TLDR at the bottom I'm curious just HOW perfect form needs to be on a particular exercise in order to warrant an increase in weight when trying to progress. Let's take Barbell Curls for example... Say we're aiming for 8 reps before increasing the weight slightly the next time we do the exercise. Just HOW perfect does form of those 8 reps need to be in order to warrant having successfully completed the 8 reps and be ready for an increase in weight? I ask this because I'm usually able to add an extra 15-20kg or so, whilst having my form only slightly suffer (a little bit of heaving the weight up, as opposed to being an EXTREMELY controlled rep). Whereas if my form was to be absolutely 100% perfect, then the weight I'm able to use on a specific exercise would unfortunately be so miniscule that I often wonder if it'd even be enough to cause sufficient damage to the muscle, to cause hypertrophy to occur. You've probably all seen this kind of person at the gym, but it'd be like one of these really skinny guys who come in (usually the much older men in their mid 50s), pick up a 5kg dumbbell and do their curls with absolutely perfect form, almost to the point of being TOO perfect, yet never actually gaining ANY size or strength over the course of a year due to focusing so much on form and not an actual increase in weight on an exercise. The reason I'm asking this is that recently I've been managing to get all of the required reps in an exercise (meaning of course that the next time I do the exercise, I'd be increasing the weight slightly), but part of me is left wondering whether I actually SHOULD be increasing the weight, considering the fact that in order to complete the last rep or two, my form hasn't been 'bad' per se, but definitely worse than my first several reps of the set. Going back to Barbell Curls as an example again, I find that my first several reps are all with decent form, yet the last one or two are almost forced, with my arms swinging slightly moreso than they do with the first several reps. I know I've gone into more detail than was probably necessary in order to describe what I'm trying to say, and I've made it sound a lot more complicated than it needs to be, but unfortunately some people don't quite understand where you're coming from unless you describe the issue in as much detail as possible. Anyway, TLDR: Basically, just HOW perfect does form need to be for all of your reps in order to warrant that exercise's weight being increased the next time I do it?