Anything you do to improve your core strength will improve your riding. Core training is one of the biggest additions to focused training that has been embraced by pro teams. Most even do core work in addition to the traditional massage post ride. When I was riding a lot, I always tried to work in yoga/pilates a couple times a week to develop my core. I ride very little these days and most of what I do is on a smart trainer. I try to add some time on my WaterRower to work on my core. I've found that wearing an increasingly heavy backpack while hiking also quickly develops core muscles - or quickly lets you know that this is an area that needs work.