There are patterns of muscle tension and slackness that fairly reliably create changes in the brain and the rest of the nervous system.
For example, if you’re slumped too much, you’ll tend to get sleepy easier. If you’re sitting too upright and stiffly by creating tension to hold yourself up, it blocks the nervous system from getting in sync with breathing.
We teach people to sit in an upright, relaxed posture, and traditionally this involves sitting on a cushion cross-legged because it forces the hips into a position that makes sitting upright require relatively little effort (most possible postures heavily engage the core, requiring a lot of tension to sit upright, while we sit in a way that is designed to minimize that effort by “locking” the torso into a position where it doesn’t have to work very hard to maintain posture).
There are patterns of muscle tension and slackness that fairly reliably create changes in the brain and the rest of the nervous system.
For example, if you’re slumped too much, you’ll tend to get sleepy easier. If you’re sitting too upright and stiffly by creating tension to hold yourself up, it blocks the nervous system from getting in sync with breathing.
We teach people to sit in an upright, relaxed posture, and traditionally this involves sitting on a cushion cross-legged because it forces the hips into a position that makes sitting upright require relatively little effort (most possible postures heavily engage the core, requiring a lot of tension to sit upright, while we sit in a way that is designed to minimize that effort by “locking” the torso into a position where it doesn’t have to work very hard to maintain posture).