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Background Bone is a plastic tissue that is responsive to its physical environment. As a result, exercise interventions represent a potential means to influence the bone. However, little is currently known about how various exercise and participant characteristics interact to influence bone metabolism. Acute, controlled, interventions provide an in vivo model through which the acute bone response to exercise can be investigated, typically by monitoring circulating bone biomarkers. Currently, substantial heterogeneity in factors such as study design, quality, exercise, and participant characteristics render it difficult to synthesize and evaluate the available evidence. Using a systematic review and meta-analytic approach, the aim of this investigation is to quantify the effect of an acute exercise bout on circulating bone biomarkers as well as examine the potential factors that may moderate this response, e.g., variation in participant, exercise, and sampling characteristics. Methods This protocol was designed in accordance with the PRISMA-P guidelines. Seven databases (MEDLINE, Embase, Sport Discus, Cochrane CENTRAL, PEDro, LILACS, and Ibec) will be systematically searched and supplemented by a secondary screening of the reference lists of all included articles. The PICOS (Population, Intervention, Comparator, Outcomes and Study Design) approach was used to guide the determination of the eligibility criteria. Participants of any age, sex, training, or health status will be considered for inclusion. We will select studies that have measured the bone biomarker response before and after an acute exercise session. All biomarkers considered to represent the bone metabolism will be considered for inclusion, and sensitivity analyses will be conducted using reference biomarkers for the measurement of bone resorption and formation (namely β-CTX-1 and P1NP). Multi-level, meta-regression models within a Bayesian framework will be used to explore the main effect of acute exercise on bone biomarkers as well as potential moderating factors. The risk of bias for each individual study will be evaluated using a modified version of the Downs and Black checklist while certainty in resultant outcomes will be assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. Discussion A better understanding of the bone metabolic response to an acute bout of exercise has the potential to advance our understanding of the mechanisms through which this stimulus impacts bone metabolism, including factors that may moderate this response. Additionally, we will identify current gaps in the evidence base and provide recommendations to inform future research. Systematic review registration This protocol was prospectively registered in the Open Science Framework Registry (https://osf.io/6f8dz)

Background Two thirds of the UK population are either overweight or obese (body mass index (BMI) 25-29.9 and >30 kg/m respectively) and are typically characterised by systemic oxidative stress (OS); deemed to play a key role in cardiovascular disease (CVD) development. OS results from chronically high reactive oxidative species (ROS) formation and reduced antioxidant status. OS plays a key role in CVD development by initiating atherosclerosis (fatty plaque accumulation within the arterial walls); therefore obese individuals are at increased risk of atherosclerosis development. Increased monocyte ROS generation instigates atherosclerotic plaque formation by increasing the recruitment, binding and transmigration of monocytes across arterial endothelial cells and into the arterial wall. An increased dietary antioxidant intake or up-regulation of endogenous antioxidant enzymes may counteract this OS state and therefore lower CVD risk. Selenium is an essential dietary micronutrient incorporated within the catalytic site of endogenous antioxidant Glutathione Peroxidase (GPx) enzymes, which protect cells from OS and consequent cell damage. There is, however, a lack of knowledge concerning the effect of selenium supplementation in an OS state representative of sedentary overweight/obese individuals. The aim of this work was to investigate the ability of selenium supplementation to modify monocyte cell viability/ROS production under OS. Materials and methods U937 monocyte cells were supplemented with sodium selenite (Na2SeO3; 100nM or 200nM) or not and cultured for 48 hours at 37°C. Paraquat (100mM) and S-Nitroso-Nacetyl-DL-penicillamine (10mM) (PQ/SNAP) were added to the cells to induce OS. Cell viability was assessed via MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) assay while ROS production was determined by Flow Cytometry using the reagent CM-H2DC-FDA.