Wall deadlifts will isolate the lower back muscles better than any other exercise out there. Excellent for strength, mobility and helping to deal with lower back pain.
There are many good exercise to train the lower back: back extensions, reverse back extension and conventional deadlifts.
None of these exercises will completely isolate the lower back though: glutes and hamstrings are always activated and they do a great deal of the work.
Wall deadlift is likely the only real isolation exercise for the lower back. In wall deadlifts you are leaning towards a wall which takes the hips out of the equation. This means that there is no longer any glute, hamstring or other leg muscle activation present.
Conventional deadlifts will work the lower back to a great degree but because almost every other muscle of the posterior chain is also involved and the lift is often done with some momentum, the lower back is never thoroughly strengthened to its full potential.
Even back extensions which are considered an excellent lower back exercise, will utilize the glutes and hamstrings to a massive degree.
To fully strengthen a muscle and build mobility, you want to be able to contract the muscle in its entire range of motion and for this purpose you often need to learn how to isolate the muscle.
This makes the wall deadlift a real game changer.
Wall deadlift will allow you to isolate the lower back and strengthen it in its full range of motion. Your middle back will also work to some degree but it doesn't make the exercise any worse.
The best part of this exercise is that it's incredibly effective without any weights. In fact, you should start with bodyweight only and learn the correct execution by doing high reps and using the full range of motion.
Your hip position and angle can alter the difficulty and emphasis of the exercise. The higher the hips, the harder it will be because your body is in a bent-over position. When your hips are low and the body is relatively upright, there is less resistance which means the exercise is easier.
You may notice that just after 2 sets and 10 to 20 repetitions, your lower back experiences a pump like never before. 3 to 6 sets for 10+ repetitions per set is an excellent range to start with. Once your lower back becomes stronger, you can add small amounts of weights like 10 to 20 pounds (5-10 kilos).
It's possible that you have never fully contracted your lower back muscles before trying the wall deadlift. By practicing wall deadlifts, you can improve the condition of your lower back in a dramatic fashion. This exercise can be a big help for lower back pain.
Train hard, stay safe.