Anxiety is in your body, not your mind

Haha, i don't know right now. but from the point of view that yoga is a systematiztion of techniques that is useful for connecting to energy, correcting the flow of and balancing the energy in the body, and opening the channels in the body to allow it to handle higher bandwidth of different sorts of energies safely, I suppose that perhaps these great saints already knew how to do that on some level even if they weren't following sort of formal practices. Of course that's just a theory we'd have to look back into the past to make sure.

another perspective is maybe they discovered or were taught techniques even more advanced than what's commonly know as yoga. Maybe that helped them somehow attain their heights as you said.

From another point of view I think there's an idea that yoga is probably for the common people, you know, everyone. Maybe there's some exceptional people whose bodies are already highly tuned somehow and they sort of don't need to do that...could be possible. But that would probably be rare like Olympic level athlete rare. And maybe some of those great saints weren't even human. So maybe techniques for the everyperson human form don't apply to them.

Harder to speculate about those things than it is to know that yoga is good for me from experience, and have a theory for why correct yoga would be good for most others as well, especially meditators.

Aside from what i already said, biomedically the long holding, and the precise poses, sooth and calm the parasympathetic nervous system, which helps correctly regulate many other systems, and help massage and promoting flow in the lymphatic system, i think. Even leaving aside the energy perspectives, relaxedly holding poses for a handful of breaths, is a great tune up for your body.

Yoga is only very recently regarded as mostly physical exercise. Of the 8 limbs of yoga only one is Asana (postures)

If you read Patanjali (the foundational text) there is very little or no mention at all of posture.

It’s certainly both. “Anxiety” it’s your brains response to given sensory input and tends to trigger a release of cortisol and in more extreme situations adrenaline. While cortisol and adrenaline are normal responses it’s a very slippery slope and they can have extremely negative effects on the body.

The dangers of to much of these hormones come from both chronic exposure for normal sensory inputs like stress at work or school on a daily basis or constant instability like parents fighting regularly to single acute episodes like an extreme traumatic event. Traumatic events tend to alter neural pathways so moving forward even non stressful sensory input can trigger these strengthened pathways putting people in non stressful environments in chronic states of stress.

It’s helpful “not to think about it” whatever “it” is, but it’s often involuntary especially for those that suffered a trauma, as there’s always the risk that you are unknowingly responding to it without even thinking about it and it’s often hard to connect the dots.

The other issue is everything in the body is a feedback loop and hard to break or change. For example even just sitting in a chair all day will shorten you hip flexors, causing unnoticeable discomfort but your brain will notice and respond with release of cortisol which will in turn cause tightening of muscles and myofacia, that will further release cortisol in response to those bodily stresses, and on and on it goes with all kinds of “referred pain” (I hate that term) you do notice in maybe your neck or shoulder(s) or back. And good luck at that point you’ll be treating the area in pain that’s not even actually causing the pain only leading to more chronic stress over the inability to make the pain go away. If you work in an office my guess is you have physical pain, and you can ask anyone else in the office and odds are they have physical pain, and my bet dollars to donuts from arthritis to bursitis to joint pain the vast majority with simply blame it on getting old or some posture issue and not a single one will realize the physical pain and bodily conditions are directly related to stress.

Going off of the quoted bit because I haven't watched the video, he isn't necessarily suggesting that is the mode of action, just that the mechanism of Valium does both. The mention of GABA enhancement from the comment above alludes to that.

Behavior and attitude can influence each other. For example, happiness makes you smile, but smiling can also make you happy (to some degree). The same works for anxiety in which your mental anxiety can make you physically anxious and vice versa. What he is suggesting here, especially considering the James-Lange mention, is that Valium's mode of action is targeting the behavior side of things for anxiety, but does not exclude it from influencing more than just muscle tension.

I think the general consensus in psychology is that it's neither the mental state nor the physical state (James-Lange) that create emotion, but rather both. Both can instigate responses from each other. Valium simply influences part of the CNS to affect both, but because it's a drug, it inherently affects the "physical state" more directly.

Normal muscle relaxants aren't as effective for anxiety as Valium because they don't have any action on the central nervous system, just the neuromuscular mechanisms. Valium does much more than simply relax muscles. It affects GABA throughout the whole body.