BackgroundCompositional data comprise ‘parts’ of a ‘whole’ (or total), where the parts sum to the whole. In compositional data with fixed totals (e.g. hours within a day), only relative causal ...effects can be estimated because the effect of increasing one component (e.g. time spent physically active) cannot be distinguished from the effect of decreasing one or more other components (e.g. time spent sedentary).Compositional data are not well understood, but the structure has recently been conceptualised using directed acyclic graphs (DAGs) with deterministic nodes. This work encourages the use of a simple well-established approach, known as the isotemporal (‘leave-one-out’) model, for estimating relative causal effects in compositional data.However, the isotemporal model has been criticised as unsuitable in the presence of non-linear effects. Other, more technically demanding approaches, known as Compositional Data Analyses (CoDA) methods, are promoted instead.This study is the first to investigate the performance of DAG-informed regression-models for estimating causal effects in compositional data with fixed totals in simulated data, where the ground truth is known.MethodsUsing the DagSim package in Python, we simulated compositional data with fixed totals, using the example of physical activity data, in which sleep, sedentary behaviour (SB), light physical activity (LPA), and moderate and vigorous physical activity (MVPA) sum to a fixed total of 24 hours. The time spent in each state was then simulated to contribute to levels of an outcome (fasting plasma glucose, FPG), either in a strictly linear manner, or through non-linear relationships. We assessed the performance of using the DAG-informed isotemporal approach by comparing model estimates to the known (simulated) true relative causal effect of each component on the outcome.ResultsAccurate relative causal effect estimates were obtained using the DAG-informed isotemporal approach, provided the models were parameterised correctly. When the model was not parameterised correctly, e.g. linear terms were used for modelling non-linear relationships, the estimates were biased. In the literature, the isotemporal model is used almost exclusively with linear terms, which might explain some of the previous misconceptions that it is unsuitable for modelling of compositional data.ConclusionIn compositional data with fixed totals, a simple DAG-informed isotemporal modelling approach recovers the true relative causal effect as long as any non-linear relationships are appropriately parameterised. This method is a viable alternative to the more technically challenging and specialist CoDA methods. The findings cannot be generalised to compositional data with varying totals, which require separate investigation.
Objectives:
To provide clinicians who treat multiple sclerosis (MS) patients with evidence-based or expert opinion–based recommendations for promoting exercise and lifestyle physical activity across ...disability levels.
Methods:
The National MS Society (“Society”) convened clinical and research experts in the fields of MS, exercise, rehabilitation, and physical activity to (1) reach consensus on optimal exercise and lifestyle physical activity recommendations for individuals with MS at disability levels 0–9.0 on the Expanded Disability Status Scale (EDSS) and (2) identify and address barriers/facilitators for participation.
Recommendations:
Based on current evidence and expert opinion, the Society makes the following recommendations, endorsed by the Consortium of Multiple Sclerosis Centers:
Healthcare providers should endorse and promote the benefits/safety of exercise and lifestyle physical activity for every person with MS.
Early evaluation by a physical or occupational therapist or exercise or sport scientist, experienced in MS (hereafter referred to as “specialists”), is recommended to establish an individualized exercise and/or lifestyle physical activity plan.
Taking into account comorbidities and symptom fluctuations, healthcare providers should encourage ⩾150 min/week of exercise and/or ⩾150 min/week of lifestyle physical activity.
Progress toward these targets should be gradual, based on the person’s abilities, preferences, and safety.
If disability increases and exercise/physical activity becomes more challenging, referrals to specialists are essential to ensure safe and appropriate prescriptions.
When physical mobility is very limited, exercise should be facilitated by a trained assistant.
Purpose and methodsThis review presents established knowledge on the effects of physical activity (PA) on whole-body insulin sensitivity (SI) and summarises the findings of recent (2013–2016) ...studies.Discussion and conclusionsRecent studies provide further evidence to support the notion that regular PA reduces the risk of insulin resistance, metabolic syndrome and type 2 diabetes, and SI improves when individuals comply with exercise and/or PA guidelines. Many studies indicate a dose response, with higher energy expenditures and higher exercise intensities, including high intensity interval training (HIIT), producing greater benefits on whole-body SI, although these findings are not unanimous. Aerobic exercise interventions can improve SI without an associated increase in cardiorespiratory fitness as measured by maximal or peak oxygen consumption. Both aerobic and resistance exercise can induce improvements in glycaemic regulation, with some suggestions that exercise regimens including both may be more efficacious than either exercise mode alone. Some studies report exercise-induced benefits to SI that are independent of habitual diet and weight loss, while others indicate an association with fat reduction, hence the debate over the relative importance of PA and weight loss continues. During exercise, muscle contraction stimulated improvements in SI are associated with increases in AMPK activity, which deactivates TCB1D1, promoting GLUT4 translocation to the cell membrane and thereby increasing glucose uptake. Postexercise, increases in Akt deactivate TCB1D4 and thereby increase GLUT4 translocation to the cell membrane. The reduction in intramuscular saturated fatty acids and concomitant reductions in ceramides, but not diacylglycerols, provide a potential link between intramuscular lipid content and SI. Increased skeletal muscle capillarisation provides another independent adaptation through which SI is improved, as does enhanced β cell activity. Recent studies are combining exercise interventions with dietary and feeding manipulations to investigate the potential for augmenting the exercise-induced improvements in SI and glycaemic control.
