Most climbers are "guy A". Their idea of working out is "bouldering", which is essentially haphazard and random exercises of various muscle groups. There is no way to precisely stress the muscle (and supporting structure) to a specified amount, and there is no way to measure or record how much they have been stressed. There is no way to know if you are increasing the intensity or by how much. These "training" sessions often end in a wild dyno for some two finger pocket which the climber has absolutely no idea if he has any business trying to hold onto, then a loud "pop"!

The problem with this "method" (or lack thereof) is that the way to enlarge muscle tissue is to stress it to near failure. In random bouldering, there is no way to know when that is accomplished, but you definitely know when you're past that point (pop!) Furthermore, the supporting structure of the fingers (tendons and ligaments) take up to six years (not a typo) to respond to additional stress. That means, that if you have been climbing for six years, your ligaments may now just be starting to get stronger, whereas your forearm muscles respond in about two weeks. Therefore, your random acts of unkindness to your body are priming your forearm muscles to do major damage to the support structure, with no monitoring whatsoever. A structured training regimen allows the climber to carefully and thoughtfully stress the body enough to cause the desired adaptation without stepping over the line into injury. Aside from giving up climbing for golf, training is the best way to avoid injury!