When was the last time that you walked over a mile? When was the last time you walked for more than a mile with a backpack filled with 50lbs of gear?
If you’re preparing for a crisis, but can barely walk up a flight of stairs without getting winded then you are nowhere near where you need to be, and you really shouldn’t be thinking of yourself as a prepared person.
I can’t tell you how many people I’ve come across who prepare in almost every area of survival, except physical fitness. These are the people who have almost every piece of gear known to man, have multiple bugout bags each weighing more than 50lb+ pounds, but have never once strapped that pack to their back and walked a couple of miles to see how it feels to carry that much weight.