Sedentary behaviour, defined as prolonged periods of sitting, watching TV, using a computer or driving, has recently been linked to a number of health crises. These can include diabetes, cardiovascular disease, obesity and even an early death. While some of the sedentary behaviours are avoidable others, such as those that are job related, have become a fact of life in today working world. Certainly, making sure you stay active in periods where you are not sitting down at work has been shown to help improve health but it may not be enough. Some studies suggest that sedentary behaviour can counteract some of the beneficial effects of exercise on the brain, at least in older adults. If sitting down at work is unavoidable to some, is there anything that can be done to help prevent the harmful effects of a sedentary work environment? New research out of Indiana School of Public Health suggests there is a way to prevent the damage.
The researchers looked at the function of vessels in volunteer’s legs with or without intermittent short walks throughout periods of sitting. Before we get into the research, let’s define something known as flow mediated dilation or FMD. FMD is the ability of the arteries and veins in our body to dilate (or open up more) in response to blood flow. This is a normal process that goes on in your body, as blood flow increases, the arteries and veins carrying that blood open up. If they don’t for some reason, your blood pressure goes up. FMD is mediated by a molecule called nitric oxide (or NO). NO causes the muscle in the arteries and veins to relax and subsequently dilate. This video explains nicely what FMD is and how NO contributes and also how we measure FMD.
So the researchers got 12 non-obese volunteers and randomized them into two groups, those that would sit for 3 hours without moving their legs and those that would break up the 3 hour sitting time with 5 minute walks at a slow pace three times (at 30 minutes, 1.5 hours, 2.5 hours). In both groups, they measured the FMD at 1 hour intervals for the duration of the sit. They saw that the group of people who sat for extended periods of time without any break had decreased dilation in their vessels after as early as 1 hour of sitting. Compared to this group, the people who walked for 5 minutes were protected from this decrease in FMD. This result is interesting because it suggests that there is not much effort required to reverse the negative effects of prolonged sedentary behaviour. A simple walk could help in preventing some of the changes in our vessels we see with sedentary behaviour. This benefit is echoed by another study that showed breaking up prolonged sitting with a walk (2 minutes in length) can decrease the levels of glucose and insulin in the blood in overweight or obese individuals. More work is still needed to examine how the effects change with different diseases like diabetes or established heart disease. It would also be beneficial to know if the intensity of exercise makes any difference. Patients in this study walked slowly for 5 minutes but what about running for 5 minutes or office dodge ball? While the research is in its infancy, the results are promising and suggest that short bursts of exercise to break up the sitting can help stave off heart disease and early death. So the next time you’re at work, take regular walk breaks. It’ll help your heart, keep you sane and your boss can’t get mad.