Proper rotation of the pelvis is a key for a fluid golf swing. There are a coupe of key points in terms of how hip rotation works that help ensure you maintain your posture and don't early extend. When you don't rotate the pelvis through contact and the hips extend early your wrists have to release early and you lose control of your club face angle. When you lose control of your club face angle golf is very frustrating!
You need to use the proper muscles to rotate the pelvis. It is very easy to over use the quads in the golf swing, especially as you shift to the lead side. When you over use the quads that stops hip rotation and leads to the dreaded early hip extension. The glutes need to be used to support the pelvis rotation, not the quads. Remember that famous Tiger Woods quote about not being able to fire the glutes?
It also helps to understand that you need to direct the ground force offset from the hip sockets and not through the hip sockets. Torque is defined as force at a distance from the pivot point of the rotation. If your ground force is directed through your hip socket - especially on the lead hip socket - you don't rotate and you just straighten the lead leg and the pelvis stops rotating.
In this video Dr. Tyler Standifird goes over these points in some detail so you can understand how the pelvis structure and muscles are setup to work to enable fluid rotation.
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