Big Back, Big Deadlift?
I like rack deadlifts (aka rack pulls) for the upper back, but not for improving the deadlift specifically. People say it'll "fix your lockout" and make it less of a sticking point, but that's probably not accurate.
If they actually did help, then the likely explanation is that you had a weak upper back and it limited your ability to stabilize the posterior chain. The great majority of folks get into a completely different position when doing rack or block pulls than what their body is in when pulling from the floor in that range of motion.
And any variation of a main movement where you can use more than about 10% of your max load won't be all that transferable. Here's an example:
- Gym bro has a max deadlift of 500 pounds.
- Gym bro decides to do rack deadlifts, and he can use 600 pounds for reps.
- Gym bro doesn't realize that the rack deadlift positions are different than the regular deadlift positions.
- Gym bro goes back to deadlifts later to find out his deadlift hasn't improved.
- Gym bro is vexed and sad.
So why doesn't it work since it's intended to strengthen a sticking point? Newsflash: Training your sticking point at the sticking point itself is pointless. And that's a lot of points.
The problem area isn't the sticking point itself. It's the few inches before the sticking point where you're not able to generate enough power (the speed at which you can move the load) to get through the sticking point.
Get Strong Below Your Sticking Point
If you want to defeat a sticking point, find a way to make that movement more difficult in the area preceding it. Now get stronger in that part of the range of motion. That's how you'll eventually crush that plateau.
"But isn't that what I did with using rack pulls?"
Not if you're training the rack or block pull in a dissimilar position than you'd be in with your regular deadlift... and especially using a load greater than 10% of your deadlift max, or training the block/rack pull starting at your sticking point with the regular deadlift.
These are all the most common issues with guys using block or rack pulls, which is why I say it's something you probably shouldn't be doing to improve your deadlift.
If you're using the rack or block pull to build a stronger upper back then you still want to stick to the rule of not using loads well beyond the scope of what you can deadlift from the floor. Instead, do them with good form, slower eccentrics (negatives), and sets within the 6-10 rep range. I also suggest using bands here because doing so will make the thoracic extensors work like never before.