In 1998 I took a climbing trip to the Cordillia Real in Bolivia and was able to climb five peaks ranging in elevation form 17,500 ft to 21,200 ft. I have also run both Wasatch and Leadville, finishing tied for ninth at Leadville. I guess I'm sort of an altitude junkie. This article will try to merge what I know about the two sports and their approaches to "going high".
The body responds in various ways to high elevations (8,000+ ft). Initially your heart rate will increase as will your breathing rate. No surprises here. Your ability to perform maximum work (run) will be diminished by 3% for each 1000 ft over 5000. The key word being maximum. In other words don't push it, even if you feel strong. There are several lethal things that can happen at very high elevations (14,000+ ft) such as Pulmonary Edema and Cerebral Edema, however, the malady that effects ultrarunners at Leadville, Wasatch and other high altitude runs is Acute Mountain Sickness (AMS). The symptoms include severe headache, weakness, loss of appetite, insomnia, shortness of breath and vomiting. Swelling of fingers (rings off) and toes and a hacking cough are often associated with AMS. It can affect people as low as 6,000 ft or not until 14,000 ft. It doesn't matter if you are in top condition, male or female, it tends to affect younger people more than the masters. In short you would rather crawl under a rock and die than run one mile not to mention 100.
But wait, this affliction needn't stop any well conditioned ultra runner from the completion of his duty. The magic word is ACCLIMATIZATION ! The climbers formula is spend a day acclimatizing for every 1,000 ft above 5,000 ft. In other words a minimum of 5 to seven days in Leadville should help. If you have time drive to the race. This way you can add a few thousand feet at a time instead of suddenly sleeping at 10,000. Don't attempt to train when you first arrive at high elevation ! Your body is going through enough stress already. Put your feet up, rest, and "hang out". I usually feel very uncomfortable the first few days and then I'm able to run some. Climbers have a rule "to climb high and sleep low". This puts some stress on the body, but gives it the rest it needs at night. In other words, take a walk up Hope Pass, sleep in Leadville.
I know some of you can't take the time off to stay a week or more in the mountains before the race. There is hope for you too. I find that training at high elevations is a benefit. Please understand that you are acclimatizing of you train high once a week and return to low elevations for the rest of the week. However, it does help you to adjust to the mountain environment and gives practice in dealing with the physiological stress of elevation as well as with the intense sun, sudden storms, and poor footing. realize that your pace must be slower than in other races. Know how to power walk the hills and be aware that AMS will certainly catch you if you become dehydrated. The thin mountain air is very dry and you will lose water with each breath, even if you never sweat an ounce.
Pressure breathing helps to expel residual air (carbon dioxide) form the lungs and thus increase the intake of oxygen. Purse your lips and release your breath with an audible "whew". You may sound strange as you pass other runners, but you will pass them. I don't pressure breath all race, but when my breathing becomes shallow and rapid it sure helps.
You don't need to be acclimatized for the 12,600 ft Hope Pass because it takes about four hours to develop AMS at a specific altitude. If you are having altitude difficulty up there don't stay at the Hope Pass Aid station. Get off the mountain! By the time your body realizes you're at that elevation you should be down the other side. This is how modern alpine style climbers reach great heights in short amounts of time without bottled oxygen.
Some climbers and I suspect some runners take the drug Diamox to prevent or lessen the affects of AMS. The jury is still out on this one. I did use it at 20,000 ft and found the side effects a problem. I wouldn't suggest using it while running a race. I found that Motrin knocked out the altitude headache. Some runners take oxygen (unfair advantage?) during their events. While O2 may help to clear a foggy min, it will not prevent AMS. High altitude is more than lack of oxygen. If it were just that, you could train by stuffing a sock in your mouth.
In summary, high elevation endurance events are great challenges to the body and the mind. Acclimatize if you can. If not, run smart, hydrate, pressure breath, and enjoy the scenery. An excellent source of information on altitude is the book, Going Higher, by Charles S. Houston, MD published by little Brown and Company.