LOL Google points at a 2+2 post on dynamic rows :
http://forumserver.twoplustwo.com/sh...p;Main=9623208
HE WHO CONTROLS THE GOOGLE CONTROLS THE UNIVERSE!
Anyway, if your back is healthy and you're not injury prone then go ahead and do the dynamic row.
I find it really hard to keep good tension and shape to my lower back when I'm doing fast jerky movements like that.
For me personally, I would rather do a Pendlay Row cuz I can focus on keeping my back in good position the whole time.
It's really weird that the dynamic row is in the Starr 5x5 program but there seems to be like zero information about it on the net.