Over the past few years a slew of studies has linked prolonged sitting to cardiovascular disease and premature death. Now for the first time, scientists have some concrete experimental evidence that sheds light on how sitting actually harms the heart and arteries.  For this study, scientist had a group of healthy, non-obese men sit continuously for three hours straight. During this three-hour time period, the scientists periodically measured the blood flow in the main artery of the study subjects’ legs. Measuring blood flow within an artery is a reliable indicator of how well an artery functions, medically referred to as “endothelial function”. This is of note because endothelial dysfunction or sluggish blood flow plays a primary role in how arteries become diseased and blocked.

What the researchers found was eye-popping. In as little as one hour of sitting, blood flow in the study subjects’ leg arteries diminished by 50%. In other words, even a single hour of sitting significantly impaired blood vessel function. (Knowing that the average American adult sits eight hours a day – this is alarming to say the least!)

But there was some great news too. The researchers repeated the same experiment, but had the study subjects interrupt the sitting with short five-minute (2mph) walks on the treadmill, every hour. With the addition of these short walking breaks, blood flow did not decrease and remained at pre-sitting levels throughout the three hours. The scientists concluded that the use of muscles during walking likely counteracted the adverse changes that normally occur within arteries during prolonged sitting. So if you are feeling sluggish and sitting down, get up and move a little to get your blood flowing and to protect your heart. (Medicine & Science in Sports & Exercise, 2014; 1 DOI:10.1249/MSS.0000000000000479)