Those of you from Golfwrx might have seen this already. The following is why swinging in sync is better than isolating body parts to gain power…or even worse to fix a different body part being isolated (e.g. consciously leading with the lower body because you are coming over the top).
If you make a proper turn going back, your hands are behind your sternum when they set over the right shoulder and your sternum is behind your zipper because your upper body (shoulders) turn more than your hips.
Split second photography shows the hips have a split second lead to start the downswing.
Now, if the hands are behind the sternum and the sternum is behind the zipper and the zipper has a split second head start, if everything turns together, you get the desired affect of hips leading the shoulders and the hands trailing, yet everything is in sync.
If, however, you make a conscious effort to lead with the hips or leave the hands behind, hold the lag, delay the release, etc…., that is when you get out of sync.
It really is that simple…and turning properly is all about allowing natural body mechanics to happen without your interference.