Does the thought London’s red double-decker buses make you want to move around to prevent endothelial dysfunction and slow arterial aging?
In 1953, a landmark study of London bus crews found that bus drivers, who sat at the wheel all day, developed coronary artery disease at a younger age and more often than the conductors of the same buses, who moved around assisting passengers throughout the day. This pioneering study, and more tightly controlled studies that followed, revealed how crucial activity is to keep arteries young and healthy. Ample evidence now exists that suggests the sensitive lining of your blood vessels, the endothelium, may be what connects your activity level to your artery health.
Endothelial Function Influences How Fast Your Arteries Age
Arteries gradually develop plaque (i.e., clog) and stiffen as they age leading to cardiovascular diseases like coronary artery disease, hypertension, heart failure and even stroke. The rate at which arteries age is not constant and is strongly influenced by the health of the endothelial cells in your arteries. When healthy, the endothelium releases substances that dilate blood vessels, increase blood flow and inhibit plaque and clot formation. When the endothelium is unhealthy or dysfunctional, fewer dilators are released, blood flow is reduced, and plaque and clot formation are accelerated. This unhealthy condition is often called “Endothelial Dysfunction“.
Researchers use ultrasound and other imaging techniques to measure how well the endothelium can increase artery diameter and blood flow. We have demonstrated that endothelial dysfunction, even if observed in the arms or legs, is associated with coronary artery dysfunction, increased plaque deposition, hypertension, reduced exercise blood flow and even a low V̇O2MAX. In short, endothelial dysfunction is a marker of accelerated arterial aging.
Inactivity Induces Endothelial Dysfunction and Accelerates Arterial Aging
It is probably not a surprise that those who are chronically sedentary often have endothelial dysfunction. However, recent studies from scientists across the world indicate that even short-term inactivity elicits periods of endothelial dysfunction. My team recently found that 10 days of leg immobilization and reduced activity induces significant endothelial dysfunction. Several other groups have found that as little as 3 hours of sitting temporarily induces endothelial dysfunction resulting in periods of accelerating arterial aging. Being exposed to such periods of inactivity-induced endothelial dysfunction day after day may be why the London bus drivers had greater rates of arterial disease.
Just a Little Bit of Movement May Prevent Inactivity-Induced Endothelial Dysfunction
Just as minimal activity protected the arteries of the bus conductors, very little activity seems to be necessary to mitigate the negative impact of inactivity on endothelial function. Simply getting up and doing some air squats or just fidgeting your legs has been shown to prevent inactivity-induced endothelial dysfunction. This may explain why the little activity performed by the bus conductors was enough to reduce cardiovascular risk. In cases of immobilization, where exercise is not an option, we found that simply raising muscle temperature to exercise-like levels is enough to prevent endothelial dysfunction.
Exercise Training to Improve Endothelial Function and Slow Arterial Aging
Lifelong exercisers typically have greater endothelial function and lower incidence of cardiovascular disease than their sedentary counterparts. Many studies have found that exercise training can significantly improve endothelial function in previously sedentary people. Overall, endurance training is more proven than strength training, but research is still ongoing. With aerobic training, intensity may be important. Several studies indicate that aerobic high-intensity-interval training (HIIT) improves endothelial function to a greater extent than an equal volume of moderate intensity aerobic training. In cases where exercise is not possible, it has been found that heat stress, like sauna or hot tub, can improve endothelial function nearly as much as endurance training.
Conclusion
Seventy years since the London Bus Study, we can say with more confidence than ever that inactivity accelerates and exercise slows down arterial aging, partially through endothelial health. So, next time you see one of those double-decker buses, think of your endothelial cells and get up and move. Your arteries will thank you.
Jayson Gifford, PhD, is an associate professor of exercise science at Brigham Young University and has been a proud member of the ACSM for many years. He completed his PhD in cardiovascular exercise physiology and post-doctoral training in geriatrics at the University of Utah and Salt Lake Veteran’s Hospital. His research focuses on cardiometabolic causes of exercise intolerance and the effect of (in)activity on cardiovascular health. When not in the laboratory with his students, you can probably find him hiking through the mountains of Utah with his wife, kids and chihuahua.
