The young sea squirt has a brain and a spinal cord. It swims about looking for a good stone to settle on, lands, attaches itself – then eats its own brain and spinal cord since neither are now needed now it isn’t moving about any more.
Therefore no movement means no brain is needed.
No movement means spineless.
In order for any brain and body to function well, it needs stimulation from movement and mental challenges; it needs us to eat very well and to breathe well – which means the diaphragm goes down on the in breath and up on the out breath.
Neglect any of these and just think, ‘sea squirt’.