Predictors of the Acute Postprandial Response to Breaking Up Prolonged Sitting

Long-term ambient air pollution exposure and prospective change in sedentary behaviour and physical activity in individuals at risk of type 2 diabetes in the UK

BACKGROUND

Air pollution may be a risk factor for physical inactivity and sedentary behaviour (SED) through discouraging active lifestyles, impairing fitness and contributing to chronic diseases with potentially important consequences for population health.

METHODS

Using generalized estimating equations, we examined the associations between long-term particulate matter with diameter ≤2.5 μm (PM2.5), ≤10 μm (PM10) and nitrogen dioxide (NO2) and annual change in accelerometer-measured SED, moderate-to-vigorous physical activity (MVPA) and steps in adults at risk of type 2 diabetes within the Walking Away from Type 2 Diabetes trial. We adjusted for important confounders including social deprivation and measures of the built environment.

RESULTS

From 808 participants, 644 had complete data (1605 observations; 64.7% men; mean age 63.86 years). PM2.5, NO2 and PM10 were not associated with change in MVPA/steps but were associated with change in SED, with a 1 ugm-3 increase associated with 6.38 (95% confidence interval: 0.77, 12.00), 1.52 (0.49, 2.54) and 4.48 (0.63, 8.34) adjusted annual change in daily minutes, respectively.

CONCLUSIONS

Long-term PM2.5, NO2 and PM10 exposures were associated with an annual increase in SED: ~11-22 min/day per year across the sample range of exposure (three standard deviations). Future research should investigate whether interventions to reduce pollution may influence SED.

Physiology of sedentary behavior

Sedentary behaviors (SB) are characterized by low energy expenditure while in a sitting or reclining posture. Evidence relevant to understanding the physiology of SB can be derived from studies employing several experimental models: bed rest, immobilization, reduced step count, and reducing/interrupting prolonged SB. We examine the relevant physiological evidence relating to body weight and energy balance, intermediary metabolism, cardiovascular and respiratory systems, the musculoskeletal system, the central nervous system, and immunity and inflammatory responses. Excessive and prolonged SB can lead to insulin resistance, vascular dysfunction, shift in substrate use toward carbohydrate oxidation, shift in muscle fiber from oxidative to glycolytic type, reduced cardiorespiratory fitness, loss of muscle mass and strength and bone mass, and increased total body fat mass and visceral fat depot, blood lipid concentrations, and inflammation. Despite marked differences across individual studies, longer term interventions aimed at reducing/interrupting SB have resulted in small, albeit marginally clinically meaningful, benefits on body weight, waist circumference, percent body fat, fasting glucose, insulin, HbA1c and HDL concentrations, systolic blood pressure, and vascular function in adults and older adults. There is more limited evidence for other health-related outcomes and physiological systems and for children and adolescents. Future research should focus on the investigation of molecular and cellular mechanisms underpinning adaptations to increasing and reducing/interrupting SB and the necessary changes in SB and physical activity to impact physiological systems and overall health in diverse population groups.

A multicomponent intervention to reduce daily sitting time in office workers: the SMART Work & Life three-arm cluster RCT

Background

Office workers spend 70-85% of their time at work sitting. High levels of sitting have been linked to poor physiological and psychological health. Evidence shows the need for fully powered randomised controlled trials, with long-term follow-up, to test the effectiveness of interventions to reduce sitting time.

Objective

Our objective was to test the clinical effectiveness and cost-effectiveness of the SMART Work & Life intervention, delivered with and without a height-adjustable workstation, compared with usual practice at 12-month follow-up.

Design

A three-arm cluster randomised controlled trial.

Setting

Councils in England.

Participants

Office workers.

Intervention

SMART Work & Life is a multicomponent intervention that includes behaviour change strategies, delivered by workplace champions. Clusters were randomised to (1) the SMART Work & Life intervention, (2) the SMART Work & Life intervention with a height-adjustable workstation (i.e. SMART Work & Life plus desk) or (3) a control group (i.e. usual practice). Outcome measures were assessed at baseline and at 3 and 12 months.

