Not sure how believable this will sound, but it's true.
When doing squats I keep my lumbar area arched and go down as far as possible until the heads of the femurs reach their full range of motion in the acetabulum. This gives a sort of binding feel and that's when I know if I go lower I'll have to start rounding my lower back.
At that depth, which puts the crease of my hip about an inch below my knee joint, I set the cross bars to catch the barbell while I pause at the bottom for about 1 second before going back up. That way the load is released at the bottom and it makes it much harder to come back, supposedly increasing the rate of force development substantially.
So, that being said, I'm 5'10" weigh 155lbs, look more like a 400 meter sprinter and I do 1 set like that with 135lbs for 8-10 reps and my upper hamstrings are DONE. I have to do this exercise last because it's always very hard to walk afterwards. I've been told it could have something to do with muscle attachments because very few people get that thrashed from squats.
I can not believe most of you are doing more than 1/4 or 1/2 squats, even if y'all sincerely think you are doing a legit squat, but maybe I just have some extremely weak hamstrings or strange muscle attachments.
On the flip-side, I can deadlift 295lbs for 8-10 reps and don't get sore at all. Go figure.