I squat with the bar fairly low. Occasionally, and it seems like it is happening a lot lately, the bar will slip further down the last or close to the last rep. I was talking to a a guy I lift with occasionally about it. He said, for him, that is an indicator that he is falling forward and using his back to lift.
I'd like to think I have good form and I have it checked periodically. I am not opposed to the idea that this is a cause as falling forward and using my back has been a problem in the past. It hasn't been, I think, lately. So my basic question is if the bar is slipping down, is that a solid indicator of me using my back?