Travel Risks for Endurance Athletes: Or How Being Healty Can Kill You

One of the benefits of being the editor of my triathlon club’s newsletter is that some great material comes across my (virtual) desk. One of our members, Dr. Al Delaney, is both an MD and a scientist. He also runs a practice ‘Rehab to Racing‘ with his wife Mary which is aimed at rehabilitating injured athletes so they can get back to competition.  Al wrote an article for the September 2007 TriCATs newsletter that I am reproducing here. As someone who travels for a living, it has important advice which all endurance athletes – even duffers like me – need to be aware of. I for one am taking aspirin before my flights.

As an endurance athlete you experience many benefits of your good health. Good diet and endurance exercise significantly improve your chances of surviving a heart attack and almost surely reduce the chance that you will ever have one. Endurance athletes generally have far fewer deaths from what the statisticians call “all cause” reasons. If you are a woman you may well have a lower risk of developing breast cancer. You can get your daily legal high from the regular endorphin release during endurance exercise. Your joints will probably last just as long as those of couch potatoes, and you are much less likely to need prolonged nursing home care prior to departing this world.However, air, train, and car trips may expose you to excessive risks of blood clots that are practically unknown and unexpected by your doctors and certainly are off your radar screen from a health risk perspective!

Just the fact that you are an endurance athlete means you have a increased risk of developing blood clots when you travel and recent competition even further increases your risk.

Traveling in planes exposes us to reduced air pressures equivalent to 6,000 to 8,000+ feet of elevation. Humidity levels are kept low to decrease costs and to prevent condensation and the corrosive destruction of the aircraft skin and structure. (Moisture condensing on the aluminum parts cooled by the -70 temps outside at 37,000 feet causes this.)

We spend much of our flight time seated with our legs in a dependent position. Literature research suggests that the net result of these environmental and low activity patterns of modern jet travel is an increase in the incidence of Deep Vein Thrombosis or DVT. DVT is the abnormal formation of clots in your veins, usually in the leg or pelvic veins. The incidence of DVT after airplane travel is also increased over what we would expect by simply sitting for the same period of time say in a movie theater for reasons that are largely unexplained by science at this point. (see


However, when we put this science together with some incidence data from other sources, it appears that endurance athletes may suffer increased risk compared to the general population that is largely unreported. One study suggests that as much as 3/4 of all DVT and Pulmonary Embolism or PE in air travelers, without other known risk factors, occurs in endurance athletes. A PE occurs when a blood clot, usually from your legs or pelvis, busts loose and travels north only to get stuck in your lungs, obstructing blood flow and oxygen transport. If the clot is large enough, it may block the blood flow through your lungs. That may really shorten your racing season as it may be your last day.Endurance athletes have expanded blood volumes and slow resting heart rates. This is part of the physiological adaptation that allows the massive increases in oxygen delivery to your muscles that allows you to train and race. You can increase your cardiac output to several times the maximum that an untrained individual can sustain. We do this for hours and even call it fun. However, when we get on a plane, and sit in our seats, we then have slower blood flow velocities in our veins, and even if we are not returning from a race may have an increased risk of clot formation due to this by-product of our good health. 

After racing, especially if we race long and hard (i.e. long or ultradistance), our risk of clotting is increased by the blood vessel and muscle damage and enhanced tendency of the blood to clot caused by the stress of racing. Steve Lehman’s story of DVT and PE after winning a national Pursuit championship in the 55-59 age group in 2005 doesn’t involve air travel, just a long car trip after racing, but illustrates the hazard. Long trips of any kind after racing pose increased risk.


You can educate yourself more about risks of DVT and PE at:

Clearly, the longer your trip, the greater the risk. Also, in the first several days after long, intense competition, endurance athletes may be at increased risk of DVT due to increased tendency of the blood to clot. Some data suggest that the risk is much higher than commonly believed by physicians. Many cases may go undetected. Asymptomatic DVT may go undetected unless the clot breaks loose and becomes a pulmonary embolism. You may think you have just sore muscles from racing, or you may have no symptoms at all.


There is little data to help you decide what to do. We can gain some information from medical practice, where strategies have been developed to help reduce the risks of DVT and PE in medical and surgical patients.


See the following article from New Zealand to open your eyes on this subject: The information is good, but the author is biased toward nutritional supplements. His recommendation about wearing graduated compression hose or socks is probably valid as a preventative strategy, and has been shown in medical tests to have preventative value.

The medical community also recognizes some risk factors unrelated to endurance athletics. Those risks include:


q       Prior episode of DVT or PE

q       Taking birth control pills, especially when combined with smoking

q       Females taking hormone replacement therapy (HRT)

q       Genetic problems associated with increased tendency of the blood to clot

q       Travel during late pregnancy.

q       Some post-surgical patients, especially with total hip replacement (as many as a third or more of these patients may have a post-op clot if untreated. Medical standards dictate that some form of serious blood thinner be used routinely in these total joint replacement patients.)


