When the fist is on one side you have to press the arrow on the side the fist is on (fist on the left, press left, fist on the right, press right). If the fist points towards you, press up. If it points up, press down.
You can use the cursor keys for this (it makes it so much easier).
BTW. This one baffled me for a while before I figured it out and I still find it rather confusing.