Main outcome measures

The primary outcome was device-assessed daily sitting time compared with usual practice at 12 months. Secondary outcomes included sitting, standing, stepping time, physical activity, adiposity, blood pressure, biochemical measures, musculoskeletal issues, psychosocial variables, work-related health, diet and sleep. Cost-effectiveness and process evaluation data were collected.

Results

A total of 78 clusters (756 participants) were randomised [control, 26 clusters (n = 267); SMART Work & Life only, 27 clusters (n = 249); SMART Work & Life plus desk, 25 clusters (n = 240)]. At 12 months, significant differences between groups were found in daily sitting time, with participants in the SMART Work & Life-only and SMART Work & Life plus desk arms sitting 22.2 minutes per day (97.5% confidence interval -38.8 to -5.7 minutes/day; p = 0.003) and 63.7 minutes per day (97.5% confidence interval -80.0 to -47.4 minutes/day; p < 0.001), respectively, less than the control group. Participants in the SMART Work & Life plus desk arm sat 41.7 minutes per day (95% confidence interval -56.3 to -27.0 minutes/day; p < 0.001) less than participants in the SMART Work & Life-only arm. Sitting time was largely replaced by standing time, and changes in daily behaviour were driven by changes during work hours on workdays. Behaviour changes observed at 12 months were similar to 3 months. At 12 months, small improvements were seen for stress, well-being and vigour in both intervention groups, and for pain in the lower extremity and social norms in the SMART Work & Life plus desk group. Results from the process evaluation supported these findings, with participants reporting feeling more energised, alert, focused and productive. The process evaluation also showed that participants viewed the intervention positively; however, the extent of engagement varied across clusters. The average cost of SMART Work & Life only and SMART Work & Life plus desk was £80.59 and £228.31 per participant, respectively. Within trial, SMART Work & Life only had an incremental cost-effectiveness ratio of £12,091 per quality-adjusted life-year, with SMART Work & Life plus desk being dominated. Over a lifetime, SMART Work & Life only and SMART Work & Life plus desk had incremental cost-effectiveness ratios of £4985 and £13,378 per quality-adjusted life-year, respectively.

Limitations

The study was carried out in one sector, limiting generalisability.

Conclusions

The SMART Work & Life intervention, provided with and without a height-adjustable workstation, was successful in changing sitting time.

Future work

There is a need for longer-term follow-up, as well as follow-up within different organisations.

Trial registration

Current Controlled Trials ISRCTN11618007.

Effect of Acute Walking on Endothelial Function and Postprandial Lipemia in South Asians and White Europeans

INTRODUCTION

South Asians (SAs) have an elevated risk of cardiovascular disease (CVD) compared with White Europeans (WEs). Postprandial endothelial function (flow-mediated dilatation (FMD%)) in SA women and SA men with central obesity has not been investigated. Research in other populations has highlighted that a 1% higher FMD% is associated with a ~13% lower risk of future CVD events. We investigated whether FMD% and lipemia, two markers for CVD risk, were higher in SAs versus WEs, whether walking improved FMD% and lipemia, and if there were ethnic differences in the response.

METHODS

Lean premenopausal women (study 1; 12 SA, 12 WE) and men with central obesity (study 2; 15 SA, 15 WE) completed two 2-d trials. On day 1, participants walked for 60 min at 60% of their peak oxygen uptake or rested. On day 2, participants rested and consumed two high-fat meals over 8 h. Repeated ultrasound assessments of endothelial function and venous blood samples for CVD risk markers were taken.

RESULTS

Compared with WEs, SAs had lower postprandial FMD% (study 1, -1.32%; study 2, -0.54%) and higher postprandial triacylglycerol concentrations (study 1, 0.31 mmol·L -1 ·h -1 ; study 2, 0.55 mmol·L -1 ·h -1 ). Walking improved postprandial FMD% (study 1, 1.12%; study 2, 0.94%) and resulted in no significant change or small reductions in postprandial triacylglycerol concentrations (study 1, -0.01 mmol·L -1 ·h -1 ; study 2, -0.25 mmol·L -1 ·h -1 ). Exercise-induced changes in FMD% and triacylglycerol were consistent between ethnic groups.

