The Line, the Midline, the Postural Curve and Problems of Stance

Pages: 22-35
Year: 1991
Notes on S.I

Notes on S.I.


Ida Rolf’s discovery of gravity as the major physical factor determining the shape of the body, its structure, culminates in the extremely simple block model. It demonstrates that the alignment of all segmental gravity centers, which should optimally be vertical, is the most succinct indicator for the degree of integrity or its lack in a given structure.

It is interesting to note that she didn’t follow up much on this discovery which appears so elementary and powerful in that it determines the approach to the problems of the field categorically and provides nearly all the means necessary to understand structure. This intrigues the mind and calls for attempts to explain the curious fact.

Part of the explanation may actually be the sheer overwhelming simplicity of the concept. One hesitates to accept it as the base from which one is to understand such an extremely complex and complicated matter as the form of the human body. But more often, strong reservations of an ideological nature seem to be superimposed. Simple models and concepts are experienced as a threat to the mystery of human life endangering the dignity of man. The attitude is understandable considering the history and present state of Western civilization. But it also appears that its effect has not been the one that was intended but rather the opposite. It also effectively blocks the development of knowledge about the “human condition”.

It is also obvious that the concept like all simple models is highly abstract. Gravity centers are nothing to be touched or seen, and they can’t be determined in something as abstract as the segments of the human body, nor can they be measured exactly enough. One observes all the time when theory is attempted, seriously or otherwise, that one is strongly seduced to revert to the tangible, visible, “solid” parts of the body like bones. This leads immediately, as far as the practice is concerned, to something like “anatomical integration” which is often highly beneficial to the client but is of course something very different from Structural Integration.

But part of the reason may also be contained in the block model itself which is somewhat misleading in several respects. A stack of blocks is a compressionally stable structure and so does not represent the principles of the construction of the body at all. Single blocks are in indifferent equilibrium (Fig.1). They may be shifted a little right or left, forward or back, and equilibrium of a kind still prevails. So the alignment of the blocks’ gravitational centers is shown visually but differences have little consequences concerning balance. Fig.1 shows a version of the block model which makes the importance of the alignment of the gravity centers obvious.

<img src=’https://novo.pedroprado.com.br/imgs/1991/1041-1.jpg’>
Fig.1 – A stack of blocks (left). The gravity centers of the blocks are found at the geometrical centers of the rectangles. The figure on the right shows the same arrangement of the gravity centers but the “blocks” are drawn as inverted pyramids or cones. This “labile block model” demonstrates the mechanical consequences of a non-normal arrangement of gravity centers clearly.

Another misunderstanding is suggested by the block model concerning rotations. Rotation around the vertical axis is almost irrelevant. It correctly represents the situation in the body where rotation proper is the least important type of deviation because it is neutral with respect to gravity. But rotation around the two horizontal axes, tilt and side-tilt, suggests a false priority. They can’t even be shown in the block model, but if they occurred it is intuitively evident that the stack of blocks would collapse quickly. This is different in the body which constitutes a structure which is held stable mostly by tensional means. A certain degree of tilt and side-tilt is almost negligible in the body. The alignment of the gravitational centers clearly takes precedence. A certain preoccupation with “horizontalizing the pelvis”, which refers to tilt and side-tilt, too often seems to effectively block the attention which should be paid to the much more important alignment of the gravitational centers. It should usually be replaced or at least preceded by “verticalizing the gravity centers”. With reference to Ida Rolf’s “blocks-in-the-sack” model (Rolf, p.32), Fig.2 and Fig.3 compare the two issues. The labile version of Fig.1 is shown with rotations only but no shifts and shifts only without rotations respectively.

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Fig.2 – Shifts vs. rotations. On the left is the “labile block model” of I11.1. Only shifts are present but no rotations. On the right the gravity centers are arranged on the Line, no shifts are present but rotations are.

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Fig.3 – The same arrangements with an “elastic sack” around the blocks. They are held stable by tensional means, and comparison shows that shifts are more important than rotations.

