Women, prick up your ears.  When you stand like Wonder Woman for two minutes (legs slightly apart, arms akimbo, head up, back straight, body balanced) it changes your internal feelings of power and control.   Your testosterone levels increase and your cortisol decreases helping you feel more able and more relaxed.  This feeling lasts and is likely to cause people to relate to you differently.  No, you do not have to stand in the middle of a crowded room to do this, you can do it discreetly in the Ladies or a private space before (not during) meetings, presentations, interviews and you will feel more able and assertive and will come across as having presence.  Your stress levels will go down.
 
Men, now it is your turn.  Listen up.  You know the alpha male poses? Yes, you know the ones – for example, when you lounge back in your chair with your legs open and almost crossed with your ankle balanced on the opposite knee (by the way, women in skirts never sit like this) and your hands crossed behind your head.  Be aware that the person you are talking to is likely to complement your stance by sitting or standing in a more submissive way.   You will, no doubt, feel powerful and relaxed but what impact will your body posture have on the other person? It is quite likely that they will be feeling less power, less control and their stress levels will increase. 
 
Our body language effects not only the way others see us, it also effects the way we see ourselves.  When we bring into awareness the ways in which our bodies communicate we have choice and if we have choice we can start to build our repertoire and flexibility so that we influence, engage and get the best from people.  We also get the best from ourselves.
 
Take a look at Amy Cuddy in this TED video.  She says it all.