Originally Posted by Brian Ratliff

This is actually what I am questioning. Rather than using the quads at the top of the pedal stroke where the knee angle is most closed, I switched to focusing on the hip extensors and letting the knee do what it's going to do. It's not like the quads are taken out of the picture, but as rkwaki said, using two or three muscle groups to extend the leg on the downward portion of the pedal stroke rather than one. The hip extensors will provide power as long as the hip is still opening.

But one of the keys, I think, is working on lower back strength and rigidity. I found just focusing on keeping my back rigid was almost all I needed to do to get my hamstrings (and glutes maybe?) involved.