sentence: Two professional bikers are biking at the Peckham BMX Club. sentence:  The bikers are going over a curbed surface at full speed. sentence:  There are several other bikers doing the same activity on another curved surface. sentence:  There are five bikers wearing helmets standing ready to start a race. sentence:  They begin racing at high speed over a curved road. sentence:  Two more batches of racers start the same race. sentence:  A single biker is going through the curved road at very high speed.