Strength is an element of power, power is an element of speed, a muscle is a muscle is a muscle, make the muscle bigger it will in turn provide the ability for the muscle to be stronger.
A few things IMHO:
1) Conventional Deadlifts have never directly strengthend my lower back...however, one must have a strong back in order to perform the conventional movement correctly and hold the spine in proper alignment.
In otherwords, the low back/lumbar musculature must be strong BEFORE one attempts to perform the conventional deadlift correctly.
This means that OTHER exercises, BESIDES the conventional deadlift must be used to strengthen this area.
Yes, conventional deadlift work the lumbar muscles isometrically, which does, to some extent, strengthen them, but it does not work these muscles through a full ROM.
No mechanical work is apparent to the lumber.
2)Many people, PT's namely, talk about using a flat back/neutral spine when doing any type of movement involving the low back.
Fine, but as I noted above, these will not strenghten these muscles through a full ROM.
You have to have a strong back in order to maintain this type of position during back extensions, good mornings, deadlifts, RDL's, & SLD's, but, as I've already said, other exercises work the lumbar musculature better, and will get one ready to perform all of the above movements with the neutral spine.
3)If you want to use a form of the deadlift to maximize low back and posterior chain involvement, then the SLD is an obvious choice, where the back is slightly rounded at the bottom.
Again, the lumbar muscles will not be working through a full ROM, but much more so than the conventional deadlift.
Also, the effect on the hamstrings, upper back, traps make the SLD "THE" movement for strenghtening the ENTIRE posterior chain.
4)In order to essentially "isolate" the low back muscles you must
(A) perform a movement which takes the hips and glutes out the movement to the greatest degree possible
(B) perform a movement that takes you through the greatest range of pain free movement possible and has you begin in a position of spinal/trunk flexion.
The MedX or kieser low back and exercise lumbar pieces will do both of these. Now, I know many on this board have never tried either of these, but these are the real deal.
5)A movement I kind of "came up with" one day which really smoked my low back is the following: use a straight bar, feet shoulder width with a "soft" knee (maintain this knee position throughout), and peform a Romanian Deadlift (keep the head up, and shove the butt back and keep a neutral spine).
Keep the bar close to the body, and go down until the bar is at mid-shin (remember, keep the neutral spine).
Once you've reached mid shin with a neutral spine, round out the back slowly until the plates touch the floor.
Now, using only the lumbar muscles, extend back up, slowly and smoothly, into the neutral spine position.
Do not come all the way erect (like when you began the set).
Once you reach neutral spine, round out again and repeat the extension. 15-20 reps. You won't need much more than the bar to start this, and your low back will be screaming after 15 reps. It is kind of an RDL, SLD, Good Morning, and back extension all rolled into one. Try it.
Andy.
