Some elliptical machines fold up to save space when not in use. They generally fall in the economy or moderate range for price in comparison to gym or fitness club memberships. Recumbent exercise bikes, which put users in a slightly reclined position, place less stress on the back and knees but tend to cost more. Some people find the position and motion uncomfortable if they are in good physical shape. Some stomachs have a small curve, and all the crunches in the world won't change that. However, the exercises and equipment discussed below will help tone, strengthen and define your abdominal muscles. With all the choices for home fitness equipment is the treadmill. While this tends to be a large piece of equipment and can be quite expensive, it is also a very versatile piece that is suitable for exercise enthusiasts of varying fitness and skill levels. The most expensive models are extremely durable and can handle a great deal of intense use by serious runners. More mid-range models are not quite as durable, and the