The final and perhaps most important reason for confusion arises easily when structure and function are not kept apart strictly. Structural rotations are more constant than shifts; they can be reversed functionally less easily. Especially in the sagittal dimension, apparent segmental shifts are often in one or the other direction, switching frequently across neutral, dependent on a multitude of factors. The front-to-back alignment is so much the domain of function that frequently an analysis of the structural state is not even attempted. Moreover, structure is generally assessed with the client standing. Standing is a specialized function, however. One of its features is that an anterior pelvic shift is favorable. The large majority of people present such an anterior pelvic shift in standing, but only with some of them is it also structurally anterior; with others the pelvis is posterior structurally.

It would seem that structural side-shifts are more constant and less often subject to functional reversals. This is probably true if the weight is distributed equally on both legs. But this is a rare phenomenon because for most people this stance seems “unnatural”. But even if employed consciously this artificial stance has not yet produced clear and unambiguous criteria to diagnose the side-to-side arrangement of the segmental gravity centers with complete confidence. Shifts in the transverse dimension appear to be more variable than one would guess at first. One gets a sense of it when one stands on one leg with that hip out, then on the other with this hip out. The two stances are definitively different – because of the structural state of course-but both are possible and fairly easy to do.

The Line and the Midline

The Line has been defined as that vertical line which goes through the gravity center of the body. It is a property of the gravity field, not of the body. The body, by its gravity center, determines its location, i.e. decides which of the infinite number of verticals is the Line at any moment in time. But otherwise the gravity center and therefore the Line tell nothing about the body’s arrangement. Its parts may be distributed in any way one can imagine around the center of gravity. The Line is the basic reference to which all considerations concerning gravity and weight relate. It is not directly relevant for the fascial net and its properties.

However, the Line is extremely relevant for balance and its mechanical representation: equilibrium. Balance is a “functional-plus” term. It comprises all of the structural body and the functional element, the tonus pattern, plus on top of this, the gravity field. In a two-dimensional “object”, any straight line through the gravity center divides the “body” into two halves. The two halves are equal as to their rotational momenta, although their weight is not equal in the general case. The difference becomes clear when the body is imagined to consist of little parts of matter all of the same unit weight. The number of these parts on either side is not the same. But the sum of the rotational momenta is the same on each side. The rotational momentum of such a part is given by the product of unit weight times the distance to the dividing line as measured from the gravity center of that part (Notes on S.I. 89/1, p.11).

Any straight line through the gravity center possesses this quality of dividing a body in half, “balancing” the two halves. But since balance of the human body, erect in the gravity field, is of interest and needs to be understood, it is only the vertical line through the gravity center of the body, the Line, which is important. Gravity and normal force act along it.

In three-dimensional objects, as in human bodies, it is straight planes through the gravity center which divide them in half. The sagittal plane through the gravity center of the body, which in the front view projects as the Line, divides the body into a left and a right half. The sum of the rotational momenta is equal on either side. The frontal plane through the gravity center, which also projects as the Line in the lateral view, divides the body into a front and a back half. Again the sum of the rotational momenta is equal on both sides. The horizontal plane is not relevant as far as gravity, weight, normal force and support are concerned. These considerations apply to whatever configuration a body possesses at any given moment in time but are usually made for the body on its feet, of course.

It should be kept in mind that these concepts refer to geometrical entities, not anatomical ones. So the frontal plane as defined in anatomy is a straight plane only for an anatomically “average” structure in anatomical “standard stance” which is very different from the structural “neutral stance”. In a strict sense the frontal and sagittal planes of Structural Integration are somewhat different from their anatomical definitions because they refer to normal structure in neutral stance. In real structures, and clearly visible when the body holds a strongly twisted posture, the “frontal plane” in the anatomical sense, defined in a reasonable way, e.g. as passing through the centers of shoulder, hip, and knee joints, is not a straight Euclidian plane at all. But any straight plane “averages out” the twisting and if passing through the gravity center still divides the body in two halves, of course.

Matters are simplified if the two-dimensional projection of the body is examined. Fig.4 shows a numerical example using the block model. The gravitational centers of the blocks of Fig.1 are shown as well as the center of gravity of the whole “body” which determines the Line. The example simplifies matters very much because the blocks are assumed to have the same weight (unit weight). The sum of the rotational momenta is the same on both sides of the Line by definition. The total of either side would be a measurement, a quantitative expression, for the “degree of deviation from neutral”, which constitutes a statement about function, not structure, however. This is linked directly to the amount of energy which must be spent to maintain the arrangement shown against the destructive effect of gravity. Balance of a kind is always present when a posture is held. Its quality is expressed by the “degree of deviation from normal”. The closer the gravitational centers are aligned to the Line, the less deviation from normal, and therefore the less energy must be spent to maintain it against gravity. This is a primary concern in the field of Structural Integration because it refers directly to its basic economical principle.

