Long days at school or work often leave us glued to our chairs for hours at a time. Although long periods of sitting can seem harmless, this sedentary behaviour can severely impair the ability of our blood vessels to distribute blood around the body. A new study from Applied Physiology, Nutrition, and Metabolism found that a single session of prolonged sitting significantly impaired blood flow to the legs, regardless of how physically active the individual is.
According to Statistics Canada, the average Canadian adult is sedentary for 9.5 hours a day. Compared to previous decades, we spend large portions of our waking day in scenarios that require limited physical activity whether this is at work, home, or on the road. A review article published in Mayo Clinic Proceedings suggests that the rise in sedentary behaviour also coincides with the ongoing technological revolution—people are spending more time glued to computer, TV, or phone screens. Accordingly, another study found that since the 1970s there has been a dramatic increase in the number of light-activity, technology-driven jobs in combination with a proportional decline in the number of high-activity, manual labour based jobs.
Importantly, a large scope of research has demonstrated that sedentary behaviour is associated with a multitude of adverse health outcomes including impaired blood vessel function that can contribute to the development of cardiovascular diseases.
Other evidence has consistently established that a healthy active lifestyle that incorporates regular endurance exercise can improve blood vessel function. Physical activity has been shown to cause rapid and robust increases in blood pressure pushing against blood vessel walls, which can promote blood vessel expansion and subsequent relaxation. Ultimately, studies have shown that regular physical activity can improve blood vessel function by preventing blood vessels from becoming constricted, rigid, and immobile—a problem commonly associated with inactive lifestyles.
With this in mind, researchers from Virginia Commonwealth University sought to investigate whether aerobically fit individuals who regularly participated in physical activity had a protective effect against the negative impact of sedentary behaviour—and it turns out, sitting for long periods takes a toll on everyone’s circulation.
Lead author Dr. Ryan Garten and colleagues recruited 20 healthy individuals to participate in the study. Ten of these individuals were untrained and inactive, while ten were aerobically fit and regularly active. Each subject sat in an upright position with their knees bent at a 90 degree angle for a total of 3 hours. The participants were asked to perform a passive leg movement test, involving bending and straightening the legs. During the maneuver, changes in blood flow were measured from the femoral artery in the upper thigh. Measurements were made before sitting, after 1.5 hours, and after 3 hours.
As expected, the prolonged sitting protocol significantly decreased leg blood flow at 1.5 hours and 3 hours in both the untrained and aerobically fit groups. This suggests that regular physical activity doesn’t seem to combat the negative impacts of sitting for long periods of time.
The experiment clearly demonstrated that prolonged sitting can have significant adverse effects on leg blood vessel function. Accordingly, Garten and colleagues recommend taking regular and frequent physical activity breaks throughout the day to keep your circulation going. So if you’re reading this from your office chair, maybe it’s time to sit up, stretch, or hit the stairs!
Read the full study: Aerobic training status does not attenuate prolonged sitting-induced lower limb vascular dysfunction in Applied Physiology, Nutrition, and Metabolism.