CONCLUSIONS

Walking mitigated the adverse postprandial effect of a high-fat diet on FMD% to a similar extent in SA and WE women and men, even with no/small improvements in triacylglycerol. This study highlights the importance of exercise to clinically improve FMD% in SAs and WEs.

A potent physiological method to magnify and sustain soleus oxidative metabolism improves glucose and lipid regulation

Slow oxidative muscle, most notably the soleus, is inherently well equipped with the molecular machinery for regulating blood-borne substrates. However, the entire human musculature accounts for only ∼15% of the body’s oxidative metabolism of glucose at the resting energy expenditure, despite being the body’s largest lean tissue mass. We found the human soleus muscle could raise local oxidative metabolism to high levels for hours without fatigue, during a type of soleus-dominant activity while sitting, even in unfit volunteers. Muscle biopsies revealed there was minimal glycogen use. Magnifying the otherwise negligible local energy expenditure with isolated contractions improved systemic VLDL-triglyceride and glucose homeostasis by a large magnitude, e.g., 52% less postprandial glucose excursion (∼50 mg/dL less between ∼1 and 2 h) with 60% less hyperinsulinemia. Targeting a small oxidative muscle mass (∼1% body mass) with local contractile activity is a potent method for improving systemic metabolic regulation while prolonging the benefits of oxidative metabolism.

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We developed a method to capitalize upon the unique phenotype of the soleus

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“A high quality versus large quantity perspective” for muscle activation

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Singular movement targeting the 1 kg soleus easily sustains oxidative metabolism

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This method provides a distinct muscular activity stimulus for metabolic control

Protocol for a randomized controlled trial of sitting reduction to improve cardiometabolic health in older adults

Older adults with obesity spend the majority of their waking hours sedentary. Given substantial barriers to regular physical activity in this population, approaches to reduce sedentary time could be an effective health promotion strategy. We present the protocol of a randomized controlled trial to reduce sitting time in older adults with a body mass index of 30 kg/m² or above. Participants (N = 284) will be randomized to receive a sitting reduction intervention (termed I-STAND) or a healthy living focused attention control condition. I-STAND includes 10 contacts with a health coach (10 sessions total) and participants receive a wrist-worn prompting device and portable standing desk. The healthy living condition includes 10 sessions with a health coach to set goals around various topics relating to healthy aging. Participants receive their assigned intervention for 6 months. After 6 months, those receiving the I-STAND condition are re-randomized to receive five booster health coaching sessions by 'phone or no further contact; healthy living participants receive no further contact and those in both conditions are followed for an additional 6 months. Measurements initially included wearing an activPAL device and completing several biometric tests (e.g., blood pressure, HbA1c), at baseline, 3 months, 6 months, and 12 months; however, during the COVID-19 pandemic we shifted to remote assessments and were unable to collect all of these measures. The primary outcomes remained activPAL-assessed sitting time and blood pressure. Recruitment is anticipated to be completed in 2022.

The impact of COVID-19 restrictions on accelerometer-assessed physical activity and sleep in individuals with type 2 diabetes

AIMS

Restrictions during the COVID-19 crisis will have impacted on opportunities to be active. We aimed to (a) quantify the impact of COVID-19 restrictions on accelerometer-assessed physical activity and sleep in people with type 2 diabetes and (b) identify predictors of physical activity during COVID-19 restrictions.

METHODS

Participants were from the UK Chronotype of Patients with type 2 diabetes and Effect on Glycaemic Control (CODEC) observational study. Participants wore an accelerometer on their wrist for 8 days before and during COVID-19 restrictions. Accelerometer outcomes included the following: overall physical activity, moderate-to-vigorous physical activity (MVPA), time spent inactive, days/week with ≥30-minute continuous MVPA and sleep. Predictors of change in physical activity taken pre-COVID included the following: age, sex, ethnicity, body mass index (BMI), socio-economic status and medical history.

