We've all read articles and heard TV commentary about restricting your hip turn on the backswing to develop more coil and increase your X-Factor (the differential in degrees of rotation between shoulder rotation and hip rotation). For many athletes a simple increase in backswing hip rotation increases their clubhead speed and turns their over-the-top fade into a draw. Let me explain why.
First off, we all need to have as large of an X-Factor as we can to achieve maximum clubhead speed. But there is one aspect that is often overlooked. In Jim McLean's original writings in the early 90's he mentioned that the player with the largest X-Factor on the PGA Tour was John Daly. By no small coincidence he was the longest driver on tour at the time. Here's the catch: Daly also had the most hip rotation of the players measured.
A simple equation
What we find is that roughly for every degree of hip rotation, you get two degrees of shoulder turn. So when we say the model backswing normally has around 90 degrees of shoulder rotation and 45 degrees of hip rotation we see this 2-1 ratio develops an X-Factor of 45.
If the hip rotation is increased to 46 degrees that should lead to a shoulder rotation of 92 degrees and an X-Factor of 46. This scenario has limits, but I have found that for many average players, increasing their hip rotation leads to more shoulder rotation. They don't have the flexibility to just restrict their hip turn and turn their shoulders more. The most profound impact is with players who tend to slide their hips more than they rotate them. Those players tend to have some or all of these characteristics.
Without overthinking this, many times simply making sure that the hips turn more on the backswing can change these flaws and produce a swing plane that allows players to deliver the club to ball on an inside path, encouraging a draw. For some of these players it's the first time they are aware of properly moving their core midsection, and how activating that can really be the engine that drives their swings. They also feel the production of centrifugal force that helps them properly release and square the clubface.
Finally, remember these points that will prevent too much hip rotation: As long as you keep your front heel down, your back knee flexed and not allow it to float out over the outside half of your back foot, I say go for it and start turning those hips.