Reflexions on breathing and posture and their relation to the vagus nerve

Before reading this post, I recommend that you read the page "Introduction and Exercises".

In my first article I evoked the serious bout of reflux which led to my interest for the vagus nerve and the parasympathetic nervous system. I got cured overnight with the help of a Swiss body researcher, Benita Cantieni, who advised a breathing technique where the diaphragm expands mostly sideways, thus limiting the effect of its movements around the entrance to the stomach. You can find here a good description of this breathing technique.

But I was then faced with a problem: what about the belly breathing that I had been using for myself and teaching to my pupils for so many years? I was afraid that my new breathing technique would have negative effects on singing.

I was encouraged by the discovery that some trumpet players who also had to quit belly breathing because of reflux were actually very pleased with their new breathing technique. And I could at last understand Caruso's description of his breathing (1909): "To take a full breath properly, the chest must be raised at the same moment the abdomen sinks in". As well as the earlier description given by Manuel Garcia (1847): "Raise the chest in a slow and regular movement, and bring the pit of the stomach in".

I noticed that the practice of this breathing technique besides singing, or just the practice of the posture shoulders back/breast out/pit of the stomach in, always bring with them fluidity of the saliva, which means that they have a stimulating effect on the parasympathetic nervous system. Why would it be so?

I emit three theories:

1 - The expanding chest which results from this type of breathing means that the vagus nerve, present everywhere in the chest, has room to function properly (we all know how much pressure on nerves can impair their function).

2 - The fact that the diaphragm expands also sideways means that it is not pushed very much down the body, as it can happen in belly breathing if it is exaggerated. The consequence is that it can very quickly go up again after breathing out, reaching easily its relaxed position. Again, that means a lot for the vagus nerve, which crosses the diaphragm together with the oesophagus.

3- Upper costal breathing means that one does not need to contract the muscles of the lower abdomen during breathing out. The lower abdomen stays relaxed, which could mean that the vagus nerve, present in two-thirds of the abdomen, and the pelvic splanchnic nerves, present in the resting one-third, enjoy a relaxed environment allowing their proper function.