These are bad to the bone once you figure out how to do them. Set up the "stops" so you can enjoy this dead-stop variation.
The main point is to pull the bar into your abs – just a shade above the bellybutton – by driving the elbows up. Don't pull the bar up with the arms – drive with your elbows.
As with any row, keep your back flat and tight and wear a belt. Watch the video, especially the last set in the drop set, and see how my body position is fixed and I'm just driving with my elbows.
Sometimes it's really interesting to dig into the microscopic details of training and nutrition, to dissect the body of academia and examine every little study. That's how we learn things. That's how we refine the science that later helps us get bigger and stronger and leaner.