Background Increasing evidence highlights that accumulating sitting time in prolonged bouts is detrimental to cardiometabolic health. Objectives This systematic review aimed to compare the effects of fractionating prolonged sitting with frequent short bouts of standing and light-intensity walking on cardiometabolic health markers and conduct a meta-analysis for differences in systolic blood pressure (SBP), postprandial glucose and insulin. Methods Experimental randomised crossover trials with at least three intervention arms that assessed interrupting sitting with frequent short bouts of standing and light-intensity walking over a single day compared to a prolonged sitting condition were retrieved. These studies measured at minimum one marker of cardiometabolic health in adults > 18 years. An electronic search was completed on the 2nd of August 2021, searching PubMed and Web of Science Core Collection, Scopus, Embase, Cochrane Library and APA PsycINFO. Risk of bias was assessed using a modified Downs and Black checklist. A meta-analysis was conducted using calculated Cohen’s d quantifying the magnitude of difference between experimental conditions. Results Seven studies met the inclusion criteria for the systematic review. All seven studies were included within the meta-analysis for postprandial glucose, four studies were pooled for postprandial insulin and three for SBP. Biomarkers of cardiometabolic health were discussed qualitatively if fewer than three studies measured and reported the variable. A meta-analysis of seven acute, 1-day randomised crossover trials that sampled mixed-sex adults (aged > 18 years) who were predominately overweight or participants with obesity found that standing as an interruption to prolonged sitting significantly reduced postprandial glucose (∆ = − 0.31, 95% CI − 0.60, − 0.03; z = − 2.15, p < 0.04) but had no significant effect on insulin or SBP. Light-intensity walking was shown to significantly attenuate postprandial glucose (∆ = − 0.72, 95% CI − 1.03, − 0.41; z = − 4.57, p < 0.001) and insulin (∆ = − 0.83, 95% CI − 1.18, − 0.48; z = − 4.66, p < 0.001) compared to continued sitting. When comparing light-intensity walking breaks compared to standing breaks a significant reduction in glucose (∆ = − 0.30, 95% CI − 0.52, − 0.08; z = -2.64, p < 0.009) and insulin (∆ = − 0.54, 95% CI − 0.75, − 0.33; z = -4.98, p < 0.001) was observed. Both standing and light-intensity walking showed no effect on SBP. Conclusions Frequent short interruptions of standing significantly attenuated postprandial glucose compared to prolonged sitting; however, light-intensity walking was found to represent a superior physical activity break. The feasibility and longitudinal implications of breaking sedentary behaviour with light-intensity walking should be investigated in a free-living setting. Registration Not available.

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Purpose: 1) To determine the contribution of diet, time spent outdoors and habitual physical activity (PA) on vitamin D status in men with cerebral palsy (CP) compared to age matched controls (TDC) without neurological impairment. 2) To determine the role of vitamin D on musculoskeletal health, morphology and function in men with CP compared to TDC.Materials and methods: A cross-sectional comparison study where, twenty-four active, ambulant men with CP aged 21.0±1.4 years (Gross Motor Function Classification Score I-II) and 24 healthy TDC aged 25.3±3.1 years completed in vivo assessment of musculoskeletal health, including: Vastus Lateralis anatomical cross-sectional area (VL ACSA), isometric knee extension maximal voluntary contraction (KE iMVC), 10m-sprint, vertical jumps (VJ), radius and tibia bones T and Z scores. Assessments of vitamin D status through venous samples of serum 25-hydroxyvitamin D (25(OH)D) and parathyroid hormone, dietary vitamin D intake from food diary and total sun exposure via questionnaire were also taken. Results: Men with CP had 40.5% weaker KE iMVC, 23.7% smaller VL ACSA, 22.2% lower VJ, 14.6% lower KE iMVC/VL ACSA ratio, 22.4% lower KE iMVC/body mass (BM) ratio and 25.1% lower KE iMVC/lean body mass (LBM) ratio (all p<0.05). Radius T and Z scores were 1.75 and 1.57 standard deviations lower than TDC, respectively (p<0.05), whereas neither tibia T nor Z scores showed any difference compared to TDC (p>0.05). 25(OH)D was not different between groups, and 90.9% of men with CP and 91.7% of TDC had low 25(OH)D levels when compared to current UK recommendations. 25(OH)D was positively associated with KE iMVC/LBM ratio in men with CP (r = 0.500, p=0.020), but not in TDC (r = 0.281, p=0.104).Conclusion: Musculoskeletal outcomes in men with CP were lower than TDC and despite there being no difference in levels of 25(OH)D between the groups, 25 (OH)D was associated with strength (KE iMVC/LBM) in the CP group, but not TDC. The findings suggest a greater sensitivity to low vitamin D in men with CP with regards to bone and muscle content and functional outcomes.

Purpose: (1) To determine the contribution of diet, time spent outdoors, and habitual physical activity (PA) on vitamin D status in men with cerebral palsy (CP) compared to physical activity matched controls (TDC) without neurological impairment; (2) to determine the role of vitamin D on musculoskeletal health, morphology, and function in men with CP compared to TDC. Materials and methods: A cross-sectional comparison study where 24 active, ambulant men with CP aged 21.0 ± 1.4 years (Gross Motor Function Classification Score (I–II) and 24 healthy TDC aged 25.3 ± 3.1 years completed in vivo assessment of musculoskeletal health, including: vastus lateralis anatomical cross-sectional area (VL ACSA), isometric knee extension maximal voluntary contraction (KE iMVC), 10 m sprint, vertical jumps (VJ), and radius and tibia bone ultrasound (US) Tus and Zus scores. Assessments of vitamin D status through venous samples of serum 25-hydroxyvitamin D (25(OH)D) and parathyroid hormone, dietary vitamin D intake from food diary, and total sun exposure via questionnaire were also taken. Results: Men with CP had 40.5% weaker KE iMVC, 23.7% smaller VL ACSA, 22.2% lower VJ, 14.6% lower KE iMVC/VL ACSA ratio, 22.4% lower KE iMVC/body mass (BM) ratio, and 25.1% lower KE iMVC/lean body mass (LBM) ratio (all p < 0.05). Radius Tus and Zus scores were 1.75 and 1.57 standard deviations lower than TDC, respectively (p < 0.05), whereas neither tibia Tus nor Zus scores showed any difference compared to TDC (p > 0.05). The 25(OH)D was not different between groups, and 90.9% of men with CP and 91.7% of TDC had low 25(OH)D levels when compared to current UK recommendations. The 25(OH)D was positively associated with KE iMVC/LBM ratio in men with CP (r = 0.500, p = 0.020) but not in TDC (r = 0.281, p = 0.104). Conclusion: Musculoskeletal outcomes in men with CP were lower than TDC, and despite there being no difference in levels of 25(OH)D between the groups, 25 (OH)D was associated with strength (KE iMVC/LBM) in the CP group but not TDC. The findings suggest that vitamin D deficiency can accentuate some of the condition-specific impairments to musculoskeletal outcomes.