Wrist hurts after long bicycle ride?

I just bought a new bicycle and have been riding to the beach and back which is about 10 miles round trip. My wrist starts hurting after a while so I was going to raise my handlebars up and found out that its a threadless stem. All the spacers are at the bottom so its already at the highest point it can go. Are there any other options that would take the strain off my wrists? I was wondering if lowering the seat a little bit would do the trick but then that might move the strain to my knees. I'm about 6 foot if that matters.