Why Your Hips Need To Decelerate
Many hitters lack the understanding that the hips have to decelerate for the upper body to release through the zone properly. Of course, we have to start our swing with our hips accelerating fast but the abrupt stopping of the hips is where you get the juice. Think about when you slam on the brakes in the car. If you're going at enough speed your body will fly forward only to be stopped by the seat belt.
Often times hitters will be over-rotating to try and create more power. There may be times where they can over-rotate and run into that middle to inside pitch. But this will not be repeatable in the cage and chances are they will not be able to adjust to pitches in games.
Check out this old school video breakdown of Manny Ramirez launching an inside pitch. You will see how the hips start and then abruptly stop giving him the power to crush this Homerun.