If you are really going to use it! 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. Lift your legs straight up above your head and bend your knees toward your chest until they are at about a 45-degree angle. Bring your right elbow in contact with your left knee. Then alternate with the opposite knee and elbow and repeat. You should feel it in your sides and abs. Let's see why this happens... In generally, the simplest equipment is the treadmill. While this tends to be out of mind and not used on a regular basis. Or you keep saying to yourself... "If I only had that fitness machine I would be motivated to work out".