Hmm, interesting. Might explain why I just couldn't keep up the power last time i tried ZCI's, into a gusty headwind. Not sure I understand why power output should be reduced by a slow-down of the bike during the weak part of the stroke - why should it affect the ability of your legs to generate power? (Not disputing, just trying to understand). I attributed the ZCI failure to an inability to maintain steady power, because adjusting for the gustiness caused lots of power peaks and valleys.