I was not really an athletic kid.  I didn’t like a lot of the things they tried to make me do, and my mom’s idea of motivating you to exercise was basically making you run stairs as a punishment when you did something wrong.  That might’ve been a big part of it.  But that being said, when you are trying to motivate a child, stop calling it exercise, it sounds so unappealing, and definitely don’t ever make it a punishment.  Punishment is always bad.  Second of all, invite them to play with other kids who are being rather active whether they are just being more active running around or playing a sport.  Make it a game whether you are dancing around with them, they are jumping rope, or they are playing soccer or something.  My mom wasn’t really aware that she could sign us up for anything but dance, and even if some kids enjoy it, if your kids don’t, they aren’t going to want to do it and will give you a struggle for it.  Another thing you can do is actually to invite them to run over to the neighbor’s house to drop something off and give them I don’t know a fruit or maybe some kind of money reward, even a quarter when they’re young or have them walk the dog.  A lot of kids love the animals, and letting it be something that’s a sort of reward will really make it appealing.  Plus dogs really will generally get going.  There are easy ways to teach your kids exercise habits, you just have to actually bother using them.