How do you understand whether you have a low or high vagal tone?
tired=high vagal stone
speed, energy, strss= low vagal stone
am i good ?
Not really, it is more complex than that. The vagus nerve and all of the parasympathetic system it belongs to has many effects, everywhere in the body.
Here is an overview:
signs/effect of a high vagal tone:
slower and weaker heartbeat, stimulating effect on bowel movement , facilitate urination, cause bronchoconstriction, cause hypotension, high production of tears, of saliva, of gastro-intestinal mucus, of sweat, of nasal mucosa.
Signs of very high/too high vagal tone:
nausea, dizziness, abdominal cramps, diarrhea, racing thoughts, frequent urination, severe hypotension ( extreme manifestation leads to fainting, and is called a vasovagal syncope, see
http://en.wikipedia.org/wiki/Vasovagal_response ), control freak behaviors, mental hyperactivity, tinnitus, tremor, stomach acidity
The signs for a low vagal tone are in the opposite direction:
Dry eyes, dry nose, low intestinal mucus production, constipation, urinary retention, low level of sweat production, bronchodilatation, lower mental activity,
Signs of very low vagal tone: bowel obstruction, slow digestion, low stomach acidity, drowsiness, brain fog, memory problems, lack of organization, lack of interest, confusion, torpor ( As you may have noticed, stimulation of the vagus nerve / raising of the vagal tone, in theory, should help those who have POIS cognitive symptoms - brain fog, memory problems, etc )
If you want more information, start with
https://en.wikipedia.org/wiki/Parasympathetic_nervous_system .
Take note that those signs and symptoms are not exclusive effects of the parasympathetic system, so some interpretation and medical supervision is needed. For example, the sympathetic system always interact and counteract the parasympathetic, so you have to interpret the signs and symptoms correctly ( a car slowing down may be due to releasing of the gas pedal or due to pressure on the break pedal, or to both in different proportions, and may as well be due in part to compression when clutch is engaged....). Having nausea and dizziness can comes from many possible causes, so it is not automatically a sign of high vagal tone.
In research, vagal tone is measured through respiratory sinus arrhythmia (RSA), which is a naturally occurring variation in heart rate that occurs during a breathing cycle. The Rutgers team will use devices that measure the RSA, in the on-going POIS study, obviously as a way of assessing one's vagal tone at a given moment. RSA is a reliable way to measure the level of vagal tone and its variations in time.
As a side note, ten years ago, I bought one of the first software/device available on the market for measuring RSA. It was called the Freeze-Framer, from the HeartMath Institute, and was the ancestor of the current emWave products of HMI. Those products can be used as biofeedback devices, in order to learn how to consciously work toward inner balance of your nervous system, and stay in "the zone". If you are not fond of meditation, those are a more "technological" alternatives.