Never forget about the power of core work! Cyclists think that they are in great shape from riding alone... but if they neglect a good bone stomping run or some other kind of additional training they can really get off their game. I did, and it has been a major set back!
I have had a re-occurring back injury that re-surfaces every season because of one simple omission. Core exercise!
You really need to build up those muscles that support your spine in order to stay comfortable in the saddle and reach your maximum output. See attached video for some basic exercises that can help build core strength on and off the bike.