Do you feel that it strengthens the tendons? Does it make your bones more dense? Does it give you striking power and does it improve your movement? etc.
It does all kinds of things depending on where you are at in your training and how long you do it.
Firstly it allows the muscles to fatigue in such a way as to gas them and over time let you use your skeletal structure and your tendons to support you. It burns the shape you are holding into your nervous system and memory and once again over time lets you separate all the disparate parts of your body (muscles, veins, organs etc) from one another thereby giving you the ability to learn and control the inner landscape of your body to allow a higher degree of manipulation of the shape of the body itself...compressing and expanding, opening and closing the joints etc.
All of this separating (once again over a long period of time) is a huge act of releasing long bound stagnation of the feedback loop which is basically your ego. Your sense of self is an incredibly complex set of self imposed instructions based on your whole lifetime of experiences in your body. You are basically a whole bunch of "if this then that" commands based on using your brain to keep you safe...say you break your arm when you are a kid...you have huge pain and worry and all kinds of shit associated with that event and you tell yourself things as commands to prevent more danger or whatever...you hold tension there to keep it from getting hurt again and over time. As you stand and the stagnation starts to clear you see more deeply into the nature of your mind and get a clearer picture of how your emotions and intellect are connected to your body and you start to see how they work which allows you more control over it and eventually lets you choose how the brain and body interact rather than being subject to the reactive state most peeps live in..being able to turn off your fear, not have your mind distract you in a danger situation because it's trying to analyze shit when it would be better served reacting spontaneously...in short it gets rid of yo bad brain syndrome.
The greater degree of mental freedom and control you acquire through this puts you in a position to start putting in your own commands...burning more functional shapes into your nervous system and commands between your body and brain.
Anyway...it's a good practice. I'm for it...and of course it's sister circle walking.
I could expound on it some more, but I think I'm ready to go back to sleep again.
Best,
S- little bit of insomnia tonight.