<img src=’https://novo.pedroprado.com.br/imgs/1991/1041-4.jpg’>
Fig.4 – The gravity centers of the blocks of Fig.1 are shown (with their lateral displacement exaggerated) as well as the gravity center of the whole “body”. Blocks are assumed to have the same weight (unit weight =uw). The distance of the gravity centers to the Line in millimeters times uw is the rotational momentum of each block. The sum of the rotational momenta on either side is the same.

It must be emphasized again that the fascial net and structure do not come in at this point. Gravity acts on mass and doesn’t “know” shortness. It can’t “recognize” whether a well aligned posture is held easily because structural integrity is high or whether it is forced by muscular effort.

In I11.5 only the gravity centers of the block model used earlier are shown and connected by straight lines. One can easily visualize gravity’s effect. It pushes out the gravity centers farther in the direction of their deviation.

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Fig.5 – Construction of the midline. It is thought to contain the whole weight of the body.

The number of blocks can be increased; they then become flatter. This procedure can be continued until the blocks have become very thin slices or disks. For each disk the gravity center is determined. If the disks are made extremely thin, the gravity centers follow each other so closely when going from bottom to top that they form a line. This has been defined as the “line” but is referred to in the following as “midline”. The concept is formed as a direct analogy to that of the gravity centers. The midline is thought to contain all the weight of the body. It indicates, at any level above the ground, the point around which the weight in front and in back, left and right, is exactly balanced. Unlike the Line, the midline is a property of the body. It does not express structure, however, but indicates more exactly than the segmental gravity centers alone, the arrangement of the body’s mass in space. The midline changes in movement or when one goes from one posture to another; it is “functional” therefore. In combination with the Line it allows one to recognize gravity’s impact on the body more clearly and to make certain statements concerning energy expenditure.

The midline can be approached by determining the midpoint between the body contours in a geometrical sense at different levels above ground in neutral stance. It must then be calibrated against differences in specific weight on either side, including the resulting modification of lever arms, to truly indicate the place where the weight is balanced all around. The midline must not be confused with an as yet undefined “line of support” which would show how the weight is distributed downwards to the ground.

I11.6 shows a variation of midlines and their relationship to the Line. They can be thought to represent one and the same body in different postures. The straighter the midline, the less energy must be spent to maintain the posture against gravity. Again, it says nothing about the structural state of the body. The effort necessary to counteract gravity is directly proportional to the shaded area between midline and Line(1).

<img src=’https://novo.pedroprado.com.br/imgs/1991/1041-6.jpg’>
Fig.6 – Various midlines and their relationship to the Line. They can be thought to represent the same body in different postures. The shaded areas on the left and right of the Line are equal and indicate how much energy must be spent to hold up the “body” against gravity.

The concept of the midline as the line around which the rotational momenta are balanced makes it possible to understand certain aspects especially in the area of function. It should also turn out to be productive in problems not yet understood. Besides the shape of the midline, its length also plays a role, since it is slightly variable. In “normal function” the midline initially lengthens and straightens out instead of shortening and being bent more.

The Postural Curve and the Structural Point

The shape of the midline of a given body tells how much energy must be spent to maintain this posture against gravity. If this is linked to the total amount of energy necessary to hold the posture, we are able to make a statement about the quality of the structure, its degree of integrity. The concept of the Postural Curve and the Structural Point has been advanced earlier (Notes on S.I. 87/1 ).

In “neutral stance” the term “neutral” is used in a very narrow sense(2). It means that the mass of the body is arranged “neutral” with regard to gravity. This is the case if all the gravitational centers are on the Line and if no rotation is present. The more precise formulation demands that the midline coincides with the Line. The “degree of deviation from neutral” is a highly abstract concept. One may visualize a body in perfect “neutral stance” where it is granted that this is also an abstraction, an idealized image. “Neutral stance” cannot be attained absolutely. This posture always needs some muscular effort – and usually a considerable amount of it – to overcome the inequalities in the fascial net(3). So although gravity does not disturb this arrangement, the body would collapse immediately if muscle tension were zero. Imbalances in the passive tissue tension of the fascial net would cause it to do so, with gravity beginning to “help” collapsing as soon as stance would no longer be exactly neutral.

