Cady Goldfield wrote:
This is a basic example of a lack of understanding about what is going on in the body during training. Contrary to what so many martial arts students believe, there is no such thing as "conditioning and strengthening" the body through thrusting fists into pots of sand, punching boards, or falling and slapping the ground.
It is what we call, in Yiddish, a bubbe meise
(old grandmother's tale).
Slapping the ground does...nothing -- except to burst blood vessels and bruise bone. The long-term outcome of that "conditioning" is, at best, to deaden and kill nerves so you no longer feel pain when doing damage to your arms.
Same for punching makiwara (which, by the way, I did for 20 years when I was making an extensive and intensive study of punching and striking). Striking a hard surface does nothing for the hands, but it does do damage TO the hands, by rupturing the tissue around the knuckles and causing painful swelling that in later years can exacerbate arthritis. Punching into pots of sand does that too. Sand punching can callous and thicken the skin, but callous plays little or no role in protecting hands during punches and strikes. Except, maybe, to keep the sand you're punching from scratching the tender skin under the callous.
I am sorry, but I disagree strongly. Doing such exercises e.g. regular hitting exercises on forearms, is known to stimulate the periosteum, that's the skin around the bone. Irritating is the more correct expresion probably as the periosteum is made to believe that the bone is broken which results in the production of bone replacement substance, which is significantly harder than the bone itself (a bone never breaks twice in exactly the same spot): With time and proper execution of such techniques the bone (and joints, as this can be done with joints as well, in most cases the wrist or the fist) will grow significantly. Such training will create layer after layer of bone replacement substance coating around the exposed spots leading to e.g. forearms 50% thicker than before (we are talking about years of course)
I would dare to say that almost every kung fu school has these exercises in its regular curriculum, both northern and southern styles, although the northern styles put more emphasis on it. So far every kung fu student knew what I was talking about when I mentioned it and had one ore more variations to show me. For me this is a fact as it is for thousands and thousands of martial artists throughout China and Southeast Asia for hundreds of years now.
It is a little bit uncomfortable for me as a new user to aikiweb to question your striking experience mentioned before. Are you sure you did everything right? Did you have proper instructions how to perform these exercises? Especially the advanced ones involve quite a proficiency in Chi Gong (=the art of Ki). These exercises are not only to harden the hands, arms and feet but also, especially the advanced ones, a very powerful Chi Gong exercise itself.