Breaking up prolonged sitting time with walking does not affect appetite or gut hormone concentrations but does induce an energy deficit and suppresses postprandial glycaemia in sedentary adults

Exercise Prescription for Postprandial Glycemic Management

The detrimental impacts of postprandial hyperglycemia on health are a critical concern, and exercise is recognized a pivotal tool in enhancing glycemic control after a meal. However, current exercise recommendations for managing postprandial glucose levels remain fairly broad and require deeper clarification. This review examines the existing literature aiming to offer a comprehensive guide for exercise prescription to optimize postprandial glycemic management. Specifically, it considers various exercise parameters (i.e., exercise timing, type, intensity, volume, pattern) for crafting exercise prescriptions. Findings predominantly indicate that moderate-intensity exercise initiated shortly after meals may substantially improve glucose response to a meal in healthy individuals and those with type 2 diabetes. Moreover, incorporating short activity breaks throughout the exercise session may provide additional benefits for reducing glucose response.

Breaking prolonged sitting increases 24-h physical activity and self-perceived energy levels but does not acutely affect cognition in healthy adults

INTRODUCTION

It is unknown whether predetermined (un)interrupted sitting within a laboratory setting will induce compensatory changes in human behaviours (energy intake and physical activity) once people return to a free-living environment. The effects of breaking up prolonged sitting on cognition are also unclear.

METHODS

Twenty-four (male = 13) healthy participants [age 31 ± 8 y, BMI 22.7 ± 2.3 kg/m2 (mean ± SD)] completed 320 min mixed-feeding trials under prolonged sitting (SIT) or with 2 min walking at 6.4 km/h every 20 min (ACTIVE), in a randomised crossover design. Human behaviours were recorded post-trial under free-living conditions until midnight. Cognitive performance was evaluated before and immediately after SIT and ACTIVE trials. Self-perceived sensations (appetite, energy and mood) and finger prick blood glucose levels were collected at regular intervals throughout the trials.

RESULTS

There were no differences between trials in eating behaviour and spontaneous physical activity (both, p > 0.05) in free-living conditions, resulting in greater overall total step counts [11,680 (10740,12620) versus 6049 (4845,7253) steps] and physical activity energy expenditure (PAEE) over 24-h period in ACTIVE compared to SIT (all, p < 0.05). Greater self-perceived levels of energy and lower blood glucose iAUC were found in ACTIVE trial compared to SIT trial (both, p < 0.05). No differences were found in cognitive performance between trials (all, p > 0.05).

CONCLUSION

Breaking up sitting does not elicit subsequent behavioural compensation, resulting in greater 24-h step counts and PAEE in healthy adults. Breaking up sitting reduces postprandial glucose concentrations and elicits greater self-perceived energy levels, but these positive effects do not acutely translate into improved cognitive function.

How should robots exercise with people? Robot-mediated exergames win with music, social analogues, and gameplay clarity

Introduction: The modern worldwide trend toward sedentary behavior comes with significant health risks. An accompanying wave of health technologies has tried to encourage physical activity, but these approaches often yield limited use and retention. Due to their unique ability to serve as both a health-promoting technology and a social peer, we propose robots as a game-changing solution for encouraging physical activity. Methods: This article analyzes the eight exergames we previously created for the Rethink Baxter Research Robot in terms of four key components that are grounded in the video-game literature: repetition, pattern matching, music, and social design. We use these four game facets to assess gameplay data from 40 adult users who each experienced the games in balanced random order. Results: In agreement with prior research, our results show that relevant musical cultural references, recognizable social analogues, and gameplay clarity are good strategies for taking an otherwise highly repetitive physical activity and making it engaging and popular among users. Discussion: Others who study socially assistive robots and rehabilitation robotics can benefit from this work by considering the presented design attributes to generate future hypotheses and by using our eight open-source games to pursue follow-up work on social-physical exercise with robots.

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.

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.

Sedentary Behaviour-A Target for the Prevention and Management of Cardiovascular Disease

Cardiovascular disease (CVD) is highly prevalent and can lead to disability and premature mortality. Sedentary behaviour, defined as a low energy expenditure while sitting or lying down, has been identified as an independent risk factor for CVD. This article discusses (1) the association of total sedentary time and patterns of accumulating sedentary time with CVD risk markers, CVD incidence and mortality; (2) acute experimental evidence regarding the acute effects of reducing and breaking up sedentary time on CVD risk markers; and (3) the effectiveness of longer-term sedentary behaviour interventions on CVD risk. Findings suggest that under rigorously controlled laboratory and free-living conditions, breaking up sedentary time improves cardiovascular risk markers in individuals who are healthy, overweight or obese, or have impaired cardiovascular health. Breaking up sedentary time with walking may have the most widespread benefits, whereas standing breaks may be less effective, especially in healthy individuals. There is also growing evidence that sedentary behaviour interventions may benefit cardiovascular risk in the longer term (i.e., weeks to months). Reducing and breaking up sedentary time may, therefore, be considered a target for preventing and managing CVD. Further research is needed to determine the effectiveness of sedentary behaviour interventions over the long-term to appropriately inform guidelines for the management of CVD.

Sex differences in the acute effect of stair-climbing on postprandial blood glucose levels: A randomized controlled trial

Single, short stair climbing and descending (SCD) bouts of low to moderate intensity effectively lower postprandial blood glucose but previous reports have found conflicting results on interactions by sex during exercise. We hypothesize that SCD at a self-selected intensity will be equally effective at lowering postprandial blood glucose in males and females. Methods and Results: Thirty subjects (age: 23.8 (3.0) years) performed 0, 1, 3, and 10 min of SCD following consumption of a mixed meal. SCD was performed at a self-selected comfortable pace and all bouts ended at minute 28. Postprandial blood glucose was measured every 15 min for 1 h and analyzed as glucose over time, area under the curve (AUC), and incremental AUC (iAUC) using mixed-design ANOVAs with repeated measures. Although there was no interaction between sex and condition or time (p = .129 to .541) for glucose over time, AUC, or iAUC, there was a main effect for sex for glucose over time (p = .004) and AUC (p = .006), but not iAUC (p = .125). Females had higher blood glucose throughout each trial (22% (13 to 31%), p = .004) but both males' and females’ postprandial blood glucose was lowered following 10 min of SCD relative to the seated control condition. Conclusions: Males and females benefited equally from single, short SCD bouts of low to moderate intensity despite females having higher blood glucose at all time points. Previous findings of sex differences in the attenuating effect of exercise on postprandial blood glucose are likely due to the use of absolute workloads leading to varying relative intensities.

