Active Voice: Voice: Breaking Up Sitting Time—Should We Stand Up, Sit Down or Keep Moving?
By Joseph Henson, Ph.D.

Joseph Henson
Exorbitant sitting, commonly termed sedentary time, now resides as the default setting for the large majority of individuals, with those identified at high risk of chronic disease spending up to 80% of their waking time sedentary. Current physical activity guidelines now include specific recommendations to reduce and interrupt prolonged sitting. These guidelines have been informed by emerging research suggesting that sitting time is an independent risk factor for cardiometabolic morbidity and mortality. In recent years, epidemiological research has been complemented by acute experimental studies showing that breaking up bouts of prolonged sitting with standing or light-intensity activity elicits significant benefits on markers of metabolic health. However, there is considerable inter-individual variability in the effectiveness of such interventions. Future prevention strategies should be stratified and targeted at those who could derive the greatest benefit. Therefore, it is necessary to determine the factors that may predict a favorable response to breaking up prolonged sitting with a low-intensity intervention.

Our findings from a pooled analysis of four acute, randomized experimental trials [n=129, body mass index (BMI) range 19.6 - 44.6kg/m2; South Asian=31.0%; high risk of T2DM=27.1%] were published in the June 2020 issue of Medicine & Science in Sports & Exercise®. We examined the postprandial glucose and insulin response following a standardized breakfast and lunch to three treatment conditions: prolonged sitting (6.5 hours) or prolonged sitting broken-up with either standing or light-intensity physical activity (five minutes every 30 minutes). We also explored whether BMI, demographic (age, gender, ethnicity: white European vs. South Asian) or a cardiometabolic variable [Homeostatic Model Assessment of Insulin Resistance (HOMA-IR)], a commonly used index of insulin resistance, modified responses.

The results demonstrate that simply breaking up sitting time every 30 minutes with light activity, but not standing, lowered postprandial glucose and insulin levels. Reductions in postprandial insulin were more pronounced if individuals were South Asian compared with white European (-23.5 vs. -9.3%), female compared to male (-21.2 vs. -17.6%) or had a BMI =27.2kg/m2 (-22.9 vs. -18.2%). Similarly, being female (-6.8 vs. -1.7%) or having a BMI =27.2kg/m2 (-6.7 vs. -3.4%) modified the postprandial glucose response. No significant interactions were found for HOMA-IR or age.

Our findings build on previous work by reporting potential differences in the postprandial response based on an individual’s ethnicity, gender or BMI. Our results may be used to guide future individualized tailored interventions in high-risk participants for whom breaking prolonged sitting time could be a viable and effective prevention or treatment strategy. Currently, there is low attainment of physical activity guidelines, particularly in high-risk participants. Thus, a reasonable goal may be to first break up sitting time with light-intensity physical activity before progressing to higher intensity activities. This may also be more culturally acceptable to high-risk groups (e.g., South Asian women). Although we found no change in the glucose or insulin postprandial values for the standing condition, replacing sitting with standing is still likely to yield other health benefits. The main message remains, all individuals are encouraged to simply sit less and move more, regardless of the intensity.

About the author:
Joseph Henson is a research associate in sedentary behavior, physical activity and health at the Diabetes Research Centre at the University of Leicester in the United Kingdom. His research, which encompasses both epidemiological and experimental work, focuses on the interaction between physical activity, sedentary behavior, cardiorespiratory fitness and health with a particular focus on type 2 diabetes (T2DM). Connect with Dr. Henson at jjh18@leicester.ac.uk, @LeicesterBRC or https://www.leicesterbrc.nihr.ac.uk/.

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