Swing your arms and upper body

[Summary]
In type 1, the way to get rotation is to jump with leaning forward and swinging your arms.
In type 2, the way to get rotation is to swing your arms and upper body.
Swinging something contributes to rotation while your feet are on the ground.
Your arms should be swung from the top to the bottom before taking off.
And in type 2, your upper body should be swung from the position of leaning back to the position of leaning slightly forward.
(cf. the appropriate swing direction)

He swing his upper body and his bent arms.
His hip joint is being closed before takeoff.
And he pushes the ground by extending only his knees.(So, his standing front flip is type 2.)

You can easily see he swings his arms from the top to the bottom.

[Details and Theory]

– The 2nd way of initiating rotation –

Pinch a pen and swing.
If you release the pen, the pen will fly away with rotation. It is based on the same principle as getting rotation by swinging upper body.
This is the 2nd way of initiating rotation.
The 1st way is Tip 1 : Slightly arch your back and jump.

In regards of standing back flip, even if you don’t shift CG with jumping, you can get rotation by swinging upper body backward from leaning forward position (but it’s not enough).

– Upper body and Lower body move forward –

It can be affirm that this way of getting rotation makes use of friction.
In the air if you change your posture from the posture with your back warped to the posture with your waist straight, CG doesn’t move and both of upper body and lower body move without any fixing.
(cf. Not Tip 1 : When tucking , bring knees to chest, not chest to knees)

Therefore, feet moves forward.
However, in the case feet are on the ground, feet is fixed by friction.
The direction of that friction force is backward because it disturbs the forward movement of feet. Friction occurs backward ,so your body starts rotating by that.