Researchers have solved a longstanding mystery about how flexing muscles “tell” nearby blood vessels that they need more blood to perform, according to a study published Feb. 15 in the journal Circulation Research. The study mechanism suggests new ways to treat conditions that involve poor circulation like peripheral artery disease, which comes with aging, affects 10 million Americans and leads to amputation in the worst cases. Furthermore, the same signals that influence circulation in some tissues drive cell growth elsewhere. That could lead to an ointment that would speed healing when spread across chronic wounds.