Of course the legs propel both but we jump by throwing our hands into the air and following them.
We wanted to do a run where Peter moved his arms in opposition to his arms and then one where he moved them together. The second move is really a leap. At first the problem seemed to be one of confusion, but the solution was to work out which was leading. When the legs led it was nearly impossible not to do the arms in opposition like running. In order to do them on the same side the arms had to go first. It changed from an uncoordinated run into a balletic jump.
Working what leads and what follows is crucial to it looking right. The eyes come alive when it's right.