A very deep stretching session can actually calm down your brain a lot. I don't get how it happens, but it happens.

You're absolutely right. If you look at yoga, the traditional yoga, you start off with an asana, which is movement. Then you move into breath, which is pranayam. Then it makes meditation way easier. If we just try to start meditating right now, some of us may be able to do it easily. A lot of us will struggle because you prepare for that step. When you're flexible or when you do these deep stretches, like you said,? More blood circulation? More blood circulation means more oxygen, more nutrient flow to cells in your body. Now you're calmer after the stretch and you can meditate more easily.