It is very important to have the correct posture during the golf swing for several reasons. First what is the correct posture? Well a 30 degree spine angle is the perfect posture.
This will allow you to rotate without hurting your spine.
If you are leaned over too much it puts stress on the lower back as well as does not allow you to rotate and stay in balance. Proper posture will not only help prevent injury but it will allow you to hit the ball further with less work.
For this and other great tips consult your local PGA of Canada professional.