Does the type of activity "break" from prolonged sitting differentially impact on postprandial blood glucose reductions? An exploratory analysis

Interrupting sitting with moderate-intensity physical activity breaks improves cognitive processing speed in adults with overweight and obesity: Findings from the SITLess pilot randomized crossover trial

INTRODUCTION

Prolonged sitting can acutely reduce working memory (WM) in individuals with overweight and obesity (OW/OB) who show executive function deficits. Interrupting prolonged sitting with brief PA bouts may counter these effects. However, the benefits of such interventions on behavioral and neuroelectric indices of WM and whether neurocognitive responses are associated with postprandial glycemic responses in young and middle-aged adults with OW/OB remain unknown. To address this gap, this study examined the acute effects of interrupting three-hour prolonged sitting every 30 min with 3.5-min moderate-intensity physical activity (MPA) bouts (MPA + SIT condition) relative to sedentary social interaction condition (SOC + SIT) on behavioral measures of WM and the P3b component of event-related potentials (ERP) in young and middle-aged adults with OW/OB.

METHOD

Nineteen adults with OW/OB (63 % females; 29.9 ± 7.5 years; BMI = 30.0 ± 3.64 kg*m-2) were included in the SITLess pilot randomized crossover trial. Choice RT and WM were measured before, after, and four times during each condition with 1- and 2-back letter tasks. They were expressed as the incremental area under the curve (iAUC). Choice RT was expressed as d-prime, target, and nontarget accuracy, and RT on the 1-back and nontarget RT on the 2-back task. WM was expressed as d-prime, target accuracy, and RT on the 2-back task. The amplitude of the P3b-ERP component was used to measure attentional resource allocation during both tasks; the P3b-ERP fractional area latency measured cognitive processing before and after each condition. Two-hour postprandial glycemic responses (expressed as iAUC) were measured using an oral glucose tolerance test (OGTT). Time (pre, post) x Condition (MPA + SIT vs. SOC + SIT) interactions and the main effect of Condition (iAUCs) were tested using Linear Mixed Models.

RESULTS

No significant intervention effects on glucose were noted (p = 0.74). Compared to SOC + SIT, MPA + SIT resulted in shorter 1-back target P3b latency (F(1, 17.0) = 5.14, p = 0.037; Mdiff = -9.77, SE = 4.31 ms, 95%CI: -18.9, -0.68) at post-test. No effects on behavioral measures were noted (ps ≥ 0.06). However, the between-condition difference in 1-back P3b latency correlated positively with the between-condition difference in RTs on 1-back;shorter P3b latency was related to shorter RTs in the MPA + SIT relative to SOC + SIT (r = 0.65 and 0.55 for target and nontarget trials, ps ≤ 0.02).

CONCLUSION

Interrupting sitting with short MPA bouts can enhance some aspects of cognitive processing in adults with OW/OB. Future studies are needed to better understand behavioral responses to interrupting prolonged sitting with MPA bouts and the underlying mechanisms.

Effect of Interrupting Prolonged Sitting with Frequent Activity Breaks on Postprandial Glycemia and Insulin Sensitivity in Adults with Type 1 Diabetes on Continuous Subcutaneous Insulin Infusion Therapy: A Randomized Crossover Pilot Trial

