I'm running into a problem in my own training, and hoping someone here has some suggestions. This only shows up working on the heavy bag with bare hands (my personal preference). I have some arthritis in the base of my left thumb (the knuckle where it meets the hand). Because of this, my left thumb doesn't fold in quite as far as the right. Until recently, this has been irrelevant. Lately, though, it seems to have reached a point where the thumb doesn't fold down far enough. When I hit a heavy bag (bare-handed) with even moderate force, I sometimes feel the bent point of the thumb making contact with the bag as the bag compresses around the fist. In and of itself, it's not a problem during training. The next day, however, the knuckle is very tender from the repeated pushing in.
So, I'm wondering if there's another way to make a fist that would be better suited to that arthritic knuckle. I make what I'd consider the most common fist - the thumb wraps around, folds across the first two fingers, like this:
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I've seen other fists; I think I remember someone in Ryukyu Kempo using one with the thumb compressed on top (on the side of the first finger). I'm wondering if any of them will alleviate the problem (knowing which one would let me look for someone to teach it to me), or if I just need to settle for open-hand strikes on that side.