I can't do planks holding dumbbells because of wrist pain. I've tried 2 different WAGs but neither size worked for me. I went back to using yoga blocks. I have them on top of my exercise mat which is covered with a thick carpet. This combination works the best for me. My wrists leave small indentations in the yoga blocks that take a while to return to normal.
Another suggestion: Think of planks initially as training your wrists and joints with support from core muscles. Same for push ups. Joints take much longer to adapt. Going from vertical (90 degree angle) to horizontal (zero degree) can be too much of a leap. If the stress on the wrists is too severe, the body will not be able to repair. You end up doing more damage. If you've been trying to do planks for a while and not progressing, do planks on a step with several risers. This is what I did to strengthen my weak wrists. Any angle between vertical and horizontal will allow you to progress slowly and will give bones and connective tissues time to adapt. The higher the elevation, the less of your body weight you're putting on your wrists. Pick an elevation that doesn't cause wrist pain to start with and start with a short workout. Just focus on form (ie keeping your body as straight as possible, no hinging) and you'll feel the work. Remove risers 2 to 4 weeks after a level becomes too easy. It might take a year or more to go safely from a step with 4 to 6 risers on each side to the floor.
I have a thick mat that I put on the step (about 1" thick) when I use the step.
