"There you are. Blind again.What dance figure is it giving a describtion of.
One step Forward or Backward .Waltz Foxtrot or Quickstep. The technique remains the same."

Quickstep, you are the BLIND one ignoring the OBVIOUS DIFFERENCE OF RISE AND FALL.

Don't you think rise and fall will effect how straight your legs are during the step?

"Just think about this. I believe that you haven't lowered with both knees flexed which includes the left as we step forward left foot. This will cause the knee to naturally straighten at the extent of the stride."

You mistake is not realizing that if you lower fully into the knees - as ALL SKILLED DANCERS DO - you will not be able to achieve fully straight legs at mid-stride. On the other hand, if you do not lower into the knees so much (and you should not in the WALKING EXERCISE, because it does not involve any lowering, only softening) then you will quite easily achieve fully straight legs at mid stride.

How is it that you can take such a simple fact and make a mess of it?

Your last paragraph. I dont know if you are agreeing or disagreeing. I'll take it you are disagreeing. If you push off a compressed standing foot and push right to the tip of the toe your knee must straighten. Just think of what an ugly picture will be created with a bent knee all through the mid stride to the fully extended. Terribly ugly.
Lets go to the Social Foxtrot. We call it Rhythm Dancing. A step forward is still a step forward, just not so big. Imagine what it will look like if the knees are permanently bent.
The final words on this are. Get a technique book and understand it.. And last of all I only quote the technique book I didn't write it. For those following this go and look for yourselves.

"If you push off a compressed standing foot and push right to the tip of the toe your knee must straighten."

That rather depends on how compress - how low to the floor - you start.

If you are just below normal standing height, as in the WALKING EXERCISE, then yes you will easily be able to fully straighten your leg at mid stride.

On the other hand, if you execute the extreme lowering used by championship dances, then you will not be able to get your feet far enough apart to be able to fully straighten your legs. With the center this low to the floor, it would be quite awkward and inadvisable to get the legs fully straight. They straighten, but they are not as fully straight in this DANCING as they would be in the WALKING EXERCISE.

"Lets go to the Social Foxtrot. We call it Rhythm Dancing. A step forward is still a step forward, just not so big. Imagine what it will look like if the knees are permanently bent."

The knees would not be permanently bent. Social foxtrot is essentially performing the WALKING EXERCISE with a little musicality. It does not have the kind of LOWERING seen when skilled dancers perform the slow foxtrot, so the difficulty/inadvisability of fully straightening the legs seen in the heel lead steps of slow foxtrot would not apply to social foxtrot. IT IS A SIMPLE FUNCTION OF THE DIFFERENT HEIGHT IF THE CENTER ABOVE THE FLOOR in the two cases.

"The final words on this are. Get a technique book and understand it."

You can't claim to understand the technique book until you pay attention to the CONTEXT of what it is saying. A WALKING EXERCISE with the center almost standing height above the floor has details which are INCOMPATIBLE with slow foxtrot heel lead taken after a FULL LOWERING.

Let us remember that dance ever has and ever will be an evolving dance form. Techniques and stylings inevitably change as time and fashion pass along. To declare a technical description written in 1948 as wrong comparing it to today's undoubtedly altered standards is ludacrous. In addition to this, it is being forgotten that body movement is a very intangible concept to try to make concrete. It is extremely difficult to give a complete and detailed description of how to evoke a particular way to move the body especially when trying to include the techniques of the head position, the left and right arm, the angle of body in relation to the room, the body in relation to the partner, the action of the knee, the hip etc etc. Dance is so objectionable and so personal to each individual it is small minded to make any blanket statements about the correctness of one person's methods of teaching. In summary, don't be a hater.

