They've helped me a lot. For one thing strengthening your wrist (which is very important), flattening your hand, and after zillions of them you get used to hard contact on your fist. Do them on wood or cement floor.....but I did a lot of things.
It's fairly lengthy process with 1 by lumber, ceramics like pots and saltillo tile. I did a lot of breaking, but was NOT trying to punch thru the target, but only slightly. I practices on painted cindar block walls and tilt wall to learn how to make
heavy contact without damaging my hand. I also had to stop increasing the pressure at the right time. I was fortunate, I worked for for a company (at that specific time) that made ceramic transducers for missiles. Fairly large cylinders up to an inch thick. They had plenty of rejects I could use for breaking, inch thick pots are expensive. I hit flat mostly, but I'll roll my fist onto the first and second knuckles depending on what kind of damage I want to do. I did this in a four year period in the '70s and it's never caused me problems.
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Before I hear it, no my hand's not flat. I'm trying to take a photo.