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Linear vs Rotational Test the "Crack of The Whip" Theory Mechanics that Generate Bat Speed Letter from: Physics Dept Rotation and the Stationary Axis Increase in Batting Stats Does Bat Speed = Pop The Illusion of Power Wrist Action or Torque The Fence Drill and Bat Inertia

As I understand it, the fence drill should help the hitter develop a swing that allows him to hit the ball with real authority, like Mantle and McGwire. But I would suggest that you to test the concept yourself before teaching it to your players. Stand close enough to a fence so that the bat will reach from your belly button to the fence. Without moving away from the fence, self-toss (or have someone feed you) balls and see just how effectively you can hit. --- Good luck.

I have often wondered where the idea for the mechanics used in the fence drill came from. Why would we think that accelerating the heel of the bat (or the hands) while keeping the bat head back during a good portion of the swing would result in greater bat speed and a shorter stroke than actively trying to accelerate the bat head from the start? I am sure faulty information from the scientific community regarding the transfer of kinetic energy ("crack the whip") is partly to blame. But I think the major part of the idea was derived from a few coaches viewing hitters on film or videotape.

While watching a hitter swing in slow motion, one would note that the hands are accelerated a good distance before the bat head arcs outward with much authority. I would agree that most of the angular displacement (or arcing out) of the bat head occurs as the hands nears it's full forward travel component. An overhead view of the swing will clearly show this. My problem is with the conclusion that therefore the batter should delay applying forces that generate angular bat head acceleration until later in the swing. Rather, the large resistance offered by the inertia (resistance to acceleration) of the bat head retards the batter's effort to gain more angular displacement earlier. Although the arcing out of the bat head in the early part of the swing may appear slow on film, it is important to keep in mind that it takes a great amount of force over time to overcome inertia an attain a higher rate of angular acceleration.

Delay in applying forces to overcome inertia until later in the swing will not lessen its impedance to bat speed development. Great hitters initiate the swing with torque and rotational forces to develop as much bat speed as early in the swing as possible.