Bat speed. Where does it start and how is it created? This could possibly be one of, if not, the most controversial aspects of the swing among those looking for the best way.
The problem for most people in regards to bat speed or barrel acceleration is when it actually happens. The magic word there is "ACTUALLY." Outside of The Baseball Rebellion, anybody I discuss the swing with will immediately say that, "The barrel should be moving the fastest at contact." This idea would make sense because speed at contact is what we want right? WRONG! We want speed into the zone (path of the ball). As we continue to turn, we will maintain that ACCELERATED barrel. Once the barrel gets to a point, we release through the rest of the zone. Now, I know that seems like a lot of technical jargon but simply put, we want the barrel to be fast way before contact. The same principals of bio-mechanics and physics are at work in other sports. The golf swing is like the distant cousin of the baseball swing. Here is a great video about the "flail principle" and how it relates to golf. Try to bridge the gap to the baseball swing for yourself as you are watching.
Notice anything similar in the next two pictures? Below are photos of Bryce Harper and Tiger Woods. I have lined up the points where true acceleration happens in the top photos. In the bottom photos, I have marked where the flail lines back up with the front forearm of both players. Notice the arrows pointing in the direction of acceleration.
The major differences in these two swings is the location of the ball, the length of the "flailing" object, and the bat/club alignment at contact. If done properly, Harper's bat will flail to the point of the elbow on his lead arm. Tiger's club will flail to the point of the elbow on his lead arm, which is also in line with his lead shoulder. The faster the hitter can get the barrel lined up with the lead elbow, the faster the the barrel is. If the hitter can get into this alignment as the barrel enters the zone, the bat will be fully accelerated before turning all the way to contact. You hear coaches talk about "quick hands at contact," along with a ton of other bad cues which you can read about here. Once Bryce and Tiger get the bat/club to the end of the alignment, they just keep turning while they release the bat/club out. How many times have you seen either of these two monsters stop turning their bodies? Never.
The hands will be used more passively in a high-level swing than most people realize. In order for the "law of the flail" to work for baseball, the hitter must start the barrel in motion back behind his shoulder and then with his/her turn, transfer energy through his unwinding body and into the hands. At this point the hands will act like a hinge, as mentioned in the video we saw earlier. If the hands are rigid or actively moving at the ball, the hinge is broken and deep acceleration can not happen. Here is a video of Chipper Jones showing us a high level barrel path and deep acceleration.
I think most people do not realize this because they never see it. This part of the swing happens so fast and without close analysis of slow swings, you will never pick it up. The average viewer sees the bat get to the ball at super speed and thinks the hands must be fast because the bat is held by the hands. Always remember that the "rule of the flail" can not work properly without the correct footwork and hip rotation. This is why "hands first swings" and "knob to the ball coaching cues" do not work from a mere physics perspective. If the knob of the bat is moving at the ball, then what is the barrel doing? It is not picking up speed, not turning, and not coming around. The player can not generate enough speed with "hand snapping" to catch up to high level pitching.
Like I usually do here, I urge you to think about what coaches are asking you or your player to do at practice or lessons. Look out for one-handed bat drills where top hand or bottom hand dominance is the goal. Remember, early bat speed is not just a power generator, but also an extra ten feet of distance to watch and read the pitch. Thus, having more decision time and ultimately selecting better pitches. This concept will become more and more important for your player as he or she reaches faster pitching levels.
JK Whited, Leader of the Baseball Rebellion