I'm not familliar with all methods of conditioning but when I train punches from that short distace it's to develop 'short power'. You know like 'one inch punch'. Explosiveness. However I mostly do it with a training partner and take turns and hit solar plexus with it. Open hand strikes (palm) is also used.
I've trained breaking and conditioning for about 3 years and I hit logs of wood (about 30 pounders), trees and cement/bricks regulary. I'm concentrating on stone breaking now (nature stones) and can breake stones that are ca 6 cm thick without much hassle. It's hard to do it on a first strike though, and somethimes it takes hundreds of strikes to get one. (all rocks are very different in structure etc. Some are solid as hell, nearly impossible)
Hitting a piece of wood like this is to make you feel less pain when you strike. It's controversial and some say it can damage your hand. If your taught right there shouldn't be a problem. I would never do this on my own without proper guidence first. To hit something solid with full power and speed without hesitation is a mind thing. To go past those mental barriers that say you'll hurt yourself. Breaking/conditioning is painfull but it teaches you to go beyond limits, builds streangt and explosive power in movement
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