MedicalResearch.com Interview with:
MPhEd, PhD in Medicine (expected June 2016)
Physical Physical Activity and Behavioural Epidemiology Laboratory
Baker IDI Heart and Diabetes Institute
MedicalResearch.com: What is the background for this study? What are the main findings?
Response: In addition to too little physical activity (PA), sedentary behavior – defined as any waking sitting or reclining behavior with low energy expenditure – has emerged as a ubiquitous and significant population-wide influence on cardiometabolic health outcomes, with potentially distinct and modifiable environmental and social determinants. There is now a consistent base of epidemiologic evidence reporting deleterious associations of excessive sedentary behaviors (e.g. TV viewing, car use, and desk work) with mortality and cardiometabolic morbidity, independent of moderate-vigorous PA.
To date, efforts to influence participation in moderate-to-vigorous exercise (i.e. 30 min a day of ‘exercise’ on most days a week for health) at the population level, such as through large-scale campaigns to promote walking, and other initiatives to encourage people to exercise during their leisure time have achieved only modest success. There may, however, be untapped preventive-health and clinical management potential through shifting the high volume of time spent sedentary to light-intensity physical activity interspersed throughout the day. As such, sedentary behavior represents a potentially feasible and therapeutic target, particularly in the promotion of metabolic health.
We posited that people with type 2 diabetes (T2D) were likely to derive the greatest benefits from interrupting their sitting time. However, until now the contributions of prolonged sitting and/or interrupting prolonged sitting with very-brief bouts of light-intensity PA had never been experimentally tested in patients with T2D. Moreover, this study for the first time moved beyond interrupting sitting with standing or ambulatory bouts (although walking bouts were also examined), which may have differing levels of metabolic stimulus (i.e. not physiologically taxing the body enough), practicality, or health efficacy, to examine a potential addition/alternative: simple resistance activities (SRA). A key premise behind these SRA bouts (half-squats, calf raises, gluteal contractions, and knee raises) were that they required no specialized equipment, only small amounts of space, and could be easily performed in a fixed position behind a work desk or at home with minimal disruption to work tasks or leisure pursuits. In addition, they also markedly increase muscle activity, and may also have other longer-term benefits (for example physical function, muscle strength, bone density), however we can only speculate on these aspects at present.
In this study in men and women with type 2 diabetes, plasma glucose, insulin and C-peptide (marker of insulin secretion and pancreatic beta cell function) levels following standardized breakfast and lunch meals were all markedly attenuated when prolonged sitting was regularly interrupted with light walking or resistance activities (3 min every 30 min) over an 8 hour day. Plasma triglyceride levels were also reduced for both types of activity bout; however, the reduction was only significant for the SRAs. Interestingly, the magnitude of glucose reduction for the walking bouts was greater in women for glucose levels.