A number of published studies report that prolonged sitting – like many people do daily at their jobs, associates with risk factors such as higher cholesterol levels and greater waist circumference, that can lead to cardiovascular and metabolic disease. Saurabh Thosar, from Indiana University (Indiana, USA), and colleagues enrolled 11 non-obese, healthy men between the ages of 20-35 years, who participated in two randomized trials. In one trial they sat for three hours without moving their legs. Researchers used a blood pressure cuff and ultrasound technology to measure the functionality of the femoral artery at baseline and again at the one-, two- and three-hour mark. In the second trial, the men sat during a three-hour period but also walked on a treadmill for 5 minutes at a speed of 2 mph at the 30-minute mark, 1.5-hour mark and 2.5-hour mark. Researchers measured the functionality of the femoral artery at the same intervals as in the other trial. The team demonstrated that during a three-hour period, the flow-mediated dilation, or the expansion of the arteries as a result of increased blood flow, of the main artery in the legs was impaired by as much as 50% after just one hour. The study participants who walked for 5 minutes each hour of sitting saw their arterial function stay the same — it did not drop throughout the three-hour period, suggesting a beneficial effect of increased muscle activity and blood flow . Reporting that: “Three hours of sitting resulted in a significant impairment in shear rate and [superficial femoral artery flow mediated dilation],” the study authors report that: “When light activity breaks were introduced hourly during sitting, the decline in [flow mediated dilation] was prevented.”
