Shizentai:
It is not quite Natural posture.

Shizentai means "natural posture". However, it is not your ordinary posture.

You must learn the natural posture in order to stand naturally. Yes. Very complicated but you will get used to the posture.

The key points are;

• to straighten the back of your neck,
• to pull your chin in,
• to tighten the butt cheeks.

It does not sound like a natural posture. Very uncomfortable for the first time you try.

You know there is a difference between being relaxed and being lazy.

We do not want to be lazy. We need to make an effort to maintain your posture but you can still be relaxed.

That is what we want. Now, this is how we create this natural posture. 

Upper body: 

1. lift your shoulders
2. bring your shoulders back (it feels like your shoulder blades meet at the back) 
3. drop your shoulders.

This naturally sticks your chest out so that your shoulders will not roll forwards.

4. keep your chin in but not too much.
5. keep the back of your neck straight.

Lower body: 

1. tighten your buttocks
2. heels together and toes apart (45 degrees between toes)

When you tighten your buttocks, probably you feel the abs and the hamstrings tightened too.

You feel taller.

Now I know it feels weird but you will get used to it. In other words, do it until it becomes "natural".

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