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Re: Drag Hesitation
Posted by interested
8/20/2008  7:40:00 PM
At the end of a Double reverse spin the alignment is say DC. The first step of the Drag Hesitation then also has a DC alignment. So the turn of the DRS has stopped whilst step 1 of the next figure is placed. What stops the turn ? If I do not lower at the end of the DRS I tend to carry on spinning past my alignment (like on an overspin). The forces generated by muscles during the lowering only work forwards and upwards not towards the centre of rotation - so they do not stop me rotating. Surely, only friction is left. I always assumed that this is the reason turn was always lead on the toes [ie to reduce friction}. The relative movement of surfaces to generate friction comes from the rotation.

Even with regards forwards motion, wouldnt there be a limit on the extent to which momentum can be maintained.
I can see that following a DRS the centre of gravity would continue to move forward as result of the downswing at the end of the figure and that this is where the energy carried into the first part of the next step comes from. BUT, as soon as weight is transferred, the reaction force from the floor would tend to oppose the forwards motion and the energy would be dissipated doing work against that force. By this time the centre of gravity would be roughly above the feet, and, in normal gait, you would reach a stable equilbrium at this position. And just as in normal gait, if you want to carry on moving forwards, surely you have to flex your muscles all over again ?

(this argument my well be flawed, i'm
really just trying to think this through ! )


Re: Drag Hesitation
Posted by interested
8/21/2008  6:09:00 AM
I found some scientific figures on this (that come from measuring muscle activity and overall movement kinetics during gait). During normal gait, some energy is carried into the next step, typically some 50%.This is because although work is done against the ground on landing, the landing can be softened by using the knee, so that not all of the energy from the original downswing is used up. A skilled dancer probably uses this effect to some advantage and I guess this is crucial to the quality of softness. I guess the % carry over will also be increased if more energy is generated in the first place (ie through a powerful swing). The carry over also seems to be quite critically dependent on the speed (cf running where it is hard work to actually stop) i guess because more energy is created initially.

This means that to maintain a steady speed the downswing on the first step needs to be more powerful than that on subsequent steps.

Of course this will be tempered by the fact that in dancing you are not always swinging one continuous line (or maybe you are and this is the reason you should be - this perhaps goes back to anymouses idea of a swing to a side position being totally forwards).

However it does mean that only 25 % of energy is carried forward ober three steps and even less of this can be exploited if there are directional changes.

Anyway, this explains why walking aimlessly (ie stopping and starting) around the shops is more tiring than walking continuously in a straight line. It is also the reason why reabilitation after leg injury is best acheived through establishing a rhythmical and sustained pattern of activity.
Re: Drag Hesitation
Posted by anymouse
8/21/2008  8:08:00 AM
"I found some scientific figures on this (that come from measuring muscle activity and overall movement kinetics during gait). During normal gait, some energy is carried into the next step, typically some 50%."

"The carry over also seems to be quite critically dependent on the speed (cf running where it is hard work to actually stop) i guess because more energy is created initially."

"This means that to maintain a steady speed the downswing on the first step needs to be more powerful than that on subsequent steps."

In ordinary walking or running, we tend to analyze step by step, as each step is identical.

But to analyze dancing we have to look at most situations as a cycle over three steps, that together make one energy cycle - one downswing, coast through, and upswing cycle. The leg action used is one that largely hides the fact that there are three steps, and instead makes the resulting body movement almost that of taking a single impossible large step per measure.

"However it does mean that only 25 % of energy is carried forward over three steps"

The movement over three steps in dancing does not have the per-step "bump" rise of arrival due to the leg action evening everything out into a big smooth swing.

"and even less of this can be exploited if there are directional changes."

This is a good concern. If you take that concern and analyze where the line segments making up the characteristic swing dance figures break - where the actual changed of direction are, you find that they almost always occur at the point of maximum rise. At that point, most of your energy is in gravitational potential energy form, which has no direction across the floor, and very little of your energy is in kinetic form, which does have a direction.

You CBM while you are moving, but you don't actually change direction of movement until that point in the swing cycle where the majority of your energy is in non-directional form. You then convert the energy back into kinetic form by executing a downswing in the new direction.
Re: Drag Hesitation
Posted by anymouse
8/21/2008  7:56:00 AM
"So the turn of the DRS has stopped whilst step 1 of the next figure is placed. What stops the turn ?"

