Hi @chris4, basically while playing you should not feel any pain.
Here’s a list of things you can do:
1. Make sure your fingering is the best possible, then stick to it.
Keep your hand above the wanted voicing’s keys, and use the fingers that are closest to the notes of the voicing, do not stretch if not necessary. Also you can move your whole hand deeper to the piano (Meaning more above the black keys than white), that can help you reduce finger stretches.
2. Make sure you’re sitting in the middle of the piano
Plae yourself in the middle of the piano, then if you need to reach lower/higher notes, lean in with your upper body. Try to keep your fore arm and hand (palm) as straight as possible when playing, meaning:
3. The strength of your fingers is not coming from your fore arm or you palm/fingers, it should be coming from your triseps.
This might be hard to describe, but here we go: Take one finger, and play a note (or tap table like you would be playing) while keeping your wrist totally relaxed. You can hold the wrist with your other hand to make sure there is no tension and no force. Then try to gradually put more power into the note/tapping the table, and try to direct the stregnth from you upper arm to the finger.
Once you start to find the strength this way, first practice it with every finger individually, then with slow melodies, and finally with chords.
Point is that once you direct the strength this way, your hands will never get tired of playing loud or fast. This helped me a lot when I had same kind of issues with my wrists as what you described having.
Thanks, let me know if you have any further questions!