In the late 1980's I purchased one of the first VCRs that had frame-by-frame capabilities. I immediately saw it would be a great tool for studying the mechanics of the baseball swing and started taping Major League games from TV broadcasts.
When I first studied each frame of the swing, I realized I did not have a clue what I was looking for, or what constituted good or poor mechanics. I decided the best way to learn would be to take notes on the differences I saw between the great hitters and average hitters.
After a couple of weeks or so, I reviewed my notes and found a disturbing pattern in my writing. The more I read the more it become apparent that I was trying to make what I saw conform to my long held linear batting principles. It also became apparent that if I was to make a serious study of the swing, I must rid my mind of what I had taught and record my observations with a completely open mind.
To this end, I made a sign and placed it over my desk. It read " Have no preconceived theory, report only what you observe." Mike Epstein makes the point well with his question, "Do we actually teach what we see." I could clearly see that the hands were not being extended in a straight A-to-B path. They were following a more circular path I had always referred to as "casting."
This and many of my other observation led me to question the swing mechanics I had always taught. If the straight extension of the hands and the Whip theory were not responsible for the bat's acceleration -- then what was? In the following months, I discussed the bat's trajectories with a number of physics labs. I will place below video clips that resulted from those tests and discussions.
The first clip below is of me demonstrating the PathFinder. It is similar to the bat we used in physics lad tests to eliminate handle torque as a factor in generating bat speed. The accelerating force is applied at a single point (eliminating torque applied by the hands). This clip shows the bat's reaction to being accelerated from a straight and circular hand path.
The second clip demonstrates the second force we found that generates bat speed " Torque " induced from the hands applying force from opposing directions.
Pendulum Effect vs Whip Theory
Demonstrating Handle Torque
Those that teach mechanics based on the "Crack of the Whip" theory would say that torque was not a factor. That once the hands slowed near full extension, just like a whip, the bat-head comes flying around. Forces applied at the handle by the hands had no roll in accelerating the bat-head. --- Study the clips closely and draw your own conclusions.