An ultramarathon is any race longer than the 26.2 miles of a standard marathon, and many of them are significantly longer. Some of these are distance races in the conventional sense: you cover a specified distance (say, 50 miles); in others you run for a specified time and the winner is the runner who covers the most distance during that interval. Hundreds of these races take place around the world every year. In 2012, there will even be two in the Antarctic - one of them 250 kilometers long. Some ultramarathons are obstacle courses that take you up steep mountains, through deserts, the Amazon jungle or the Australian Outback. Many are attempted in extremes of humidity and temperature and through wilderness areas where it isn't easy to find medical care if you run (literally) into problems.
A recent study of health concerns that developed in 396 athletes who took part in a 7-day desert ultramarathon race found surprisingly few serious injuries. Even though 85 percent of the runners needed medical care at some point during the race, 95 percent of the problems reported were minor - blisters, swelling, tendonitis or dehydration. The study's lead author, Brian Krabak, M.D., of the University of Washington in Seattle, reported that the majority of people who participate in these races finish without any significant type of injury. Of course, individuals who compete in them are usually in superb shape to start with.
Dr. Krabak's study focused on short-term injuries. We don't have much good information (yet) about the potential for long-term problems in athletes competing over the years in ultramarathons. A study from the Netherlands published in 2007 found that most of the lower extremity injuries found among men who habitually ran more than 40 miles a week affected the knee but that the risk declined by increasing the weekly distance.
If you decide to attempt an ultramarathon, training is key, but so is focus - the intense, single-minded mental discipline you need in order to train and to compete in these events. You can find ultramarathon training plans online for whatever type of race interests you. I've read that most ultramarathon competitors don't run the whole way - they alternate 15 to 20 minutes of running with five minutes of walking.
To avoid dehydration during these events, runners are advised to drink continuously. As long as you have to stop to urinate, you're getting enough water. If you can't urinate or see blood in your urine, seek medical help - you could be en route to dangerous dehydration and kidney damage.
If you're in great shape and well-trained, you probably can get through an ultramarathon without serious injury. But bear in mind that making a habit of running these super-long races could take a toll on your health over time. We just don't know yet what that's likely to be.
Andrew Weil, M.D.