I've had problems with extending my lumbar on the deadlift for a long time. Here are two videos of my recent mock meet for reference.
355:
YouTube
365:
YouTube
Some comments on what is happening:
I am aware of how to extend my lumbar, and I can do so successfully on squats. In fact, I can do so successfully on a stiff-legged deadlift oddly enough, but my conventional deadlift cannot. I can get it nearly neutral, but it is very difficult to keep in that position, and it leaves my lower back very fatigued even during warm ups. I activate my lumbar extensors as much as I can, but I feel nowhere near "locked" in extension like I do on a squat or a stiff-legged deadlift. Today I tried rack pulling and felt I could get my lumbar into extension much better, and it completely changed how the movement felt in comparison. Does anyone have any advice for things to try here? Any explanation for why I can do this successfully on a stiff-legged deadlift, but not a conventional deadlift?