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SCD at a self-selected, comfortable pace for 3 min reduced postmeal blood glucose.

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Men and women benefit equally from SCD postprandial glucose attenuations.

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Previous sex differences were likely due to unequal relative intensity of exercise.

Interrupting Prolonged Sitting with Intermittent Walking Increases Postprandial Gut Hormone Responses

INTRODUCTION

Continuous exercise can increase postprandial gut hormone such as glucagon-like peptide 1 (GLP-1) and peptide YY (PYY) responses, but it is unknown whether interrupting prolonged sitting with intermittent walking elicits this effect.

METHOD

Ten participants with central overweight/obesity (7 men and 3 postmenopausal women, 51 ± 5 yr; mean ± SD) completed a randomized crossover study in which they consumed breakfast and lunch in the laboratory while either sitting continuously for the entire 5.5-h period (SIT) or the prolonged sitting interrupted every 20 min by walking briskly (6.4 km·h-1) for 2 min (BREAKS). Blood samples were collected at regular intervals to examine postprandial plasma GLP-1, PYY, and glucose-dependent insulinotropic polypeptide concentrations. Adipose tissue samples were collected at baseline and at the end of the trials to examine changes in net dipeptidyl peptidase 4 secretion from primary explants.

RESULTS

Mean (95% confidence interval) postprandial GLP-1 and PYY incremental area under curve values were elevated by 26% and 31% in the BREAKS trial versus SIT (8.4 [0.7, 16.1] vs 6.7 [-0.8, 14.2], P = 0.001, and 26.9 [8.1, 45.6] vs 20.4 [5.1, 35.8] nmol·330 min·L-1, P = 0.024, respectively) but without any such effect on glucose-dependent insulinotropic polypeptide (P = 0.076) or net adipose tissue dipeptidyl peptidase 4 secretion (P > 0.05).

CONCLUSIONS

Interrupting prolonged sitting with regular short bouts of brisk walking increases postprandial GLP-1 and PYY concentrations in healthy middle-age men and women with central adiposity.

Lower Amounts of Daily and Prolonged Sitting Do Not Lower Free-Living Continuously Monitored Glucose Concentrations in Overweight and Obese Adults: A Randomised Crossover Study

This study compared the short-term continuously monitored glucose responses between higher and lower amounts of prolonged sitting in overweight and obese adults under free-living conditions. In a randomised crossover design, 12 participants (age 48 ± 10 years, body mass index 33.3 ± 5.5 kg/m2) completed two four-day experimental regimens while wearing a continuous glucose monitor, as follows: (1) uninterrupted sitting (participants were instructed to sit for ≥10 h/day and accrue ≥7, 1 h sitting bouts each day), and (2) interrupted sitting (participants were instructed to interrupt sitting every 30 min during ten of their waking hours with 6−10 min of activity accrued in each hour). Linear mixed models compared outcomes between regimens. None of the continuously monitored glucose variables differed between regimens, e.g., 24 h net incremental area under the glucose curve was 5.9 [95% CI: −1.4, 13.1] and 5.6 [95% CI: −1.7, 12.8] mmol/L∙24 h, respectively (p = 0.47). Daily sitting (−58 min/day, p = 0.001) and sitting bouts lasting ≥30 min (−99 min/day, p < 0.001) were significantly lower and stepping time significantly higher (+40 min/day, p < 0.001) in the interrupted sitting than the uninterrupted sitting regimen. In conclusion, lower amounts of daily and prolonged sitting did not improve free-living continuously measured glucose among overweight and obese adults.

Supervised Aerobic Exercise Training and Increased Lifestyle Physical Activity to Reduce Cardiovascular Disease Risk for Women With Polycystic Ovary Syndrome: A Randomized Controlled Feasibility Trial

Background: Polycystic ovary syndrome (PCOS) is a complex, heterogeneous endocrinopathy. Women with PCOS often present with cardiovascular disease risk factors. Physical activity (PA) interventions reduce cardiovascular disease risk factors in women with PCOS. However, sedentary behaviors have a distinct deleterious effect on cardiometabolic health. Increasing PA and reducing sedentary behaviors may be a worthwhile therapeutic target to improve cardiovascular health in this population. This study investigated the feasibility of 2 PA interventions to decrease cardiovascular disease risk in women with PCOS. Methods: This was a feasibility randomized controlled trial of 2 PA interventions in 36 women with PCOS. Participants were randomized to a supervised exercise intervention (n = 12), a lifestyle physical activity group intervention aimed at reducing sedentary behaviors (n = 12), or a control group (n = 12), for 12 weeks. Primary outcomes included the feasibility and acceptability of the interventions and procedures. Results: Recruitment rate was 56%. Adherence rate was 53% and 100% to the exercise intervention and lifestyle PA intervention, respectively. Secondary outcome data indicate a reduction in oxidized low-density lipoprotein concentrations in the exercise group, and weight loss in both intervention groups. Conclusions: The procedures for recruitment, allocation, and outcome measurements were acceptable. However, before progression to a full-scale trial, adherence to the exercise program should be addressed.

Effects of interrupting prolonged sitting on postprandial glycemia and insulin responses: A network meta-analysis

PURPOSE

This study aimed to evaluate the effectiveness of physical activity (PA) interrupting prolonged sitting (PS) on postprandial glycemia and insulin responses among adults.

METHODS

PubMed, EMBASE, Cochrane Library, Web of Science, CINAHL, PsycINFO, and the China National Knowledge Infrastructure databases were searched through September 30, 2020. Randomized controlled trials (RCTs) that examined the effect of all forms of PA interrupting PS on postprandial glycemia and/or insulin responses among adults without chronic diseases were included in this study. The risk of bias of included studies was evaluated based on the Cochrane tool. A network meta-analysis was performed to estimate the summary standardized mean differences (SMDs) with 95% confidence intervals (95%CIs) with random effects.

RESULTS

Thirty crossover RCTs were included in our review. These RCTs included 9 types of interventions that interrupted PS. When compared to PS by itself, light-intensity PA intermittent interrupting (LPA-INT) PS and moderate-intensity PA intermittent interrupting (MPA-INT) PS significantly lowered postprandial glycemia (SMD = -0.46, 95%CI: -0.70 to -0.21; SMD = -0.69, 95%CI: -1.00 to -0.37, respectively) and significantly reduced postprandial insulin response (SMD = -0.46, 95%CI: -0.66 to -0.26; SMD = -0.47, 95%CI: -0.77 to -0.17, respectively). Results of the clustered ranking plot indicated that MPA-INT was the most effective intervention in lowering postprandial glycemia and insulin responses.