RESULTS

In all, 165 participants (age (mean±S.D = 64.2 ± 8.3 years, BMI=31.4 ± 5.4 kg/m² , 45% women) were included. During restrictions, overall physical activity was lower by 1.7 mg (~800 steps/day) and inactive time 21.9 minutes/day higher, but time in MVPA and sleep did not statistically significantly change. In contrast, the percentage of people with ≥1 day/week with ≥30-minute continuous MVPA was higher (34% cf. 24%). Consistent predictors of lower physical activity and/or higher inactive time were higher BMI and/or being a woman. Being older and/or from ethnic minorities groups was associated with higher inactive time.

CONCLUSIONS

Overall physical activity, but not MVPA, was lower in adults with type 2 diabetes during COVID-19 restrictions. Women and individuals who were heavier, older, inactive and/or from ethnic minority groups were most at risk of lower physical activity during restrictions.

Effects of sedentary behavior and daily walking steps on body mass index and body composition: Prospective observational study using outpatient clinical data of Japanese patients with type 2 diabetes

AIMS/INTRODUCTION

This study examined the effect of daily walking steps on glycated hemoglobin, body mass index (BMI) and body composition while taking into consideration sedentary time (ST) in Japanese type 2 diabetes patients over a period of 12 months.

MATERIALS AND METHODS

Self-administered ST values and information regarding daily walking steps were obtained and analyzed for 236 patients with type 2 diabetes who regularly visited the outpatient clinic. The patients - divided into three categories of daily walking steps: non-step counter user, <7,500 daily walking steps and ≥7,500 daily walking steps (HS) - were prospectively observed considering ST through the monitoring of glycated hemoglobin, BMI waist circumference (WC) and visceral fat accumulation (VFA) for 12 months.

RESULTS

After 12 months, the participants categorized as the HS group had significantly reduced BMI and VFA independent of ST, as well as significantly reduced WC with high ST. WC and VFA disparities widened significantly at 12 months between the participants categorized as being in the non-step counter user group and the HS group with long ST. However, no difference in glycated hemoglobin levels and BMI were found among the three categories independent of ST. Compared with non-step counter users, the odds ratios with logistic regression models of improvement in BMI and VFA in the <7,500 daily walking steps and HS groups, and WC in the HS group after 12 months were significantly higher only among those with long ST.

CONCLUSIONS

These results suggest that consideration of sedentary behavior in combination with daily walking steps might be essential for type 2 diabetes management.

Postprandial Metabolism and Physical Activity in Asians: A Narrative Review

The widespread benefits of physical activity in enhancing health and lowering the risk of non-communicable chronic diseases are well established across populations globally. Nevertheless, the prevalence of several lifestyle-related chronic diseases, including cardiovascular disease, varies markedly across countries and ethnicities. Direct ethnic comparative studies on the health benefits of physical activity are sparse and evidence-based physical activity guidelines are not ethnicity-specific. Indeed, physical activity guidelines in some Asian countries were developed primarily based on data from Western populations even though the magnitude of potential benefit may not be the same among different ethnic groups. Unfavorable diurnal perturbations in postprandial triglycerides and glucose are risk factors for cardiovascular disease. This narrative review summarizes differences in these risk factors primarily between individuals of Asian and white European descent but also within different Asian groups. Moreover, the variable effects of physical activity on mitigating risk factors among these ethnic groups are highlighted along with the underlying metabolic and hormonal factors that potentially account for these differences. Future ethnic comparative studies should include investigations in understudied ethnic groups, such as those of East Asian origin, given that the effectiveness of physical activity for ameliorating cardiovascular disease varies even among Asian groups.

Improvements in Glycemic Control After Acute Moderate-Intensity Continuous or High-Intensity Interval Exercise Are Greater in South Asians Than White Europeans With Nondiabetic Hyperglycemia: A Randomized Crossover Study

OBJECTIVE

To examine whether circulating metabolic responses to low-volume high-intensity interval exercise (LV-HIIE) or continuous moderate-intensity aerobic exercise (CME) differ between white Europeans and South Asians with nondiabetic hyperglycemia (NDH).

