warning, this'll be long.
there are lots of structured ways to practice falling, trampoline, cycling specific workshops, skiing, gymnastics, skating (ouch)....one of the most likely ways is martial arts because at a good school that's going to be the very first thing you work on.
We need our training partners to be safe, if they can't take a fall out of the throw we'd quickly run out of people to train with :p So a good schools will slowly, methodicly and safely teach you how to fall from a variety of impacts at your own speed.
There are lots of arts to choose from, from the so called hard styles like Karate, Kung Fu, Kick Boxing or Soft Styles like Aikido, Wushu, Jiu Jitsu, Tai Chi, Kung Fu (wait a minute, didn't you list that in...).
The "soft" styles are more likely to teach falls. Hard styles often will not at all.
But if you're looking at a class specificly to learn to fall ask the teacher if they will give private lessons for that one thing. It's the honest thing to do.
Some schools have a specific night that concentrates on one aspect of the art. I know a few schools who have "ukemi" (that's Japanese for falling) class.
Now: how to pick a school.
Kind of like choosing a bike. If you know anyone who trains, ask. Look for announcments, adds, fliers, google it. Now pick a few schools and go watch a class. Things to look for:
Watch the beginners, how are they treated? If you like this thing you're going to be a begginer for a looooong *** time, all your life really. No one should be pushed beyond what they can do, is there anyone with an injury? How are they treated? My teacher finds creative safe ways for people to train through injury. When Bruce broke his arm we ALL trained one armed for weeks. You know, you could be attacked while carrying groceries and don't want to put them down, it could happen :cool: She had a hip flexor injury recently and taught....from a chair. Do they do warm ups? Again, people should be challenged to do their best but no one should be training through pain.
Now: watch the advanced people. You should feel a sense of "wow :eek: :p I want to do that"
That's your school.
Don't get too wrapped up in the style, at advanced levels if you stick with this (good winter training after all) hard styles have flowing sweeps and throws, so called soft styles like Aikido can be abrubt, brutal especially with mutliple opponents.
Just as you're looking for a frame that fits with a bike, you're looking for a teacher in a school.
Now: long words about why rolling (instead of summersaults) work.
There are tremendous stresses, centrifigal force on your head and neck when you fall. And even with a hemet you want to keep your head from slapping like a over ripe melon on the pavement.
Try this with a partner. Don't have someone handy at the moment? You should still be able to feel the difference by simply raising your head when your body is at an angle.
Flat on the floor (eww, I gotta vacuum) knees up like for crunches, hands at your sides. Raise your head straight up, what your partner does very very gently maybe just two fingers on your forhead is push down. Likely this will push your head right back down. Or do the opposite, same position, SO (gently, don't want to strain your neck) puts two fingers on your forhead and try to bring your head up. Except for V, this'll probably be hard.
Now, think 45 degree angle, you're going to turn a bit, one hip and matching shoulder is off the floor, both hands up in front of you, elbows bent as if catching a ball, and you're looking down towards your feet in the direction that you're turned, you're basicly curled a bit but in a spiral towards your feet. Now your head's already up so have your partner push down.
If I've described this correctly it's going to be much harder.
On a traditional summersault only the muscles on the side of the neck are involved pretty much. What an Aikido (or other martial art) falling position does is activates/involves all the muscles to support your head, your back, traps, core, abs all involved.
to find a local Aikido dojo near you:
www.ai-ki-do.org
I can point to other resources for other arts if you want.
I've been hit by a car, another time took a picture pefect forward roll with the bike off Alameda Creek Trail. Although I never ever want to try this again especialy the being hit by the car thing .... the stuff works. Does take practice though.