Wait, personal experience trumps empirical scientific findings? Why didn't I get the memo?

This is not based on statistical surveys or conjecture. What they've done is put a power meter into the actual pedal itself, so these conclusions are drawn from direct observation of the actual forces applied during pedal strokes. Not only do these types of power meters measure when, where and in what direction the forces are applied, it also measures each leg independently. These studies pulled from a diverse pool of cyclists, including professional cyclists, MTB, track etc. The author of this article started these tests in 1996 and routinely works with a wide range of athletes, including elite riders.

The data gathered by this method typically looks like this, courtesy of Metrigear:



("Vector" is the name of their upcoming commercialized pedal-based power meter.) On the bottom graph, the gray (flat) line in the center is an average of the forces applied during the pedal rotation. Note how the forces applied drop to zero or less on the upstrokes -- and how the result is a consistent application of force.

Other data collections, by the way, point out how most of the forces applied during the stroke are tangential. If my understanding is correct: On the down stroke, you are not successfully putting every ounce of force into pushing the pedal down; you're actually pushing the spindle forward as well, which reduces the efficiency of the pedal stroke. So when you are pulling hard on the upstroke, most of that time you are actually just pulling the spindle back rather than up. (This shouldn't be too surprising, since the pedals use a radial motion rather than an up-and-down pumping action.)

Subjective assertions and anecdotes may be persuasive for some people. Ultimately though, without an objective measuring device, we humans have no better idea what our legs are doing during a pedal stroke than, say, whether we are working aerobically or anaerobically. There is now an empirical, objective, direct, repeatable and testable means to measure exactly how much force is applied to the pedal itself, and it's far more accurate than guessing what your legs do or watching videos of pros.

On a positive note, the emphasis is still on developing a smooth stroke, so you haven't wound up doing anything counter-productive. It just turns out that your underlying assumptions about what your legs are actually doing are incorrect, but you've wound up doing what you need to do anyway.