It is well know that a huge part of communication is non-verbal. This means that when we are communicating, what people pick up on is more about tone, of voice, state of consciousness, and energy levels, among other things. So we can say that when we are communicating we are both using using our being, and communicating our being.
Confidence is an important resource for performance, public speaking, and an all round positive characteristic in pretty much any context. How can we develop a confident communication manner? Put simply, by establishing a confident physicality and awareness of our own being. Its important here to note that I'm not talking about being a body builder, or a fashion model. For instance, actors come in all shapes and sizes but what they share is a practice in the skill of using their being to communicate. Public speaking and social confidence is not so different from acting on a physical level. So we can take that by training our awareness of body, we can improve our skill in communication.
By extension, if we want to communicate a certain emotional state behind our verbal message, for example enthusiasm and high energy, or relaxed awareness or good vibes, or all of the above, then it makes sense to cultivate practices that make these states more conscious, powerful, and accessible.