How Yin Works: The Neuropsychology of Why Yin Makes Us Happy

By Erica Harrison for Yoga Medicine®.

Yin is the misunderstood sibling of vinyasa. It’s quiet. It keeps to itself and doesn’t cause a lot of commotion — but it can pack an unexpected punch.  

Yin is an intensely dynamic practice. Vinyasa strengthens the mind, but yin strengthens the psyche.  More specifically, yin strengthens the bi-directional connection between the body and the mind. 

The work is not in getting into the pose – supportive props help you with that. The work starts when the instructor says, “Now, be still, stay, and surrender to whatever comes up for you.”  

This is when your body and mind start to have a conversation, using the fascial network as their communication tool. Yin leverages the expansive hyper-sensitive and responsive fascial system to improve our psychological well-being. 

The poses impact the cells of the fascial system, which activates a process called interoception. Interoception is the process of physically detecting and cognitively interpreting sensations from inside the body, including muscles, skin, joints, and viscera (i.e., internal organs).1,2 Interoceptive practices such as yin build body awareness, and body awareness improves our ability to self-regulate our emotions. 

Practicing interoceptive practices such as yin repeatedly disrupts deeply rooted unhelpful interpretations of bodily signals and improves our ability to cope with stress and negative emotions.  Research suggests that accurate interoceptive abilities promote moment-to-moment adaption and helps one to avoid physical, mental, and emotional challenges.3 

In contrast, other research indicates that weak interoceptive abilities contribute to various disorders, including anxiety, mood, eating, addictive, and somatic symptom disorders.4

For example, let’s say Mary feels an unusual sensation in her belly. Her deeply rooted interpretation of this sensation is automatically anxiety. Her body sends the message to her brain and nervous system, “I am anxious.” The brain and nervous systems are unquestionable believers of the body, so they jump to respond. The brain begins to search for the external source of the anxiety, and the nervous system activates the sympathetic “fight-or-flight” response to protect Mary from the threat, albeit unknown. 

This response increases the body’s activation, and now Mary really is, in fact, becoming anxious as a result. Even though the instigating factor — a sensation in her abdomen — was simply a digestive sensation. 

As you can see, the bi-directional communication system between the mind and body is a powerful force on our emotions. The practice of yin pushes us to investigate these communication signals to increase the accuracy of our interoceptive perception. 

In short, Yin teaches us to notice, tolerate, and befriend our inner experiences; to approach our bodies with curiosity and compassion. And this, in turn, leads to improved well-being.

Interoception: How We “Feel” Our Bodies

 

What is Interoception?

Interoception is the process of detecting and interpreting sensations from inside the body. It involves detecting cellular changes in the fascia surrounding the muscles, skin, joints, and viscera.1,2 Interoception relies on connective tissue, namely the fascia. Therefore, the role of the fascia in yin is crucial to understanding yin’s effect on our psychological state. 

Yin, Interoception, and Fascia

 

Definition of Fascia

Fascia is a type of connective tissue that wraps every body structure, giving our bodies structural continuity and tensegrity; it serves as a scaffolding within which our bones, muscles, and organs interact. Fascial tissue envelops and permeates every object in our body – blood vessels, nerves, organs, bones, muscles, and even muscle fibers. Interestingly, fascia is considered an organ; and like other organs, it can affect our health and wellbeing.5

Fascia Function

Connection and protection are the most obvious functions of the fascia. But it also plays a central role in sensory processes, which is how it can affect our psychological well-being. Besides the skin, the fascia has the most sensory neurons in the body – six times as many neurons, in fact.5 Some scientists compare the sensitivity of the fascial system to be at least equal to – if not greater than – the retina.6

Fascia and Yin

Yin poses target the connective tissue – bones, ligaments, and tendons. And what surrounds and connects each bone ligament and tendon? Fascia. 

Our fascia responds to mechanical stimulation in important ways for interoception.5 Yin poses stimulate certain cells within the fascia, called mechanoreceptors. These mechanoreceptors respond by sending communication signals to the brain. This prompts that bi-directional communication line between body and mind.5

During yin, we mechanically stimulate the fascia during each pose in multifaceted ways. One pose can place pressure on one joint and create tension in another while twisting the spine and abdomen. For example, think about all that is going on in a sleeping swan pose. 

