Purpose: Relax the lower back and massage the internal organs in the abdominal area, especially the kidneys. 

The teacher (the one pulling) pulls the student (the one sitting) from a inclining position to a sitting position, according to the release/absorb rhythm. The student should relax and think of his lower back when being pulled. There is a natural tendency to think of one's hands when being pulled. If you think of your hands, the chi will not sink to your Dantien (lower back area) and the healing effect will be lessened. 

The role of teacher is very important because he has to know whether the student's focus is on his Dantien or his hands. An experienced teacher feels every vertebrae of his students and can help to direct their attention to where is needed.

Purpose: To increase the Dantien chi by correcting the curve of the lumbar vertebrae. More Dantien chi means more chi will flow through the meridians of the entire body and thus more healing occurs.

By holding the hands of a partner (teacher/student), you squat down slowly, paying attention to your spine. When you reach the bottom, you need to tuck in your coccyx. 

An experienced teacher will be able to guide his student to relax his lumbar vertebrae and pull up from his lower back.