Physical Parameters Causing Reverse Spine Angle and How to Diagnose Them:
In order to maintain your spine angle during the backswing several physical characteristics must be developed. First and foremost, the ability to separate your upper body from your lower body allows your shoulders to rotate around your spine without going into backward bend or excessive left lateral bend. Limited trunk to pelvis separation is usually caused by reduced spinal mobility and shortened lat flexibility. Secondly, right hip internal rotation for a right-handed golfer is paramount for full rotation into the right hip without any lateral movement. If the body is unable to rotate around your hip due to joint or muscular restrictions than a lateral sway he may occur. Any lateral sway during the backswing will force the spine to tilt into backward bend and create the reverse spine angle. Finally, the ability to stabilize your spine angle during the backswing is directly proportional to the strength and stability of your core musculature (your abs and glutes). When it comes to spinal stabilization the core is the king. These muscles help keep your trunk forward flexed throughout your golf swing.
Reverse Spine Angle can also be caused by too much pelvic tilt at address which can cause you to have an S curvature in your lower spine. If this does not return to neutral as you swing back it can cause the Reverse Spine Angle fault. (See S-Posture)