1) Cold Showers
Start with dipping your face in cold water. Progress to a scottish shower where you finish with a cold shower. You can work yourself up to taking complete cold showers.
2) Singing or Chanting
Humming, mantra chanting, hymn singing, and upbeat energetic singing all increase Heart Rate Variability. Singing has been found to increase oxytocin.
Yoga increases vagus nerve and parasympathetic system activity in general
There are two types of meditation that can stimulate the vagus nerve. Loving-kindness meditation increases vagal tone, as measured by heart rate variability. Also, Om chanting stimulates the vagus nerve.
5) Positive Social Relationships
Positive emotions, like joy, interest, amusement, serenity, and hope are correlated with a greater sense of connectedness to others and to an improvement in vagal function, as seen by heart-rate variability.
6) Breathe Deeply and Slowly
Slow breathing, with a roughly equal amount of time breathing in and out, increases the sensitivity of baroreceptors and vagal activation, which lowers blood pressure and reduces anxiety by reducing your sympathetic nervous system and increasing your parasympathetic system.
7) Laughter – As the saying goes, laughter is the best medicine.
9) PEMF – Magnetic fields are capable of stimulating the vagus nerve. Studies have found that PEMF can increase heart rate variability and increase vagus stimulation.