The direction of collapse would be different for different bodies according to what structural type they are and what kind of stance they have chosen in a certain moment. Strictly speaking the degree of deviation from neutral for different bodies cannot be compared directly because of this qualitative difference in the way they collapse. The graph in Fig.7 disregards this and so should be read as what it is: a highly abstract concept. It relates the degree of deviation from neutral for a series of consecutive postures which would occur in the process of collapsing to the energy necessary to maintain these postures. Instead of “energy” the ordinate can also be understood to indicate the amount of muscular effort and therefore “active tension” necessary.

<img src=’https://novo.pedroprado.com.br/imgs/1991/1041-7.jpg’>
Fig.7 – Postural Curve as the sum of E(G) and E(S). The degree of deviation from neutral could be indicated by the numbers of 1114., e.g. 18 uw.

E(G) shows how much energy or muscular effort is necessary to maintain the postures against gravity. The farther away from neutral stance a posture is, the more energy is necessary. E^(; is assumed to rise linearly with the distance from neutral as suggested by the law of leverage although this may not exactly be true. E^(; is the same for all structures of the same weight holding an identical posture because gravity “recognizes” mass only and its spatial distribution but not tension in the fascial net. The curve indicates the absolute minimum of energy necessary for a given posture and disregards that usually much more effort is invested than would be called for.

E(S) stands for the energy necessary to overcome the resistance provided by shortness in the fascial net. The considerable amount of permanent effort for standing in neutral stance is necessary to overcome this resistance, to cancel out the tensional imbalances resulting from shortness. If one comes from a collapsed stance straightening up stepwise toward neutral, one senses that more and more effort is necessary to maintain each of the consecutively more erect postures. As more parts of the fascial net become tensed and this tension then increases continuously, the amount of energy when going toward neutral seems to rise more steeply than a linear relationship.

E(S) is very different for different persons and expresses the degree of shortness and rigidity in the individual’s fascial net. When its increase when going toward neural is slow, it does not indicate directly that structural integrity is high, however. There often is some relation, but the situation is more complicated. It is simply and directly an expression of the softness of the connective tissue. This may be a desirable sign for the resiliency of fasciae or it may tell that fascia is too soft!

The body can collapse sideways, forward or back, all in a vast number of variations. A further simplification seems in order so the imagination is less taxed. Because Folding (and Unfolding) is probably the most important movement in the field, collapse is visualized in the sagittal dimension of Folding. One imagines a body in neutral stance with minimal effort. It may be very high or moderate depending on the softness or rigidity of the fasciae. This neutral stance is indicated in the graph by the point where the Postural Curve crosses the ordinate, where no deviation is present. If overall muscle tonus is reduced by perhaps 2%, and because overall tonus was minimal before, the body will now sink into Folding along the Postural Curve and come to stand still a little away from normal, where the 98% of tonus left is enough to cancel out gravity’s effect and the somewhat reduces resistance of passive tissue tension in the fascial net. Thus one passes through a consecutive series of stances along the Postural Curve each of which takes a little less effort. When this is continued one will notice that stances again take more and more effort. This will at least be obvious when one stands very low in a Folding posture. It is less easy than “easy stance”. The Structural Point will have been passed long ago. The Structural Point is defined as that arrangement of the body which along a course of collapse takes absolutely the least amount of energy of all comparable stances.

It is not easy to recognize the Structural Point and impossible to sense it exactly. A sense of it being there can be gained by comparing two stances at the extreme ends of the curve. First, the client is asked to stand as erect as possible. This must be in the manner of Unfolding completely, or extension against the floor, which are identical, so that the midline is as nearly vertical as possible and one still stands with the minimum effort. Clients need to be shown that, because otherwise they regularly stand with much too much effort in an anterior convex midline arrangement, the anterior convex “banana”.

As a contrast, they are asked to take a stance deep down in Folding. They will then usually recognize that stances in between these extremes take less effort and that there must exist a particular arrangement which takes an absolute minimum, the Structural Point. It can be approached and sensed more clearly when the distance between the two extreme stances is reduced in consecutive steps.