CONCLUSION

Replacing PS with MPA-INT or LPA-INT has a positive effect in reducing postprandial glycemia and insulin responses, with MPA-INT being the optimal intervention strategy.

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.

The effects of breaking sedentary time with different intensity exercise bouts on energy metabolism: A randomized cross-over controlled trial

BACKGROUND AND AIMS

Breaking up sedentary periods, particularly with light activity, increases total energy expenditure (EE), and helps provide better glycemic control. However, the effects of activities of various intensities to interrupt prolonged sedentary time are unclear. The purpose of the present study was to examine potential differences in glycemic control and EE from breaking up sedentary time with short exercise bouts of different intensities.

METHODS AND RESULTS

Nine overweight/obesity young men underwent whole body indirect calorimetry at 19:00 on day 1 and stayed overnight. After awakening on day 2, they performed short duration jogging every 30 min over 8 h (16-time bouts in total) under 3 different conditions with the same running distance: (1) lactate threshold (LT) for 2 min, (2) 60% LT for 200 s, and (3) onset of blood lactate accumulation (OBLA) for 75 s. The 24-h EE and interstitial glucose concentration (from 8:00 to 19:00 on day 2) was continuously measured throughout the trials. The standard deviation during intervention and indexes of postprandial of the interstitial glucose concentration was significantly lower at LT and OBLA than at 60% LT (p < 0.05). The 24-h EE was not significantly different among conditions, but EE at OBLA during intervention was slightly but significantly higher than at 60% LT and LT.

CONCLUSION

Breaking up sedentary time with short-duration jogging at LT and with OBLA intensities may have better glycemic control and increased use of carbohydrate as a fuel, while short-duration a jogging at OBLA intensity may increase EE.

TRIAL REGISTRATION

UMIN000041361.

A randomised-controlled feasibility study of the REgulate your SItting Time (RESIT) intervention for reducing sitting time in individuals with type 2 diabetes: study protocol

Background

People with type 2 diabetes mellitus (T2DM) generally spend a large amount of time sitting. This increases their risk of cardiovascular disease, premature mortality, diabetes-related complications and mental health problems. There is a paucity of research that has evaluated interventions aimed at reducing and breaking up sitting in people with T2DM. The primary aim of this study is to assess the feasibility of delivering and evaluating a tailored intervention to reduce and break up sitting in ambulatory adults with T2DM.

Methods

This is a mixed-methods randomised controlled feasibility trial. Participants (n=70) with T2DM aged 18-85 years who sit ≥7 h/day and are able to ambulate independently will be randomly allocated to receive the REgulate your SItting Time (RESIT) intervention or usual care (control group) for 24 weeks. RESIT is a person-focused intervention that delivers a standardised set of behaviour change techniques to the participants, but the mode through which they are delivered can vary depending on the tools selected by each participant. The intervention includes an online education programme, health coach support, and a range of self-selected tools (smartphone apps, computer-prompt software, and wearable devices) that deliver behaviour change techniques such as self-monitoring of sitting and providing prompts to break up sitting. Measures will be taken at baseline, 12 and 24 weeks. Eligibility, recruitment, retention and data completion rates will be used to assess trial feasibility. Sitting, standing and stepping will be measured using a thigh-worn activity monitor. Cardiometabolic health, physical function, psychological well-being, sleep and musculoskeletal symptoms will also be assessed. A process evaluation will be conducted including evaluation of intervention acceptability and fidelity.

Discussion

This study will identify the feasibility of delivering a tailored intervention to reduce and break up sitting in ambulatory adults with T2DM and evaluating it through a randomised controlled trial (RCT) design. The findings will inform a fully powered RCT to evaluate the effectiveness of the intervention.

Trial registration

ISRCTN, ISRCTN14832389; Registered 6 August 2020.

Investigating the rigour of research findings in experimental studies assessing the effects of breaking up prolonged sitting - extended scoping review

OBJECTIVES

Sedentary behaviour research is a relatively new field, much of which has emerged since the widespread acceptance of clinical trial registration. The aim of this study was to investigate the trial registration and related issues in studies investigating the effect of frequent activity interruptions to prolonged sitting-time.

METHODS

Secondary analysis of a scoping review including systematic searches of databases and trial registries. We included experimental studies investigating the effects of frequent activity interruptions to prolonged sitting-time.

RESULTS

We identified 32 trials published in 45 papers. Only 16 (50%) trials were registered, with all 16 trials being completed and published. Of the unregistered trials, we identified three (19%) for which similarities in the sample size and participant demographics across papers was suggestive of duplicate publication. Identification of potential duplicate publications was difficult for the remaining 13 (81%). Results from 53 (76%) of the 70 registered outcomes were published, but 11 (69%) registered trials reported results from additional outcomes not prospectively registered. A total of 46 different outcomes (out of 53 reported outcome measures, similar measures were collated) were reported across all trials, 31 (67%) of which were collected in ≤2 trials.

CONCLUSIONS

We found direct evidence of trial registration issues in experimental trials of breaking up sitting-time. The lack of prospective registration of all trials, and the large number of outcomes measured per trial are key considerations for future research in this field. These issues are unlikely to be confined to the field of sedentary behaviour research.

Levels and patterns of sedentary behavior in men and women with intellectual disability

BACKGROUND

There are limited data on the levels and patterns of sedentary behavior (SB) among U.S. adults with ID.

OBJECTIVE

To examine SB levels and patterns in U.S. adults with ID and how these differ between sexes, age-groups, and week vs. weekend days.

METHODS

Fifty-two adults with ID (25 men; age 45 ± 14 years) wore a hip accelerometer (wGT3X-BT; Actigraph) during the waking hours for 7 days. We determined total sedentary time, percent of wear time spent sedentary bouts ≥1, ≥10, ≥30, and ≥60 min, and breaks in sedentary time for bouts ≥10 min. We examined differences in SB variables as a function of sex, age-group by median split (≤48 vs. >48 years), and day of the week.

