When I deadlift heavy, lets say over 85% of my max, I find it really overproportionally taxing on my back. I undershoot my predicted max by like 10% or so and my glutes and hams are not even phased, making me feel like I am doing something wrong.

Im thinking that

1. My form breaks down and I lift less from my hips

and/or

2. My low back is the weak point in my lift and I need to bring it up

Does this make sense?

I really like training in the 75% range to "dominate" the weight as CT calls it and have good form and tire out my glutes first, but any heavy lifting I have something holding me back from getting close to my predicted one rep max and what I ~feel~ I can do.

Is the solution to start doing hyperextentions or some kind of focus on form? Im no beast but my predicted 1RM is 330+ and after working up to 295 in singles my low back is shot. Any analysis is appreciated.

could be weak lower back. could also be a weak core, which causes the back to round and put stress on the lower back.

I experience something along the lines of what your talking about. Again from my experience, I get better pulls when I first have a stomach completely full of air and core completely flexed(seems obvious but personally activating my core in a dl requires conscious effort, maybe more experienced power lifters have this come from habit?). Second thing is(again consciously) driving my heels down as I pull upwards. Almost trying to drive the back of my heels toward the bar and downwards.

Unless you feel like you're going to injure something I say don't worry about it and just get stronger. It's natural for form to breakdown some near 1RM lifts.

Hard to tell without video. So take what I say with a grain of salt.

If your back (presumably your lower) is feeling lots more then the rest of your body, your probably not using it properly.

Try doing some pull throughs for a while as an accessory. That movement is what you want to happen on a deadlift. Once the bar gets over your knee cap, it's a pull through. Shifting your torso into a straight line by pulling your hips forward so your hips and shoulders are in the same plane.

Too many times do people think that you just jerk the bar up and knock the shoulders back. This creates a weakpoint in the lower back. Don't do this.

"Pull your hips through"

Problem solved, and, for anyone having similar problems, here was my solution:

I think I was so impressed with myself lifting heavy that I was subconsciously looking at the weights instead of looking up.

Today, kept my eyes up, which straightened my back, put the stress back on my hips and worked up to a 315 pull for the first time, and it felt all kinds of right and Ill probably shoot for more next Monday.

Two weeks ago I got 295 and wanted to die afterwards, then I got sick for a week and went on a 5 day bender to celebrate getting well, so it definitely wasnt organic progress haha.

Next stop 405 in the 305.