In previewing the Ultra plan in prep for my IM goal in 2010 I noticed that there is really no mention of strength and core training. What is recommended for this?
I'm not sure how this "works into the plan," but if you're looking for applicable core based exercises one of the best programs I've found is on www.mtnathlete.com I use the hybrid training program. Thumb around the site and get back to me if you have any questions. Start light, there's nothing easy about it. Good luck.
There's actually a group associated with that topic, which Nate monitors fairly frequently. I kept strength and core training out of the plan because people's needs and available resources/equipment/etc. are very diverse.