RESULTS

Total sedentary time was 514 ± 139 min · day^-1 accumulated in bouts 1-30 min and did not differ between sexes or age-groups. Bouts ≥1 min across days were longer for men than women and longer during weekend days than weekdays (p < 0.05). The number of bouts ≥1 min was greater during weekdays than weekend days (p < 0.05). Bouts ≥60 min were longer for men than women (p < 0.05). The duration of sedentary breaks was longer during weekdays than weekend days (p < 0.001). There were no differences between age-groups.

CONCLUSIONS

Adults with ID spend a large portion of the day in SB primarily of short bouts. Despite small differences, SB levels and patterns were similar for men and women with ID and across age-groups throughout the week.

Impact of prolonged sitting and physical activity breaks on cognitive performance, perceivable benefits, and cardiometabolic health in overweight/obese adults: The role of meal composition

BACKGROUND & AIMS

Physical activity (PA) breaks may effectively attenuate the detrimental impact of prolonged sitting on acute cognitive performance, perceivable benefits (e.g. mood), vascular function, and metabolic health. To date, the impact of meal composition on the effects of sedentary behavior and/or PA breaks on health has been scarcely studied. Therefore, our aim was to investigate whether meal composition alters how sedentary behavior and PA breaks affect these acute health outcomes.

METHODS

A total of 24 overweight and obese, sedentary adults completed four conditions in randomized order in a cross-over design: [a] high-protein, low-fat breakfast (HPLF) + 4hrs uninterrupted sitting (SIT), [b] HPLF + 4hrs interrupted sitting (ACT; 5-min cycling every 30 min), [c] Western breakfast (WEST; higher in fats/simple sugars, lower in protein/fiber) + SIT, [d] WEST + ACT. WEST and HPLF were isocaloric. Linear mixed models were used to examine changes in cognitive performance (Test of Attentional Performance), perceivable benefits (Likert-scales, Profile of Mood States questionnaire), vascular health (carotid artery reactivity, blood pressure), and metabolic health (post-breakfast glucose, insulin, lipids).

RESULTS

Independent of meal composition, we did not observe any effect of PA breaks on cognitive performance, vascular health and post-breakfast lipid responses. PA breaks delayed post-breakfast mood and vigor decrements, as well as increases in fatigue and sleepiness (all p < 0.05), but effects were independent of meal composition (p > 0.05). WEST resulted in higher post-breakfast glucose levels compared to HPLF (p < 0.05), while PA breaks did not impact this response (p > 0.05). PA breaks reduced post-breakfast insulin (p < 0.05), which did not differ between meals (p > 0.05).

CONCLUSIONS

The acute impact of PA breaks and/or prolonged sitting on cognitive performance, perceivable benefits, and vascular and metabolic health was not altered by the composition of a single meal in overweight/obese, sedentary adults. Possibly, breaking up prolonged sitting, rather than meal composition, is a more potent strategy to impact acute health outcomes, such as perceivable benefits and insulin levels.

Displacing Sedentary Behaviour with Light Intensity Physical Activity Spontaneously Alters Habitual Macronutrient Intake and Enhances Dietary Quality in Older Females

Displacing Sedentary Behaviour (SB) with light intensity physical activity (LIPA) is increasingly viewed as a viable means of health enhancement. It is, however, unclear whether any behavioural compensations accompany such an intervention. Therefore, the aim of this study was to identify any dietary changes that accompany SB displacement. We hypothesised that SB displacement would improve dietary quality. Thirty-five elderly females (73 ± 5 years) were randomly allocated to one of three groups: (1) sedentary behaviour fragmentation (SBF) (n = 14), (2) continuous LIPA (n = 14), or (3) control (n = 7). Habitual diet (four-day food diary) and physical behaviour (accelerometery) were assessed at weeks 0 and 8. Out of 45 nutrients examined, only glucose exhibited a group × time interaction (p = 0.03), mediated by an exclusive reduction following SBF (-31%). SBF was also the sole experimental group to increase nutrients promoting bone health (SBF: 17%, LIPA: -34%. control: 21%), whereas both experimental groups consumed more nutrients promoting anabolism (SBF: 13%, LIPA: 4%, control: -34%) (z-scores). New ambulators (n = 8) also consumed more nutrients promoting bone health (16%)/anabolism (2%) (z-scores), including significantly increased Zinc intake (p = 0.05, 29%). Displacing SB with LIPA improves dietary quality in older females. Furthermore, SB fragmentation appears advantageous for various dietary outcomes.

Effects of Interrupting Prolonged Sitting with Physical Activity Breaks on Blood Glucose, Insulin and Triacylglycerol Measures: A Systematic Review and Meta-analysis

BACKGROUND

Physical activity (PA) breaks in sitting time might attenuate metabolic markers relevant to the prevention of type 2 diabetes.

OBJECTIVES

The primary aim of this paper was to systematically review and meta-analyse trials that compared the effects of breaking up prolonged sitting with bouts of PA throughout the day (INT) versus continuous sitting (SIT) on glucose, insulin and triacylglycerol (TAG) measures. A second aim was to compare the effects of INT versus continuous exercise (EX) on glucose, insulin and TAG measures.

METHODS

The review followed the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) recommendations. Eligibility criteria consisted of trials comparing INT vs. SIT or INT vs. one bout of EX before or after sitting, in participants aged 18 or above, who were classified as either metabolically healthy or impaired, but not with other major health conditions such as chronic obstructive pulmonary disease or peripheral arterial disease.

RESULTS

A total of 42 studies were included in the overall review, whereas a total of 37 studies were included in the meta-analysis. There was a standardised mean difference (SMD) of - 0.54 (95% CI - 0.70, - 0.37, p = 0.00001) in favour of INT compared to SIT for glucose. With respect to insulin, there was an SMD of - 0.56 (95% CI - 0.74, - 0.38, p = 0.00001) in favour of INT. For TAG, there was an SMD of - 0.26 (95% CI - 0.44, - 0.09, p = 0.002) in favour of INT. Body mass index (BMI) was associated with glucose responses (β = - 0.05, 95% CI - 0.09, - 0.01, p = 0.01), and insulin (β = - 0.05, 95% CI - 0.10, - 0.006, p = 0.03), but not TAG (β = 0.02, 95% CI - 0.02, 0.06, p = 0.37). When energy expenditure was matched, there was an SMD of - 0.26 (95% CI - 0.50, - 0.02, p = 0.03) in favour of INT for glucose, but no statistically significant SMDs for insulin, i.e. 0.35 (95% CI - 0.37, 1.07, p = 0.35), or TAG i.e. 0.08 (95% CI - 0.22, 0.37, p = 0.62). It is worth noting that there was possible publication bias for TAG outcomes when PA breaks were compared with sitting.

