Dani Andrada and Edu Marin mountain climbing

Using only two fingers, Dani Andrada is able to pull his body weight up the side of a vertical mountain face.

While you’ve probably seen mountain climbing videos and been amazed by the strength and iron nerves of the climbers, those clips rarely ever focus on what comes before the climb; the countless days spent practicing lines and improving grip strength and flexibility.

But a new clip released Thursday shows the painstaking work that goes into successfully sending some of the world’s hardest mountain climbing lines:

(If you speak Spanish than cuidado, the video contains explicit Spanish language)

The video follows Dani Andrada and Edu Marin as they spend a month preparing to try to conquer Chilam Balam — a 270-foot inverted mountain climbing route across the almost sheer ceiling of a cave outside the Spanish town of Villanueva del Rosario.

Capitalizing on perseverance, a ton of chalk dust, and the type of grip strength that could open a greased pickle jar with ease, Marin and Andrada spend the better part of a month training to prepare their bodies for the difficult climb.

The route is rated as a 8C+ on the French climbing scale, one of the six hardest grades possible for a climbing route to attain, and is considered by many to be among the challenging routes in the world.

In the video, we see Marin and Andrada using two fingers to grip nearly vertical rock walls and pull themselves one step closer to the finish.

Dani Andrada and Edu Marin mountain climbing

Just a guess, but there’s a solid chance that Edu Marin has a very firm handshake.

“For me, the route is one of the most impressive that I’ve climbed,” Marin said of the climb.

“For me it’s one of the 10 most difficult routes in the world, and it’s definitely one of the most spectacular,” said Andrada of the route. “For a climber it is a dream to send it.”

And although you might typically think of climbers as athletes with incredible upper body strength a la Sylvester Stallone in Cliffhanger, the video showcases that in order to climb the best routes in the world,climbers need to have flexibility and fluidity that would put a yogi to shame.

Dani Andrada and Edu Marin mountain climbing

Dani Andrada’s physiotherapist calls him a “monkey” due to his lanky proportions and incredible flexibility.

“I joke that Dani isn’t human, but that he’s actually a monkey,” Pablo Scorza, the team’s physiotherapist said of Andrada, who can be seen stretching ad nauseam before his attempt at Chilam Bayam. “Because he has the body of a monkey. His structure, his incredible proportions; he has an amazing ability to relax and contract the muscles.”

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