To change the orientation of the hand. Coming in, it’s pulling from elbow. Going out, the hand pulls the arm.
Differentiate the role
Every body part has a role, but which ones are primary and which ones are secondary (only getting out of the way).
Knees
Knee up / knee down. The body needs to be a physically solid structure, like a bike and the pedals are the knees. Feels like you make a foot and a half movement, but it looks like no move.
First one is 70 rear, 30 front. Front becomes long back becomes short. Second one switches the pivot to the rear side of body (rear shoulder/kua axis).