Today’s post comes from Dr Robyn Larsen. More information on Dr Larsen can be found at the bottom of this post.
The concept of breaks in sitting time is emerging as a potential intervention strategy for managing disturbances in glucose metabolism, which increases risk of developing diabetes, cardiovascular disease and other chronic health problems. Accumulating evidence from a number of laboratory-based experimental studies suggest that regularly breaking up prolonged sitting lowers glucose and insulin levels in healthy and overweight/obese adults and in individuals with type 2 diabetes.1-5
These randomized cross-over trials show consistent detrimental effects of uninterrupted sitting, compared with sitting that has been interrupted with short bouts of standing,3 light-intensity activities,1-3, 5 or moderate-intensity walking.1
A potential mechanism linking breaks in sitting with improvements in blood glucose control is increased energy expenditure (EE). As sitting is characterised by low EE, breaks in sitting provide opportunities to accumulate EE, via increases in nonexercise activity thermogenesis. In theory, the EE of each break may be manipulated by altering the frequency, duration or intensity of the breaking activity. However, the impact of breaks in sitting in relation to varying EEs has not been previously explored.
For the purpose of future intervention development, there is a need to more clearly understand the impacts of different strategies to break up sitting, and how this relates to risk markers of cardiometabolic disease. For instance:
Future experimental trials involving systematic “dose” manipulations of breaks in sitting are needed to inform the design and tailoring of interventions and programs.
In our recently published paper in Applied Physiology, Nutrition and Metabolism,6 we addressed the question of whether different types of breaks from prolonged sitting can differentially impact on post-meal (‘postprandial’) blood glucose and insulin levels, in a sample of participants from past trials,1, 2, 7.
We reported findings from an exploratory analysis of pooled data from of our three laboratory-based trials that standardized the test meal, cohort characteristics (overweight/obese adults) and the frequency and duration of the breaks in sitting. This included nine participants who completed laboratory trials comparing the acute effects of prolonged sitting with sitting interrupted every 20-minutes with 2-minute bouts of either standing, light-intensity and moderate-intensity physical activity. EE related to the conditions was estimated from formula-derived estimations,8, 9 as EE was not directly measured during conditions.
We found that the EE of the break in sitting was associated with the lowering of postprandial glucose and insulin responses in a dose-dependent manner. These findings suggest that the type of break from sitting may be important for improving these important metabolic responses.
Further studies on the direct measurement of EE are required to confirm our observations and to examine the effects of different “dose” manipulations to breaks in sitting, such as break frequencies, break durations and break intensities.
Dr Robyn Larsen is a nutritional biochemist currently employed as a postdoctoral fellow in the Physical Activity and Behavioural Epidemiology Laboratories at the Baker Heart and Diabetes institute. Her current research interests include the impact of sedentary behaviours during pregnancy and risk of developing gestational diabetes mellitus (see GLOW breaks in pregnancy study).