NEW YORK(CBSNewYork) — Imagine how hard it is to climb the world’s highest mountains. Now, imagine working out in those same conditions at your local gym, or even at home.

The ‘high altitude workout’ is a new fitness craze that some are calling extreme.

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As CBS 2’s Kristine Johnson reported, it looks like any other exercise class with weights, and lunges, but there’s something missing from the air that makes the class very different.

“You’re winded right away,” one person said.

That is the effect of working out in thin air.

At one California gym, an air filtration system sucks the oxygen out of the air in the entire room. The room is at sea level, but it feels like the class is being held at an elevation of nearly 8,000-ft. The goal is improved performance.

“In less amount of time you’re gonna get way more work done with less stress on your body, and less stress on your joints,” trainer Carlo Maravilla said.

“I’m a mom, so I’m busy like a lot of moms. It’s great to pack a whole lot of workouts into not that much time,” Irene Rose said.

There are even portable systems, like the one used by professional trainer Alex Nicholas, which can be set to a level of air so thin that it’s as if he is training halfway up Mt. Everest.

“It really disrupts your breathing,” Nicholas explained.

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David Roeske, a finance expert, is training for the New York City Marathon with his portable system in his apartment gym.

“The amazing thing is you can bring those mountains to your home gym in New York,” he said.

He even sleeps in a tent that has thinned air pumped into it.

“I just get inside, and flip this up, and sleep on the pillow,” Roeske said.

Roeske said that all of the tin air has paid off.

“It’s helped me achieve a lot of personal records. It helps me push my body hard in a short period of time,” he said.

Medical experts urge caution, saying that there can be risks to this type of training, including light headedness, and spikes in blood pressure. Only those in top shape should consider high altitude training.

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