Many runners probably think that because they’re so active a blood clot would be the least of their worries. While partly true, it can actually increase your risk in some cases. The following article by Coach Jenny describes why this
I’ve written a few columns about my experience with venous thromboembolism (VTE)—that is, blood clots—and in response, I’ve received countless questions about the risks specific to runners, the symptoms to watch for, and the recovery process.
Source: A Doctor’s Take on Runners and Blood Clots