Fascial, Interoception, and the Psychological State

So, we’ve established that the twisting, pressure, and stretch of the yin pose stimulate the fascial mechanoreceptors. These mechanoreceptors then stimulate the afferent nerves to send this message to the brain to brief it on the body’s physiological state. 

The critical thing to know here is that most of this information is sent to the insula cortex, which is the region of the brain that processes emotions.7 This may explain the association between interoception and emotion, thus explaining why yin has positive psychological benefits.8  

Yin instructors commonly encourage students to “sit with and surrender to whatever comes up.” This simple instruction is a powerful way to refine the student’s interoceptive abilities. It also helps the student to practice processing tough emotions within a safe space within themselves. 

Our interoceptive awareness is an ongoing bi-directional interplay between our physical perception of our internal body state and our cognitive response to what we perceive.  The mechanical aspects of yin activate the emotional processing center of our brain, which makes us hyper-aware of our physiological state and our coinciding psychological state. Yin offers a safe space where we can process the emotion that our body is signaling to us. 

So, when yin is practiced with regularity, the repeated increases in conscious interoception force us to face “whatever comes up.” But this emotional processing occurs while we’re in a relaxed state, thus possibly pairing “feeling our body” (i.e., interoception) with relaxation. Over time, we can disrupt deeply rooted unhelpful perceptions and interpretations of bodily signals.3  

A regular yin practice exercises our ability to ‘flex’ our interoceptive muscle and improve our ability to be present, grounded, and confident. And over time, we can disrupt deeply rooted, unhelpful perceptions and interpretations of bodily signals.3 

Interoception is a key player in creating the emotional state itself. But perhaps more importantly, it’s responsible for our ability to tolerate this emotional state, whatever it may be. The more accurate we are at interpreting our bodily signals, the better we are at emotional self-regulation both on and off the mat.

This being human is a guest house.
Every morning a new arrival.

A joy, a depression, a meanness,
some momentary awareness comes
as an unexpected visitor.

Welcome and entertain them all!
Even if they are a crowd of sorrows,
who violently sweep your house
empty of its furniture,
still treat each guest honorably.
He may be clearing you out
for some new delight.

The dark thought, the shame, the malice.
meet them at the door laughing and invite them in.

Be grateful for whatever comes
because each has been sent
as a guide from beyond.

Rumi

Copyright 1997 by Coleman Barks. All rights reserved. From The Illuminated Rumi.

References:

1. Craig, 2000, How do you feel? Interoception: The sense of the physiological condition of the body
2. Craig, 2009, How do you feel-now? The anterior insula and human awareness
3. Farb N, Daubenmier J, Price CJ, Gart T, Kerr C, Dunn BD, Klein AC, Paulus MP and Mehling WE (2105) Interoception, contemplative practice, and health. Front. Psychol. 6:763, doi: 10.3389/fpsyg.2015.00763
4. Interoception and Mental Health: A Roadmap Khalsa S.S., Adolphs R., Cameron O.G., Critchley H.D., Davenport P.W., Feinstein J.S., Feusner J.D., (…), Interoception Summit 2016 participants (2018)  Biological Psychiatry: Cognitive Neuroscience and Neuroimaging,  3  (6) , pp. 501-513.
5. Cruikshank, T & Bismarck, R. Yin and Meditation.
6. Bordoni Marelli Emotions in Motion: Myofascial Interoception
7. (Schleip and Jäger, 2012) Schleip, R., Jager, H., 2012. Interoception: A new correlate for intricate connections between fascial receptors, emotion and self recognition. In: Fascia: The Tensional Network of the Human Body. (Eds: Schleip, Findley, Chaitow, and Huijing), pp. 89-94. Churchill Livingstone.
8. 8.Chen, WG et al. (2021) The emerging science of interoception: Sensing, integrating, and regulating signals within the self. Trends in Neurosciences. Vol 44. No.