The situation is complicated because the majority of structures will not go into Folding from neutral stance by general tonus reduction. Only regular internals will usually do so easily. Locked-knee internals and regular externals have to go consciously a little away from neutral stance in the direction of Folding until they are able to glide into further Folding stances by general muscle relaxation alone. Symmetrical externals will go into Folding except for the pelvic tilt. The pelvis must not be allowed to tilt more posterior but has to be brought into a functional anterior tilt some way into Folding where the functional posterior pelvic shift makes this possible.

Fig.8 shows a collection of different Postural Curves for different structures. It demonstrates three criteria by which the degree of integrity of a given structure can be approximated. In principle it would be simple to indicate this degree by a numerical value for each criterion. In practice this would be senseless however, partly because much too many abstractions had to be made, partly because actual measurements would be difficult to take and would suffer from much too broad a range of uncertainty. But a reasonable estimate can be made especially when comparing a body before and after treatment, and perhaps also when comparing different bodies if their structures are not too dissimilar. The criteria for a high degree of integrity are:

<img src=’https://novo.pedroprado.com.br/imgs/1991/1041-8.jpg’>
Fig.8 – Three Postural Curves representing three different structures, indicating the three criteria.

1. Energy consumption is low at the Structural Point.

This criterion refers directly to the “economical premise” for the field of Structural integration. The Structural Point gives the absolute minimum effort for all stances (as long as they are compared along a continuous line of collapse). All other stances take more effort and it is not possible for that given body with its structure to stand with less effort in any way.

2. The Structural Point is close to normal stance.

This constitutes the “structural” criterion because it refers to the central concept of the field which places emphasis on the spatial arrangement of the parts of the body with respect to the gravity field. It expresses that in truly “easy stance” – with regard to overall energy consumption – the body is also aligned well spatially so that gravity only mildly disturbs the arrangement.

3. The range of “easy stances” around the Structural Point is broad.

This is indicated by the “flatness” of the curve vs. the “steep trough” for less integrated structures. It implies for one that the Structural Point is harder to find for well integrated structures and begins to resemble more a plane with a certain range than a point. It can also be interpreted to mean more “freedom” of movement. Stance can be varied more easily to a greater degree than is possible for less integrated structures which are more strongly restricted be shortness.

This third statement does not follow directly from the argument presented. There are observations from the practice of Rolfing clients which support it, though. A more theoretical reason is provided by the way the fascial net behaves and adapts. It tends to shorten constantly This tendency is, among other things, a function of the load on fascia, of how much or how little it is stretched if the load is permanent, and of the state of the functional element, active muscle tension. In chronically contracted muscles the connective tissue shortens. If a body is constantly far away from the normal arrangement, the load, passive tension induced by gravity, is high as is active tension from the muscles which must hold the body up. Fascia so tends to secure the body’s arrangement more tightly against further collapse by building up secondary shortness (Notes on S.1. 90/1). But also the loss of tension in other parts of the fascial net is more pronounced which leads to adaptive primary shortness and so makes it harder for the body to straighten up. The farther away from neutral stance the Structural Point is the more “walled in” this arrangement becomes from both sides!

This consideration must be specified because the individual “resiliency factor” of fascia varies over a wide range between rigidity and softness for different person. It seems to be strongly determined genetically. So the third criterion only applies to bodies whose “resiliency factor” is comparable. With one and the same person it is identical of course. And it is to this that observations from the practice relate. Clients whose degree of structural integrity has been raised visibly and who make use of it by “moving easy” seem to be much less subject to fascial shortening. This is understandable because the load on fascia is less, muscles are less contracted, and also the loss of tension on the “concave sides” of the body is less marked.

Some general reservations must be made concerning the Postural Curve. One has been mentioned, namely the fact that bodies can collapse in many different ways and directions. Many such Postural Curves would have to be drawn for every body to account for them. Depending on the individual structures, in one graph the Postural Curves would indicate a higher degree of integrity for one body than for another, while in a different graph this relationship could be reversed. It generally makes sense however to choose Folding because it appears to be the most important and basic form of normal function. Nearly all movements when on one’s feet require minimal Folding to be normal.

