From the perspective of primate social structures, the "low power" poses are incredibly important. For a male chimpanzee who doesn't have the physical strength or social clout to defend himself, adopting a submissive posture in the presence of higher ranking male can mean the difference between being tolerated and being beaten up. In a modern environment, I would hope that your boss would not beat you up for adopting a dominant posture, but it does raise the question about whether or not these can lead to an aggression or submissive behavior from other people in meetings. It might be wiser to neutral pose.
Crouching, having your arms crossed etc. doesn't mean "don't beat me up". Sure, you might not be completely confident, but there's a long way from there to submissive. And, as I mentioned above, is it necessarily such a good social signal to fake confidence all the time?
I was discussing their possible evolutionary origins. Hopefully being beaten up is not a possibility in your meetings, but we evolved in an environment where it was until very recently. The whole point of the original article is that such behavior is often unconscious.
Crossed arms is an interesting case because I don't think it's a submissive behavior in other primates. It probably is more indicative of boredom, which is probably also not what you want to signal in meetings. I don't really consider myself a dominant or submissive person, but in the past I think my posture and demeanor radiated distraction and boredom. This isn't very inspiring for the rest of the team. I read an article similar to the one there that inspired me to clean up my act.
Noboyd's saying it's defensive, exactly, but I think it is unambiguously a signal that you don't have social ambition in the given context, which makes you unoffensive but also uninteresting.
