[Daryl]

Super stiffen or rooting occurs just prior to impact and sustains until impact occurs. This happen so fast you can't see it nor on video can pick this up.
The hips actually counter torque and turn back away from the target a few degrees when you super stiffen . On video you won't see this occur. When the upper body catches up with the hips and impact occurs, the hips and upper body turn through to a full finish together.

I have two slow motion videos; of Brian Gay and Greg Norman where the hips actually counter torque and turn back away from the target a few degrees before Impact. So, it's possible to witness this event on Video. I'll find them and put them up for everyone's review.