Thumb muscles/ligaments getting sore??? I just picked up and '03 450 and I'm having an issue with my thumbs. I haven't ridden much for the last 10 yrs and don't ever remember having this issue before with other bikes. Is this common? Is there a way to fix it? I can't figure it out. After doing some long riding nothing else gets sore at all except for this. I'll have to take my hands off the handle bars every now and just to relax the thumbs from gripping the bike. If we stop, I'm back to normal after about 10 min. or so.