CONCLUSION

The use of PA breaks during sitting moderately attenuated post-prandial glucose, insulin, and TAG, with greater glycaemic attenuation in people with higher BMI. There was a statistically significant small advantage for PA breaks over continuous exercise for attenuating glucose measures when exercise protocols were energy matched, but no statistically significant differences for insulin and TAG. PROSPERO Registration: CRD42017080982.

PROSPERO REGISTRATION

CRD42017080982.

Are prolonged sitting and sleep restriction a dual curse for the modern workforce? a randomised controlled trial protocol

INTRODUCTION

Prolonged sitting and inadequate sleep are a growing concern in society and are associated with impairments to cardiometabolic health and cognitive performance. However, the combined effect of prolonged sitting and inadequate sleep on measures of health and cognitive performance are unknown. In addition, the circadian disruption caused by shiftwork may further impact workers' cardiometabolic health and cognitive performance. This protocol paper outlines the methodology for exploring the impact of simultaneous exposure to prolonged sitting, sleep restriction and circadian disruption on cardiometabolic and cognitive performance outcomes.

METHODS AND ANALYSIS

This between-subjects study will recruit 208 males and females to complete a 7-day in-laboratory experimental protocol (1 Adaptation Day, 5 Experimental Days and 1 Recovery Day). Participants will be allocated to one of eight conditions that include all possible combinations of the following: dayshift or nightshift, sitting or breaking up sitting and 5 hour or 9 hour sleep opportunity. On arrival to the laboratory, participants will be provided with a 9 hour baseline sleep opportunity (22:00 to 07:00) and complete five simulated work shifts (09:00 to 17:30 in the dayshift condition and 22:00 to 06:30 in the nightshift condition) followed by a 9 hour recovery sleep opportunity (22:00 to 07:00). During the work shifts participants in the sitting condition will remain seated, while participants in the breaking up sitting condition will complete 3-min bouts of light-intensity walking every 30 mins on a motorised treadmill. Sleep opportunities will be 9 hour or 5 hour. Primary outcome measures include continuously measured interstitial blood glucose, heart rate and blood pressure, and a cognitive performance and self-perceived capacity testing battery completed five times per shift. Analyses will be conducted using linear mixed models.

ETHICS AND DISSEMINATION

The CQUniversity Human Ethics Committee has approved this study (0000021914). All participants who have already completed the protocol have provided informed consent. Study findings will be disseminated via scientific publications and conference presentations.

TRIAL REGISTRATION DETAILS

This study has been registered on Australian New Zealand Clinical Trials Registry (12619001516178) and is currently in the pre-results stage.

Randomised Controlled Feasibility Study of the MyHealthAvatar-Diabetes Smartphone App for Reducing Prolonged Sitting Time in Type 2 Diabetes Mellitus

This study evaluated the feasibility and acceptability of a self-regulation smartphone app for reducing prolonged sitting in people with Type 2 diabetes mellitus (T2DM). This was a two-arm, randomised, controlled feasibility trial. The intervention group used the MyHealthAvatar-Diabetes smartphone app for 8 weeks. The app uses a number of behaviour change techniques aimed at reducing and breaking up sitting time. Eligibility, recruitment, retention, and completion rates for the outcomes (sitting, standing, stepping, and health-related measures) assessed trial feasibility. Interviews with participants explored intervention acceptability. Participants with T2DM were randomised to the control (n = 10) and intervention groups (n = 10). Recruitment and retention rates were 71% and 90%, respectively. The remaining participants provided 100% of data for the study measures. The MyHealthAvatar-Diabetes app was viewed as acceptable for reducing and breaking up sitting time. There were preliminary improvements in the number of breaks in sitting per day, body fat %, glucose tolerance, attitude, intention, planning, wellbeing, and positive and negative affect in favour of the intervention group. In conclusion, the findings indicate that it would be feasible to deliver and evaluate the efficacy of the MyHealthAvatar-Diabetes app for breaking up sitting time and improving health outcomes in a full trial.

Perceived Barriers and Facilitators to Breaking Up Sitting Time among Desk-Based Office Workers: A Qualitative Investigation Using the TDF and COM-B

High amounts of sedentary behaviour, such as sitting, can lead to adverse health consequences. Interventions to break up prolonged sitting in the workplace have used active workstations, although few studies have used behaviour change theory. This study aimed to combine the Theoretical Domains Framework (TDF) and the Capability, Opportunity, and Motivation to Behaviour system (COM-B) to investigate perceived barriers and facilitators to breaking up sitting in desk-based office workers. Semi-structured interviews with 25 desk-based employees investigated barriers and facilitators to breaking up sitting in the workplace. Seven core inductive themes were identified: ‘Knowledge-deficit sitting behaviour’, ‘Willingness to change’, ‘Tied to the desk’, ‘Organisational support and interpersonal influences’, ‘Competing motivations’, ‘Emotional influences’, and ‘Inadequate cognitive resources for action’. These themes were then deductively mapped to 11 of the 14 TDF domains and five of the six COM-B constructs. Participants believed that high amounts of sitting had adverse consequences but lacked knowledge regarding recommendations and were at times unmotivated to change. Physical and social opportunities were identified as key influences, including organisational support and height-adjustable desks. Future research should identify intervention functions, policy categories and behaviour change techniques to inform tailored interventions to change sitting behaviour of office workers.

Breaking up prolonged sitting with moderate-intensity walking improves attention and executive function in Qatari females

Background

Cultural, environmental and logistical factors promote a sedentary lifestyle within Qatar, particularly for females. Sedentary behaviour is acutely associated with poor cognitive function and fatigue, and chronically may be implicated with cognitive decline (i.e. Alzheimer’s disease).

Purpose

To examine the effects of breaking up sitting with short-duration frequent walking bouts on cognitive function and fatigue in Qatari females.

Method

Eleven sedentary (sitting ≥7 h/day) females completed three visits; the first being familiarisation. In a cross-over randomised manner, experimental visits two and three were identical, except participants either remained seated for 5-h (SIT) or interrupted their sitting every 30-min with a 3-min moderate-intensity walk (WALK) on a motorised treadmill. The Computerised Mental Performance Assessment System (COMPASS) assessed cognition at baseline (-15-min), and then at 2.5-h and 5-h into the experimental conditions. Specific COMPASS tasks employed were; serial-3 subtractions (2-min), serial-7 subtractions (2-min), simple reaction time (RT; 50 stimuli), rapid visual information processing [RVIP (5-min)], choice reaction time (CRT; 50 stimuli), and Stroop (60 stimuli); and a visual analogue scale for fatigue (VAS-F) was completed at the same time intervals.

