Originally Posted by
Dastardly
In the last rep at 70kg your slide forward at the bottom.
Every rep of 90kg you slide forward at the bottom.
I am correcting a similar issue for myself. I spent the whole of last year squatting with exaggerated sit-back.
I squatted today with knees forward cue and it felt loads better, I was able to get more hip drive and my low back was tighter.
The easiest way to do it is forget everything you have learnt about 'sitting back' and go straight down, letting knees go however forward they want to at the beginning.
As long as you are using the low-bar, your back is tight and you keep the bar over centre of gravity then the form just deals with itself as its the most balanced/efficient way for it to work.