I can't believe that guys that argue tooth and nail and talk mad shyt on here don't know what midsection conditioning is for. It's the same reason guys get a medicine ball bounced off their stomachs. To condition the fighter to getting hit in the midsection.
Doing it with wood is more of a martial arts influenced angle, but it does the same thing. Tapping the ribs like that hurts like a bytch but it does make the nerves less sensitive.
Old school technique popular among asia especially on muay thai fighters Stick training to condition your nerves all over the body and to improve pain tolerance. Thats why he was able to absorb all the bodyshots margarito unleashed on his ribs and not go down.
that bamboo stick got tiny nails attached tried it once and it was very painful after you get smacked repeatedly.