Objective: This study examined acute effects of interrupting prolonged sitting with short activity breaks on postprandial glucose/insulin responses and estimations of insulin sensitivity in adults with type 1 diabetes (T1D). Method: In a randomized crossover trial, eight adults (age = 46 ± 14 years [mean ± SD], body mass index [BMI] = 27.2 ± 3.8 kg/m2) receiving continuous subcutaneous insulin infusion (CSII) therapy completed two 6-h conditions as follows: uninterrupted sitting (SIT) and sitting interrupted with 3-min bouts of simple resistance activities (SRAs) every 30 min. Basal and bolus insulin were standardized across conditions except in cases of hypoglycemia. Postprandial responses were assessed using incremental area-under-the-curve (iAUC) and total AUC (tAUC) from half-hourly venous sampling. Meal-based insulin sensitivity determined from glucose sensor and insulin pump (SiSP) was assessed from flash continuous glucose monitor and insulin pump data. Outcomes were analyzed using mixed models adjusted for sex, BMI, treatment order, and preprandial values. Results: Glucose iAUC did not differ by condition (SIT: 19.8 ± 3.0 [estimated marginal means ± standard error] vs. SRA: 14.4 ± 3.0 mmol.6 h.L-1; P = 0.086). Despite CSII being standardized between conditions, insulin iAUC was higher in SRA compared to SIT (137.1 ± 22.7 vs. 170.9 ± 22.7 mU.6 h.L-1; P < 0.001). This resulted in a lower glucose response relative to the change in plasma insulin in SRA (tAUCglu/tAUCins: 0.32 ± 0.02 vs. 0.40 ± 0.02 mmol.mU-1; P = 0.03). SiSP was also higher at dinner following the SRA condition, with no between-condition differences at breakfast or lunch. Conclusion: Regularly interrupting prolonged sitting in T1D may increase plasma insulin and improve insulin sensitivity when meals and CSII are standardized. Future studies should explore underlying mechanistic determinants and the applicability of findings to those on multiple daily injections. Trial Registration: Australian and New Zealand Clinical Trial Registry Identifier-ACTRN12618000126213 (www.anzctr.org.au).

Interrupting sitting acutely attenuates cardiometabolic risk markers in South Asian adults living with overweight and obesity

PURPOSE

This study examined the acute effects of interrupting sitting with light-intensity walking on postprandial cardiometabolic risk markers in South Asian adults.

METHODS

South Asians with overweight/obesity (n = 19; body mass index [BMI] > 23 kg·m-2) and normal-weight (n = 8; BMI 18.0-22.9 kg·m-2) aged 48.8 ± 5.6 years completed two, 5-h conditions: (1) prolonged sitting (SIT), and (2) interrupted sitting with 5-min bouts of light-intensity walking every 30-min (INT-SIT). Blood samples and resting expired air samples were collected throughout each condition. Statistical analyses were completed using linear mixed models.

RESULTS

In participants with overweight/obesity, postprandial glucose, triglycerides (TAG) and metabolic load index (MLI) over time were lower, whereas resting substrate utilisation and resting energy expenditure (REE) were higher, in INT-SIT than SIT (all p ≤ 0.05). Compared with SIT (0.18 [95% CI 0.13, 0.22] kcal.min-1), INT-SIT (0.23 [95% CI 0.18, 0.27] kcal.min-1) increased postprandial REE iAUC in participants with overweight/obesity (p = 0.04, d = 0.51). Postprandial TAG concentrations over time were lower in INT-SIT versus SIT (p = 0.01, d = 30) in normal-weight participants, with no differences in any other outcomes for this sample group.

CONCLUSION

These findings suggest that interrupting sitting with 5-min bouts of light walking every 30-min acutely attenuates cardiometabolic risk markers among South Asians living with overweight/obesity, whereas limited effects may be seen in individuals with normal-weight.

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.

Effects of reducing sedentary behaviour duration by increasing physical activity, on cognitive function, brain function and structure across the lifespan: a systematic review protocol

INTRODUCTION

Greater engagement in sedentary behaviours has been related to poorer cognitive functions in epidemiological research. However, the effects of reducing sedentary behaviour duration on cognitive function, brain function, and structure remain poorly understood. This systematic review aims to synthesise the evidence on the effects of reducing sedentary behaviour duration by increasing time spent in physical activity on cognitive function, brain structure and function in apparently healthy children, adolescents and adults.

