These exercises will help counteract the effects of adrenaline. I would invite you to look at how the breathing worked for me. It wasn't until the forth presentation that I began to breathe more easily. Then, I started to engage my audience even more effectively.
In the morning I lay on my back for a couple of minutes with my eyes and mouth open and my knees upward so that it looks like I am in a sit up position and gently breathe in. By adjusting the angle of my knees I can find the most comfortable position that allows my diaphragm to expand with little effort. I can see and feel my diaphragm expand and my belly looks like I am a couple of months pregnant. What I am learning here is how to exercise my diaphragm so that it takes in air like a bellows. I gently breathe in and out for a minute, then I fully inhale, hold the air in for 5 - 10 seconds and then slowly exhale until my lungs are fully exhausted. Repeat a couple of times.
Exercising the diaphragm regularly will allow you to counteract the muscle tensing in the solar plexus associated with adrenaline. This will allow you to keep yourself calm while at the podium if you experience a rise in adrenaline.
I believe you will find it beneficial to start breathing exercises beneficial sooner rather than later. If you forget to do it in the morning...no problem, just spend a couple of minutes breathing standing up with your hand on the belly to feel the diaphragm expand.