The entire Leadville Trail 100 takes place at over 9,000 feet, maxing out at 12,424 feet, so you’re right to worry about the acclimatizing. So far, most research explores how effective altitude tents are at allowing athletes to “live high, train low” while living at low altitude. So we posed your question to Grégoire Millet, altitude researcher and professor of exercise physiology at Switzerland’s University of Lausanne. Here’s what he had to say:
“I would recommend you spend as much time as possible in real altitude,” Millet says. Researchers at a U.S. Army lab on Colorado’s Pikes Peak “recently showed that sleep in a hypoxic chamber is less efficient than sleeping in real altitude," he says. "The pre-acclimatization will be more efficient at real altitude.”
What’s the difference between being at real altitude and hanging around in an altitude tent? In real altitude, you’ll experience hypobaric hypoxia. In other words, the concentration of oxygen in the air is the same as at sea level—21 percent—but the air is thinner, so the oxygen is less abundant. Most altitude tents are normobaric, meaning the air inside the tent is just as thick as it is normally at sea level, but a machine attached to the tent replaces some of the oxygen with nitrogen so you’ll breathe less oxygen.
Millet says just seven nights at altitude directly before the race will help more than sleeping in an altitude tent. But if you can’t get the time off, “sleeping in a tent is better than not,” because it will “increase your ventilatory responses. For example, you might expect a slight increase in your ventilation,” or breathing rate. However, you’ll likely need to spend three weeks or more in the tent—and at least 12 hours a day—to induce this change.
And don’t expect the tent to trick your body into increasing your red blood cell count. “It’s very unlikely that the altitude level and the exposure duration would be long enough for really inducing an increase in your hemoglobin mass,” Millet says. But neither will a single week at altitude. “Going to altitude the week before the event is probably the best thing for ventilatory adaptation, but you need to go for at least three weeks, four weeks is better,” to significantly increase your red blood cell count, he says.
Additionally, you need to consider that your sleep quality may suffer in the altitude tent, which may affect your ability to recover and feel fresh for your race.
So is the $4,000+ to buy—or $400 per month to rent—a tent worth it? That’s up to you. This Wired cyclist says no.