Hyperextensions, GM'ings and SLDL's allow (for the most part) a 90 degree range of motion for the lower back. Regular DL's require the lower back to act as a stablelizer betweem the lower and upper body. The legs (with help from the hips and glutes) do the actual pushing off the floor . That being so, the lower back is required as a static/hold factor, more or less, when DL'ing. For all around back strength both the static holds (DL's) and extensions movements like Hyper's and GM'ings.shold be included in serious back training. The SLDL is different because the weight is held nearer the body (or should be) when preforming the lift, not out and away like any form of a extension.
BB rows can be an exceptional movement for muscle thickness and strength of the lower back muscles. When people begin to round the back in that lift, the odd's of injury can increase. Keep the lower back in a static/fixed position (like the DL) for the most part. There are exceptions of course. Like doing BB rows while coming up to an almost standing position. I know this is not by the PC training book, but it is an excellent mass builder for the back (lower and upper), traps and even arms.
If doing Hyperextensions try holding a BB plate straight out and at arms length at the starting postion, rather than the usual holding behind the head method. Extensions are leverage exercises and having the weight out and away from the body increases the resistance even more. You will not need a lot of weight in this version.
If your training the lower back strongly, than the ab's should be trained just as strongly. Does not mean higher rep ab work, but reps between 8-15 with a heavier weights included. Two or three sets should take very good care of the upper and lower abs. As a short range muscle there are a very powerfull group. As most short range muscles are. Good Luck.
