Players jog in a limited area without the ball.
You can think of more variations. Follow each pause with more jogging, but vary the rhythm so that sometimes there is a long wait between instructions while other times several instructions come quickly one after the other. Each player passes and then runs between the other two players. Service should be rapid enough so that the player volleying is in constant movement. On coach's signal, the other player bowls a ball through the tunnel, runs to the end of the tunnel and collects the ball, bowls it back through the tunnel and joins the end of the tunnel.