If you are getting pain in your hands after only 20 miles, this probably has something to do with your position on the bike and your hands taking too much of the beating.
You might want to increase the height of your handlebar or slide your saddle forward a bit, for instance.
It might be a good idea to show us a picture of yourself riding your bike so we might help you with this.
Another good way to achieve this is to ask your LBS to help you with fitting your bike.
I don't think barends will solve this ... barends are mainly good for doing highspeed steep climbing while not sitting on the saddle.
Two other options might be:
1) get a suspension fork ... this will reduce the hammering of the handlebar on your wrists.
2) get an aerobar ... as with an aerobar you will be able to put pressure on your arms and elbows instead of on your wrists and hands.
Good luck