Cats (like humans) tend to get fat when they sit around and do nothing all day long. To give people exercise, you can use a treadmill. To give cats exercise, you can give them an exercise wheel that looks like a giant hamster wheel.
When a friend’s cat exercise wheel wasn’t working properly, Adam Savage of “The Myth Buster’s” fame, stepped in to fix the problems. After fixing and improving the exercise wheel, you can see that it now works perfectly. Whether the cat wants to exercise on it though is an entirely different story.