METHODS AND ANALYSIS

The protocol follows Preferred Reporting Items for Systematic Reviews and Meta-Analyses. The literature search will be conducted (search dates: August-September 2022) across six databases: PubMed, Scopus, Cumulative Index to Nursing and Allied Health Literature (via EBSCO Host), PsycINFO (via ProQuest), SPORTDiscus and Web of Science (Science and Social Science Citation Index). The inclusion criteria are as follows: randomised and non-randomised experimental studies as defined by the Cochrane Handbook, published in English, in peer-reviewed journals, and as theses or dissertations. References of included papers will be screened for additional studies. Acute and chronic interventions targeting children (≥ 4 years), adolescents, younger adults (≥ 18-40 years), middle-aged (40-64 years) and older adults (65+ years) will be eligible. Methodological quality will be assessed with the Effective Public Health Practice Project quality assessment tool for quantitative studies. Qualitative synthesis will be stratified by intervention type (acute vs chronic), intervention content (reducing sedentary time or interrupting prolonged sitting) and outcome (cognitive, brain structure and function).

ETHICS AND DISSEMINATION

No primary data collection will be conducted as part of this systematic review. Study findings will be disseminated through peer-reviewed publications, conference presentations and social media.

PROSPERO REGISTRATION NUMBER

CRD42020200998.

Descriptive Epidemiology of Interruptions to Free-Living Sitting Time in Middle-Age and Older Adults

National guidelines recommend physically active interruptions to sitting time, however, the characteristics of these interruptions are broadly stated and ill-defined. A robust methodology for population surveillance for such interruptions is needed.

PURPOSE

To describe the frequency and characteristics (i.e., duration, stepping time, and estimated intensity) of all interruptions and physically active interruptions to adults' free-living sitting time (i.e., transitions from sitting to upright posture) across segments of the population.

METHODS

Australian Diabetes, Obesity and Lifestyle (AusDiab) study participants (321 men; 406 women; mean ± SD 58.0 ± 10.3 years) wore the activPAL3TM for ≥1 valid day. The characteristics of interruptions from laboratory studies demonstrating health benefits were selected to define active interruptions (≥5 min upright and/or ≥ 2 min stepping) and ambulatory interruptions (≥2 min stepping). The frequency and characteristics of all, active, and ambulatory interruptions were described and compared by age, gender, diabetes status, and body mass index.

RESULTS

Adults averaged 55.0 ± 21.8 interruptions per day, but only 20.3 ± 6.7 were active and 14.0 ± 5.4 were ambulatory. Median (25th, 75th percentile) duration was 2.6 (0.9, 7.8) minutes, stepping time was 0.8 (0.3, 2.0) minutes, and estimated energy expenditure was 4.3 (1.4, 12.5) MET-min. Those who were older, had obesity, or had diabetes had significantly (p < 0.05) fewer interruptions of all types and less stepping time during active interruptions than their counterparts (Cohen's d < 0.2).

CONCLUSION

Free-living interruptions were often less active than interruptions performed in effective acute laboratory studies and their content varied widely between population groups. Monitoring all interruptions as well as those that are more active is advisable to provide a comprehensive understanding of free-living sedentary behavior.

Leg Fidgeting During Prolonged Sitting Improves Postprandial Glycemic Control in People with Obesity

OBJECTIVE

Studies have shown that fidgeting augments metabolic demand and increases blood flow to the moving limbs, whereas prolonged sitting suppresses these factors and exacerbates postprandial glucose excursions. Therefore, the hypothesis of this study was that leg fidgeting during prolonged sitting would improve postprandial glycemic control.

METHODS

Adults with obesity (n = 20) participated in a randomized crossover trial in which blood glucose and insulin concentrations were measured during a 3-hour sitting period following the ingestion of a glucose load (75 g). During sitting, participants either remained stationary or intermittently fidgeted both legs (2.5 minutes off and 2.5 minutes on). Accelerometer counts, oxygen consumption, and popliteal-artery blood flow were also measured during the sitting period.

RESULTS

As expected, fidgeting increased accelerometer counts (P < 0.01), oxygen consumption (P < 0.01), and blood flow through the popliteal artery (P < 0.05). Notably, fidgeting lowered both glucose (P < 0.01) and insulin (P < 0.05) total area under the curve (AUC) and glucose incremental AUC (P < 0.05). Additionally, there was a strong negative correlation between fidgeting-induced increases in blood flow and reduced postprandial glucose AUC within the first hour (r = -0.569, P < 0.01).

