how can skateboarders jump off of high surfaces like buildings and over stairs without breaking their legs?
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It does shake you a bit, but a lot of the initial shock is absorbed by riser pads, wheels and bushings, aswell as your stance
The same way freerunners can. You absorb most of the shock by bending your knees and using it as a shock absorber/dampener. Freerunners can dissipate some momentum by executing a roll upon landing as well. Skaters just have to rely on their board, wheels and legs, as well as be ready to bail sideways if the landing goes wrong.
Hey, I skateboard!
If you land on the board properly, then a lot of the energy is transferred into your continued horizontal momentum. A key thing in skateboarding is to keep your knees bent, which goes a long way to help absorb the impact. If you Ollie a 5 stair and land with your legs straight, I guarantee you will break your legs.
Now if you don’t land on the board properly, you do your best to roll or otherwise dissipate all that energy. There is an art to falling to minimize getting hurt – kind of similar to how in parkour you roll when dropping from a large height. And of course if you don’t fall right, you can absolutely get hurt.
Practice. Successive approximations.
And speaking as someone who takes CT’s and X-rays for a living, your premise is slightly flawed. Scooters, skateboards, longboards, and all those types of things account for a LOT of trauma in younger patients.
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.
Have you encountered the equation Force = mass * acceleration? Another way to write that is Force = mass * change in speed / time.
When landing, your change in speed is the speed you’re falling at the moment of impact, to zero (since you’re no longer falling). What matters though, is the time component. Since your mass and initial speed are already set, by the time you hit the ground, you’ve got the time variable left to work with.
Increasing time it takes to decelerate from your initial speed to zero, will proportionally reduce the forces acting on your body. Reducing the forces acting on your body directly reduces the risk of breaking bones. So slow your rate of impact, by making the landing take more time.
The main way people do this is by using their leg muscles to cushion the blow. You need to bend your knees and use your legs like shock absorbers.
Parkour rolls are just the flashier version of using your legs as shock absorbers.
TL;DR: Make the impact take more time. That directly reduces the forces on your body.
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