Another weakness is due to the simplified assumption that gravity’s effect is countered and balanced entirely by active muscle tension. This is only partly true because fascia, especially where it is in secondary shortness, does part of the job. This does not consume energy of course, and so the curve of E(G) of Ill.7 should be shown sometimes to rise less steeply, with deviation from neutral increasing. This function of fascia is in some respects desirable but varies widely and depends on several factors. One is the individual “resiliency factor”. Bodies whose connective tissue is very soft have less of this “fascial support” available. Another is the direction the deviation takes from neutral. Front-to-back asymmetries in the anatomical design of the body are relevant here. Generally fascia provides less resistance – which can sometimes be seen as “support” – in the direction of physiological movement. This is obvious for the flexion side of hip and knee when compared with extension/hyperextension(4). But the most important aspect which is extremely applicable stems from functional considerations. If function is normal – especially when referring to Folding – the midline lengthens distinctly. This means that the fascia on the convex side of the body is distended or “stretched”. It exerts an elastic force against gravity and so relieves muscles to some degree. If sinking or collapse of the body is not normal, the midline shortens, and the fasciae which are not stretched then do not help the muscles.

Still another abstraction has been made which distorts the picture a little. The Postural Curve indicates the minimal or base tension necessary to hold a certain posture. Some parts of the musculature exert active tension which just suffices to cancel out the disturbing effect of gravity and tensional disparities in the fascial net. Other parts, the “antagonists”, don’t have a function and should not tense the fascial net at all. This is never absolutely the case, however, because even very relaxed muscles possess a residual activity which adds tension to the fascial net. This also disturbs the arrangement of the body and so the active tension in the “agonists” is a little higher than would be necessary from physical considerations alone. They must also cancel out this residual tension introduced by their “antagonists”. Fig.9 shows the Postural Curve with a line a little above it which runs more or less parallel. It indicates the somewhat higher tension which can optimally be reached because of this physiological limitation. Spontaneous postures are actually almost always characterized by the presence of a large amount of excess tension. Stances are usually clearly somewhere above the postural curve. To approach the minimum, the client is asked to relax muscles as much as possible without allowing himself to sink. The body will then “settle” a little more to the ground without changing its spatial arrangement much and without its gravity center sinking. To suggest a general relaxation will not do the job, though. Clients are asked to successively relax one part of the body after the other by feeling it become soft and sensing weight.

<img src=’https://novo.pedroprado.com.br/imgs/1991/1041-9.jpg’>
Fig.9 – Postural Curve with some of the ramifications shown. Stances are only possible in the shaded area. When in a given stance tonus is reduced consecutively without allowing the body to sink, it will approach the curve. Afterwards, stances with lower tonus enforce a spatial change in the direction of the arrangement at the Structural Point.

When the effort needed to hold the given posture has been minimized and approaches base tension, further relaxation is no longer possible if the given conditions are to be met. If tonus is reduced more, the spatial arrangement will change. The body will assume postures down along the Postural Curve. When it is at the Structural Point an absolute minimum has been reached. All other kinds of stance require more effort. Further improvement can only come from raising the degree of structural integrity in the body.


Standing is function. It can be conceived as the material body with its structure, the “structural body”, in which a certain state of the tonus pattern is present, arranged more or less lengthwise in the field of gravity. The tonus pattern is variable and therefore stance will be, too. Exclusively stances on a Postural Curve are considered, where only base tension is found. Excess tension, which is present in stances above the Postural Curve, is not interesting because it doesn’t change the spatial arrangement of the body with respect to the stance on the curve noticeably. It only serves to introduce additional tension originating from muscle contraction which must be balanced by more tension from muscle activity.

Still, a large number of Postural Curves exist. This can be visualized in the following way. Going from neutral stance, only the pelvis is allowed to shift sideways. It will slip out in the direction of the shorter leg. The head can hang down a little on the side of the longer leg, increasing the radius of the curved midline at the upper pole. Or it can be left to sink down a little on the other side, introducing a counter-curve in the midline. Also the upper thorax can sink with an increase of the curve of the midline or countering it. And so on down through the body. The midline has an irregular wave-form with a different number of waves which can go in opposite directions. Of course, the pelvis can also be made to shift out on the side of the longer leg. This takes a slight effort initially which is necessary to overcome the resistance from primary shortness and gravity. As soon as the effect of gravity has overtaken that opposed to it, and resulting from the inequality of passive tension on the right and left side, further sinking will be passive.

