Athletes and Blood Clots

Pitcher Baseball PlayerHealthcare providers may delay or miss blood clot diagnoses, including deep vein thrombosis (DVT) and pulmonary embolism (PE), among athletes who exhibit classic symptoms.


Because healthcare providers often do not consider blood clots something that affects athletes. Blood clots are uncommon in young, healthy individuals – and most athletes are young and healthy. So, for that reason, DVT, PE, and arterial clots in athletes are not the norm.

To understand how this problems affects athletes and the health professionals who treat athletes, you must first understand blood clot terminology. Your body is composed of an endless tunnel of arteries and veins through which blood flows throughout the body. Arteries are the blood vessels that carry the blood from the heart into the outside of the body: the brain, the internal organs, the legs, and the arms. Clots in an arteries lead to stroke, heart attack, or limb-threatening peripheral arterial clots, causing a painful, cold, and pale arm or leg.

Many people think of blood clots as a problem that occurs  in elderly people and not in young and apparently healthy individuals. Symptoms may, therefore, be misinterpreted as something less serious. Especially in athletes, healthcare providers often interpret the leg symptoms from DVTs as “muscle tear,” a “Charlie horse,” a “twisted ankle,” or shin splints. Chest symptoms from PE are often attributed to a pulled muscle, costochondritis (inflammation of the joint between ribs and breast bone), bronchitis, asthma, or a “touch of pneumonia.”

Veins carry blood back to the heart from the rest of your body. Clots in the deep veins of the legs, arms, pelvis, abdomen, or around the brain are called deep vein thrombosis (DVT). If a piece of the clot breaks off from a leg or arm and travels to the lung, it can cause a clot in the lung. A clot in the lung is called a Pulmonary Embolism or PE. A PE can be a life threatening medical emergency. You need to seek immediate medical attention if you have symptoms of a PE.

Athlete-Specific Risk Factors for Clots

Being apparently healthy and being an athlete does not prevent a person from developing blood clots. Several circumstances put the athlete, as well as the non-athlete, at increased risk for DVT and PE (table 2). Athletes, coaches and trainers should be particularly aware of these risk factors.

  • Traveling long distances to and from a sports competition (by plane, bus, or car);Close up of male basketball athlete gripping the ball
  • Dehydration (during and after a strenuous sporting event);
  • Significant trauma;
  • Immobilization (brace or cast);
  • Bone fracture or major surgery;
  • Birth control pills and patch, pregnancy, hormone replacement therapy;
  • Family history of DVT or PE;
  • Presence of an inherited or acquired clotting disorder (Factor V Leiden, prothrombin
    20210 mutation, antiphospholipid antibodies, and others);
  • Presence of a congenital abnormality of the anatomy of the veins;
  • May-Thurner Syndrome (narrowing of the major left pelvic vein);
  • Narrowing or absence of the inferior vena cava (the main vein in the abdomen);
  • Cervical rib causing thoracic outlet obstruction

Black referee calling time out or a technical foulTime Out:  Recent Studies Show Important Trends

Recently, two studies have evaluated the risk for blood clots associated with Marathon or endurance athletes. These studies, conducted by Claire Hull, PhD, and her colleagues in the United Kingdom, appear below.

Hull and Harris (2013)_Circulation (2)

Hull et al. (2014)_Scand J SMS

Also, several high profile athletes have been struck by blood clots recently, heightening attention of the potential risk for blood clots among athletes.  Read more here.

Go on Offense:  Know the Risk Factors for DVT and PE in Athletes

The most common clots occurring in athletes are DVTs of the leg and PE.  In addition to the potential risk factors for athletes and non-athletes outlined above, there exist a few unique risk factors that predispose younger people and athletes to DVT and PE include Thoracic Outlet Syndrome or Effort Thrombosis, May-Thurner Syndrome, and Congenital Absence or Malformation of the Vena Cava:

  • Thoracic Outlet Obstruction or Effort Thrombosis.  In some individuals an extra (cervical) rib or excess muscle or tendon tissue compresses the big vein in the upper chest (subclavian vein) that drains the blood from your arm. This compression typically gets worse when you lift your arm up. This obstruction, often combined with repeated trauma to your vein (from throwing activities, weight-lifting, or gymnastics maneuvers), may cause a DVT to form in this area, extending into your arm veins. This is called “effort thrombosis” or “thoracic outlet obstruction/syndrome.” If the DVT resolves, for example, after clot buster treatment, you may need a resection of the extra rib or the excess tissue to increase space in the thoracic outlet.
  • May-Thurner Syndrome. This is a common congenital anatomic or mechanical variation that predisposes you to DVTs in the left leg. DVTs form with May-Thurner Syndrome when the main left pelvic vein is compressed by the overlying main right pelvic artery. This increases the risk of clot formation at the site of this narrowing in the left pelvis (hip area) with extension of the clot going down into the left leg. If the DVT resolves, for example, after clot buster (thrombolytic) treatment, the narrowing can be opened up by a radiologist with a balloon angioplasty and then kept open by placing a stent (or tube) to keep the site open.
  • Congenital Absence or Malformation of the Vena Cava. Congenital abnormalities of the anatomy of the big vein in the abdomen (vena cava) or pelvic veins can be a cause of DVT in young people. The abnormal anatomy probably leads to disturbed blood flow and an increased risk of clotting.