So, don’t get your tri shorts in a tight wad just quite yet as there are some common sense things to do to reduce your risks. As a physician, I became very interested in this subject after suffering a PE from a completely asymptomatic DVT while racing in Sweden in 2004.


I probably developed the DVT during the 14 hours/ two plane flights it took to travel from the USA. My only predisposing factor was that I was an endurance athlete. The PE was accompanied by acute localized chest pain, marked shortness of breath, coughing up bright red blood, increased heart rate, and a dramatic drop in exercise performance that persisted for hours. My research suggests the following things can be done to reduce your risks of this very bad complication of simply being healthy.Common sense DVT and PE risk reduction strategies while traveling: 

q       Avoid dehydration: The adage to drink plenty of water may be misplaced as at least one study suggests that water drinkers in planes actually have an increased tendency toward clotting compared with those drinking an electrolyte replacement drink. (this one reinforces my biases – water is best poured over one’s head for its cooling effect. Your electrolyte replacement beverage is now for drinking while training, racing AND traveling).


q       Move about often while travelling: Walk about your plane or train periodically. If you are driving, get out once an hour and walk about for several minutes. Exercise your legs in place while seated at least once an hour.


q       Get an aisle seat: In one of the articles referenced below, there was no incidence of DVT in any subjects sitting in an aisle seat.


q       Consider graduated low leg compression socks: Some professional sports teams regularly use these during travel. This is especially important if your journey lasts longer than 2-3 hours.


q       Think about low risk blood thinners if you have no risk factors: There are a number of ways to reduce platelet adhesiveness including red wine, aspirin, niacin, and tea. If none of these bother your stomach, the risk factors of using one or more is negligible. Note that these strategies do not necessarily reduce DVT or PE in high risk individuals.


q       Take medical blood thinners when traveling if you have risk factors: As an athlete setting out to perform an inherently hazardous activity by practicing or competing in a triathlon or road race, you cannot afford to have really thin blood while competing or training. A minor accident while your blood is thinned by drugs could turn into a disaster for you as your blood would not clot normally. Thus, your only real choice of a real blood thinner is heparin. This drug has a short enough half-life (the time it takes to clear out of your system) that you can take it in the morning on your travel day and be free of it the day after.


q       Take medical blood thinners if you are traveling and have NO risk factors: Here I may be a medical outlaw, as many physicians would not support this policy. The real medical controversy is whether or not blood thinners are indicated if your only risk factor is that you’re traveling to a race or traveling home the day after your long distance race.


Endurance athletes haven’t been studied as a group to look at the risks of DVT and PE in travel. However, the evidence makes a good argument that the risk is very real and it’s something you should think about. Your post-competition increase in risk is even higher but probably abates after several days, so tacking on three or four vacation days at the end of a big race probably has some health benefits that aren’t immediately apparent.


I personally take heparin on trips longer that 2+ hours and drive seat mates and plane crews crazy with how much I move around the plane and how often I want to stop the car and  walk around, since I try to get out of the car and walk around for 5 minutes  every hour when driving. Trains are easy due to the amount of space in the aisles for walking about.


See the link below for a study looking at the positive value of one dose of heparin prior to long air travel. Note that other studies have found blood clots on much shorter flights: you, the reader, get your chamois in a knot about the idea of injecting yourself with a syringe before each trip, trust me – it is easy. As a lifelong needle-phobic red blooded American male, even I have no problem with modern syringes made for insulin use. The needle is microscopic, and absolutely doesn’t hurt! I figured that if I could do an ultra distance race, I could get up the nerve to inject myself. After the first time when I nearly passed out, I thought…..”Whew what a fool I am, I didn’t even feel that!”

It is a no-sweat deal now, and I know I’ll have a better chance of being “the last man standing,” as Jimmy Buffett’s song says, when I am continuing to race years from now. I figure if I can just live long enough, I may win a few races in the 90-94 age group!



2 responses to “Travel Risks for Endurance Athletes: Or How Being Healty Can Kill You

  1. Wow! Having HBP problems, getting under control. But (up to struggling with the medicines, and perhaps some thyroid problems, as of 2 weeks ago, a 6-9 hour per week biker, skater, Xcountry skier.

    Going on a plane trip late Nov. GLAD I READ THIS!

    Mark H. Mpls, MN

  2. If you’re curious to know what kind of healthy foods that are not boring, mild example would be a very low fat brownie. Yes, you can eat candy, as long as health and prepared with less sugar and fat. If you’ve heard of quinoa, the super grain of the Incas took their health can also be cooked and an excellent supplement to your diet!

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