I would suggest getting rid of that. Wiggling your spine under a heavy load is not good.
Low Back Positions - Flexion, Extension, and Overextension with Mark Rippetoe - YouTube
Fixing Your Squat Set Up - Stop Overextending Your Low Back - YouTube
These might help.
You want to do your valsalva, tighten everything up, and then start the movement. No need to "throw" anything.