The simpler way to get free fitness is when it's incidental.
Americans don't even build their cities where they can walk anywhere, so exercise is seen as this thing you compartmentalize into a gym. You go there for exercise. Outside of it, you don't move at all. It's bleak and probably hard to notice until you've lived elsewhere.
The ideal is probably when you don't have to think "uh oh, gotta get my exercise in" at all—you've already done it going about your day.
I know wood heat is unpopular on HN, but firewood is a great example of what you're suggesting. There's an old saying that it heats you four times: once when you cut it, once when you split it, once when you stack it, and once more when you burn it.
Why would that be? That wood is going to turn into carbon dioxide when aging anyway.
Sure open fireplace are now accepted to be bad for the health but it's not complicated to "upgrade" an open fireplace into a closed one (which moreover offer much better efficiency).
Last winter I warmed the (relatively small) house with the closed fireplace only.
Now, granted, it may not be an option for city dwellers living one on top of another: negative externalities of chimneys are a thing.
But for anyone living in suburb or in rural, wood heat is great.
Americans don't even build their cities where they can walk anywhere, so exercise is seen as this thing you compartmentalize into a gym. You go there for exercise. Outside of it, you don't move at all. It's bleak and probably hard to notice until you've lived elsewhere.
The ideal is probably when you don't have to think "uh oh, gotta get my exercise in" at all—you've already done it going about your day.