Windshield Wipers - compression

I am starting on WWs and I have read some things in the forums in reference to "compression." 

Can someone explain what that means?

Also, I don't have stall bars. I use a pull up/squat rig with a couple of strategically racked and banded in empty barbells. Looking at the video for this movement, it looks like the main points of contact are actually above the neck. Looks like around the base of skull/triceps and above. Is that right? Are we not really in contract with the stall bars in the upper back?

HI MIchael , "compression" refers to the ability to hold the lower limbs as much closer as possible to the body without moving away too much the upper body from the stallbar.