You may opt to shift the seat forward and back on a recumbent exercise bike. To have a full pedal stroke, your legs should be almost fully stretched out in front of you, similar to an upright bike. You may also change the angle at which your seat leans back. For example, if you prefer to sit more upright, then you can move the seat forward for a more upright position. Generally speaking, you want to be able to touch your knees when your legs are straight. This gives you maximum range of motion with minimal strain when pedaling. However, since you're sitting much lower than on an upright bike, your legs will be extending further away from your body. So to have your legs reach full extension, you need to set your seat farther back. Some people like having their legs way out in front of them when they ride recumbents because it makes balancing difficult! There are two ways to adjust the distance between your pedals: using shims under the seats or by moving the chain stay assembly. Using shims is easy enough; just get some that are appropriate for the distance that you want between your pedals and put them under the seats. Moving the chain stay is more involved but allows you to fine-tune the distance between your legs without affecting the overall length of the frame.