I recently switched from heavier 5x5@80% supplemental work to 5x10 @40% of 1RM and tweaked my back on the 3rd set doing deadlifts. At the time, it was a very mild discomfort with pain ranging from 0-2 out of 10 that day. The pain and limited mobility got worse 36 hrs later and has remained for 1.5 weeks. I never ever experience such a tweak doing 5x5@70-85%. When I do higher sub-maximal reps, my technique gets a tad more sloppy and I end up taking shorter breaks, which makes me more prone to injury.
