For a long time we would include board breaks as part of our belt tests as a demonstration, but in recent years have been moving increasingly away from doing them.
While it can make for an impressive demonstration, is there any particular value in practicing or performing board breaks or is it an artifact of the days of doing traditional bone conditioning? If it is valuable, under what circumstances?
I think there is a lot of value in it still.
It has little to do with conditioning in particular - board breaking can indicate that your striking point is conditioned, but it isn't used for conditioning.
Rather, it is a demonstration and test of focus and power. You can hit thin air and a bag all you want, but none of that demonstrates focus. Breaking a 12" x 12" x 1" thick untreated pine board is supposed to be the equivalent of breaking a human rib, hence the demonstration of power.
Selective breaks are interesting and bound to generate the most debate. I have practiced and accomplished several different types of selective break, this shows my capability at changing my focus and delivering power/energy to very specific spots.
One reason for discontinuing breaking is the price of wood and/or the difficulty of sourcing good breaking material. There are plastic rebreakable boards that you can get in various thicknesses which are a good replacement (depending on manufacturer their integrity is pretty good, i.e. they still take the same force to break on the 50th time as what they did when they were new, although you should expect some degradation over the lifetime of the plastic board).
So while I am a traditionalist, I still believe that breaking has an important role to play and shouldn't be discontinued (although it can be a good idea to re-evaluate the who/how/when of the breaking).
We don't practise board breaking in our dojo. When asked why, our sensei will alternatively quote Bruce Lee, "Boards don't punch back" or if he's in a generous mood he'll say that being able to punch through ice may demonstrate great focus and power and courage, but it isn't helpful to be proud of hitting stationary objects hard. Any meaningful expression of martial power has to be applied against another person.
Personally though I think courage is courage. If it takes courage to drive your first through wood or ice, that courage will also be of use when someone tries to attack you, or you find yourself facing a bigger opponent.
I agree very much with Kamil, board breaking should not be used as a form of hard body training. It would not be at all effective; the biggest concept in hard body training is striking objects which reflect energy back into the striking body. A board breaks when it absorbs the energy of your strike, and any remaining energy dissipates into motion past the board. I know of two good uses of board breaking:Demonstration, and building confidence. Demonstration is Obvious. As for confidence, I would use this with low level(2-3 months) students who have gained competence with basic techniques. Breaking a board is a satisfying way to demonstrate to them (without hurting anyone) the capability of their strikes.
