This is a PowerCranks secondary web page intended to be less wordy, less detailed, more visual and easier to understand for those without a technical background. If you are a "detail" person you might find our main page, www.powercranks.com, more informative.
This is going to be misinterpreted by the vast majority of the "pedaling technique doesn't matter" crowd (see: http://forum.slowtwitch.com/forum/Slowtwitch_Forums_C1/Triathlon_Forum_F1/Differences_in_pedalling_technique_between_road_cyclists_of_different_competitive_levels_P5973765/?search_string=impulse%20proportion#p5973765 as an example) because they don't understand that unweighting is actually contributing to power generation even though no positive torque is seen on the pedal there. It takes work to get the heavy foot and leg from the bottom of the stroke to the top. That work either comes from pulling up with the hip flexors and hamstrings or pushing down harder with the glutes and quads on the opposite pedal. In both cases potential energy is gained when the leg goes up that is reclaimed as kinetic energy on the downstroke because of gravity. Most of us (before we are PowerCranks trained, at least) do some of both with about 90% of the lifting coming from the hip-flexor and hamstring muscles and the other 10% coming from the opposite leg pushing harder.
I would be interested in seeing the entire study to see if there are any differences between what is going on over the top. In our experience, the weakest part of most peoples stroke is over the top and we find that the more one does on the backstroke the more one also tends to do over the top, since pedaling is a continuum and over the top follows the upstroke.