Hi! I can endorse the book of core exercises by Mark Verstegen - "Core Performance" , and I really like his DVD "Stability Ball total core program". I got the book from Amazon, and the DVD at Target, of all places! I like the DVD alot - it is quick, succinct, and he talks you through coaching points of the exercises. Some of the exercises while building great core strength have also almost eliminated my chronic shoulder pain from my old rotator cuff tear! My cycling coach has me do core strength year round - I am small and not as fast as I would like to be, so I consider my core strength to be my "secret weapon". It has definately helped!My coach and PT both recommend doing lat pull downs too for core strength in cycling, and since doing the ball work for 2 months, I can almost do them again without shoulder pain. Enjoy! I think the ball work is kind of fun! Carol