Cat fitness really can be fun. However, it is important to start any fitness program only when you feel like it. Don't let a few extra pounds intimidate you into becoming more active. The most important aspect of fitness is: when to start the program. The best time is at about 2 a.m. The house is quiet; there are no distractions. The warm-up is critical. Cats are experts at stretching, so this won't be a problem. Start with a few wind sprints, full speed, toenails clicking on the tile or linoleum floors. A few low but loud growls will help you feel charged up.
Now it is time to add some eye-paw coordination work. Find a marble (the big steelies work even better) and roll that down the floor as the sprints continue. See how many times you can ricochet it off the wallboards before it disappears under the fridge. Finally, work on that upper body strength. Climbing is a great exercise. Use draperies, macrame plant hangers, or clothing on hangers. You can even find some carpeting on some basement walls. Backs of chairs work well, too.
Now put it all together. A speed sprint to the end of the hall! A race around the living room! Leap to the back of the rocking chair! Let the rebound launch you to the top of the swinging planter! Rock that baby! Feel those muscles work. Just as the hook pulls loose from the ceiling, dash to the bedroom and dive under the covers. Establish your alibi just in time to hear the crash of the plant to the floor below.