Freewheel adjustable wheels and fitness bike therewith

A fitness bike, comprising:

• a frame part supporting a saddle part and a handle part;
• a pedal part being disposed at a rotation disc that is disposed on a lateral surface of the frame part;
• a rotation gear part receiving power of the pedal part to rotate, and being rotatably disposed outside a shaft;
• a spline gear being fixed to an outside of the rotation gear part, and rotating together with the rotation gear part;
• a fixation case which rotatably supports the rotation gear part and a rotation of which is restricted;
• a rotation case receiving power of the rotation gear part to rotate, and being rotatably disposed in the fixation case;
• a clutch bearing being disposed between the rotation gear part and the rotation case, and transferring power at a time when the rotation gear part rotates forward;
• a first gear part having one side that is fixed to the rotation case, and the other side that is disposed in a way that surrounds an outside of the clutch bearing to receive power thought the clutch bearing;
• a driving part being fixed to the fixation case, and providing rotational power;
• and
• a movement gear part moving based on power of the driving part, and operating in a non-freewheel mode where the movement gear part engages with the first gear part, and in a freewheel mode where the movement gear part is spaced from the first gear part.