I have a question which I hope someone can help me with or just lead me in the right direction. I have a new mountain bike (Cannondale f400) and it has thumb shifters as opposed to my old old Mongoose with its grip shifters. I have been riding the bike a couple of weeks now and as a consequence of the shifters, my thumb is swollen and causing me quite a bit of pain. I did take a couple of days off to see if that would help- then I rode 8 miles yesterday which left me with a thumb that does not want to bend without painfulness. Ouch.

Suggestions?

As an aside, I have been reading this forum and have found it quite helpful! Thanks in advance.