This is an advanced exercise that needs a perfect squat and a perfect back press.
This exercise is a combination of a squat and a back press.
The ready position is the same as for the back press, stand tall with the chest expander in your back.
Now squat down as you press into the back press. Your squat should be down when your arms are extended. Now squat back up and slowly release the chest expander back into ready position.
Start training this exercise with little resistance because it needs a lot of concentration and coordination.