Wall-bag Training

[Big One]

Furthermore having conditioned knuckles has little to nothing to do with punching power. Yes, if you are less afraid to make contact you have deliver a harder blow (much like a thai fighter with conditioned shins).

Maybe somebody can coraborate or completly bash this but:
I think that I once read that knuckle conditioning causes the knuckles to develop a kind of very hard bone-skin. Much like a scar will often stand out from the skin around it that bone-skin is harder then the bone it grew on and stands out from the fist.
Knuckles conditioned that wy stand out further which creates an effect similar to wearing brass knuckles.
I know that my kuckles stand out compared to the knuckles of most other people (my sister once pointed that out to me calling it disgusting).
So althought the power of the punch does not increase the effect when going bare knuckle might be higher.

That said, I agree with the rest that hitting a bag filled with rocks is a bad idea. This is bound to have some nasty long term effects. Conditioning kuckles and shins is, in my opinion, sensefull and necessary but Makiwara mitts or wall bags filled with rice are enough.

[LI GUY 1]

Conditioning shins and hands, or anythng, beyond what you get from sparring, seems senseless. I have been in numerous street fights throwing bare knuckle punches and have never had a problem. Adrenaline takes care of it. Conditioning does not make you punch harder either, it makes your hands look nasty.
I have also thrown a head kick KO with my shin in an MMA fight, my shin did not explode due to me not conditioning it.

Of course I was a bit sore afterwards, but not during the fight. Makes no sense at all to me to spend all that time conditioning your body to do what it already can do.

[tataksarella]

Conditioning main purpose is about paint-resist control , yes it is true that adrenalin takes care of it, but for a quite-long time fight ( kyokushin 30 man sparr) the adrenallin tend to drop. There are many mistakes in conditional traing, like punch a tree, rock or any hard static object. For conditional is better use a hanging bag fill with beans that weight not more than 15 kgs and punch it with moderate power.