Deadlifting With A Neutral Spine
When setting up for a conventional or sumo deadlift, the bar should be at a height where you can maintain the natural arch in your lower back (otherwise known as a neutral spine).
If you’re not able to do this with the weight you have on the bar you should elevate the bar either by using the safety pins in the squat rack or by placing aerobic steps under the weights on either end of the bar.
This puts you in the optimal pulling position, without risking injury to the lower back by having you in the rounded (think: hunched over) position.