Introduction 

Thrombosis is a condition in which clots form in the blood vessels, which restricts blood flow. There are multiple predisposing factors for developing thrombosis, which are: damage to the endothelial lining of the vessel wall, inflammatory factors, trauma to the vessel from surgery, arterial blood stasis and hypercoagulable states.¹ These causes will be explored later in this article. Exercise can affect the hemostatic system through a temporary increase in fibrinolytic activity ( occurs after vigorous sport to reduce the risk of clot formation), platelet aggregation ( acute intense exercise may increase platelet aggregation temporarily ) and blood coagulation ( can be impacted by Vitamin K deficiency and dehydration). Whilst athletes generally posess excellent fitness, they are also at risk of developing thrombosis. This is due to dehydration, prolonged immobility, trauma, compression gear, as a result of underlying conditions and/or overtraining. In this article, we will explore the causes and risk factors of thrombosis in physically active individuals.

Understanding thrombosis 

Thrombosis occurs when a blood clot forms in a vein or artery, blocking normal blood flow. This can cause serious complications of varying severity depending on its location. This includes deep vein thrombosis (DVT), pulmonary embolisms (PEs) and heart attacks. They are significant risk factors for many forms of thromboembolism if untreated and can result in complications or death. The two primary forms of thrombosis are Venous thrombosis and Arterial thrombosis.

Venous thrombosis occurs when a clot forms in a vein, usually deep in the legs, causing a deep vein thrombosis (DVT). Suppose a portion of the clot breaks free and travels to the lungs. It will cause a pulmonary embolism (PE), which is a life-threatening situation accompanied by difficulty in gas exchange because of the clot that is blocking the lung.⁴

Compared to venous thrombosis, which is frequently caused by slow blood flow, arterial thrombosis tends to be associated with high cholesterol and vessel damage, a condition known as "atherosclerosis”. In coronary arteries, it leads to a heart attack, also known as myocardial infarction, where patients can develop heart disease as a result of multiple heart attacks, as pieces of heart tissue become permanently damaged. This blockage caused by the clot formation must be present for longer than a couple of hours before it can develop into either an embolism or septic embolus. They are both life-threatening conditions where pieces of the clot travel through the bloodstream to other parts of the body and cause further inflammation.

Causes of thrombosis in athletes 

Despite that athletes have excellent physical fitness, they may still suffer from thromboembolism. 

This is largely due to factors that are unique to intensive training and competitions, which may contribute to an increased risk of thrombus formation:

Dehydration

Athletes can lose a significant amount of fluid through sweating, particularly during intense training or competition. When the body is dehydrated, blood thickness increases and is more likely to form a clot, which is made worse by insufficient fluid intake.

Blood stasis (reduced blood flow)

After intense exercise, if you stay still for a long time, your blood circulation can slow down. This slower flow increases the chance of forming blood clots. Long periods of inactivity, like sitting on a long flight or in a car for many hours, create the perfect conditions for a dangerous condition called deep vein thrombosis (DVT).² Even activities like biking help keep blood moving because the muscles in your legs contract and push blood through the veins, which is known as the skeletal-muscle pump. But when you sit still without moving your leg muscles, blood flow slows, raising the risk of clots and possible tissue damage.²

Trauma or injury

Athletes frequently suffer from injuries, which increase their susceptibility to thrombosis. Trauma to blood vessels, muscles and bones (e.g., fractures, severe sprains) results in inflammation and subsequent clot formation. Surgical procedures required to repair sports injuries and their subsequent immobilisation may also heighten the risk.

Excessive endurance exercise and overtraining

Regular exercise usually supports heart health, but too much endurance training or overtraining can result in increased blood clotting factors. Intense physical stress can also throw off the body’s normal anticoagulant mechanisms, leading to a higher chance of embolism, especially in endurance athletes.²

Performance-enhancing substances and drugs

Some athletes use anabolic steroids, hormone therapy or another form of performance-enhancing drugs to help them build strong muscles or perform better at athletic events. Some women who use oral contraceptives may also have a higher risk of blood clots, especially if they are using them with other risk factors such as dehydration or if they are not moving around much.² Furthermore, tobacco may be one of the possible postulated factors in the etiopathogenesis of vascular thrombosis.²

These were just some of the possible causes of thrombosis in athletes, and the potential symptoms to look out for will be discussed in the next section.

Recognising the symptoms of thrombosis in athletes 

Different thrombosis types present different symptoms, which is key to receiving the correct treatment :

1. Signs of deep vein blood clots (DVT)

• Swelling, often in one leg
• Pain, red colour, and heat in the leg with the problem
• A heavy or tight feeling in the leg⁹

2. Signs of pulmonary embolism (PE)

• Quick loss of breath
• Pain in the chest, more so when you take deep breaths
• Fast heartbeat and feeling dizzy
• Chest palpitations
• Blood being coughed up
• Sweating¹⁰

3. Signs of arterial thrombosis

• A cold, numb, or light limb   
• Feeling weak or having  stroke-like signs
• Angina
• Heart attack¹¹

 Athletes with any of these aforementioned signs would need to seek out medical help in order to guarantee  a swift recovery. 

Prevention and risk reduction strategies for athletes 

There are several methods athletes can use to prevent developing thrombosis. Drinking enough water is key to keeping blood thin and stopping clots from forming. Athletes should drink good amounts of water before, during, and after working out to keep blood from getting thick and eat foods that are good for the heart and stop swelling, like omega-3 fats, dark leafy veggies, and full grains.¹²

 Long periods of inactivity, be it while travelling or after working out, may increase your risk of blood clots. To cut down on this, athletes should avoid sitting for long periods of time whilst cooling down from intense exercise and do stretches before and after to maintain a good blood flow.¹² Another suggestion is to wear compression gear to help move blood in that affected area.¹² If an athlete has a family history of cardiovascular problems, it is advisable to have routine cardiovascular assessments.¹² Certain medications ( birth control as an example) and performance-enhancing drugs can cause blood clots, and athletes should be made aware by a medical professional as to what the repercussions or side effects are of taking these.¹² 

Summary

While thrombosis is a condition that is usually associated with more sedentary lifestyles, it's also a concern for athletes as other factors can come into play, such as dehydration, prolonged immobility, trauma and overtraining that can increase the chance of clot formation. Proper hydration, a balanced diet, regular movement, and compression therapy can help prevent venous thromboembolism. It is recommended to perform a full health evaluation in order to identify the health condition and maximise health. Substances and medications could be controlled during training periods, which trainees would have to be informed of during this period.