Prolonged Sitting with Interrupted Activity Improves Vascular Function in Type 2 Diabetics

by | Mar 5, 2021 | 2021, Cardiovascular Health, Diabetes

Written by Angeline A. De Leon, Staff Writer. This study suggests that for patients with type 2 diabetes (T2D), more frequent and shorter breaks may be more beneficial for their vascular health than longer, less-frequent breaks.

agingAs a result of atherosclerotic complications (e.g., myocardial infarction, stroke, aneurysm), individuals with type 2 diabetes face higher risk of cardiovascular disease (CVD) mortality 1,2. Vascular function, which in type 2 diabetes is generally impaired 3, is used as a marker of CVD risk and has been the target of intervention programs in diabetes management 4. Sedentary behavior is known to be associated with adverse health effects, with evidence suggesting a specific link between prolonged periods of sitting and reduced vasodilatory function 5. In fact, elevated levels of endothelin-1 (ET-1, vasoconstrictor) are considered a marker of microvascular and macrovascular complication in patients with type 2 diabetes 6 and correlate to higher levels of sedentary behavior 7. Experimental evidence suggests that reducing prolonged sitting time with short periods of light physical activity may help vascular function in overweight and obese adults 8, however, it is not known whether such effects are evident in diabetic individuals as well. To this end, a recent study 9 in the American Journal of Physiology-Heart and Circulatory Physiology examined the vascular effects of interrupting prolonged sitting in subjects with type 2 diabetes.

A three-arm, randomized, crossover trial was carried out in a group of 24 individuals with type 2 diabetes (aged 35-70 years) who reported sitting for 5 or more hours each day and qualified as being physically inactive (not engaging in 150 minutes or more of moderate- to high-intensity exercise on a weekly basis). Each subject completed three 7-hour-long experimental conditions in a randomized order with a 6-day washout period in between treatment arms. The three conditions were: prolonged, uninterrupted sitting (SIT); 3-minute simple resistance exercises every half hour (SRA3); and 6-minute simple resistance exercises every hour (SRA6). At the beginning of each experimental session, vascular function was assessed based on femoral artery flow-mediated dilation (FMD) measures, and resting femoral shear rate was calculated as an index of shear stress on the artery wall (associated with the regulation of endothelial function). Fasting blood samples were also collected at baseline and at 1h, 3.5h, 4.5h, and 7h for analysis of ET-1 concentrations.

Data indicated that femoral artery FMD averaged across the 7-hour experimental period was significantly higher in the SRA3 group vs. SIT (4.1 +/- 0.3% vs. 3.7 +/- 0.3%, respectively; p = 0.04). No significant differences were evident between SIT and SRA6 nor SRA3 and SRA6 for mean femoral artery FMD. Mean resting femoral shear rate averaged over 7 hours was also found to be significantly higher for subjects in the SRA3 (45.3 +/- 4.1/s, p < 0.001) and SRA6 groups (46.2 +/- 4.1/s, p < 0.001), compared to SIT (33.1 +/- 4.1/s). No significant differences were observed for ET-1 concentrations between the different treatment conditions.

Based on reported findings, the importance of interrupting prolonged periods of sitting with frequent activity breaks designed to stimulate blood flow is clear. Results suggest that shorter but more frequent breaks are more beneficial for vascular function than longer but less frequent breaks. Over a period of 7 hours, a 3-minute physical activity break every half hour showed the greatest benefit for mean femoral artery FMD. Given that no significant changes were detected for blood pressure or for ET-1 levels, additional work is needed to verify the vascular mechanisms involved in mitigating sitting-induced impairments in cardiovascular function. A notable study limitation relates to the fact that many subjects were taking prescription medication during the time of their participation (54% taking blood pressure medicine). Given the laboratory setting in which the trial was carried out, the ecological validity of the present trial is also limited, and findings should be replicated in home or work-based settings with larger sample sizes. Researchers should also continue to explore the optimal frequency, duration, and type of physical activity breaks required for maintenance/improvement of vascular function in diabetic patients.

Source: Taylor FC, Dunstan DW, Homer AR, et al. Acute effects of interrupting prolonged sitting on vascular function in type 2 diabetes. Am J Physiol Heart Circ Physiol. 2021; 320(1): H393-H403. DOI: 10.1152/ajpheart.00422.2020.

Posted March 5, 2021.

Angeline A. De Leon, MA, graduated from the University of Illinois at Urbana-Champaign in 2010, completing a bachelor’s degree in psychology, with a concentration in neuroscience. She received her master’s degree from The Ohio State University in 2013, where she studied clinical neuroscience within an integrative health program. Her specialized area of research involves the complementary use of neuroimaging and neuropsychology-based methodologies to examine how lifestyle factors, such as physical activity and meditation, can influence brain plasticity and enhance overall connectivity.

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