There are a growing number of individuals becoming involved in endurance sports including marathons and triathlons. There are also a growing number of reports among this population presenting with life threatening blood clots. Beth Parker has done extensive research on this population of athletes after competition. However, it should be known that risk for a blood clot may occur during training and not solely after a strenuous endurance event.

Deep vein thrombosis (DVT) can be defined as a blood clot in a major vein that usually develops in the legs and/or pelvis. It is estimated that DVT affects 117 per 100,000 people each year. This number does not account for the cases that go undetected or resolve on its own. If left untreated, the DVT can evolve into a pulmonary embolism (PE) which is a life threatening condition. A pulmonary embolism occurs when the blood clot breaks off and travels through the circulatory system into an artery causing a blockage. DVT is commonly associated with the elderly population or individuals with cancer, chronic illnesses, or a post operative status. However, endurance athletes are exposed to many physical factors that contribute to DVT including: repetitive microtrauma, cell injury, dehydration, and periods of immobility for recovery following an athletic event.

Many case studies have been published that report DVT and pulmonary embolism in athletes following strenuous physical activity. For example, a female triathlete traveled 5 hours by car the morning after competing in a half ironman triathlon and was diagnosed with DVT and PE 3 weeks after her race. Two male marathon runners were diagnosed with DVT 1 week after the race in which both cases were initially misdiagnosed. Other self reports and articles detail cases of an Olympic cross-country skier, a triathlete competing in the US National Track Championships who drove 9 hours home, and a recreational bicyclist who all suffered from DVT. The diagnosis for each of these athletes was initially overlooked due to the assumption that these individuals were young and healthy. Medical professionals often contribute the symptoms of endurance athletes to the musculoskeletal system following strenuous physical exertion with no consideration to the circulatory system.

There are many additional risk factors for DVT that may affect healthy athletic individuals after extended physical activity. The use of oral contraceptives and genetic clotting disorders may increase risk for blood clots in athletes. Slower blood flow associated with lower heart rate and higher venous compression due to muscle hypertrophy result in increased venous stasis. Traveling and prolonged periods of immobility following athletic competition may shift hemostatic balance. Many athletes travel to participate in events and must catch flights soon after competition to get back home which also presents risk for DVT. All of these are examples of contributing risk factors for DVT among a healthy athletic population.  

Avid exercisers and competitive athletes are considered to be healthy, thereby, increasing the potential for misdiagnosis or lag in diagnosis for a blood clot. Physicians and medical professionals should become more familiar with risk factors for DVT relative to this active population. In addition, medical professionals, sports participants, and coaches must understand prevention of DVT after competition. Prevention includes avoiding long periods of immobility after strenuous activity and active recovery. If you must fly soon after an endurance event, be sure to remain hydrated, avoid crossing your legs, and perform leg exercises hourly. In order to reduce occurrences of DVT and PE in a healthy and active population, medical professionals and sports participants must be educated and guidelines must be developed for prevention.