Background. Physically active lessons have not often been assessed with randomized controlled trials. Aims. Evaluate the effects of the “Virtual Traveller” (VT) intervention delivered using classroom ...interactive whiteboards on physical activity, on-task behavior, and student engagement. Methods. Participants were 219 children aged 8 to 9 years from 10 schools in Greater London, assessed in a cluster-randomized controlled trial between March 2015 and May 2016. For 6 weeks, intervention children received 10-minute VT sessions three times a week during math and English lessons (VT group: n = 113). Children in control schools received regular teaching (COM group: n = 106). Outcomes were school-day, weekend-day, and lesson-time sedentary behavior (SB), light physical activity (LPA) and moderate-to-vigorous physical activity (MVPA), and on-task behavior and student engagement, assessed at baseline (T0), 2 weeks (T1), and 4 weeks (T2) during the VT intervention and 1 week (T3) and 3 months (T4) postintervention using multilevel modeling. Results. VT pupils engaged in significantly more school-day MVPA at T1 only, with no other significant differences between groups in overall school-day or weekend-day activity. VT pupils engaged in significantly less SB and more MVPA during lesson time than COM pupils. More on-task behavior was shown in VT pupils than COM pupils but there was no difference in student engagement. Discussion. VT reduced sedentary behavior and increased physical activity during lesson time but not across overall school or weekend days. VT improved on-task behavior but had no effect on student engagement. Conclusion. Physical activity can be integrated into teaching using interactive whiteboards with no detriment to educational outcomes.
Schools are well-positioned to provide physical activity opportunities to help youth achieve the recommended 60 or more daily minutes of moderate-to-vigorous physical activity. The Children's ...Physical Activity Research Group (CPARG) at the University of South Carolina has focused on understanding physical activity in school-aged youth for 30+ years. The purpose of this article was to critically review (CPARG) contributions to the field in school settings and school-age youth. We reviewed 127 published CPARG articles from six research projects conducted between 1993-2019. The review was guided by questions in five categories: measurement of physical activity and its determinants, characteristics of physical activity behavior, correlates/determinants of physical activity, physical activity interventions, and race/ethnicity and physical activity. Results were summarized by question and synthesized across categories. CPARG contributions included assessing physical activity levels, patterns, forms, and contexts; identifying and measuring physical activity correlates/determinants; and conducting school-based physical activity interventions. Identifying multiple domains of physical activity determinants enables researchers and practitioners to select/design age-appropriate, valid, and reliable instruments to assess determinants. Focusing on determinants enables them to create effective physical activity interventions, environments, programs, and policies in schools. These efforts must address race/ethnicity differences, ensuring that measurement instruments and intervention strategies are culturally appropriate.
Objectives
Investigate the independent associations of objectively measured or self-reported physical activity at different intensities with cognitive performance in middle-aged adults.
Design
...Cross-sectional.
Methods
156 middle-aged adults (age: 40.6 ± 1.5, 58.3% female) participated in the physical activity sub-study of the Personality and Total Health through life (PATH) project. Physical activity was measured objectively with the SenseWear™ armband (SWA), worn for seven consecutive days, and measured
via
self-report with a Physical Activity Recall survey (PAR). Cognitive performance was assessed with the Symbol Digit Modalities Test, the Digit Span Backwards, and an Immediate and Delayed Recall task. Associations between physical activity intensity and cognitive function were investigated in general linear models, controlling for age, sex, and education.
Results
Neither objectively measured nor self-reported physical activity were associated with cognitive function at light-, moderate-, vigorous-, or combined moderate-to-vigorous intensity in this cohort of well educated, healthy middle-aged adults. Sensitivity analyses with additional moderators (e.g., body mass index, hypertension, alcohol intake) and the use of composite cognitive measures did not alter the results.
Conclusion
In this cohort of middle-aged adults, objectively measured and self-reported physical activity do not appear to be associated with cognitive function. Longitudinal follow-ups utilising objective physical activity measures may be important in determining the impact of mid-life behaviours on the trajectory of cognitive changes into older age.
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