The answer to the headline question is: the hips. Unfortunately, bad habits formed in everyday life — slumping over a computer for hours on end, for example — often carry over to our golf posture. The good news is, it's a relatively easy problem to fix, and it can greatly improve your swing. Bending from the waist can be detrimental to your health as well as your swing. It puts the back in a curved or C-shaped position that stresses the spine and muscles, while restricting rotation during the swing and causing the arms to become too involved. Bending from the hips, on the other hand, straightens the spine and allows your body to rotate comfortably around it.
Should You Bend from the Waist, or the Hips? Golf Video – by Pete Styles
I often hear golfers talk about how when they get a set up for the golf ball they like to line themselves up nicely, get forward into their good posture and bend from the waist. Although they're not far apart, bending from the hips and bending from the waist makes a massive difference to the way you set up to the golf ball. So if you're unsure, we really well need to work on bending at the hips and not at the waist. The waist should be nice and straight as we tilt forward in the hips. So think about tilting from below your belt down here in the hips but not above your belt up here in the waist so a really good checkpoint for you here would be to use your golf club as a ruler. Place your nose, your chin and your belly button against the shaft and then tilt forward.
You may expect your life to be exactly the same after you have had your hip replacement--minus the pain. If you adhere to the exercise program and movement techniques your physician and physical therapist recommend, you may actually function even better than before, at least if you had severe arthritis that resulted in this operation. However, you need to be patient and cautious so that the hip heals properly. You will need to make certain lifestyle changes, especially when it comes to flexing--bending--the hip.
Bending from the hips instead of the waist in a golf setup promotes good swing mechanics and helps prevent injury. Many players who bend from the waist exhibit C-posture, in the parlance of the Titleist Performance Institute. Looking down the target line, the upper back often exhibits a C-shaped curvature. Learning to bend from the hips requires improved daily habits, physical fitness, swing technique and club fitting.