The Physiology of Sedentary Behavior

Sedentary behaviors (SB) are characterized by a 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 towards 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 on 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.</p

Accumulating Physical Activity in Short or Brief Bouts for Glycemic Control in Adults With Prediabetes and Diabetes

Clinical practice guidelines on physical activity and diabetes currently stipulate physical activity can be accumulated in bouts of ≥10 minutes to meet recommendations for health benefits. Individuals are also encouraged to interrupt prolonged sitting with brief activity breaks of ∼1 to 5 minutes in duration. Growing research highlights accumulating activity in shorter bouts across the day as a potential strategy to improve glycemic control and to help those who are largely sedentary meet physical activity guidelines. Research has shown favourable glycemic benefits for postprandial glucose and glycated hemoglobin with either 3 short (10 to 15 minutes) or frequent brief (1 to 5 minutes) bouts of activity spread around meals or throughout the day. To date, most studies examining accumulated activity were done with people with type 2 diabetes compared with sedentary conditions, were short term and measured various indices of glycemic control using continuous glucose monitoring. The 7 trials comparing accumulating 3 short bouts to a single bout showed comparable benefits for glycemic control (i.e. fasting glucose, 24 h mean glucose and postprandial hyperglycemia). Furthermore, timing short bouts around meals may improve postprandial glucose and hyperglycemia more than a single bout. It is unknown whether a threshold for the duration of accumulated bouts exists---that is, “how much is enough?” In this narrative review, we focus on the glycemic effects of physical activity accumulated in short or brief bouts for people with prediabetes and diabetes as compared with a single continuous bout. Given that poor adherence to physical activity recommendations and that fewer opportunities exist in modern societies for incidental (nonexercise) physical activity, accumulating activity may be a choice strategy for improving glycemic control in those with and at risk of diabetes.RésuméLes lignes directrices sur la pratique clinique en matière d’activité physique et de diabète stipulent actuellement que l’activité physique peut être cumulée en périodes de ≥ 10 minutes afin de respecter les recommandations en vue d’obtenir des bienfaits sur la santé. Les individus sont également encouragés à entrecouper les périodes prolongées en position assise par des pauses brèves d’une durée de ∼1 à 5 minutes pour faire une activité physique. De plus en plus de recherches mettent en évidence que le cumul de périodes plus courtes d’activité tout au long de la journée est une stratégie potentielle pour améliorer la régulation de la glycémie et aider les personnes très sédentaires à respecter les lignes directrices en matière d’activité physique. La recherche a montré que 3 périodes courtes (de 10 à 15 minutes) ou brèves fréquentes (de 1 à 5 minutes) d’activité réparties en fonction des repas ou tout au long de la journée ont des effets favorables sur la glycémie postprandiale et l’hémoglobine glyquée. Jusqu’à maintenant, la plupart des études qui portaient sur l’activité physique cumulée ont été réalisées auprès de personnes atteintes du diabète de type 2 par rapport à des conditions de sédentarité, étaient de courte durée et portaient sur l’évaluation de plusieurs indices de régulation de la glycémie au moyen de la surveillance de la glycémie en continu. Les 7 études qui portaient sur la comparaison du cumul de 3 périodes courtes à une seule période ont montré des effets bénéfiques comparables sur la régulation de la glycémie. De plus, la coordination de courtes périodes en fonction des repas peut davantage contribuer à l’amélioration de la glycémie postprandiale et de l’hyperglycémie qu’une seule période. On ignore s’il existe un seuil pour la durée des périodes cumulées, c’est-à-dire « Combien faut-il en faire pour en faire assez ? » Dans cette revue narrative, nous nous penchons sur les effets de l’activité physique cumulée en périodes courtes ou brèves par rapport à une seule période en continu sur la glycémie des personnes prédiabétiques et diabétiques. Étant donné que l’observance des recommandations d’activité physique est médiocre et qu’il existe moins de possibilités d’activité physique spontanée (autre que l’exercice planifié) dans les sociétés modernes, le cumul de l’activité physique peut être une stratégie de choix pour améliorer la régulation de la glycémie chez les personnes diabétiques ou exposées au risque de diabète.</div

Four-Year Increase in Step Cadence Is Associated with Improved Cardiometabolic Health in People with a History of Prediabetes

Purpose  To investigate associations between 4-year change in step cadence and markers of cardiometabolic health in people with a history of prediabetes and to explore whether these associations are modified by demographic factors. Methods  In this prospective cohort study, adults, with a history of prediabetes, were assessed for markers of cardiometabolic health (body mass index (BMI), waist circumference, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), triglycerides, and glycated haemoglobin (HbA1c) and free-living stepping activity (activPAL3™) at baseline, 1-year, and 4-years. Brisk steps/day were defined as the number of steps accumulated at ≥100 steps/minute and slow steps/day as those accumulated at Results  794 participants were included (age = 59.8 ± 8.9 years, 48.7% women, 27.1% ethnic minority, total steps/day = 8445 ± 3364, brisk steps/day = 4794 ± 2865, peak 10-minute step cadence = 128 ± 10 steps/minute. Beneficial associations were observed between change in brisk steps/day and change in BMI, waist circumference, HDL-C, and HbA1c. Similar associations were found between peak 10-minute step cadence and HDL-C and waist circumference. Interactions by ethnicity revealed change in brisk steps/day and change in peak 10-minute step cadence had a stronger association with HbA1c in White Europeans, whereas associations between change in 10-minute peak step cadence with measures of adiposity were stronger in South Asians. Conclusions  Change in the number of daily steps accumulated at a brisk pace was associated with beneficial change in adiposity, HDL-C, and HbA1c; however, potential benefits may be dependent on ethnicity for outcomes related to HbA1c and adiposity.</p

Walking pace and the time between the onset of non-communicable diseases and mortality: a UK Biobank prospective cohort study.

PurposeTo estimate trajectories of time spent in various cardiovascular disease (CVD) and cancer states, according to self-reported walking pace.Methods391,744 UK Biobank participants were included (median age=57 years; 54.7% women). Data was collected 2006-2010, with follow-up data collected in 2021. Usual walking pace was self-defined as slow, steady/average or brisk. Multistate modelling was used to obtain the transition rate and mean sojourn time in and across three different states (healthy, CVD/cancer, death) upon a time horizon of 10 years.ResultsThose reporting an average or brisk walking pace at baseline displayed lower rates across all transitions (vs. slow walkers). The mean sojourn time in the healthy state was longer while that in the CVD/cancer state was shorter in individuals reporting an average or brisk walking pace (vs. slow). A 75-year-old woman reporting a brisk walking pace spent, on average, 8.4 years of the next 10 years in a healthy state; an additional 8.0 (95% CI: 7.3, 8.7) months longer compared to a 75-year-old woman reporting a slow walking pace. This corresponded to 4.3 (3.7, 4.9) fewer months living with CVD/ cancer. Similar results were seen in men.ConclusionsAdults reporting an average or brisk walking pace at baseline displayed a lower transition to disease development and a greater proportion of life lived without CVD/cancer.Availability of data and materialsResearch was conducted using the UK Biobank Resource under Application #33266. The UK Biobank resource can be accessed by researchers on application. Variables derived for this study have been returned to the UK Biobank for future applicants to request. No additional data are available