The Evidence-Based Clinical Practice Guidelines from the American College of Chest Physicians suggests the use of properly fitted compression socks to mitigate blood clot risk in high-risk populations. The use of compression socks, or mechanical prophylaxis, to maintain hemostatic balance has been studied with participants at rest and has been shown to be effective in reducing VTE in some clinical populations (eg, patients with a previous history of DVT or recent surgery). Although these informal (albeit common-sense) recommendations are grounded in evidence derived from clinical populations, the efficacy of compression socks to attenuate marathon-induced hemostatic activation has been tested only recently.
With funding from Hartford Hospital, our group examined the safety and efficacy of compression socks worn during a marathon on hemostatic activation immediately following the 2013 Hartford Marathon in Connecticut. These results have been published in the journal Physician and Sportsmedicine. Briefly, we randomly assigned 20 runners to a compression sock group or a control group at the initial screening.We measured markers of clot formation and clot breakdown the day before, immediately after, and the day following the marathon and found that overall hemostatic activation following a marathon was lower with compression socks than with typical athletic socks. Most importantly, compression socks did not appear to adversely influence markers of clot formation during a marathon and thus they appear safe for overall use in runners.
We caution that there is a need for larger studies, especially in combination with other risk factors (eg, oral contraceptive use, prolonged travel, and genetic predisposition for VTE). However, given that prolonged travel (greater than four hours) activates the coagulatory system, and many marathoners travel long distances to an event, the use of compression socks as a preventive measure should be considered, assuming they are tolerable and properly fitted. Although further research is needed, common sense preventive measures such as compression socks are readily available. A few key points to consider, include:
- Normally, muscle movement in our legs act as a pump to direct the blood in our legs back up to the heart. However, during periods of prolonged restricted rest (such as a travel), there is less movement and more opportunity for blood to collect and pool in our lower legs and feet. Sitting in one position for too long can also constrict our blood vessels. This increase in venous pressure causes fluid to leak into our surrounding tissues resulting in swelling and pain or edema.
- Graduated compression socks act as an external pump to help squeeze or “milk” blood flow up the leg and back towards the heart. The pressure is “graduated” meaning that the pressure is tightest at the ankle and loosest at the knee. This pressure gradient helps increase blood flow velocity and clear fluid waste from the lower extremities by reducing tissue swelling space.
- There are no known risks of wearing compression socks so long as they are properly fitted. They should feel snug, but never painful. To ensure a proper fit, always size according to calf circumference (as opposed to shoe size). This will ensure that socks are not too tight, which can be harmful.
- Be weary of manufacturer claims and make sure that you are spending your money on the real deal. They should be “graduated” meaning that the pressure is tightest at the ankle and loosest at the knee. Most compression pressures will range from 15-20 mmHg or 20-30 mmHg. If you have had a recent blood clot or have a prescription for medical grade compression socks, the pressure might be even higher.
- When searching, you might come across compression “sleeves”, which are a footless alternative to compression socks. However, the elastic band on the bottom of the sleeve may promote swelling and pooling below the band and cause more harm than good.
- Although rare, certain fabrics and materials in compression socks can be a source of unknown allergic reaction (i.e., contact dermatitis) for some. Many individuals also find compression socks to be very uncomfortable, hot, and/or itchy in warmer environments.
Additional Common Sense Recommendations During Travel to/from An Endurance Event
- Wear loose fitting clothing and adjustable shoes
- Make use of cabin overheads to leave yourself plenty of leg room
- Pass on the salty food, which can contribute to water retention
- Exercise: Take a short walk every hour or so. Rotate ankles, point toes, and flex calves while seated. Elevate feet whenever possible
- Drink plenty of water to prevent dehydration—drinking lots of fluids can serve as a natural “alarm clock” to ensure you get up and “go” every so often!
- Avoid excessive alcohol consumption, which can contribute to dehydration and/or result in sitting in one position for too long
- Be cautious of sleep sedatives, which can result in sitting in one position for too long
- Certain individuals (i.e., previous history of VTE, acute injury) may consider prophylactic use of nonsteroidal anti-inflammatories, baby aspirin, or blood thinner only after careful appraisal of risk by a clinician
- Discuss family history and risks and benefits of prescription and over the counter medications with your clinician