I think I've been doing this without knowing for awhile now. Mostly I haven't wanted to pay money to buy the power equipment.
I don't exercise as much as I would like to. But the things I do not require power or really any harm to the environment. My latest thing is jumping rope. It is a good exercising thing with little time and little equipment. You can take a jump rope wherever.
My favorite thing to do is walk. Last summer I would go for a 4 mile walk every day. It was very nice. Granted, I did listen to my MP3 player, and if you were no go now for no power, that would have to be taken out. It is a lovely time to ponder and think things out. My problem? Dogs. After two dogs scared me while walking, I decided I didn't want to do it afterall. I've thought about going somewhere to walk (the dogs are only in the neighborhoods) but something about driving somewhere to go for a walk just sort of bothers me.
Another good exercise is dancing. Okay, it uses power as well if you want to listen to music, but it is very exercising to just dance around your room however you want.
Bike riding is probably the best. I do not do this. I was going to buy a new bike, mine was crap and old and broken, but I recently had to buy a car because my old one broke and now I have no money. I often find it crap that this is the reason I can't buy a bike seeing as how I wanted the bike so I wouldn't need my car as much. But it gets cold in the snow. Bike riding is good because if you can take it places you get your exercise on the way to places so you don't have to put a specific time for exercise.