Exercise machines, resembling modern stationary bicycles, have existed since the end of the eighteenth century; the Gymnasticon was a prominent early example of this. The basic principles have changed little over the centuries.
Most exercise bikes provide a mechanism for applying resistance to the rotation of the pedals, and this is used to increase the intensity of the exercise. Resistance mechanisms include magnets, fans, and friction mechanisms.
In recent years, many new stationary bikes have appeared. These include those in recumbent positions, upright bikes, and indoor cycling bikes. The later are bikes built for riding in indoor cycling classes.
Some stationary exercise and fitness models feature handlebars that are connected to the pedals. This means that the users upper body can be exercised along with the lower body.