It’s called legs. I would love to talk about technique, but that’s not the real prerequisite for those stunts.
The real deal is that people that jump as a hobby, develop pretty powerful legs.
Example: Me, snowboarder, met a friend of a friend which is a former pro.
We were relaxed and just jumping for fun, he joined. Minutes later, he did a rodeo!! off a rail!! 4 meter high!! landing on flat packed snow in a parking lot below. Any of us would have broken both legs trying that. I wasn’t surprised he was that agile, I was surprised he had enough legs to absorb that landing. That was a true leg breaking stunt, 4 meters free fall onto flat packed terrain.
Yes proper technique is a thing, but all in all, it won’t make that much kinetic energy disappear. You have to absorb the hit, phisically, period.
Absorbing 4 meters of fall onto flat, with your legs is not something you can get away with, unless you are incredibly fit. Any of us could have done a rodeo off a rail, none of us would have survived the 4 meter drop onto flat.
To be clear, we call flat whatever landing in which you don’t have a slope on the landing. Your vertical speed can’t be transformed into forward motion. If you can land on slope, then techniques may be enough, but that’s a different story and everyone can potentially do it without any strength, and is not what you are asking I guess.
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