Exercise bikes are non-weight bearing. You can achieve all the benefits of an exercise program with less stress to knees and other joints.
Upright bikes put the user in a similar position as a traditional bicycle. The user sits on small seat, with his or her back upright and unsupported, and legs vertical to the floor. It takes up less space than a recumbent and will simulate the feel of a traditional bike better. An upright bike emphasizes the quadriceps (the front of the thigh).
Exercise bikes have a smaller “footprint.” They take up little room relative to a treadmill. They are also easy to move around.