What’s the fastest way to calm the nervous system?

Sources:

The fastest way to calm the nervous system, according to , involves using breathing techniques, specifically the "physiological sigh." This method consists of taking two inhales through the nose and then a long exhale through the mouth. This technique is grounded in physiology and neuroscience and is considered the most effective and quickest method to reduce stress response in real-time. It activates the parasympathetic nervous system, promoting calm and reducing arousal levels almost instantly 1 2 3 4.

Calming Physiology

Andrew explains how respiration can be used to calm us down and introduces the physiological sigh as a tool to reduce stress response in real-time. He distinguishes physiological sighs from breath work and explains how breathing can directly control heart rate through the interactions between the sympathetic and parasympathetic nervous system.
Huberman Lab
Tools for Managing Stress & Anxiety | Huberman Lab Podcast #10
1
2
3
4
5

In addition to the physiological sigh, mentions that other forms of breath control can also help modulate the autonomic nervous system. Slow, controlled breathing can engage the parasympathetic nervous system, diminishing the stress response and helping to feel relaxed quickly 3.

For a more extensive practice, he suggests different breathing patterns that can help manage one's internal state, like emphasizing exhales to calm down or breathing more quickly and shallowly to become more alert 5.