CONCLUSIONS

Leg fidgeting is a simple, light-intensity physical activity that enhances limb blood flow and can be incorporated during prolonged sitting to improve postprandial glycemic control in people with obesity.

Does Interrupting Prolonged Sitting With 10- or 20-Min Standing Attenuate Postprandial Glycemia and Blood Pressure in Middle-Aged and Older Adults With Type 2 Diabetes?

We carried out three types of 2-hr experimental sessions with middle-aged and older adults with Type 2 diabetes in order to examine the acute effect of interrupting prolonged sitting with varying periods of standing on postprandial glycemia and blood pressure (BP): (a) prolonged sitting after breakfast; (b) standing for 10 min, 30 min after breakfast; and (c) standing for 20 min, 30 min after breakfast. Glucose and BP were assessed before and after breakfast. A generalized linear model revealed no significant differences for the incremental area under the curve of glucose between standing for 10 min, 30 min after breakfast, versus prolonged sitting after breakfast (β = -4.5 mg/dl/2 hr, 95% CI [-17.3, 8.4]) and standing for 20 min, 30 min after breakfast, versus prolonged sitting after breakfast (β = 0.9 mg/dl/2 hr, 95% CI [-11.9, 13.7]). There was no difference in area under the curve of systolic and diastolic BP among the sessions. Interrupting prolonged sitting time with 10 or 20 min of standing 30 min after breakfast does not attenuate postprandial glycemia or BP in middle-aged and older adults with Type 2 diabetes.

Exercise-nutrient interactions for improved postprandial glycemic control and insulin sensitivity

Type 2 diabetes (T2D) is a rapidly growing yet largely preventable chronic disease. Exaggerated increases in blood glucose concentration following meals is a primary contributor to many long-term complications of the disease that decrease quality of life and reduce lifespan. Adverse health consequences also manifest years prior to the development of T2D due to underlying insulin resistance and exaggerated postprandial concentrations of the glucose-lowering hormone insulin. Postprandial hyperglycemic and hyperinsulinemic excursions can be improved by exercise, which contributes to the well-established benefits of physical activity for the prevention and treatment of T2D. The aim of this review is to describe the postprandial dysmetabolism that occurs in individuals at risk for and with T2D, and highlight how acute and chronic exercise can lower postprandial glucose and insulin excursions. In addition to describing the effects of traditional moderate-intensity continuous exercise on glycemic control, we highlight other forms of activity including low-intensity walking, high-intensity interval exercise, and resistance training. In an effort to improve knowledge translation and implementation of exercise for maximal glycemic benefits, we also describe how timing of exercise around meals and post-exercise nutrition can modify acute and chronic effects of exercise on glycemic control and insulin sensitivity. Novelty: Exaggerated postprandial blood glucose and insulin excursions are associated with disease risk. Both a single session and repeated sessions of exercise improve postprandial glycemic control in individuals with and without T2D. The glycemic benefits of exercise can be enhanced by considering the timing and macronutrient composition of meals around exercise.

Metabolic Effects of Three Different Activity Bouts during Sitting in Inactive Adults

PURPOSE

This study aimed to determine whether interrupting prolonged sitting with three different walking-bout schedules improves glycemic metabolism relative to continuous prolonged sitting in sedentary adults.

METHODS

In a randomized, crossover trial, 16 inactive healthy adults (7 men, 24 ± 3 yr old) completed four 26-h laboratory sessions, including 22.5 h in an energy expenditure (EE)-testing calorimeter chamber. The four 9-h intervention periods were as follows: 9-h uninterrupted sitting (SIT), 30-min sitting/3-min brisk (60% V˙O2max) treadmill walk (WALK3), 45-min sitting/5-min (WALK5), or 60-min sitting/8-min (WALK8). Coprimary outcomes included the difference in the mean interstitial glucose concentration, total area under the curve (tAUC), and incremental area under the curve (iAUC) for the entire 26 and 9 h (intervention period) during three activity-bout conditions compared with SIT.

