Exercising - not a blog

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Not to mention, strong fingers are essential in advanced climbing. At the early stages foot placement and balance is much more important (and overusing your fingers can result in life long ailments) but when you start climbing some difficult routes you really need to have the finger strength. Check out this video of one of the best climbers in the world doing a ONE ARM ONE FINGER pull up (he has climbed many of the worlds highest skyscrapers without ropes):

I hope you guys appreciate how outrageously difficult this is. Anyway, just saying there is a practical use for finger strength (maybe not in martial arts but in climbing and many other sports there is).

Still, how do the climbers train their fingers? By resting their body weight on them, bending them backwards? If you want to train fingers for hanging from them, why not hang from them, like from a bar?

There's a great deal of debate on how to train your fingers. Given that climbing is a sport and not simple bodybuilding, many think the best way to train your fingers is to just climb. There are plenty of great climbers that trained their fingers just by practicing this way. Others use what is called a campus board, which is a board with various holes differing in size intended to train the fingers explicitly. The reason why there is so much controversy regarding this is the fact that there are no muscles as such in the fingers. The only thing that supports your weight when hanging on your fingertips are little ligaments called pulleys. These pulleys are incredibly weak because humans aren't really designed for climbing. After years and years of climbing these pulleys eventually get strong enough, to the point where you basically cannot tear them. However, in the 3-5 year period that precedes it, you have to watch out for the pulleys constantly.

Most people who don't really know what they're doing train finger pull ups on small holds (called crimps) because they think that is the only thing that makes a good climber great. The best climbers put most of the weight on their feet because it preserves energy and because the feet can take your weight (otherwise you wouldn't be able to stand or walk). The hands are really only supposed to be used to hold on to the wall, putting all the weight on your feet and using some tricks to dynamically shift your center of balance, allowing you to reach up higher on the wall without pulling. It's kind of complicated and you're probably not interested in hearing all of it. The bottom line is, there is no one consensus regarding the fingers. They can become stronger but strenuous training is almost guaranteed to pop a pulley, which usually requires surgery and can take up to 3 years to heal. Personally I err on the side of caution and use my finger strength only in emergencies. Even hanging on the wall exclusively (as opposed to pulling with your hooks constantly) gives you a lot of bi- and tricep strength which can be used. I for example can scale a 5m ladder using only my arms, and I am barely considered anything more than a beginner/intermediate climber! I've seen some people do it one handed (switching arms of course) and others using only a few fingers.

EDIT: @ your edit: Yes, actually. Finger-sized holes are all you get sometimes. As I said before, talented climbers will try to just hang onto it, using their weight to get up to the next hold rather than their strength, but sometimes it just isn't possible. You have to be prepared for anything.