I did this core exercise program for biking that I stumbled on in online Bicycle Magazine---just printed it out without having to buy anything.
http://www.bicycling.com/article/1,6...5681-2,00.html
I made a mistake the way I did number four, the plank however.
When I was doing the plank, I would put the weight of my body on my forearms on the floor with no padding underneath, and I ended up crushing part of the Ulnar nerve in my left arm. I have had limited feeling in my left pinky finger ever since. I am not a heavy guy or anything either.