RESULTS

Compared with SIT, the 26-h mean glucose concentration was attenuated in WALK8 (Δmean -0.22 mmol·L [95% confidence interval = -0.43 to -0.001], P = 0.048) without adjustment for EE and attenuated in WALK3 (Δ-0.47 mmol·L [-0.75 to -0.10]), WALK5 (Δ-0.47 mmol·L [-0.83 to -0.10]), and WALK8 (Δ-0.53 mmol·L [-0.92 to -0.13]) after adjustment for EE (all P < 0.01). The 26-h tAUC was reduced in WALK3 (Δ-11.18 mmol·L per 26 h [-20.07 to -2.29]), WALK5 (2.12.67 mmol·L per 26 h [-22.54 to -2.79]), and WALK8 (Δ-13.85 mmol·L per 26 h [-24.60 to -3.10]) (all P < 0.01), as well as the iAUC (all P < 0.05), only after adjustment for EE. The 9-h mean glucose concentration, tAUC, and iAUC decreased in the three activity-break conditions regardless of EE adjustment (all P < 0.05).

CONCLUSIONS

All three walking-bout conditions improved glycemic metabolism compared with SIT, independent of EE, in inactive, healthy adults.

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.

Energy utilisation and postprandial responses during sitting interrupted by regular activity breaks

Interrupting sedentary behaviour with regular activity breaks benefits glycaemic control; however, the influence of the energy utilised during these activity breaks on postprandial metabolic response is relatively unknown. Therefore, the aim of this study was to investigate whether the energy utilisation of regular (every 30 min) short (1 min 40 s or 2 min) activity breaks was associated with the lowering of postprandial glycaemia, insulinemia and lipidemia.

Using separate data from two previously performed studies (ALPhA Study n = 65, age 25.7 (5.2) y, 40% male, BMI 23.6 (4.1) kg · m^-2. ABPA study n = 35, age 25.1 (3.7) y, 31% male, BMI 23.4 (3.2) kg · m^-2) we investigated the association between energy utilisation (measured by indirect calorimetry) and postprandial glucose, insulin and triglycerides during prolonged sitting, and regular activity breaks.Results.

Mixed effects regression models indicated that energy utilisation was not consistently associated with postprandial glucose, insulin or triglyceride responses (p > 0.05 for all). Additionally, there was some indication that energy utilisation was obscuring (mildly suppressing) the effects of regular activity breaks on glucose, insulin and triglyceride iAUC.Conclusions.

If energy utilisation does not mediate the association between regular activity breaks and postprandial glycaemic response, it is possible that it is the frequency of the activity breaks that is beneficial.

Sedentary Behavior and Public Health: Integrating the Evidence and Identifying Potential Solutions

In developed and developing countries, social, economic, and environmental transitions have led to physical inactivity and large amounts of time spent sitting. Research is now unraveling the adverse public health consequences of too much sitting. We describe improvements in device-based measurement that are providing new insights into sedentary behavior and health. We consider the implications of research linking evidence from epidemiology and behavioral science with mechanistic insights into the underlying biology of sitting time. Such evidence has led to new sedentary behavior guidelines and initiatives. We highlight ways that this emerging knowledge base can inform public health strategy: First, we consider epidemiologic and experimental evidence on the health consequences of sedentary behavior; second, we describe solutions-focused research from initiatives in workplaces and schools. To inform a broad public health strategy, researchers need to pursue evidence-informed collaborations with occupational health, education, and other sectors.

Controversies in the Science of Sedentary Behaviour and Health: Insights, Perspectives and Future directions from the 2018 Queensland Sedentary Behaviour Think Tank

The development in research concerning sedentary behaviour has been rapid over the past two decades. This has led to the development of evidence and views that have become more advanced, diverse and, possibly, contentious. These include the effects of standing, the breaking up of prolonged sitting and the role of moderate-to-vigorous physical activity (MVPA) in the association between sedentary behaviour and health outcomes. The present aim is to report the views of experts (n = 21) brought together (one-day face-to-face meeting in 2018) to consider these issues and provide conclusions and recommendations for future work. Each topic was reviewed and presented by one expert followed by full group discussion, which was recorded, transcribed and analysed. The experts concluded that (a). standing may bring benefits that accrue from postural shifts. Prolonged (mainly static) standing and prolonged sitting are both bad for health; (b). ‘the best posture is the next posture’. Regularly breaking up of sitting with postural shifts and movement is vital; (c). health effects of prolonged sitting are evident even after controlling for MVPA, but high levels of MVPA can attenuate the deleterious effects of prolonged sitting depending on the health outcome of interest. Expert discussion addressed measurement, messaging and future directions.

