I'm stoked to find this thread, as I too was surprised at how spent my legs/hips were after learning to properly position my body to improve my cornering.
I've been doing the stairmaster/spinning/rowing machine regularly and that certainly helps for general leg strength and endurance but I've found that the deep squatting motion we're using while actually moving around on the bike wasn't getting closely simulated enough for me.
The squat w/rocking exercise described by Dr. Price looks like just the ticket! And the lateral leg lifts suggested by KP.Craig are also on my to-do list now as well.
Many thanks Cobie and Dr. Price!