Why You Don't Have A Deadlift Lockout Problem
If you frequent any Powerlifting forums or follow Powerlifters on social media, then you'll often see lifters asking how to fix their deadlift lockout. They'll ask what exercise(s) they need to do or what muscle(s) they need to build up in order to make their lockout stronger. In most of these cases, the lockout isn't actually weak. What is weak is technique, which leads to poor positioning at the time of the lockout. Most of the time the lifter is rounding their back with their hips tucked under them at the beginning of the pull. Once they get passed their knees, then they need to unravel their spine which either causes the lifter to fail or take a long time to lockout.
So, the solution to this problem is starting in an efficient position when initiating the pull and maintaining this position throughout. This means we want as little lumbar flexion as possible. This will make it a little slower to break the barbell off the ground, because the hips are in a less mechanically advantageous position compared to having the rounded back. But, this will make the overall pull more efficient, allow you to pull more weight in the long run, and is safer.
The best way to do this is to practice the competition deadlift with weights where the proper starting position can be achieved and maintained throughout the range of motion. This is going to strengthen the muscles in the proper position and ingrain the proper motor pattern. Then, if you want, you can implement various deadlift variations that reinforce this position. Some examples would be tempo deadlifts, pause deadlifts, and deadlift to knees. Just like the competition deadlift, these variations should be done with weights where the proper starting position can be achieved and maintained throughout the full range of motion. This may mean starting off with very light weights, like 50% of your 1 rep max. Then the intensity can slowly increase over the course of a training cycle, so you can practice the new technique with heavier and heavier weights.
This entire process of changing the technique to a more efficient and safer pull may take some time to master with max weights. For some, it may take a few months to learn the new motor pattern and strengthen the necessary muscles to maintain the proper position. For others, it may take an entire year to hone the technique down. But if you truly want to improve your deadlift and lower your risk of injury, then you should be willing to put in the time to make the change.