Often you see hitters moving a lot before the ball is thrown, not to be confused with as the ball is thrown; pumping, swaying, etc.
A lot has to do with the principal, body in motion stays in motion, which helps with timing and rhythm. Which it does help, but what most don’t realize is that it has a lot to do with vision as well.
When someone stays perfectly still and stares at an object their vision begins to blur due to exhaustion. The eyes are a muscle. Think of it as holding something without moving. If you simply move side to side just so slightly your eyes will never get focused or tired and your vision will stay clear.
Try this test. Set up a tee with the writing on a ball facing you. Then get in your stance. Stand perfectly still and stare at the wall in front of you. Now look down. You will find the ball small and blurry. Now repeat the same thing again but this time shift your weight slightly back and forth. Now look.
Sharp and Clear.
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