One approach that I learned was to use your fingers to underline the current line that you're reading, going at a "normal" speed when you're tired and then trying to "drag" your eyesight along when you want to push yourself.

The reason given is that it prevents you from accidentally rereading a line or skipping over one or changing lines midsentence.

This seems like one of those gimmicky approaches, and I remember being sold on this approach rather than being entirely convinced. Have you seen this before?