Stationary bikes are a type of workout machine found in most gyms that mimic riding a standard bicycle. They primarily work the quadriceps, hamstrings, glutes and heart.
The purpose of a stationary bike is to give a workout similar to riding a normal bike without having to go outside. In addition to the various leg muscles, the calves and core muscles will also be somewhat engaged on a stationary bike.
Pedaling plays a large role in determining which muscles are worked while biking. If you only push the pedals downward, your quadriceps and glutes will be worked the most, while pulling back and up on on the pedals will also work the hamstrings.
Stationary bikes offer a very effective cardiovascular workout. They are an especially good choice for those with joint or muscle problems who cannot handle the impact of running, for example.
Stationary bikes come in upright and recumbent models. The model you choose can shift the balance of which muscles are worked most intensely.
Stationary bikes do not require the balance of normal bikes, and, therefore, the upper body can be more at rest on a stationary bike.