Most bicycle hubs incorporate a freewheel to allow the pedals to remain stationary while the bicycle is in motion, so that the rider can coast, i.e., ride without pedalling using forward momentum. A fixed-gear drivetrain has the drive sprocket (or cog) threaded or bolted directly to the hub of the back wheel, so that the pedals are directly coupled to the wheel. During acceleration, the pedal crank drives the wheel, but in other situations, the rear wheel can drive the pedal cranks. This direct coupling allows a cyclist to apply a braking force with the legs and bodyweight, by resisting the rotation of the cranks. It also makes it possible to cycle backwards.