Physically energy in the kinetic chain is passed by decelerating the prior link. For example in a baseball swing the hips reach their peak speed about two frames before contact and then start to decelerate, the shoulders peak after that but also before contact (Dave Forthenbaugh in his piece “Biomechancs of the baseball swing” cited a max shoulder rotation speed of 766 degrees per second about 57 ms before contact slowing down to 430 degrees per second at contact in elite minor leaguers).
You want to swing through the ball and not decelerate prematurely but for optimum stability and energy transfer you need to strengthen rotation and anti rotation.
A good way to train that is doing stop swings. For strong adult players I would use a 36-40 ounce bat like in the overload training. Basically is is like a check swing that is a little too late so that the bat stops around perpendicular to the pitch flight in what would be the contact position or better a hair before that. Make sure you stop with bent arms and the back elbow down and front elbow up.
Accelerate as hard as you can and then stop as hard as you can by tightening all torso muscles, back, arms and forearms. The front leg blocks hard and back foot will be pulled forward a couple inches with the torso being slightly leaned back in line with the front leg.
Position should look basically look like that:
This trains the anti rotation muscles of the torso but also improves forearm strength and teaches to reach a good contact position.
Kids need to learn to complete the turn and finish the bat path. Many kids stop their rotation prematurely or never rotate at all and many don’t accelerate through contact. The shoulder rotation does slow down before contact but first it turns full speed until the chest almost faces the pitcher and even then it doesn’t go to zero but continues until the rear shoulder almost points to the pitcher.
So better only do this drill with advanced hitters who already turn well and finish their swings and not with kids who don’t have great intent and a good finish because it could cause them to stop prematurely. Learn to turn hard first and then worry about timing deceleration and optimal funneling of that turn energy into the bat. This is definitely an advanced exercise and great for hitters who pull off the ball and spin through without good direction through contact.