The thought of racing at altitude often produces an avoidance response from endurance athletes. It's easy to understand; oxygen seems to be at a premium when the road tips up and some people even become sick when traveling to altitude.
Getting physically ill is referred to as acute mountain sickness. Typical AMS symptoms include headaches, nausea, sleep disturbances and an overall lousy feeling. And while not everyone experiences these symptoms, there is no getting around the fact that the density of oxygen in the air decreases in direct proportion to an increase in altitude. In other words, when you take a normal breath of air at altitude, you will have less oxygen in your lungs than you would if you were to take the same breath at sea level.
There are many studies that support the concept of living high and training low. Typically, athletes live and sleep at moderate altitudes to acclimatize their bodies. One of the main results from acclimatization is the body's natural response to build more red blood cells. This increase is the body's way of compensating for the lower oxygen levels in each breath of air.
The downside to living at altitude is that it is nearly impossible to train at the same intensity as when training at sea level. Therefore, athletes train low to maintain their power and speed. This is commonly done by living in the mountains and commuting to lower altitudes for training sessions.
A very low percentage of the total athletic population has the resources to live high and train low, or even to simply live high for several weeks.
Short of Data on Short-term Exposure
What is not well studied is the body's aerobic and anaerobic response to short-term altitude exposure--less than one week, for instance.
I started looking at this issue because of a recent personal experience. I live at an elevation of roughly 5,000 feet and I travel to altitudes between 8,000 and 10,000 feet for endurance events on courses that go as high as 14,000 feet. I usually feel pretty good when I drive up, compete and return home the same day. But if I stay overnight at elevation and do the event the next day, 18 to 20 hours after arriving I don't feel good and generally do not sleep well. Although I do not suffer from bad AMS symptoms, after I travel from 5,000 to 10,000 feet and stay overnight, I can feel my heart pounding just laying in bed.
Unfortunately, my husband, Del, suffers from all of the typical AMS symptoms. Although he is not an endurance athlete, he is critical to my success by providing sag support for week-long rides and crew support for long races.
Our experience during a week-long bike trip this year made me wonder about traveling to an event earlier than the 24-hour time frame that is normal for me. During our first night, which we spent at a relatively low altitude of 6,700 feet, I didn't sleep well and had a slightly elevated heart rate. I didn't think much of it, attributing the symptoms to event excitement. After talking about the incident later, Del said he also felt an elevated heart rate and AMS symptoms.
The next four nights were spent at elevations of 7,411 feet, 9,040 feet and two nights at 9,087 feet. Actual bike riding was done between those base-camp elevations and 11, 992 feet.
As the trip progressed, we noticed a couple of things. First, Del's AMS symptoms gradually diminished. This is relatively normal for AMS symptoms. I also felt better on the bike, though I wasn't collecting data so I didn't have a sense of relative heart rate and power outputs.
The night that made us most take notice was spent in Leadville, Colorado, at 10,152 feet. This followed a night at 9,087 feet. I did not experience the pounding-heart-at-rest problems I've had in the past when staying at that elevation, and my husband's AMS symptoms were very much diminished as well.
As we discussed the situation, I recalled reading a research paper which concluded that arriving at altitude about three days before an event decreased the negative effects of altitude on aerobic performance. Or was that conclusion the interpretation of someone else reading the research paper? What was the conclusion of the actual abstract, not an author's interpretation?
The search for research began.
In Part II, I will summarize the limited research papers I found. Additionally, I will share my personal experiment-of-one heart rate data comparing the 2007 Leadville 100 race with the 2006 race.
More information on the Leadville race can be found at my blog site and at the Leadville site. Or read my previous articles: Race across the sky: The Leadville 100 Part I and Part II.