My interest in this area of research began when my sister suffered a deep vein thrombosis (DVT, a blood clot in one of the deep veins of the leg) following the combination of doing a long run with me in Connecticut and then later flying home to Seattle. Blood clots are extremely rare in healthy younger adults, and I immediately set out researching possible causes (out of self-interest, predominantly. Could it happen to me?) Endurance exercise alone does not increase the risk of blood clot formation, as both clot formation and clot breakdown are augmented with exercise such that hemostatic balance is maintained. However, since air travel approximately doubles the risk of DVT, I wondered whether the combination of sustained endurance exercise AND air travel could predispose an otherwise healthy athlete to blood clots. At the time, there were several case studies depicting exactly such a phenomenon in triathletes and runners, but no rigorous study data.
Consequently, since 2010, our group has conducted field research at the Boston Marathon and Hartford Marathon to better understand factors underlying venous thromboembolism in otherwise healthy athletes.