Thank you guys, all very helpful. One specific question.

I live in the low country of South Carolina, and that means my hikes are through swamps, and that means flat. I would rather be outside but do you think I should spend a few days training on a treadmill so I can get the incline walking in?

At least outside I get my feet and the rest conditioned for uneven ground, rocks, logs, etc.

Can't do much about the decline and walking down hill.