Thumb pain

[KnottedYet]

My first thought is that the bars are too low or two far away.

My second thought is that the position of your hands/wrists may be putting too much weightbearing stress on your thumbs instead of on your palms.

Or maybe you need something like an albatross bar or moustache bar (or drop bar) for your hands, or a "flat" bar with more rise (which isn't called a flat bar then... I think that's a touring bar, but don't quote me on that.)

Can you go to your bike shop and have them check out your postioning on the bike? They might be able to make some suggestions about bars to switch to, or adjusting the bars you already have.

I had problems in both thumbs at that joint from my job. I wore splints for a while as they healed and worked on changing the way I used my hands at work.