Jennifer - I think you're right - my hands are smaller - I have long fingers but a fairly small hand - in fact - using a regular size mouse is very uncomfortable for me so we have a little baby mouse that we use instead - normally if I grip too tightly my hands soon go numb... what I'm experiencing is pain in the base of my thumb - from about the wrist joint to the first knuckle which seems to be made worse by wrapping my thumb around the bulk of the handlebar

Lisa - I don't think it's hand position - but I have considered getting a different type of handlebar and trying it out to see if it helps

Kaludurga - I had wondered if wrapping instead of grips would be a viable option - because like you pointed out - it is safer to ride with your thumb curled under the handlebar! I know nothing about wrapping handlebars!! LOL hmm.... I'll have to check into that.

Thanx for the help - these are great suggestions