The forward drive generated by letting the body weight get ahead of the standing foot overcomes the angular momentum and converts it to a more linear movement. The body however will keep rotating somewhat during this nearly linear movement, the body rotation now being known as the CBM of the new figure.

"The forces generated by muscles during the lowering only work forwards and upwards not towards the centre of rotation - so they do not stop me rotating."

You are trying to analyze rotate and translation seperately, but any translation force that is not applied exactly through the center of rotation will in fact alter the rotation.

"Surely, only friction is left."

Floor friction can only dissipate energy if you allow movement (rotation) of the foot against the floor. During the toe spin you will have some frictional losses. But when the foot lowers, even though your body may still be turning, you are no longer letting the foot rotate on the floor, so no energy is lost to floor friction. Friction is merely holding your foot in place. No movement of foot against the floor = no mechanical work = no loss.

"I can see that following a DRS the centre of gravity would continue to move forward as result of the downswing at the end of the figure and that this is where the energy carried into the first part of the next step comes from. BUT, as soon as weight is transferred, the reaction force from the floor would tend to oppose the forwards motion and the energy would be dissipated doing work against that force."

What reaction force?

If you place your leg ahead of you and brace the knee, then you will see a reaction force that slows you, because it is causing your path to curve upwards - you are coasting up hill, and indeed that is one of the ways we can rise in dancing (leading a heel turn would be a good example). But if you let your knee flex as you arrive over it, you will not rise and you will not slow.

That's more typical of step one in for example waltz - limited rise and limited slowing during step one, more dramatic rise and more dramatic slowing during step 2.
Re: Drag Hesitation
Posted by SocialDancer
8/20/2008  5:13:00 PM
OK, I probably do two variants of the DH.
The more standard one to be followed with a back lock does not carry in much inertia and uses no sway.
The more dynamic variant carries inertia through from the DRS, as though dancing a second one, only for it stall in the hesitation. Any sway probably comes from the need for a wide second step, and again I probably take this wider than necessary as I tend to finish in line to follow with a contracheck. Not strict syllabus I'm afraid.
Re: Drag Hesitation
Posted by interested
8/20/2008  5:21:00 PM
surely if you follow with a contra check you are in effect doing something more like a change of direction. i myself often use the change of direction on non-standard alignments.
Re: Drag Hesitation
Posted by SocialDancer
8/21/2008  4:01:00 AM
"surely if you follow with a contra check you are in effect doing something more like a change of direction."

Yes it is very similar to steps 1&2 of a CoD extending the second step with the hesitation. I did suggest comparing and contrasting the two figures because AFAIK the CoD is not listed as a waltz figure, or QS for that matter.

"I often hear it said that the technique specifies the status at the end of a step."
Yes, see Guy Howard's definition of foot position.
"Then I hear people saying the end of a step is defined as when the feet pass (or close)."
Different book and different situation.

"So how you define the end of the step depends on what aspect of technique you are considering."

At last someone who understands the problem of taking one person's definition and applying it to another's description. Although maybe we see this when trying to follow some of Polished's posts.
Re: Drag Hesitation
Posted by interested
8/21/2008  5:57:00 AM
yes - the guy howard on foot position (right at the beginning of the book)was exactly what i was thinking about.

i apologise for not having thought more about your suggestion for comparing the change of direction. lack of time. but i will get round to it.

i think comparing figures is useful. even if they turn out to be not comparable (and people often shout "but hey they're just not comparable), understanding why that is the case, will often shed more light on the basis of technique, i find.

thanks also for the exam tips. this is more for my own interests than for exam purposes. in response to your comments - from what i hear, it certainly isnt a requirement to have an opinion, even at fellowship level.
Re: Drag Hesitation
Posted by interested
8/20/2008  11:33:00 AM
the reduced amount of turn would also call for more sideways placement. i guess you can only get to end "to side" position-wise with nothing other than a forward swing from the hips (ie getting to side solely through a foot swivel)without turning more than 1/4.
Re: Drag Hesitation
Posted by interested
8/19/2008  10:39:00 AM
By basic rise and fall I meant the standard rise and fall such as that on 1-3 of a reverse turn.

The fact that on step 2 you are down but on toes seems slightly odd.

Maybe it is simply a matter of lead and follow. I certainly can't think of any other obvious reason.

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