Effect of Breaks in Prolonged Sitting or Low-Volume High-Intensity Interval Exercise on Markers of Metabolic Syndrome in Adults With Excess Body Fat: A Crossover Trial

BACKGROUND

This study analyzed the effect of walking breaks or low-volume high-intensity interval exercise (LV-HIIE) on markers of metabolic syndrome relative to a day of prolonged sitting.

METHODS

Twenty-five adults with excess body fat participated in this crossover trial: (1) 10-hour sitting day (SIT), (2) LV-HIIE followed by a sitting day (EX+SIT), and (3) sitting day with 5-minute walking breaks for every 20 minutes (SIT+WB). Glucose and blood pressure (BP) were measured before and 1 hour after 4 meals and 2 hours after lunch. Triglycerides were measured at baseline, 2, and 3.5 hours after lunch. Generalized mixed models were used to identify differences in the area under the curve (AUC) of BP and incremental AUC (iAUC) of glucose and triglycerides among the sessions.

RESULTS

iAUC-glucose was lower in SIT+WB than SIT (β = -35.3 mg/dL·10 h; 95% confidence interval, -52.5 to -8.2). AUC-diastolic BP was lower in SIT+WB than SIT (β = -14.1 mm Hg·10 h; 95% confidence interval, -26.5 to -1.6) and EX+SIT (β = -14.5 mm Hg·10 h; 95% confidence interval, -26.9 to -2.1). There were no differences in triglycerides and systolic BP levels among the sessions.

CONCLUSION

Adults with excess body fat present lower glucose and diastolic BP during a day with breaks in sitting time compared with a prolonged sitting day with or without an LV-HIIE session.

Breaking up sitting time after stroke (BUST-stroke)

OBJECTIVES

People with stroke sit for long periods each day, which may compromise blood glucose control and increase risk of recurrent stroke. Studies in other populations have found regular activity breaks have a significant immediate (within-day) positive effect on glucose metabolism. We examined the effects of breaking up uninterrupted sitting with frequent, short bouts of light-intensity physical activity in people with stroke on post-prandial plasma glucose and insulin.

METHODS

Randomized within-participant crossover trial. We included people between 3 months and 10 years post-stroke, ambulant with minimal assistance and not taking diabetic medication other than metformin. The three experimental conditions (completed in random order) were: sitting for 8 h uninterrupted, sitting with 3 min bouts of light-intensity exercise while standing every 30 min, or sitting with 3 min of walking every 30 min. Meals were standardized and bloods were collected half- to one-hourly via an intravenous cannula.

RESULTS

A total of 19 participants (9 female, mean [SD] age 68.2 [10.2]) completed the trial. The majority ( n = 12, 63%) had mild stroke symptoms (National Institutes of Stroke Scale score 0-13). There was no significant effect of experimental condition on glucose (mean [SD] positive incremental area [+iAUC] mmol·L·h-1 under the curve during sitting 42.3 [29.5], standing 47.4 [23.1], walking 44.6 [26.5], p = 0.563) or insulin (mean + iAUC pmol·L·h-1 sitting 14,161 [7,560], standing 14,043 [8,312], walking 14,008 [8,269], p = 0.987).

CONCLUSION

Frequent, short bouts of light-intensity physical activity did not have a significant effect on post-prandial plasma glucose and insulin in this sample of people with stroke. Further studies are needed to identify strategies that improve inactivity-related glucose metabolism after stroke.

