A climber who summited the world's tallest peaks explains how he trains by keeping his body in Everest-mode

• Mountaineer and Everest guide Garrett Madison summits the tallest mountains in the world.
• He's summited Everest 14 times, and just earned his second "triple crown," a rare mountaineering achievement.
• When he's not on expedition, he keeps his body in Everest-mode by staying active in the mountains of his home state, Washington.

Garrett Madison has built a career on risking his life to stand atop the world's tallest peaks. The mountaineer and expedition guide has summited Mt. Everest 14 times, and has led more than 80 other climbers to the top since 2009.

In May, he earned his second "triple crown" by summiting Mt. Everest and two of its neighboring peaks, Mt. Lhotse and Mt. Nuptse, in a single season. Few have achieved this rare feat.

"I feel really lucky and privileged to get to go on these expeditions," he told Business Insider.

But this epic lifestyle also pushes his body to the limit. Being in shape can mean the difference between life or death when climbing a nearly 30,000-foot-tall mountain.

Low oxygen levels, brutally cold temperatures, and long days spent navigating treacherous terrain take a toll on the body. Even fit mountaineers can succumb to exhaustion, altitude sickness, or injury.

"Fortunately, I'm on expedition quite a bit throughout the year on big mountains, so my body and mind kind of stay in mountain shape," Madison said.

But during those rare times when he isn't on expedition, he's preparing for the next one. Madison has developed a strategy for keeping his body in Everest mode in the off-season.

Always seek high-elevation

When he isn't climbing massive Himalayan peaks, Madison spends time skiing and hiking in the smaller, but still mighty mountains in and around his home state of Washington.

"Continuing to stay in the mountains throughout the year is very, very beneficial if that's where you want to be," he said.

That's because the body adapts to the low-oxygen levels at higher elevations. The top of Mt. Everest has only a third of the oxygen available at sea level. Spending time in low-oxygen environments —even ones that are less extreme than the top of Everest — actually changes your blood.

Lack of oxygen causes the body to produce more red blood cells, which carry oxygen from the lungs to the rest of the body. It also produces more hemoglobin, a protein in red blood cells that helps them do their job. At extreme elevations, climbers' supercharged blood helps make sure all their organs receive enough oxygen.

This enhanced fleet of blood cells lasts long after a climber has returned to low elevation, sticking around for about 120 days. But after that, they'll start to die off. That's why Madison makes sure to spend as much time as he can at high altitudes to keep his blood Everest-ready.

How you can whip your body into Everest shape

When he's not working out at great heights, Madison said he makes sure to stay active in the gym.

"If I'm not skiing or out hiking or climbing, I'll definitely go to the gym and do a mix of strength training, and some balance, flexibility, agility work," he said.

His company, Madison Mountaineering, has even created a training guide that can help whip your body into shape for an Everest-level climbing expedition.

The cardio exercises include things like hour-long runs and steep day hikes. Muscle training includes lunges, push-ups, and jumping exercises.

It's best to train for an expedition outdoors on hilly terrain, according to the Madison Mountaineering website. But not everyone has access to this where they live.

If you're limited to working out in the gym but want to train for a big climb, try the stair mill. It mimics mountain terrain by making you lift a portion of your body weight each step, the website says.

Training for a mountaineering expedition takes a lot of time and work, but all of that effort is important to your safety on the mountain.

"It's a lot of work, but it's definitely worth it," Madison said.