Originally Posted by dealt_with
Psychological effects are dependant on if you believe they are. If you believe that your posture between rounds matters then it will, your opponents beliefs count as well. Most people need to calm down during combat to slow their heart rate and be more metabolically efficient, not become more aroused. As long as you don't see bending over at the waist and breathing heavily as a sign of weakness then it won't affect you negatively. If you believe it is a sign of weakness it will have the opposite effect you're talking about. When you're in a fight it's unusual for you to have to tell your body and mind to go, generally speaking people are too aroused and that impairs fitness and recovery. Everybody has a different level of optimal arousal and how the athlete perceives that arousal is correlated to successful performance.
I agree with Marcos.
Try walking down the street hunched over, head down, shoulders rounded forward. You'll feel far less confident than someone walking with their chest out and head held high. It's a natural alpha male characteristic, it doesn't matter what you try and think it means. I know this is different to being in a fight, but posture definitely tells your body something, nothing to do with psychology.