How are these trikes able to spin around backwards? I found a video of some trikers who start out going backwards, but spin around to moving forwards (watch just the first 10 seconds). As best as I know, my trike can only go forwards. How is such a trick achieved?
They're back pedaling as they go, this lets the drive train move backwards.

You'll often see BMXers doing the same, you see more in the first part of this video.