Racing at high altitude: a myth exposedAugust 27, 2007
My friend Henry Wigglesworth said the following in a recent email:
I just got back from New Mexico, where I had a disappointing race at the La Luz Trail Run. I was 90 seconds slower that last year, which is not a lot (1:43:03 vs. 1:41:33), but I frankly thought I was in a little better shape. Also, after the race this year, I felt like crap for about two hours. The main difference I can point to is that this year, I only had 18 hours to get used to the elevation change whereas last year (and the year before when I ran 1:36), I had 4 days. I know that the conventional wisdom is that it takes about 2-3 weeks to acclimate, and if you don’t have that amount of time (i.e., you have a job), then the best thing is to arrive the day before a race. But in my case, that did not seem to be true. I would love to hear your thoughts on this topic, since I know (along with the many well-intentioned volunteers at Western States) that you have a Ph.D. in physiology.
Henry, the conventional wisdom is not especially wise in this case. A close inspection of the relevant data suggests a very simple rule: the more acclimation time, the better. Yes, two to three weeks of preparation at altitude can be very helpful (and four to eight weeks is even better), but if you can’t get out to the race site weeks in advance, four days of acclimation is probably better than one.
The questionable “arrive right before the race” advice arose from an interesting observation made back in the 1960s by David Dill and his colleagues. Dill et al. found that, if someone was put in a low-oxygen chamber and immediately subjected to a VO2max test on a bicycle ergometer, he or she performed better than if transported to high altitude (with oxygen levels equivalent to those in the chamber) and given the same VO2max test after a couple of days there (Journal of Applied Physiology 21: 1168, 1966; Journal of Applied Physiology 23: 555, 1967; JAMA 205: 747, 1968).
Dill concluded that a gradual decline in exercise capacity takes place during the first two to three days of residence at altitude. This conclusion led to the recommendation that athletes should arrive at a high-altitude race shortly before it starts — that is, before the body suffers through its two- to three-day decline.
Dill never proved that performance is worse after two days at altitude than after, say, a few hours. However, his assumption of a gradual multi-day decline went largely unchallenged until a 2001 report by Adele Weston and coworkers (Medicine and Science in Sports and Exercise 33: 298, 2001). The subjects of this study performed various exercise tests 6, 18, and 47 hours after reaching an altitude of 5600 feet; they did significantly better after 18 or 47 hours than after 6 hours. A subsequent study (Burtscher et al., International Journal of Sports Medicine 27: 629, 2006) found that cyclists fared better in a 50-minute time trial at 10,500 feet when they had 45 hours of exposure to high altitude, rather than two hours.
Do these two papers give us the final, infallible word on high-altitude racing? No, of course not. But they do suggest that endurance performance bottoms out within the first few hours of arrival at altitude and then improves steadily after that. In other words, the more pre-race time you are able to log at altitude, the more success you are likely to have.
Better luck next year, Henry!