1. What is it about gentle extension and lateral bends that’s useful for fatigue/depression?
2. And what is it about twists and forward folds that’s useful for anxiety?

Here is my answer:

First, just to be super clear – I’m not suggesting that yoga is a substitute for healthcare, but rather can support whatever care a person is already receiving.

Extensions and lateral bends are considered “Brmhana“ – that means they create some activation in the nervous system – and I’m not  talking exclusively sympathetic activation of the Autonomic Nervous System (ANS). What I’m talking about is the effect of these postures on the vagal brake, which I’ll explain in a moment.

But first let me say, that I am very inspired by, practice and teach mostly breath-centric postures. I learned this kind of asana practice from my teachers in India, and also from my Viniyoga teachers, including Gary Kraftsow.

So, if you teach that way, you think about the poses as moving from the breath. And then it makes sense that postures that promote the function of the musculature of inhalation lend themselves to energizing the nervous system.

Extensions and laterals optimize the inhalation process. They activate the ANS because of their effect on the respiratory musculature (diaphragm and the external intercostals) and other apparatus (bones, cartilage, lungs, the heart, and fascial connections) of inhalation.  This is why they create a more brmhana or energizing effect on the system.

Read more here…