I had a plan to walk a half marathon last year. High impact has never agreed with me, even when I was young, but definitely not now. Everything got put on hold when I got diagnosed with arthritis but I’m trying to get back in now.

If I recall correctly runners estimate about 1 second per km per extra pound carried. That might not hold for body weight (cyclists had an old 1:2:10 rule of thumb that suggests that it might be better to lose 5 lbs than spend a fortune on a pack/bike that weighs 1 lb less, but that rule has been challenged and I don’t know what the new wisdom is.

Edit: kilometers not miles.