Effects of interrupting prolonged sitting with high-intensity physical activity on postprandial metabolism

A thesis submitted to the University of Bedfordshire, in fulfilment of the requirements for the degree of MSc by ResearchAims The aim of this thesis was to explore the effects of interrupting prolonged sitting with high-intensity activity on cardiometabolic risk markers. Methods In study 1, participants completed 3, 8 hour trials: 1) uninterrupted sitting (SIT) 2) continuous moderate-intensity activity followed by sitting, and 3) sitting interrupted with hourly high-intensity activity (SIT-ACT). In study 2, participants completed 3, 6.5 hour trials: 1) SIT, 2) a continuous high-intensity interval exercise session followed by sitting (CON-HIE), and 3) sitting interrupted with high-intensity activity bouts (SIT-HIE). Postprandial incremental area under the curve (iAUC) was calculated for cardiometabolic risk markers and compared between conditions. Data are mean (95% confidence intervals). Results In study 1, glucose iAUC was not different between conditions (p= 0.606). Triglyceride (TG) iAUC was lower and high-density lipoprotein was higher in SIT-ACT than SIT (p=<0.05). In study 2, glucose iAUC was significantly lower in SIT-HIE than SIT (p=0.026), while TG iAUC was significantly lower in CON-HIE than SIT (p=0.014). Conclusion Study 1 observed beneficial TG and HDL responses to interrupting sitting with high-intensity activity. Study 2 observed suppressed glucose in response to interrupting sitting with high-intensity activity, but postprandial TG was reduced only in response to a high-intensity interval exercise session

Effects of breaking up prolonged sitting following low and high glycaemic index breakfast consumption on glucose and insulin concentrations

Purpose: Breaking up prolonged sitting can attenuate the postprandial rise in glucose and insulin. Whether such effects are dependent of the glycaemic index (GI) of the consumed carbohydrate is unknown. This study examined the acute effects of breaking up prolonged sitting following a low GI and a high GI breakfast on postprandial glucose and insulin concentrations. Procedures: Fourteen adult males aged 22.1 ± 1.2 years completed four, 4 h experimental conditions: high GI breakfast followed by uninterrupted sitting (HGI-SIT), low GI breakfast followed by uninterrupted sitting (LGI-SIT), high GI breakfast followed by 2 min activity breaks every 20 min (HGI-ACT), and low GI breakfast followed by 2 min activity breaks every 20 min (LGI-ACT). Positive incremental area under the curve (iAUC) for glucose and insulin (mean [95% CI]) for each 4h experimental condition was calculated. Statistical analyses were completed using linear mixed models. Results: The sitting × breakfast GI interaction was not significant for glucose positive iAUC (P=0.119). Glucose positive iAUC (mmol/L4 h−1) was significantly lower in the activity breaks conditions than the uninterrupted sitting conditions (2.07 [2.24, 2.89] vs. 2.56 [1.74, 2.40], respectively, P=0.004) and significantly lower in the low GI conditions than the high GI conditions (2.13 [1.80, 2.45] vs. 2.51 [2.18, 2.84], respectively, P=0.022). Insulin concentrations did not differ between conditions (P ≥ 0.203). Conclusions: Breaking up prolonged sitting and lowering breakfast GI independently reduced postprandial glucose responses. This indicates that interrupting prolonged sitting and reducing dietary GI are beneficial approaches for reducing cardiometabolic disease risk

Beneficial postprandial lipaemic effects of interrupting sedentary time with high-intensity physical activity versus a continuous moderate-intensity physical activity bout: a randomised crossover trial

Objectives To compare the postprandial cardiometabolic response to prolonged sitting, continuous moderate-intensity physical activity (PA) followed by prolonged sitting, and interrupting prolonged sitting with hourly high-intensity PA breaks. Design Three-condition randomised crossover trial. Methods Fourteen sedentary and inactive adults aged 29 ± 9 years took part in three, 8-h conditions: (1) prolonged sitting (SIT), (2) a continuous 30-min moderate-intensity PA bout followed by prolonged sitting (CONT-SIT), and (3) sitting interrupted hourly with 2 min 32 s high-intensity PA bouts (SIT-ACT). The treadmill PA in conditions 2 and 3 were matched for energy expenditure. Two standardised test meals were consumed during each condition. Incremental area under the curve (iAUC) for each 8-h condition was calculated for glucose, insulin, triglyceride, and high-density lipoprotein cholesterol (HDL-C) concentrations. Statistical analyses were completed using linear mixed models. Results Compared with SIT, SIT-ACT lowered triglyceride iAUC by 2.23 mmol/L ∙ 8 h (95% CI −4.33, −0.13) and raised HDL-C iAUC by 0.99 mmol/L ∙ 8 h (0.05, 1.93) (all p ≤ 0.038). There was no significant difference in triglyceride or HDL-C iAUC between CONT-SIT and SIT or SIT-ACT (p ≥ 0.211). There were no significant differences between conditions for glucose or insulin iAUC (p ≥ 0.504). Conclusions This study suggests that interrupting prolonged sitting with hourly high-intensity PA breaks acutely improves postprandial triglyceride and HDL-C concentrations compared with prolonged sitting, whereas a continuous moderate-intensity PA bout does not

