Hands going numb some... Ideas why? Any fixes?

[Zune]

Hello all, question for everyone out there. I have a Spyder F3 Base and the wife has a Ryker 900. We added the leather like foam grips in hopes that it will help, which it has helped some but her hands especially and mine after some time will go numb. Is that generally because the bars need raised or further out position wise? What should I try to combat this?

Thanks to everyone.

Zune