The corner is established when the rear hip socket coils rearward and reaches it's range of motion limit against the ball of the femur, which is internally rotating.
The amount of movement is not great. Maybe 30 degrees or so. But this 'offset' is where the true separation in a swing and throw exists. It is very specific. Very deep inside the rear hip ball and socket joint.
Most people define separation as the differnce between the shoulder line and the hip line. This is far too general in nature and does not require use of the proper muscles to attain. Shoulder to hip separation is too 'big' and 'sloppy' compared to hip socket separation. It creates separation at the waist, not deep in the hip socket.
The difference between the two is shown in these video clips.
Front View
Side View
Establishing the corner is very important. But maintaining it, stretching against it, and using it to launch the swing are critical parts of the high level swing.
See "Stretching Around The Corner" for information on why the corner is so important.
The high level swing is a release of stretch that was established during the loading process. This stretch is accomplished by stretching against the corner. The corner was established by coiling the rear hip rearward over/around the ball of the femur. You then stretch against the corner by 'pulling back' with your lower back and retracting the scapula moving it toward the spine and clamping it down. Basically, you pull rearward with your back muscles to help the hip maintain it's coiled position around the ball of the femur. While this 'pulling back' is happening, the rear leg is attempting to internally rotate. So you have a 'fight' going on between the hip, lower back, and scapula, which are all pulling rearward against the rear leg, which is trying to turn forward.
We refer to this action as the rag wring. If you had a rag in your hands and were to wring it out, the top hand would turn one way against the bottom hand turning the other way. In hitting, the hip, lower back and scapula are represented by the top hand. The rear leg is represented by the bottom hand.
The rag wring action is the 'stretching around the corner'.
Here is a video clip of a professional player. He has preset his load on the left. You can clearly see and feel how his back is working to wring his rag.
http://www.hittingillustrated.com/im...lvMomentum.gif
The clip on the left is a great visual of 'stretching around the corner'.
Most amateur hitters do not use their lower back properly.
This 'pull back'....or 'stretch around the corner'....is never given up. It is a constant and increasing action. The hip and back continue to pull rearward and never reverse that pulling action.
Sounds wrong? Try it.
See "Using The Corner" to see why and how to unload the swing.
Establishing the corner, and stretching around the corner are critical elements of the swing. But they are worthless unless you learn how to use the corner to launch the swing. Most amateur hitters do not use stretch to create a release of their swing. Instead, they use brute force to swing the bat. In other words, when they load, they are simply looking for more distance over which to 'move back' or 'coil', so they have a larger range of motion to 'move forward' or 'uncoil'. The more distance they create the more speed they reach. The problem with that is they never get up to speed until they are far out front. This creates all kinds of problems when facing quality pitching.
What professional hitters do is different. They learn to create stretch and then release the stretch, making their swing sudden and compact. They do this by using the corner to unload. Or, said differently, they unload from behind the corner, not in front of it. Amateurs turn to align with the ball first, and in so doing bleed their corner, then they swing. Professionals stretch around the corner, maintain that stretch until 'go', then unload from behind the corner and allow the unload itself to turn them into the ball.
They do that by turning the barrel rearward.
If you get stretched around the corner, and then push the bat forward to swing, you have given up the benefit of the stretch that you created. To push the bat forward you must first know where to push it. You first must know where you expect contact to be made. So, you first must turn to align with the ball, and in the process lose your corner, and lose the stretch that you created, then push forward to swing to the expected contact point. That is what amateurs do.
Professional hitters establish a corner, stretch around the corner, and then unload the barrel rearward. The weight and direction of the barrel launched rearward INCREASES the stretch. The barrel continues rearward until it reaches roughly horizontal at which time the point of no return is reached. The stretch increases as the barrel arcs rearward but at/near horizonal the stretch is suddenly lost. The rearward resistance that the speed and direction the barrel was offering, helping the hip and lower back and scap stretch against the rear leg, is suddenly overcome by the rear leg. When the bat gets flat/horizontal the resistance goes to zero and everything is suddenly yanked forward and directed into the ball.
By sending the barrel rearward the hitter 'used the corner to unload'. He didn't bleed the corner then swing. He unloaded around behind the corner, allowed the barrel to continue into a rearward arc. When it reaches horizontal the corner yanks the barrel forward. He used the stretch around the corner to power his swing.
No brute force swing can match the power of the the high level 'corner produced' swing. But most importantly, no brute force swing can get up to speed as quickly nor have the late adjustability which is so important as you advance.
Establish the corner, stretch around the corner, then use the corner to launch the swing. A whip develops that produces the suddenness of launch that only the greats achieve.
Watch these clips and look for the above.
http://www.hittingillustrated.com/library/Pujols2.gif http://www.hittingillustrated.com/library/Bonds4.gif http://www.hittingillustrated.com/library/Manny26.gif http://www.hittingillustrated.com/library/Kent.gif