Genomic assessment of quarantine measures to prevent SARS-CoV-2 importation and transmission

Mitigation of SARS-CoV-2 transmission from international travel is a priority. We evaluated the effectiveness of travellers being required to quarantine for 14-days on return to England in Summer 2020. We identified 4,207 travel-related SARS-CoV-2 cases and their contacts, and identified 827 associated SARS-CoV-2 genomes. Overall, quarantine was associated with a lower rate of contacts, and the impact of quarantine was greatest in the 16–20 age-group. 186 SARS-CoV-2 genomes were sufficiently unique to identify travel-related clusters. Fewer genomically-linked cases were observed for index cases who returned from countries with quarantine requirement compared to countries with no quarantine requirement. This difference was explained by fewer importation events per identified genome for these cases, as opposed to fewer onward contacts per case. Overall, our study demonstrates that a 14-day quarantine period reduces, but does not completely eliminate, the onward transmission of imported cases, mainly by dissuading travel to countries with a quarantine requirement

Breaking up sitting with short frequent or long infrequent physical activity breaks does not lead to compensatory changes in appetite, appetite-regulating hormones or energy intake

The aim of this study was to determine the appetite-related responses to breaking up prolonged sitting with physical activity bouts differing in frequency and duration among adult females. Fourteen sedentary females aged 34 ± 13 years with a body mass index of 27.1 ± 6.3 kg/m2 (mean ± SD) took part in a randomised crossover trial with three, 7.5 h conditions: (1) uninterrupted sitting (SIT), (2) sitting with short frequent 2-min moderate-intensity walking breaks every 30 min (SHORT-BREAKS), and (3) sitting with longer duration, less frequent 10-min moderate-intensity walking breaks every 170–180 min (LONG-BREAKS). The intensity and total duration of physical activity was matched between the SHORT-BREAKS and LONG-BREAKS conditions. Linear mixed models were used to compare the outcomes between conditions with significance being accepted as p ≤ 0.05. There were no significant between-condition differences in hunger, satisfaction, prospective food consumption or overall appetite area under the curve (AUC) (all p ≥ 0.801). Absolute ad libitum energy intake and relative energy intake (REI) did not differ significantly between conditions (all p ≥ 0.420). Acylated ghrelin and total peptide YY incremental and total AUC did not differ significantly between conditions (all p ≥ 0.388). Yet, there was a medium effect size for the higher acylated ghrelin incremental AUC in SHORT-BREAKS versus SIT (d = 0.61); the reverse was seen for total AUC, which was lower in SHORT-BREAKS versus SIT (d = 0.69). These findings suggest that breaking up sitting does not lead to compensatory changes in appetite, appetite hormones or energy intake regardless of physical activity bout duration and frequency among adult females.</p

Genomic reconstruction of the SARS-CoV-2 epidemic in England

AbstractThe evolution of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus leads to new variants that warrant timely epidemiological characterization. Here we use the dense genomic surveillance data generated by the COVID-19 Genomics UK Consortium to reconstruct the dynamics of 71 different lineages in each of 315 English local authorities between September 2020 and June 2021. This analysis reveals a series of subepidemics that peaked in early autumn 2020, followed by a jump in transmissibility of the B.1.1.7/Alpha lineage. The Alpha variant grew when other lineages declined during the second national lockdown and regionally tiered restrictions between November and December 2020. A third more stringent national lockdown suppressed the Alpha variant and eliminated nearly all other lineages in early 2021. Yet a series of variants (most of which contained the spike E484K mutation) defied these trends and persisted at moderately increasing proportions. However, by accounting for sustained introductions, we found that the transmissibility of these variants is unlikely to have exceeded the transmissibility of the Alpha variant. Finally, B.1.617.2/Delta was repeatedly introduced in England and grew rapidly in early summer 2021, constituting approximately 98% of sampled SARS-CoV-2 genomes on 26 June 2021.</jats:p