[6bmike]

left arm swivel takes place before or after impact?

Both- if you are a Swinger. A Swinger uses a Release Swivel before impact due to the Standard Wrist Action and employs a Finish Swivel after impact.

A Hitter uses ONLY a Finish Swivel since he uses a Single Wrist Action.

And add a third for a Swinger if you count the Start Up Swivel used by the Standard Wrist Action.

Three for Swingers and one for Hitters. Don’t allow the Swivel to haphazardly take you off the Plane Line.