Originally Posted by chucky

While it is true that in theory one doesn't have to lift the foot to unweight the pedal, studies show that even the best top level athletes still apply a little downward pressure on the upstroke. Physically separating the foot from the pedal, on the other hand, guarantees there will be zero pressure on the upstroke (even for untrained riders) and if you can retain the foot a few mm above the pedal then you won't waste any time putting it back down.