IntroductionGreater engagement in sedentary behaviours has been related to poorer cognitive functions in epidemiological research. However, the effects of reducing sedentary behaviour duration on cognitive function, brain function, and structure remain poorly understood. This systematic review aims to synthesise the evidence on the effects of reducing sedentary behaviour duration by increasing time spent in physical activity on cognitive function, brain structure and function in apparently healthy children, adolescents and adults.Methods and analysisThe protocol follows Preferred Reporting Items for Systematic Reviews and Meta-Analyses. The literature search will be conducted (search dates: August–September 2022) across six databases: PubMed, Scopus, Cumulative Index to Nursing and Allied Health Literature (via EBSCO Host), PsycINFO (via ProQuest), SPORTDiscus and Web of Science (Science and Social Science Citation Index). The inclusion criteria are as follows: randomised and non-randomised experimental studies as defined by the Cochrane Handbook, published in English, in peer-reviewed journals, and as theses or dissertations. References of included papers will be screened for additional studies. Acute and chronic interventions targeting children (≥ 4 years), adolescents, younger adults (≥ 18–40 years), middle-aged (40–64 years) and older adults (65+ years) will be eligible. Methodological quality will be assessed with the Effective Public Health Practice Project quality assessment tool for quantitative studies. Qualitative synthesis will be stratified by intervention type (acute vs chronic), intervention content (reducing sedentary time or interrupting prolonged sitting) and outcome (cognitive, brain structure and function).Ethics and disseminationNo primary data collection will be conducted as part of this systematic review. Study findings will be disseminated through peer-reviewed publications, conference presentations and social media.PROSPERO registration numberCRD42020200998.

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