Linear > Rotational
We are talking baseball mechanics. Obviously, there is some necessary rotation in baseball (I'm not a complete idiot). When it comes to pitching and hitting, how we deliver our energy should be linear. Take boxing for example. What do you think would happen if a boxer started spinning around, in circles, with their arms out trying to connect with his or her opponent? One, it'd be hilarious to watch. Two, he or she wouldn't hit with any kind of real force. Finally, he/she would get his/her teeth knocked out quick.
Hitting and pitching mechanics are really quite similar when you stop and think about it. There's a load, have to stay balanced, stay in line with the target, etc. With both mechanics, there is a certain point where everything has to be in the correct position and then everything "explodes" to the target. We are going to focus on the part about the explosion today.
As I mentioned before, everything has to be in the correct position before we get to the explosion. We will use pitching for example with this one. When a pitcher rushes down the mound and "leaks", he is not only losing power but he's also not giving his body enough time to catch up. The ability to throw consistent strikes decreases, and so does the velo, while the risk for potential injury increases. Everything has to be in sync for the explosion to work properly.
When I say linear, I am referring to the delivery of our energy (or force, power, etc.) to the or through the baseball. Any movement outside the direction of our target, other than loading, is wasted movement. We want everything we have, (weight, momentum, bat path, etc.) going to our target. Before you start wondering, "i thought you were supposed to keep your weight back and squash the bug", you're wrong. It isn't your fault, that is what you heard all your life. In the effort of keeping this semi short in length, we won't go too far in-depth on that yet. But, long story short, keep your weight with the bat/ball. The weight is transferred with the swing/pitch, not before.
Now-a-days, some people are teaching the "elevate & celebrate" swing. You know the kid that'll put 1 of 50 out but "K" and fly out on the other 49. When we talk about staying linear, we are looking for the bat to stay on the same plane as the pitch, for as long as possible. Our arms run out of room eventually after we make contact and have to roll over. The goal is to make that happen as far out front as humanly possible. That is when you see those loopy line drives turn into missiles. Let the extension/ leverage work for you, just make sure its in line with your target.
In conclusion, keeping everything in-line and focusing all your energy to your target leads to limited- no wasted movement. Load up, stay balanced and explode in the direction you want to go.