Sedentary Behavior at Work and Cognitive Functioning: A Systematic Review

Background: It is now well-established that sedentarity has a negative impact on the physiological functioning and health of humans, whereas very little is known about the psychological repercussions, especially in cognitive functioning. Yet, studying the cognitive effects of the sedentary lifestyle is particularly relevant in the short term for productivity and in the long term for cognitive health (accelerated aging). This systematic review therefore aims to make an inventory of the potential cognitive effects of sedentarity at the workplace. Methods: Pubmed, PsycINFO, Cochrane, Web of Science, and Scopus were searched for English-language peer-reviewed articles published between January 1, 2000 and December 31, 2017 to identify studies including sedentary behavior and objective measures from cognitive domains (cognitive inhibition, cognitive flexibility, working memory, etc.). To carry out this systematic review, the 3 keywords "Sedentary" and "Cognition" and "Work" (and their derivatives) had to appear in the title or in the summary of the paper. Results: Of the 13 papers that met the inclusion criteria, 9 were short-term interventions, 3 medium-term interventions, and 1 long-term intervention. Nine of them reported non-significant results. Two studies study reported deterioration in cognitive performance. Two reported an improvement in performance in cognitive tasks with one study with overweight adults and the only one study with a long-term intervention. However, these studies intend to reduce sedentary behavior, but do not allow answering the question of the potential cognitive effects of the sedentary lifestyle. Conclusion: These data suggest that sedentary behavior is not associated with changes in cognitive performance in interventions that intend to reduce sedentary behavior. Then, and given the trend toward increased time in sedentary behavior, long-term prospective studies of high methodological quality are recommended to clarify the relationships between sedentary behavior and the cognitive functioning. Our systematic review identifies also the need for retrospective, longitudinal, or epidemiologic studies. It also recognizes the need to standardize methodology for collecting, defining, and reporting sedentary behavior and the need to standardize the cognitive tests used. The relationship between sedentary behavior and cognitive functioning remaining uncertain, further studies are warranted for which 8 recommendations are proposed.

Targeting Postprandial Hyperglycemia With Physical Activity May Reduce Cardiovascular Disease Risk. But What Should We Do, and When Is the Right Time to Move?

Physical inactivity and excessive postprandial hyperglycemia are two major independent risk factors for type 2 diabetes and cardiovascular-related mortality. Current health policy guidelines recommend at least 150 min of physical activity per week coupled with reduced daily sedentary behavior by interrupting prolonged sitting with bouts of light activity every 30-min. This evidence-based strategy promotes health and quality of life. Since modern lifestyle enforces physical inactivity through motorized transportation and seated office working environments, this review examines the practical strategies (standing, walking, stair climbing, and strength-based circuit exercises) for reducing sitting time and increasing activity during the workday. Furthermore, since postprandial hyperglycemia poses the greatest relative risk for developing type 2 diabetes and its cardiovascular complications, this review examines a novel hypothesis that interrupting sitting time would be best focused on the postprandial period in order to optimize blood glucose control and maximize cardiometabolic health. In doing so, we aim to identify the science gaps which urgently need filling if we are to optimize healthcare policy in this critical area.

An Under-the-Table Leg-Movement Apparatus and Changes in Energy Expenditure

Introduction: Deskwork contributes substantially to sedentariness. Here, we evaluated an under-the-table apparatus that was designed to promote leg movement (fidgeting) while seated. Our hypothesis was that the under-the-table apparatus would increase energy expenditure. Methods: We measured energy expenditure and heart rate in 26 people while they sat and worked using a standard chair, walked on a treadmill, and sat and worked using an under-the-desk apparatus that encouraged leg movement. Results: Energy expenditure increased significantly while using the under-the-table apparatus when compared to the standard office chair (standard chair, 81 ± 18 kcal/h; under-the-table apparatus, 96 ± 23 kcal/h) (P < 0.001); representing an 18 ± 16% increase. The changes in energy expenditure were not as great as walking (1 mph, 168 ± 46 kcal/h, P < 0.001; 2 mph, 205 ± 51 kcal/, P < 0.001), representing 107 ± 37% and 155 ± 48% increases over baseline, respectively. Conclusions: An under-the-table apparatus that promotes leg movement can increase energy expenditure by approximately 20%. Dynamic sitting is promoted by this apparatus and may be among a lexicon of options to help people move more while seated at work.