A large number of different Postural Curves could so be defined for every body. And on each curve a large number of different stances could be found. They would have the same number of “wave crests and troughs” which would each occupy approximately the same length of the midline, and they would have the same direction. En. would be the same for such types of midlines belonging to the same curve if the radius of the “waves” were the same. But Es, and therefore overall energy necessary to maintain a given stance would be different for different structures, of course.

Such Postural Curves have some significance functionally, especially for the sagittal dimension. They indicate the specific way in which the normal way of sinking or taking successively relaxed stances, which is Folding, is disturbed. They are much more important structurally, however, because they allow one to identify the structural state of the body to a considerable degree both in the sagittal as well as in the transverse dimension. For, the method for determining the direction of the structural aberration of a part of the body goes from neutral stance; by selectively relaxing muscles, one can observe the direction in which the part begins to move.

From the mechanics of standing, two completely different regimes must first be described.

Sleeve-supported Stance

Sleeve-supported stance in some form or other is employed habitually by a large majority of clients and by all structural types. It nevertheless does not constitute “normal standing” functionally. Only locked-knee internals are adapted to it structurally while with the others this stance obscures the structural relationships(5).

Sleeve-support is explained easier at the knee than at the pelvis. It is a convention to use the angle of the posterior or popliteal side of the knee to indicate the relationship between thigh and lower leg, as seen from the side. The angle is between the midlines of thigh and lower leg. It is 180° in “exact extension”. It becomes less with flexion of the knee; it increases to above 180° in hyperextension. To simplify matters, in the following it is assumed that in “exact extension” at 180° the midline of the whole leg is also vertical besides straight, and that in flexion, when the lower leg slants forward, the thigh slants back. In hyperextension, when the lower leg slants back, the thigh is assumed to slant forward.

For reasons of geometry, the top of the lower leg and therefore the center of the knee is highest with the lower leg vertical. With any slanting forward or back, the knee loses height.

The mechanics of the flexed knee, where the angle is less than 180°, is simple. Gravity pushes the knee forward. Regarding the fascial net and the tonus pattern, passive tissue tension in the back of the knee can be considered absent. Fasciae by themselves at most hold a negligible amount of elastic energy in the back of the knee, at least some way into flexion. Sometimes they play an important role, though. With some regular internals and symmetrical externals who are not able to extend fully at the knee, the knee extensors, however forcefully “working”, are not able to overcome the passive resistance of the fasciae in back. “Exact extension” is not possible for them for structural reasons.

Muscles, the “knee flexors”, always contribute a little tension which adds to gravity pushing forward. From the economical premise it follows that their tonus should be

The forward thrust by gravity and whatever there is of passive and active tension in the back is neutralized by tension in front, in flexed-knee stance. This is also the sum of a passive and an active component. The first is largely given by the passive tissue tension of the stretched fascial system belonging to the quadriceps. Some active tension is of course necessary. As always, it should be provided by the deep and short muscles, not by the long and superficial ones. The vasti are “working” but not the rectus femoris.

When teaching Folding, and with knees strongly flexed, it is always impressive to see how the point of view the mind takes influences the situation, and how it is experienced, radically. In the traditional view, the quadriceps by contracting counters the forward thrust at the knee. A distinct feeling of effort goes along with it. When the client is asked to switch his focus to sense how the “bones in the knee” push forward into the extensor sling, imagined to be formed by a stretched rubber band, the feeling of effort immediately disappears. There is no apparent change in the configuration of the body. Only if one looks closely enough one will find that the knee has gone forward(!) very slightly and that the ischial tuberosities have gone back a little, indicating a reduction of excess tension in the quadriceps and the hamstrings.

When the angle increases to above 180°, the knee becomes hyperextended. Gravity reverses the direction of its thrust and now pushes back. It can in principle be neutralized entirely by passive tissue tension because for anatomical reasons of design the knee cannot hyperextend much. The rapidly increasing tension in the fascia membranacea in back, that of the gastrocnemius, and the hamstring tendons restrict hyperextension and neutralize the gravitational force fully. No active tension is needed; hyperextension is extremely favorable from the local restricted economical point of view.

This constitutes an equilibrium of the stable type. When it is disturbed by contraction of the knee extensors the knee is pushed back farther. The fascia in back resists with passive tissue tension rising rapidly in it. When the extensors relax this stretched fascia takes the knee forward again to its original place of stable equilibrium.

