Just curious, I feel like the level of individual variation here doesn't get discussed enough when people are designing lifting routines. I seem to be particularly ungifted in this regard, 5/3/1 is about the max intensity level for squats and deadlifts that I can tolerate and consistently grow stronger doing. If I go to failure (say, a 9.5 or 10 on the RPS system) doing squats or deadlifts for more than a couple of weeks in a row, my body simply can't handle it and I stop getting stronger. (I also get insanely sore, especially from squats, for days and days after a max intensity lift). I basically always have to leave at least one rep in the tank doing squats or deadlifts. (Does not seem to be true for assistance exercises or smaller muscle groups, where I can go to failure week after week without issues). Just kind of interesting how genetics for exercise tolerance works. When I was younger I worked on commercial fishing boats in Alaska for a time and regularly put in 100+ hour weeks of hard labor, and actually felt OK doing it for the most part. But, my body apparently can't tolerate just a few minutes of squats to total failure lol. Seems inconsistent. Yes I'm older now, but even in my 20s failure in the gym was too much for me. But- some people with superior genetics can easily crank out failure sets week in and week out, and consistently get stronger. Maybe I'm not doing enough 'supplements' lol. I seem to be mostly slow-twitch muscle, if that helps. Yes I eat sufficiently and take creatine and protein powder daily, it's not like I'm not eating enough. Would be interested to hear perspectives from smart science-based people like @Sano @Uchi Mata etc.