I've been going jogging a bit in mostly unpopulated areas recently.
It's not all the same muscles, but it is exercise.
A few years ago I tried PIK skates (they didn't seem to me very similar to ice figure skates, but maybe I'm not good enough to take full advantage). I also have inline and quad skates, and might try them again in mostly unpopulated areas.
I personally think that if you have any type of mask or scarf, it might be worth wearing it, so if you do pass anyone, and they sneeze or breath on you, fewer droplets will get in.