Basics haven't changed at all. Basic timing along with footwork are still the same as they were before 1920. You can add alignment to that list. What has altered over the years is the positioning of the bodies between the man and lady which does affect how the different steps will be performed. Once the lady was right in front of the man with contact at the hips. Then the lady went more to the man's right. Still contact at the hips. Then there was the lady taking her bust away from the man turning a few degrees clockwise. This resulted in a man's right side to the ladies left, still with hip contact. Today we have and I will quote." The right area of the chest of each partner touches that of the other ". This results in a right side to right side position and you could swing a brick through the lower part without hitting any thighs or knees. My main gripe is even though if a video of an international competition is available showing and cofirming the above. There are teachers teaching who haven't had a lesson themselves for years and have failed to keep abreast of the times.
This we fairly recent. There was a Seminar featuring one of the really big names in dancing .I looked around and there was one professional present. The rest were all amateurs. This was by no means a one off situation.
I don't know about where you live. But here when Dancesport was formed those who had been teaching for years were given what was called a Grandfather Clause. That meant they were accepted without any examinations. There was a but. and that was after a time they were to be examined. That is the biggest joke of all.

I would agree with Quickstep that changes in the basic technique are fairly minor.

I would disagree though about what is the greatest change: not the relative positions or shapes (sure, that looks obvious) but rather the amount of rise and fall and the corresponding volume of movement - it is drastically larger today than ever before!

With that increase come changes and new obviousness, not of the technique, but of the IMPLICATIONS of the techinque. To those who understand it, the ballroom technique has never been so simple as "you should do x" - instead, it has alway described the relationship between x and y - if you do this much x, the result will be that much y, so depending on how much y you want you must adjust your amount of x.

This is the differences between being able to quote technical TRIVIA meaninglessly out of context, and being able to give sound advice for a particular DANCE SITUATON, but applying the enduring relationships to determine the details APPROPRIATE TO THAT SITUATON.

With regard to rise and fall vs. leg straightening, the dancer who fully understands his subject will recognize (intuitively or intellecutally - it matters not) that the increase in body movement achieved by the last cm of lowering is much less than that achieved by the first cm - it is in fact a square root relationship.

On the other hand, the distance required between the feet to achieve straight legs will increase much more for the last few cm of lowering of the center towards the floor than for the first few.

These two relationships do not coincide! There is a threshold of lowering above which you can apporpriately achieve straight legs, and below which you can no longer send your body fast enough to get your foot a straight-leg distance apart at mid-stride!

Simple relaxed social dancing, and the WALKING EXERCISE customarily do not lower below this threshold altitude, so achieving straight legs is no problem. On the other hand, competition dancing at championship level today lowers far below this - as a result, it is quite rare for a championship dancer to be able to achieve straight legs at mid stride, because they simply can't move their body fast enough to get the legs naturally that far apart before their arrival on the moving foot forces it to stop moving.

It's worth mentioning that todays dancers do not go any higher in rise than Vicor Silvester did in 1920. What they do is bend the knees more. One of the very top Italian dancers is small but can get what appears to be a terrific rise and fall on the floor. In relation to his own build it might be more than a six footer.

"It's worth mentioning that todays dancers do not go any higher in rise than Vicor Silvester did in 1920. What they do is bend the knees more."

Maybe a cm or two higher, but yes most of the difference is on the lowered end.

And it's that extremely lowered body altitude that usually prevents them from getting fully straightened legs - the feet would just be impractically far apart to do so.

"two straight legs" may be a useful rule of thumb with more limited lowering, but today it is not applicable. Wheras teh guding principles of technique from which the two straight legs recommendation was determined are still applicable - they just recommend something different when you lower that much!

Does the person going backwards pull the heel of the moving foot to a position under the body. Yes?
Well try that with a bent front knee.
Where does the drive come from. It comes from a push of the heel against the floor with a straight knee, not rigid.

"{Does the person going backwards pull the heel of the moving foot to a position under the body. Yes? Well try that with a bent front knee."

Please explain how you intend to get the heel under a lowered body without bending the knee? This is pointless though - we were talking about the straightness of the legs when they are at the straightest, which is to say at mid-stride. You obviously aren't pulling your heel under your body at mid-stride.

"Where does the drive come from. It comes from a push of the heel against the floor with a straight knee, not rigid."

Please learn to recognize the difference between

1) straightening = becoming straighter than it was
2) being fully straight
3) being straight AND rigidly locked.

You won't have anything of value to say until you learn that these are THREE DIFFERENT SITUATIONS.