Thanks DEATHROW, and, BTW, I hope you just made up your user name because you thought it sounds cool....
I thought I could smell something potentially unwise from about a mile away. The sad thing is that I can see myself about 10 years ago saying, "Yes sir!" and repeatedly punching a board like that without a second thought to the long-term consequences.
I actually did something vaguely like that about 10 years ago. I was a green belt in jiu-jitsu and was taking a judo class also. In judo, we did "bull in the ring" which resulted in me getting thrown about 80 times in one class. The next day, I had a back spasm and ended up in the hospital. To this day, some muscle (have no clue the name) in my back threatens to spasm about every other week. Gee, that was worth it. I was really good at breakfalls and was in tremendous shape at the time. The stupid stuff we do when we're just barely young enough to not say "No. That's stupid."