I can specifically recall installing shock absorbers which came with instructions that called for inverting the shock and "exercising" it several times to bleed trapped air. I don't claim to fully understand the concept, but I am absolutely sure that the instructions recommended the procedure. I suspect that the objective is to move air from the primary to the secondary chamber.

Here is some info from the Autozone website:

http://www1.autozone.com/az/cds/en_us/0900823d/80/04/e5/a9/0900823d8004e5a9/repairInfoPages.htm