SUF newbie here. I HATE standing, as it tires me out to the point of near exhaustion after 20 seconds, but, that said: I’m trying to stand, especially for higher power, lower cadence climbs and working on keeping my pedaling smooth (following Elements of Style). Although still incredibly tough, I’ve noticed that while standing, i tend to switch between a smooth pedaling stroke to a jerky one. The jerky pedaling accelerates the exhaustion I feel. So, there must be something to the idea of engaging glutes that helps with standing. Perhaps I’m imagining it but over the past 2-3 weeks (Fitness Kickstarter with a few personally chosen workout substitutions) I seem to have made minor improvements in ability to stand.