I feel I can add to this thread on what a poster has already stated. I personally use a functional purpose to all my exercise. When it comes weight/resistance training, I try everything I can to not use barbells or dumbells for workout purposes but instead use logs, rocks, weighted bags/sacks, old tires, etc. I try to emulate real life scenarios and workout around them to keep my body tip top for real world situations.
I never use a treadmill or exercise bikes, ellipticals, etc. Instead I go walk, hike, run or bicycle outdoors, even in inclement weather due to it we shouldn't expect the sun to be shining and the winds be calm when we NEED to do these things to evade or escape situations that can happen in life. Having to move tree limbs or other debris out of a path is a very usual thing that happens when there are any number of natural and man made disasters.
I also try to incorporate doing these things as part of my everyday life. For instance, if I need to pick up some things from the store, instead of driving there, I will either ride the bike (if more than a 3 mile round trip) or walk (< 3 mile round trip). These things have literally kept me in pretty good shape, as well as reduce stress and keep me familiar with my surroundings a little more intimately than driving would. I have noticed creeks, paths, wild plants and etc., that can be useable in a SHTF scenario that I would have never noticed otherwise.
Damian