Results

There was a significant condition effect for CRT (f = 26.7, p = 0.007). On average CRT was 101 s (95% CI = -47 to -156 s) quicker in WALK compared to SIT. There was a significant time effect for CRT (f = 15.5, p = 0.01). On average CRT was 134 s slower at 5-h compared to baseline (p = 0.006; 95% CI = -64 to -203 s), and 114 s slower at 5-h compared to 2.5-h (p = 0.01; 95% CI = -44 to -183 s). There was a significant interaction effect for RT in the Stroop incongruent task (f = 10.0, p = 0.03). On average RT was 210 s quicker at 2.5-h in WALK compared to SIT (p = 0.01; 95% CI = -76 to -346 s).

Conclusion

Breaking up prolonged sitting with moderate-intensity walking offers an ecologically valid intervention to enhance some aspects of cognitive function, whilst not affecting fatigue in sedentary Qatari females. Whilst these findings are promising, the long-term effects of breaking up sitting on cognitive function requires testing before population level recommendations can be made.

What is the effect of interrupting prolonged sitting with frequent bouts of physical activity or standing on first or recurrent stroke risk factors? A scoping review

The objective of this review was to ascertain the scope of the available literature on the effects of interrupting prolonged sitting time with frequent bouts of physical activity or standing on stroke and recurrent stroke risk factors. Databases Medline, Embase, AMED, CINAHL and Cochrane library were comprehensively searched from inception until 21^st February 2018. Experimental trials which interrupted sitting time with frequent bouts of physical activity or standing in adults (≥ 18 years) were included. Comparison to a bout of prolonged sitting and a measure of at least one first or recurrent stroke risk factor was required to be included. Overall, 30 trials (35 articles) were identified to meet the inclusion criteria. Fifteen trials were completed in participants at an increased risk of having a first stroke and one trial in participants at risk of a recurrent stroke. Outcomes of hypertension and dysglycemia were found to be more favourable following predominately light- to moderate-intensity bouts of physical activity or standing compared to sitting in the majority of trials in participants at risk of having a first stroke. In the one trial of stroke survivors, only outcomes of hypertension were significantly improved. These findings are of significant importance taking into consideration hypertension is the leading risk factor for first and recurrent stroke. However, trials primarily focused on measuring outcomes of dysglycemia and without assessing a dose-response effect. Additional research is required on the dose-response effect of interrupting sitting with frequent bouts of physical activity or standing on first and recurrent stroke risk factors, in those high risk population groups.

Patterns of objectively measured sedentary behaviour in adults with intellectual disabilities

BACKGROUND

The purpose of this study was to investigate the patterns of objectively measured sedentary behaviour in adults with intellectual disabilities.

METHODS

Baseline accelerometer data were pooled from two randomized controlled trials of lifestyle behaviour change programmes for adults with intellectual disabilities. Patterns of sedentary behaviours were computed including total volume, number, and duration of bouts and breaks.

RESULTS

Participants spent >70% of the day sedentary (8 hr), which was generally accumulated in short sedentary bouts (<10 min). Participants were engaged in significantly more sedentary time during the morning, although differences between time of day were small (mean bout duration range: 19.8-22.3 min).

CONCLUSIONS

The findings add valuable insight into the patterns of sedentary behaviours among adults with intellectual disabilities. Further research investigating the patterns and context of sedentary behaviour is required to develop targeted interventions to reduce total sedentary time in adults with intellectual disabilities.

Postprandial Insulin and Triglyceride Concentrations Are Suppressed in Response to Breaking Up Prolonged Sitting in Qatari Females

Background: Cultural, environmental and logistical factors challenge the Qatari population, particularly females, to engage in physical activity, and there is a high prevalence of diabetes in this population. Sedentary behavior is associated with increased cardiometabolic disease risk and early mortality and breaking up sitting can attenuate postprandial cardiometabolic risk markers. However, no studies have evaluated the cardiometabolic response to breaking up sitting in a Qatari population. Purpose: To examine the effects of breaking up sitting with moderate-intensity walking breaks on cardiometabolic disease markers in Qatari females. Methods: Eleven sedentary (sitting ≥ 7 h/day) females completed two experimental conditions in a cross-over randomized design. The two conditions were identical, except participants either remained seated for 5-h (SIT), or interrupted their sitting every 30-min with a 3-min walk (WALK) on a motorized treadmill (rating of perceived exertion 12-14). A fasting venous blood sample was obtained at baseline (-10-min) followed by samples at 0.5-, 1-, 2-, 3-, 3.5-, 4-, and 5-h. Postprandial cardiometabolic variables (insulin, glucose, triglycerides) were calculated as derivatives of total area under the curve [AUC; total (tAUC), net incremental (iAUC) and positive AUC]. Results: Data is reported as effect size; ±90% confidence limit. There was a most likely "moderate" lower tAUC (-0.92 ± 0.26), iAUC (-0.96 ± 0.33), and positive AUC (-0.96 ± 0.33) for insulin in WALK compared to SIT. Additionally, there was a most likely "moderate" lower tAUC (-0.63 ± 0.37), iAUC (-0.91 ± 0.49), and positive AUC (-0.91 ± 0.49) for triglycerides in WALK compared to SIT. Glucose did not differ between conditions. Conclusion: Breaking up prolonged sitting with moderate-intensity walking offers a culturally compatible intervention to acutely improve cardiometabolic risk markers in sedentary Qatari females. Whilst the data offers promise, the long-term chronic effects of breaking up sitting in Qatari adults requires investigation before population level and/or policy recommendations can be made.

A pilot study of metabolic fitness effects of weight-supported walking in women with obesity

Background

This is an exploratory pilot study of novel technology enabling people with mobility disability to walk with minimal effort, in the “sedentary range”. The study’s premise is that impairment of the leading physical activity of daily living, walking, is a major contributor to a dysmetabolic state driving many prevalent “civilization diseases” associated with insulin resistance.

