Prolonged sitting is associated with increased risk of diabetes, cardiovascular disease, and overall mortality.[1, 2] This is troubling, since most of us sit for most of the day. Since 1950, there has been an 83% increase in sedentary jobs. Many of us sit all day while we work, and then go home and sit for most of the evening – at the dinner table, at the computer, and on the couch.
Just like exercise, prolonged sitting has distinct physiological effects. But unlike exercise, sitting has unhealthy effects. After just a few days of bed rest, increased insulin resistance and unfavorable vascular changes can be detected in healthy subjects.
Exercise is one effective way to counteract these effects, but what about the rest of our day? If we spend an hour, or even two, exercising vigorously each day, is that enough to counteract the effects of the 8-12 hours we may spend sitting down? It turns out that the answer is no. Of course, exercise is beneficial – regular exercise reduces the risk of heart disease, diabetes, and several cancers. However, prolonged sitting has been linked to increased risk of death regardless of the amount of exercise activity performed.
In addition to exercising daily, we also need to increase our non-exercise physical activity. Non-exercise physical activity, though its intensity is low, makes a significant contribution to our overall calorie expenditure. In fact, in people who do not exercise regularly, 90% of caloric expenditure is on standing, non-exercise movement.  We can increase non-exercise physical activity simply by taking frequent breaks from sitting. When we are sitting our muscles are idle, but once we stand up, there is measurable activity in the large muscles of our legs (graphically represented in Figure 3A here) – the body is physically active when we are standing.
In a recent study, participants wore accelerometers, devices that keep track of physical activity intensity, to track their total quantity and sedentary time and number of interruptions (breaks) in sedentary time. Prolonged sitting was associated with larger waist circumference and higher C-reactive protein (a marker of inflammation) levels. But interruptions in sedentary time made a difference – regardless of the amount of time spent sitting, a greater number of interruptions in sedentary time was associated with smaller waist circumference and lower C-reactive protein.[7, 8]
Frequent but short bouts of non-exercise activity, like standing up from your desk to stretch, taking a quick walk around the office, standing up while taking a phone call, walking to a colleague’s office instead of sending an email, or taking the stairs instead of the elevator contribute to increasing the number of interruptions in our sedentary time.
Unfortunately, sedentary jobs are the norm, but we can use exercise and frequent breaks from sitting to help us counteract the unhealthy effects of our sedentary days.
1. van Uffelen, J.G., et al., Occupational sitting and health risks: a systematic review. Am J Prev Med, 2010. 39(4): p. 379-88.
2. Manson, J.E., et al., Walking compared with vigorous exercise for the prevention of cardiovascular events in women. The New England journal of medicine, 2002. 347(10): p. 716-25.
3. The Price of Inactivity. American Heart Association.
4. Hamburg, N.M., et al., Physical inactivity rapidly induces insulin resistance and microvascular dysfunction in healthy volunteers. Arteriosclerosis, thrombosis, and vascular biology, 2007. 27(12): p. 2650-6.
5. Patel, A.V., et al., Leisure time spent sitting in relation to total mortality in a prospective cohort of US adults. American Journal of Epidemiology, 2010. 172(4): p. 419-29.
6. Hamilton, M.T., D.G. Hamilton, and T.W. Zderic, Role of low energy expenditure and sitting in obesity, metabolic syndrome, type 2 diabetes, and cardiovascular disease. Diabetes, 2007. 56(11): p. 2655-67.
7. Healy, G.N., et al., Sedentary time and cardio-metabolic biomarkers in US adults: NHANES 2003-06. European heart journal, 2011.
8. European Society of Cardiology: More breaks from sitting are good for waistlines and hearts. ScienceDaily, 2011.