Most of the time when we are sleeping, our body and mind are active.
We toss and turn (yes, while asleep).
There is short period in our sleep cycle when we become motionless.
Even our breathing stops.
This is the recuperative stillness.
The longer we have this stillness in our sleep, the more refreshed we are the next morning.
One of the goals of meditation is to enter this state of recuperative stillness.
If you can remain conscious while in this state, you are aware of the energy movements (qi) in your body while recuperation is going on. With practice, you can even channel some of this energy flow at will.
This is how you can transform and modify your physical body towards nirvana.
Mental transformation is not enough; it doesn’t last long. We need a physical rewiring.