My legs—and lungs—are burning as I pedal. The cycling interval’s only 10 seconds long, but it sure feels like the clock is moving in slow motion. Coach Mauricio Andrade stands in front of me, offering support that’s motivating but firm. There’s not a chance he’ll let me slow down or slack off.

When he finally calls time and I ease up my cadence, I glance around to the view of snow-capped peaks. That, and the thin air, have momentarily transported me to a place like Leadville, Colorado or Cusco, Peru, at an altitude of about 10,000 feet.

But once I’m mercifully finished with my two rounds of 10 high-intensity intervals, I’ll step outside, inhale deeply, and get back in my car to drive to my apartment on the North Side of Chicago. That mountain view? It’s a wall-sized decal.

I’m working out this morning in the altitude chamber at Well-Fit Performance, a training hub for many of the city’s triathletes and other endurance athletes. In addition to endless pools, strength- and functional-training equipment, and a full complement of treadmills and bike trainers, Well-Fit has now installed one of the few altitude chambers in the country, and the first in the region. 

The facility’s expensive compressors essentially suck the oxygen out of the air, simulating some of what I’d experience if I hiked to Machu Picchu or ran the Leadville 100-miler. There are two other women near me, doing their own workouts on top-of-the-line Woodway treadmills; when I catch my breath enough to chat with them afterward, I learn they’re training for a trek in Kathmandu.

If I visit the room regularly—twice a week for four to eight weeks—I just might see my race times come down and my fitness level reach new heights, Well-Fit’s owner and head coach Sharone Aharon tells me. “There’s such enormous benefit to training at altitude, at high intensity,” he says. “If I say one sentence about it, you train less and you gain more.”

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Why athletes train at altitude

For decades, elite endurance athletes have headed to the mountains for altitude training. Because there’s less oxygen in the air to begin with—and less atmospheric pressure pushing it into athletes’ veins—their bodies respond by boosting the production of red blood cells. The effect is temporary, so they have to time it right. But when they then head back down to sea level for competition, these adaptations deliver hard-working muscles an augmented supply of oxygen to power each contraction.

The problem is that sweating in thinner air isn’t just harder for us mere mortals, it’s also more challenging for the likes of marathon champions like Shalane Flanagan. You just can’t pedal as hard or run as fast at higher elevation. So athletes have to find other ways to push their bodies to the limit, says Andrew Subudhi, PhD, professor and chair of the department of biology at the University of Colorado Colorado Springs, who’s studied the effects extensively.

That’s why a protocol called “live high, train low” was developed. Athletes often sleep in the mountains, then descend to knock out hard workouts. Or, rooms like the one at Well-Fit are sometimes used in reverse, to mimic lower elevations—increasing the oxygen in the air so athletes can reap altitude’s benefits to their blood but still push themselves at faster paces. In fact, that’s the primary purpose of a similar chamber at the U.S. Olympic Training facility also in Colorado Springs, Subudhi says.

Those of us stuck near sea level, and without a budget for altitude camp, have to take a different approach, such as one called intermittent hypoxic (aka low-oxygen) training. That means doing most of your workouts in normal air, but heading “higher” for short bursts of really hard efforts. And that’s what rooms like the one at Well-Fit are designed for: “We brought the altitude to the everyday person,” Aharon says.

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What the science says

Scientific research has shown support for such training plans. In one study, runners who did two tough sessions per week in a low-oxygen chamber for six weeks improved how long they could run at a comfortably fast pace by 35%, while those who did the same type of speedwork in regular air showed no improvements. In another, cyclists could complete more back-to-back sprints after four weeks of training in air simulating about 10,000 feet, an enhanced ability to work hard repeatedly that Aharon calls having “more matches to burn.”

Interestingly, simulated altitude doesn’t seem to work exactly the same way as the real deal. Most of the low-oxygen chambers, including the one at Well-Fit, do thin the air but don’t change the air pressure. Athletes in these studies didn’t show changes in their red blood cell count, meaning the training is working in another way, one that scientists are still trying to untangle.

“Some of the speculation is that maybe it’s changing how efficiently your body uses the oxygen, or maybe it just changes how your nervous system is driving the muscles independent of the oxygen,” Subudhi says. And then there’s perception, which has a real effect on your performance. In other words, if you think something’s going to allow you to run or bike for faster or longer, it just might.

Whatever the mechanisms, Aharon says he’s experienced the benefits personally. During a recent half Ironman—a triathlon with a 1.2-mile swim, 56-mile bike ride, and a 13.1-mile run—his last 10 miles on the bike were the fastest. He wasn’t as well-trained overall as he would have liked, he says, but he believes his twice-weekly altitude sessions provided the extra oomph: “I can see that also riding with my friends. All of a sudden they don’t drop me like they normally do.”

Many other Well-Fit athletes have noticed similar improvements. The facility has a testimonial page full of marathoners who’ve run personal bests and triathletes who’ve dropped along the lines of 45 minutes from their finishing times. And then there are people preparing for trips to higher peaks, like those trekkers I encountered. Logging some solid time at simulated versions of their destination elevation may help reduce the time they need to acclimatize once they get there.

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Scientists don’t agree 100% on the benefits of any of these protocols, including training at actual altitude, Subudhi points out. The evidence for intermittent hypoxic training is interesting, but may be clouded by what’s called publication bias—the fact that if a study found these methods didn’t work, it likely wouldn’t be published. That can skew an entire body of research toward the positive even when a tool or technique might not work for everyone.

Still, there’s little downside except for the cost ($230 per month, $250 for a 10-visit punch pass, or $30 for a day pass, at Well-Fit) and the risk of feeling lightheaded (in which case you should back off and step out). You can minimize these chances if you ease into the training and stick to elevations below about 12,000 feet, Subudhi says.

For a recreational athlete with an ambitious goal—in my case, re-qualifying for the Boston Marathon—logging some workouts at faux altitude just might be worth a shot. “A lot of training and getting better is letting your body experience different stresses,” Subudhi says. “You can get stale doing the same thing over and over. This is something new and different, and it is a little bit more stressful on your body, so it can help push people harder.”

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