It's the legal version of blood doping. Instead of injecting themselves with blood before competition or taking drugs to stimulate the production of oxygen-carrying red blood cells, many endurance athletes spend time in the thin air of high altitudes. The idea is to get their muscles to use oxygen more efficiently so that when they return to lower elevations, they have a leg up on their competition. But a new study on patients with a genetic disorder that makes their bodies act as if they're always living at high altitudes suggests that too much "altitude doping" is not beneficial—and it could even hurt performance.
The body responds to the thin air at high altitudes by producing proteins in the hypoxia-inducible factor (HIF) family. HIF stimulates the production of red blood cells and builds capillaries to deliver more oxygen to the muscles. Yet some people have a rare genetic disorder in which HIF never gets broken down, so the levels are always high, as if they spent their days in the mountains. "In the U.K., as far as we know, there's not more than 20 of these patients," says physiologist Federico Formenti of the University of Oxford in the United Kingdom.
To see what happens to people who have too much HIF, Formenti and colleagues recruited five of the patients and five healthy people to the university for 2 days of tests. The volunteers rode vigorously on a stationary bike, flexed their ankle while lying in a machine that measured an index of tiredness in the muscle, and had muscle biopsies taken. The researchers found that the patients weren't able to exercise as hard as the healthy controls because their muscles weren't using energy as efficiently. Even very light exercise tired them out quickly.
The patients have few symptoms; they're usually diagnosed after a routine blood test finds high levels of hemoglobin. One of the subjects was even a professional cricketer. "We had a laugh, saying cricket is not actually a sport—you don't have to run for a long time," says Formenti. He thinks that these patients may be at an athletic disadvantage because having too much HIF in the bloodstream has other effects that outweigh the benefits of more red blood cells and more capillaries.
In theory, athletes who train for long periods of time at high altitudes would be no different from these patients, says Formenti. And that means that long-term training at high elevations could actually be counterproductive for athletes who have to run, cycle, or swim for extended periods, the team reports online today in the Proceedings of the National Academy of Sciences.
"But really, right now, nobody does that kind of training," says exercise physiologist Michael Koehle of the University of British Columbia in Canada. Athletes don't generally spend all their time at high altitude. Instead, he says, many now follow a regimen called "live high, train low." They sleep at altitude, or in a tent filled with air that's low in oxygen, and train lower down. Still, Koehle says the study could help sports researchers fine-tune altitude-training regimens by showing what could happen if athletes spend too long in the mountains. The research "sheds light on why 'live high, train high' is not the best strategy for altitude training."