Paul Carter put up a really good article on "sticking points," weak points, and strong points over on his blog.
Making your strong points...stronger II - Strong from the bottom up
He makes a point that Kenny Croxdale has made repeatedly over on the EXRX forums - your "sticking point" in a lift is below the point at which it actually "sticks." The sticking point is just where you run out of momentum. You are in all likelihood weaker below that point.
The language is a little raw so be aware if you're sensitive to that. But there are no non-WFS images.