From the NY Times:
What is surprising are some early indications that increasing your flexibility might somehow loosen up your arteries, too. That was the accidental and, as yet unreplicated finding of a small 2008 study at the University of Texas at Austin. The study was designed to examine whether weight lifting increased arterial stiffness. (It didn’t, at least on this occasion.) The control group consisted of people who stretched. They were not expected to show any change in cardiac function, but over the course of 13 weeks they in fact increased the pliability of their arteries by more than 20 percent.
Mr. Yamamoto and his colleagues are currently conducting an ambitious study to determine just how and whether stretching directly affects the arteries. The results won’t be available for some time. Until then, Mr. Yamamoto says, it’s best to consider your flexibility (or lack thereof) as a marker of your probable arterial elasticity. “If you can touch your toes in the sit-and-reach test, your flexibility is good,” he says. If you can’t, you might consider talking to your cardiologist — although, remember, as Mr. Yamamoto points out, that tight arteries are not necessarily diseased arteries. They’re just less than ideally fit.