People come to cycling and have relatively poor core strength -- that is, the muscles in their back and the front of their torsos are relatively weak. Strengthening those can help you maintain a good posture on the bike. Fit is another factor (including making sure your saddle is level and not tipped down at the front) and if that is right, and your core strength is good, you should be able to ride your bike with next-to-no pressure on your hands.