Thanks, Tri Girl. I am sure the rim-to-rim was much less strenuous than an Ironman (it was longer but no more difficult than a century bike ride to me, and I simply can't imagine adding a marathon on top of that!!) But we did train quite a bit -- we went to different parks every weekend to hike, eventually working up to a few parks in the NC mountains. The biggest hike we did was very similar to the GC hike as it was from the top of Mt. Mitchell to the base, then back up. 16 miles total, and like the GC, it was cold at the top and hot at the base.
I honestly don't remember being that sore afterwards, but we did get blisters. That was probably the most difficult thing to deal with after the fact, since we still had many more hikes ahead of us as we went on to Canyonlands, Arches, Bryce, and Zion Nat'l parks!