You're still completely missing the point. Body flight is not a result of leg action, but of carrying momentum across multiple steps. You can fake the right leg action, and still not have body flight, unless you have a continuity of momentum across steps. Likewise, if you have a continuity of momentum, you can have body flight even with the wrong leg action (you will just have other problems)

As a child, the Nobel Prize-winning physicist Richard Feynman asked his father why a ball in his toy wagon moved backward whenever he pulled the wagon forward. His father said that the answer lay in the tendency of moving things to keep moving, and of stationary things to stay put. "This tendency is called inertia," said Feynman senior. Then, with uncommon wisdom, he added: "But nobody knows why it is true."

Accelerating forward pushes the ball backward.
Accelerating backward pushes the ball forward.
Decelerating pushes the ball forward.
Curving pushes the ball sideways to opposite direction of turning.

The word ball can be replaced with the word body.

Pushing forward with the supporting foot accelerates the mass of the body and a force tends your body to bend backward, because of inertia. Body flight can be demonstrated in slow motion by asking somebody to push you against your chest while you are taking first forward step. The pushing will hold your moving foot not to fall on the floor. On walking the push of the supporting feet accelerates your body and the mysterious inertia takes care to push against your chest and other accelerating parts of the body to let your body to flight.

Deceleration is decreasing of velocity, ex. by braking. When the pushing of the supporting foot ends and the moving foot hits the floor, decelerates the mass of the body causing by inertia a forward force witch pushes the body on the new supporting foot.

When turning the body tends to fall to the opposite direction and must be balanced by the sway, like a cyclist does while curving.

Momentum is mass x velocity. Momentum must be increased by impulse to keep moving continuously. Impulse is force x time. Impulse accelerates the velocity. It should be interesting to discuss at what moment of the step and time of the beat the impulse takes place. I think during the beat one if the step takes two beats, in some dances.

Interesting points SQQ, but not really relevant.

Body Flight is essentially the opposite of impulse. The total movement is the sum of a contribution from impulse and one from body flight - for a good dancer, the impulse contribution is quite small.

In terms of acceleration from the legs causing the upper body to move backwards, this is not really going to occur. The legs won't start to produce any acceleration until the weight has already overbalanced beyond the point of support in the foot. The body would pitch forward, except that the push from the legs accelerates the lower body forward faster. But in the body flight dances, this is the minor component of the motion - the major component is the already existing body flight.

Anonymous. Yes it does get interesting.Now look at it from the ladies steps. She bends the knee towards the man and provides a bit of resistance. The left leg is way behind right on the tip of the toe. Exactly where does this body flight come into play. It is simply move the body onto the now standing leg, what else can it do. If we were to measure the distance between the body at its starting point and to its final destination and divided this into thousand parts, then the body will have a thousand different positions on its move to the standing leg . I don't think any dancer will do it any other way.As Shakespeare wrote. " Much Ädo About Nothing ".

"The left leg is way behind right on the tip of the toe."

A classic mistake! The left LEG is not way behind the right, the left FOOT is. The legs are still quite close together, until the point when the body flight has carried the body halfway through the new step. Only then will the legs be - quite briefly - apart.

As for much ado about nothing, the widespread and obvious failures to make good use of body flight prove that to be nonsense. It's a quite serious issue - look where the lack of it causes trouble on some of the videos here.

Would you please give me more teaching tip about the 46 degree fex or shin to floor angle ?
Which one is the angle you mentioned : 1. the angle formed by shin and instep
2. the angle against the shin bone. (the two sides are extending from the thigh to floor and floor ).( sit up postion when body journeys from heel to ball )
thanks.
ylchen

Yichin, On a piece of paper draw a straight line level wth the edge of the paper. Then draw a line straight up. Divide that by two \ < That is 45 degrees. Straighten the knee An angle between the floor and your knee is at a right angle. As above we need half that distance. From a completely lowered position I can show an seven inch rise to my highest on step three. I think most could do better than that. Why not get somebody to measure yours. Keep the back straight and don't sit.Come down through the knees and lower the heel to the floor. One more thing the bending of the knee is to your front whether you are going forward or backward. For the lady the moving foot must be released, by about 9 inches Don't try to step back from a feet together position. Best of luck