I see a lot of questions and comments in the blogs about turning the shoulders too much in the backswing and getting deep behind the toe line and over swinging. I also see many comments about hitting both chunks and thin shots. These problems can be cured by simply making sure your back arm (right for right handers and left for lefties) is in a right angle at the top of your backswing.
Let's start by looking at the concept of tucking the back elbow and keeping it in close to the torso or hip. The thought is that this provides some connection to the torso and more control of your arm motion. There is some truth to it, but it causes more problems than it is worth and in fact it is worthless because it is not correct.
For starters, a tucked back elbow is bent at the elbow so much that it looks like a V. A tucked back elbow is in close to the torso and thus causes a narrow width backswing. So narrow that it causes the forward arm to bend at the elbow. This is a major problem because the forward arm must remain relatively straight in the backswing as this is the arm that creates the width of arc. The forward arm must remain straight because it, along with the club, is the string in the concept of a rock swinging on a string creating centrifugal force. The wider the arc (remember, the arms swing the rock) the faster the clubhead, and a faster club hits the ball farther.
Another big problem of the back arm folding to a V is that it is being pulled inward toward the torso which is opposite of remaining wide and extended. A golfer can actually pull their upper arm inward and tight to their side so much in keeping the arm and elbow tucked that they can actually push themselves into a reverse pivot or weight shift. This pushes their head and spine forward ahead of the ball instead of turning and loading over and onto their rear leg behind the ball. It can also cause too much torso turn, getting the arms behind the toe line in the Sacred Burial Ground (SBG). And, to complete the problems, the wrists can break down and cause an over swing to parallel or longer. This adds more forward tilt to the head and spine increasing the reverse weight shift and lays the club off into the heavy position.
The cure for all these problems caused by intentionally tucking the back elbow, or intentionally cocking the wrists and/or swinging to parallel and not being able to keep the forward arm relatively straight, is simple. The back arm MUST 'Never and I mean never, ever,' BEND, BREAK, or FOLD, past 90 degrees, a right angle.
We all know from science class that a 90 degree right angle is the strongest angle. In keeping the body functioning in harmony with the laws of physics the arm in a right angle is at its strongest position. Just look at arm wrestlers. The first one to start losing their flat wrist and their right angle at the elbow as it starts bending toward a V'¦looses.
Practice and learn the feeling of your back arm lifting up to form a right 90 degree angle at the top of your backswing. Keeping your wrist firm helps create the right angle. That also helps keep your backswing 3/4 and the club more vertical. Keeping the back arm in a 90 degree angle also helps control the shoulder and hip turn to the forward arm over the toe line for the perfect limited turn PPGS backswing.
The final checkpoint when the back arm is in a right angle with a vertical 12:00 o'clock club will be that both arms form a perfect Equilateral Triangle. A line drawn touching both elbows as the base of the triangle will be parallel to the ground. The final important point about this equilateral triangle with the elbows parallel to the ground at the top of the backswing is that the arms, head, neck, shoulders, and back are all in dynamic balance. And they are strong and free from stress and strain.
I think it is safe to say that a back arm in a 90 degree, right angle at the top of the backswing is simple to do and easy to feel, monitor and check. Back arm in a right angle at the top of the backswing is simply the 'right' thing to do.