I was riding behind a guy on the weekend and he had the weirdest cranks!
I will try to explain. Normal cranks operate (to my way of thinking) as opposites. If one arm goes down, the other goes up.
The guy I was behind had cranks that had both arms down at the same time! He rested both legs straight down when he wanted to coast for a few seconds.. and then when the group surged, he just pedalled normally again! (With the cranks going 'opposite', as per a 'normal' set of cranks)
Occasionally, he would do a few pedal strokes with both legs doing the same thing at the same time!
Now someone COULD tell me that these are common, or that they are a training tool, but what the ???