Methods

We explore within-subject changes in standard oral glucose tolerance (OGT) tests including metabotropic molecules after 22 twice-weekly, 30-minute bouts of weight-supported light-moderate physical activity in 16 non-diabetic obese, otherwise healthy, reproductive-age, volunteer women walking on an “anti-gravity” lower-body positive pressure (LBPP) treadmill.

Results

Subjects had reference base-line fasting plasma glucose and triglycerides (TG) but 2-hr OGT insulin levels of 467 ± 276 pmol • liter^-1 (mean± S.D.) indicating nascent insulin resistance, compared to post-study 308 ± 179 (p = 0.002). Fasting TG decreased from 0.80 ± 0.30 mmol • liter^-1 to 0.71 ± 0.25 (p = 0.03). Concomitantly plasma total ghrelin decreased from 69.6 ± 41.6 pmol • liter^-1 to 56.0 ± 41.3 (p = 0.008). There were no statistically significant changes in body weight or any correlations between weight change and cardiometabolic markers. However, there were robust positive correlations between changes among different classes of peptides including C-reactive protein–Interleukin 6, leptin–adiponectin, β-endorphin–oxytocin and orexin A (r ² = 0.48–0.88).

Conclusion

We conclude that brief, low-dose physical activity, walking on an anti-gravity LBPP treadmill may improve cardiometabolic risk, exhibiting favorable changes in neuro-regulatory peptides without weight loss in people with problems walking.

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.

Cardiovascular disease risk marker responses to breaking up prolonged sedentary time in individuals with paraplegia: the Spinal Cord Injury Move More (SCIMM) randomised crossover laboratory trial protocol

INTRODUCTION

Sedentary behaviour is a distinct risk factor for cardiovascular disease (CVD) and could partly explain the increased prevalence of CVD in people with spinal cord injury (SCI). Interrupting prolonged sitting periods with regular short bouts of walking acutely suppresses postprandial glucose and lipids in able-bodied individuals. However, the acute CVD risk marker response to breaking up prolonged sedentary time in people with SCI has not been investigated.

METHODS AND ANALYSIS

A randomised two-condition laboratory crossover trial will compare: (1) breaking up prolonged sedentary time with 2 min moderate-intensity arm-crank activity every 20 min, with (2) uninterrupted prolonged sedentary time (control) in people with SCI. Outcomes will include acute effects on postprandial glucose, insulin, lipids and blood pressure. Blood samples will be collected and blood pressure measured at regular intervals during each 5½-hour condition.

ETHICS AND DISSEMINATION

This study was approved by the Cambridge South National Health Service Research Ethics Committee. This research will help determine if breaking up prolonged sedentary time could be effective in lowering CVD risk in people with SCI. The findings of the research will be published in a peer-reviewed journal and disseminated to relevant user groups.

TRIAL REGISTRATION NUMBER

ISRCTN51868437; Pre-results.

Energy utilization associated with regular activity breaks and continuous physical activity: A randomized crossover trial

AIMS

To quantify and compare energy utilization associated with prolonged sitting alone, or interrupted with regular activity breaks and/or an additional bout of continuous physical activity.

METHODS AND RESULTS

Thirty six adults (11 males, BMI 24.1 ± 4.6) completed four interventions: (1) prolonged sitting (SIT), (2) sitting with 2-min of walking every 30 min (RAB), (3) prolonged sitting with 30-min of continuous walking at the end of the day (SIT + PA), (4) a combination of the activities in (2) and (3) above (RAB + PA). All walking was at a speed and incline corresponding to 60% V̇O_2max. Energy utilization over 7 h for each intervention was estimated using indirect calorimetry. Compared to SIT, SIT + PA increased total energy utilization by 709 kJ (95% CI 485-933 kJ), RAB by 863 kJ (95% CI 638-1088 kJ), and RAB + PA by 1752 kJ (95% CI 1527-1927 kJ) (all p < 0.001). There was no difference in total energy utilization between SIT + PA and RAB, however, post-physical activity energy utilization in RAB was 632 kJ greater than SIT + PA (95% CI 561-704 kJ; p < 0.001).

CONCLUSIONS

Short frequent activity, results in greater accumulation of elevated post-physical activity energy utilization compared to a single bout of continuous activity; however the total energy utilization is similar. Combining activity breaks with a longer continuous bout of activity will further enhance energy utilization, and in the longer term, may positively affect weight management of a greater magnitude than either activity pattern performed alone.

TRIAL REGISTRATION

ANZCTR12614000624684.

How does light-intensity physical activity associate with adult cardiometabolic health and mortality? Systematic review with meta-analysis of experimental and observational studies

Aim

To assess the relationship between time spent in light physical activity and cardiometabolic health and mortality in adults.

Design

Systematic review and meta-analysis.

Data sources

Searches in Medline, Embase, PsycInfo, CINAHL and three rounds of hand searches.

Eligibility criteria for selecting studies

Experimental (including acute mechanistic studies and physical activity intervention programme) and observational studies (excluding case and case–control studies) conducted in adults (aged ≥18 years) published in English before February 2018 and reporting on the relationship between light physical activity (<3 metabolic equivalents) and cardiometabolic health outcomes or all-cause mortality.

Study appraisal and synthesis

Study quality appraisal with QUALSYST tool and random effects inverse variance meta-analysis.

Results

Seventy-two studies were eligible including 27 experimental studies (and 45 observational studies). Mechanistic experimental studies showed that short but frequent bouts of light-intensity activity throughout the day reduced postprandial glucose (−17.5%; 95% CI −26.2 to −8.7) and insulin (−25.1%; 95% CI −31.8 to –18.3) levels compared with continuous sitting, but there was very limited evidence for it affecting other cardiometabolic markers. Three light physical activity programme intervention studies (n ranging from 12 to 58) reduced adiposity, improved blood pressure and lipidaemia; the programmes consisted of activity of >150 min/week for at least 12 weeks. Six out of eight prospective observational studies that were entered in the meta-analysis reported that more time spent in daily light activity reduced risk of all-cause mortality (pooled HR 0.71; 95% CI 0.62 to 0.83).

Conclusions

Light-intensity physical activity could play a role in improving adult cardiometabolic health and reducing mortality risk. Frequent short bouts of light activity improve glycaemic control. Nevertheless, the modest volume of the prospective epidemiological evidence base and the moderate consistency between observational and laboratory evidence inhibits definitive conclusions.