RESEARCH DESIGN AND METHODS

Thirteen white Europeans and 10 South Asians (combined median [interquartile range] age 67 [60-68] years, HbA_1c 5.9% [5.8-6.1%] [41.0 (39.9-43.2) mmol ⋅ mol^-1]) completed three 6-h conditions (sedentary control [CON], LV-HIIE, and CME) in a randomized order. Exercise conditions contained a single bout of LV-HIIE and CME, respectively (each ending at 2 h), with meals provided at 0 and 3 h. Circulating glucose (primary outcome), insulin, insulin resistance index (IRI), triglycerides, and nonesterified fatty acids were measured at 0, 0.5, 1, 2, 3, 3.5, 4, 5, and 6 h. Data were analyzed as postexercise time-averaged area under the curve (AUC) adjusted for age, sex, and preexercise AUC.

RESULTS

Glucose was similar in each condition and with ethnicity, with no condition-by-ethnicity interaction (P ≥ 0.28). However, insulin was lower in LV-HIIE (mean [95% CI] -44.4 [-23.7, -65.1] mU ⋅ L^-1) and CME (-33.8 [-13.7, -53.9] mU ⋅ L^-1) compared with CON. Insulin responses were greater in South Asians (interaction P = 0.03) such that values were similar in each ethnicity during exercise conditions, despite being 33% higher in South Asians during CON. IRI followed a similar pattern to insulin. Lipids were unaffected by exercise.

CONCLUSIONS

Reductions in insulin and insulin resistance after acute LV-HIIE and CME are greater in South Asians than in white Europeans with NDH. Further trials are required to examine the longer-term impact of LV-HIIE and CME on cardiometabolic health.

Interrupting prolonged sitting with repeated chair stands or short walks reduces postprandial insulinemia in healthy adults

We determined if interrupting prolonged sitting with practical "activity snacks" could reduce postprandial glycemia and insulinemia in healthy adults. Fourteen participants (7 males, 7 females; 24 ± 5 yr; 25 ± 5 kg/m²; 40 ± 8 mL/kg/min; 7,033 ± 2,288 steps/day) completed three 7.5-h trials in a randomized order consisting of uninterrupted sitting (SIT), sitting with intermittent (every 30 min) walking (WALK; 2 min at 3.1 mph), or sitting with intermittent squats (SQUAT; 15 chair stands with calf raise). Mixed-macronutrient liquid meals provided 20% ("breakfast") and 30% ("lunch") of daily energy needs to mimic Western meal patterns. Blood samples were obtained for analysis of postprandial plasma glucose and insulin concentrations, and skeletal muscle biopsy samples were collected to measure markers of contraction- and insulin-mediated glucose uptake signaling. Postprandial glucose and insulin did not differ across conditions following breakfast. After lunch, peak insulin concentration was lower in SQUAT (52 ± 27, P < 0.01) and WALK (62 ± 35, P < 0.05) compared with SIT (79 ± 43 μIU/mL). The insulin incremental area under the curve (iAUC) 1 h following lunch was 37 and 29% lower in SQUAT (P < 0.01) and WALK (P < 0.05) compared with SIT, respectively; however, 3-h insulin iAUC was reduced in SQUAT only (24% vs. SIT, P < 0.05). The 3-h insulin:glucose iAUC was reduced following lunch in both SQUAT (30%) and WALK (23%) compared with SIT (P < 0.05). Phosphorylation of AKT^Thr308, AKT^Ser473, and AS160^Ser318 was not different between conditions (P > 0.05). Interrupting prolonged sitting with short walks or repeated chair stands reduces postprandial insulinemia in healthy adults. Our results may have implications for mitigating cardiometabolic disease risk in adults who engage in periods of prolonged sitting.NEW & NOTEWORTHY Breaking up prolonged sitting with intermittent walking breaks can improve glycemic control. Here, we demonstrated that interrupting prolonged sitting every 30 min with 1 min of repeated chair stands was as effective as 2-min treadmill walks for lowering postprandial insulinemia in healthy adults. Markers of contraction- and insulin-mediated muscle glucose uptake were unchanged. Repeated chair stands as a form of body-weight resistance activity may represent a cost- and space-efficient activity break for mitigating cardiometabolic-disease risk.