Get Your Head in the Game:  Recognize Blood Clot Symptoms

Athletic, sporty, muscular, healthy black male running along a road outdoors with a mountain background.It’s important to remain vigilant about the signs and symptoms of blood clots.  These include:

Deep Vein Thrombosis – DVT
  • Swelling, usually in your leg (can also occur in your arm especially in weight-lifters, gymnasts, rowers, etc.)
  • Leg (or arm) pain or tenderness, usually described as a cramp or Charley horse
  • Reddish or bluish skin discoloration
  • Leg warm to touch
Pulmonary Embolism – PE
  • Sudden shortness of breath
  • Chest pain-sharp, stabbing; may get worse with deep breath
  • Rapid heart rate
  • Fainting or passing out
  • Unexplained cough, sometimes with bloody mucus

Treatment Considerations

Treatment decisions for people who have blood clots must be individualized. This is particularly true for young, apparently healthy individuals, such as athletes. In the case of unexplained DVT, testing for an inherited or acquired clotting disorder may be appropriate. When first diagnosed with the DVT, clot busting medication (fibrinolytic or thrombolytic therapy) should be considered to quickly dissolve the clot. However, clot busting treatment has not been systematically studied to determine whether it really decreases the risk for long-term damage to the veins of the leg and arm, i.e. the postthrombotic syndrome.

  • Stephan Moll, MD University of North Carolina, Chapel Hill, NC
  • Edward Libby, MD University of New Mexico, Albuquerque, NM
  • William Roberts, MD University of Minnesota Medical School, Minneapolis, MN

Defense Wins Games:  How to Prevent Blood Clots

  • Take breaks and stretch legs when traveling long distances
  • Stay well hydrated (during and after a strenuous sporting event and travel)
  • Know the symptoms of DVT and PE and seek early medical attention if they occur
  • Realize that DVT and PE can occur in the athlete
  • Know the risk factors for blood clots
  • Know whether you have a family history of blood clots
  • In case of major surgery, trauma, prolonged immobility, or when in a cast: ask your doctor whether you should receive DVT prophylaxis and, if yes, for how long

The Clotting Process

Beautiful girl with a basketballYour body is designed with a natural balance between factors in your blood that cause your blood to clot and other factors that cause your blood to dissolve clots.

Blood clots can occur when:
  • You have an imbalance between the two systems that keep the clotting process in your blood in check; either (A) too much activity of the proteins and blood platelets that form clots (the procoagulant system), or (B) too little activity of the system that dissolves blood clots as they form (the fibrinolytic system);
  • You have trauma to a blood vessel wall, like you might have after a bone fracture or in thoracic outlet obstruction (see discussion below);
  • Your blood return from your arms and legs to your heart is impaired or not functioning properly, like when you sit with your legs bent in a cramped positions for a prolonged period of time;
  • Your blood is “thicker” than usual, which occurs when athletes are dehydrated, using the drug erythropoietin (EPO), or  receiving excessive blood transfusions (blood doping).

Unfortunately, few studies exist that investigate the influence of physical training on blood clot formation and dissolution. So, we don’t know the exact net effect of training on this clotting balance mechanism. We do know, for example, that blood levels of the clotting protein Factor VIII increase with exercise and that the elevation persists during recovery. Theoretically, this could lead to an increased risk of blood clots in athletes. However, data also indicate that the fibrinolytic system that dissolves blood clots is overactive in people who exercise. With this over activity, athletes would be protected from having a blood clot. Yet, we do not know the net effect of these changes in athletes.

You can find a detailed scientific discussion of the coagulation issues relevant to exercise and training in a published review listed as reference 1. However, the conclusions are sparse and vague, because of a lack of data and conflicting results from different studies.

Psychosocial Implications

Athletes need to appreciate that significant deconditioning can occur after a DVT or PE. Depression can also set in after such a life-changing event. This is not surprising, given that athletes often view themselves as healthy and, from a health point of view, invincible, and now suddenly realize that they are vulnerable, sick, and sometimes even disabled. Patient support groups may be helpful in this situation, as may antidepressants.

Selected References for the above article: (More resources below)

El-Sayed MS et al: Exercise and training effects on blood haemostasis in health and disease: an update. Sports Med 2004;34(3):181-200. 

Shrier I, Kahn SR: Effect of physical activity after recent deep venous thrombosis: a cohort study. Medicine and Science in Sports and Exercise 2005;37: 630-634.

Roberts WO, Christie DM: Return to training and competition after deep venous calf thrombosis. Medicine and Science in Sports and Exercise 1992;24:2-

Resources for Athletes

    1. NBCA Sports and Wellness Institute – It is our goal to provide athletes of all levels with a strong support system to help them bounce back and ultimately thrive following a blood clotting event. We are here to help. You have what it takes to join the team, and you can skip the try-outs! This is a team where everyone gets to play, no matter what their experience level may be. Join us today.
    2. Clot Buster – Our friend Roland Varga has an incredibly inspirational blog that follows athletes return to their sport after blood clots.
    3. Venous thrombosis in athletes. (2013) Article from the Journal of the American Academy of Orthopaedic Surgeons. (Abstract only) Authors: Grabowski G, Whiteside WK, Kanwisher M.
    4. Skater Tara Lipinski Speaks Out About DVT (2011) from NIH Medline Plus National Institutes of Health
    5. Venous Thromboembolism and Marathon Athletes (2013) A patient oriented article that discusses why athletes are at risk of blood clots, signs and symptoms of blood clots, and advice to returning athletes From the American Heart Associations’ Circulation Journal


Read Stories of Athletes who have had Blood Clots

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