Interrupting Prolonged Sitting with Regular Activity Breaks does not Acutely Influence Appetite: A Randomised Controlled Trial

Regular activity breaks increase energy expenditure; however, this may promote compensatory eating behaviour. The present study compared the effects of regular activity breaks and prolonged sitting on appetite. In a randomised, cross-over trial, 36 healthy adults (BMI (Body Mass Index) 23.9 kg/m² (S.D. = 3.9)) completed four, two-day interventions: two with prolonged sitting (SIT), and two with sitting and 2 min of walking every 30 min (RAB). Standardized meals were provided throughout the intervention, with an ad libitum meal at the end of Day 2. Appetite and satiety were assessed throughout both days of each intervention using five visual analogue scales. The five responses were combined into a single appetite response at each time point. The area under the appetite response curve (AUC) was calculated for each day. Intervention effects for appetite response AUC and ad libitum meal intake were tested using linear mixed models. Appetite AUC did not differ between interventions (standardised effect of RAB compared to SIT: Day 1: 0.11; 95% CI: -0.28, 0.06; p = 0.212; Day 2: 0.04; 95% CI: -0.15, 0.24; p = 0.648). There was no significant difference in energy consumed at the ad libitum lunch meal on Day 2 between RAB and SIT. Interrupting prolonged sitting with regular activity breaks does not acutely influence appetite or volume of food consumed, despite inferred increases in energy expenditure. Longer-term investigation into the effects of regular activity breaks on energy balance is warranted.

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 4 h 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/L 4 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.

Leisure-time physical activity, sedentary behaviors, sleep, and cardiometabolic risk factors at baseline in the PREDIMED-PLUS intervention trial: A cross-sectional analysis

Limited data exists on the interrelationships between physical activity (PA), sedentary behaviors and sleep concerning cardiometabolic risk factors in aged adults at high cardiovascular disease risk. Our aim was to examine independent and joint associations between time spent in leisure-time PA, sedentary behaviors and sleep on the prevalence of obesity, type 2 diabetes (T2D) and components of the metabolic syndrome (MetS) in Mediterranean individuals at high cardiovascular risk. Cross-sectional analyses were performed on baseline data from 5776 Spanish adults (aged 55-75y in men; 60-75y in women) with overweight/obesity and MetS, from October 2013 to October 2016, in the PREDIMED-PLUS trial. Employing multivariable-adjusted Cox regression with robust variance and constant time (given the cross-sectional design), higher prevalence of obesity, T2D and abdominal obesity as component of the MetS were associated with greater time in TV-viewing (Relative Risk, RR: 1.02, 95%CI: 1.01, 1.03; RR:1.04, 95%CI: 1.02, 1.06 and RR: 1.01 95%CI: 1.00, 1.02; respectively, all P < .01). Conversely, greater time in moderate-vigorous PA (MVPA) was associated with lower prevalence of obesity, T2D, abdominal obesity and low HDL-cholesterol (RR: 0.95, 95%CI: 0.93, 0.97; RR: 0.94, 95%CI: 0.89, 0.99; RR: 0.97, 95%CI: 0.96, 0.98; and RR: 0.95, 95%CI: 0.91, 0.99, respectively, all P < .05). For these outcomes, theoretically substituting 1-h/day of MVPA for 1-h/day TV-viewing was also significantly associated with lower prevalence (RR 0.91 to 0.97, all P < .05). Similar lower RR in these outcomes was observed when substituting 1-h/day of MVPA for 1-h/day of sleeping. Longer time watching TV and not meeting MVPA recommendations were jointly associated with higher RR of the prevalence of obesity and T2D. We concluded that, in senior individuals at high cardiovascular risk, greater time spent on MVPA and fewer on sedentary behaviors was inversely associated with prevalence of obesity, T2D, and some of the components of MetS.

Standing economy: does the heterogeneity in the energy cost of posture maintenance reside in differential patterns of spontaneous weight-shifting?

PURPOSE

Due to sedentarity-associated disease risks, there is much interest in methods to increase low-intensity physical activity. In this context, it is widely assumed that altering posture allocation can modify energy expenditure (EE) to impact body-weight regulation and health. However, we have recently shown the existence of two distinct phenotypes pertaining to the energy cost of standing-with most individuals having no sustained increase in EE during steady-state standing relative to sitting comfortably. Here, we investigated whether these distinct phenotypes are related to the presence/absence of spontaneous "weight-shifting", i.e. the redistribution of body-weight from one foot to the other.

METHODS

Using indirect calorimetry to measure EE in young adults during sitting and 10 min of steady-state standing, we examined: (i) heterogeneity in EE during standing (n = 36); (ii) EE and spontaneous weight-shifting patterns (n = 18); (iii) EE during spontaneous weight-shifting versus experimentally induced weight-shifting (n = 7), and; (iv) EE during spontaneous weight-shifting versus intermittent leg/body displacement (n = 6).

RESULTS

Despite heterogeneity in EE response to steady-state standing, no differences were found in the amount or pattern of spontaneous weight-shifting between the two phenotypes. Whilst experimentally induced weight-shifting resulted in a mean EE increase of only 11% (range: 0-25%), intermittent leg/body displacement increased EE to >1.5 METs in all participants.

CONCLUSIONS

Although the variability in spontaneous weight-shifting signatures between individuals does not appear to underlie heterogeneity in the energy cost of standing posture maintenance, these studies underscore the fact that leg/body displacement, rather than standing posture alone, is needed to increase EE above the currently defined sedentary threshold.

Exercise, Appetite and Weight Control: Are There Differences between Men and Women?

Recent years have witnessed significant research interest surrounding the interaction among exercise, appetite and energy balance, which has important implications for health. The majority of exercise and appetite regulation studies have been conducted in males. Consequently, opportunities to examine sex-based differences have been limited, but represent an interesting avenue of inquiry considering postulations that men experience greater weight loss after exercise interventions than women. This article reviews the scientific literature relating to the acute and chronic effects of exercise on appetite control in men and women. The consensus of evidence demonstrates that appetite, appetite-regulatory hormone and energy intake responses to acute exercise do not differ between the sexes, and there is little evidence indicating compensatory changes occur after acute exercise in either sex. Limited evidence suggests women respond to the initiation of exercise training with more robust compensatory alterations in appetite-regulatory hormones than men, but whether this translates to long-term differences is unknown. Current exercise training investigations do not support sex-based differences in appetite or objectively assessed energy intake, and increasing exercise energy expenditure elicits at most a partial energy intake compensation in both sexes. Future well-controlled acute and chronic exercise studies directly comparing men and women are required to expand this evidence base.