There are several dynamics that make for good public speaking but the one component that far outweighs all others is the need to breathe while speaking. Without air, there is no voice. And yet, many novice speakers never think about that life-giving force when addressing an audience. In fact, it is often the last thing on their minds when indeed it should be the first.
As a people, we are renowned for being lazy or shallow breathers. What this means is that we are using only the upper portion of the chest for respiration instead of making use of the diaphragm and the entire mid-torso region to support our air supply. [Your diaphragm is a muscular partition that separates your chest from your abdominal cavity. Its primary function is to support breathing.]
To find your diaphragm, place your hands under your rib cage and cough as in the picture below.
Did you feel that muscle kick out? If you have ever had a cold in which you coughed all day long, you may have felt sore under your rib cage. Another time this muscle gets a workout is after laughing for a couple of hours during a funny movie. You may remember feeling sore in that area.
Why is breathing so important during public speaking? Obviously because you need air; however, the breathing I am referring to is that which you take all the way down to your diaphragm. In doing, so you will find that you are more relaxed. However, a huge breath is not what I mean: I am talking about a deep breath. That deep breath is healthier because it sends more oxygen to the brain which means that your body is able to rid your blood of nasty toxins. Shallow or lazy breathing, on the other hand, actually increases the toxins which results in an increase in stress.
For the purposes of public speaking, deep, supported breathing allows you to take control of your nervousness and put it to good use. That wonderful rush of adrenaline makes you more alert and more focused in your delivery.
While you certainly need to know your material, make eye contact with your audience, speak with emotion, and believe in yourself, breathing with the support of your diaphragm should be the first thing you do when approach the lectern. You will be amazed at how much better you feel, how much more confident you look, and how much more in control you are of those nervous jitters.
To see how voice training can improve your life, both professionally and personally watch a brief video as The Voice Lady describes Dynamic Public Speaking.