When the disturbance is forward, the “knee flexors” have to push up against gravity. When they relax the knee also sinks back to its place of equilibrium. Gravity is the acting force in this case.

The range of stable equilibrium is not restricted in back but limited in front. When the contraction of the “knee flexors” pushes the knee forward beyond “exact extension”, it will not go back anymore by itself. After relaxation gravity will push the knee forward more, not back.

Locked-knee stance is characterized by hyperextension of the knees geometrically and by the specific stable equilibrium described mechanically. It is only possible for persons whose structure permits hyperextension of the knees relatively easily. Locked-knee types are structurally adapted to locked-knee stance. They stand there most comfortably. Typically, the hamstrings have gone wide and forward, and frequently the lower legs show a structural posterior shift relative to the thighs.

At the level of the pelvis, sleeve-supported stance is present when the pelvis leans forward into the sleeve. The pelvic segment is shifted anterior functionally. Gravity pushes it forward more. Its thrust is countered fully by fascia in front and no muscle activity is needed in principle.

The body is so also in a state of stable equilibrium at the level of the pelvis. When muscular effort is applied to push the pelvis forward more, passive tension in the fascia in front rises quickly, and after relaxation takes the pelvis back to equilibrium again. If the pelvis is to go back, a muscular effort is necessary, too, because the pelvis has to go up besides going back. The force of gravity needs to be overcome. After relaxation, gravity will take the pelvis forward again to its place of equilibrium.

The range of stable equilibrium is not limited in front. In back it extends to neutral stance exactly; with a further functional posterior shifting, gravity will push the pelvis out in back instead of forward. The exact point where the pelvis leaves the range of stable equilibrium is a little variable, though. Besides gravity the elastic forces exerted by the fasciae in front and in back must be considered. In locked-knee internals this point of transition will be a little farther back than neutral stance because generally the fasciae in back hold more passive tension than those in front in neutral stance.

Locked-knee internals are structurally adapted to locked-knee stance and use it habitually. It is rare that one sees regular externals or symmetrical externals as structurally locked-knee types. The decision that they are so structurally is probably best made at the knees. They should go into hyperextension easily and demonstrate some structural signs of adaptation to it. Regular internals can of course not be locked-knee types as a matter of definition.

Sleeve-supported stance so has two properties which define it in the mechanical view. First, no active tension is needed to maintain the position of pelvis and knees. The disturbing gravitational force is met and fully neutralized by passive tissue tension. Secondly, a local stable equilibrium exists. This means that movement out of this position in either direction, front or back, needs active muscle tension and therefore consumes energy.

Nevertheless, despite its favorable economics, locked-knee stance does not constitute normal function for two reasons. The more theoretical being that the object under examination is not an isolated posture but “circular movement” and what the body does over extended periods of time. If walking is taken as an example, it definitely takes more effort to do it “sleeve-supported” than normal walking, which is in minimal Folding. And if the body goes into the functionally normal arrangement first it takes a considerable amount of energy to do so. Knees and pelvis must be “heaved up” and brought to the other side of the Line every time. An additional consideration is that standing still, without moving, is relatively artificial and does not usually occur over prolonged periods of time. But one has also sometimes the impression that some locked-knee internals prefer to stay in sleeve-supported stance and hesitate to go into larger movements. The fact that they need some effort to do so would make this behaviour understandable.

More practically, it appears that sleeve-supported stance at the level of the pelvis is rarely “pure”. Generally the fasciae in front seem to hold some active tension, too, which prevents the pelvis from hanging forward too much. This cuts down the economical advantage of sleeve-supported stance, of course. On the other hand, if it is “pure”, fascia is constantly being stretched by gravity and will give in to it in the long run more and more, increasing the structural sagittal deviation from neutral stance of pelvis and knees. This again will render the effort necessary to come out of it even greater.

As so often, the suspicion arises that locked-knee stance is not really preferred for its economy or ease in the physical sense, which appears as rather dubious anyway when all aspects are examined. It rather seems to be chosen for its clear advantages of “neurological economy”. It is easy for the central nervous system to control and monitor locked-knee stance; or, because of its stable equilibrium, a much less sophisticated “program” is needed than for any kind of free stance.

<img src=’https://novo.pedroprado.com.br/imgs/1991/1041-10.jpg’>
Fig.10 – Flexed, fully extended, and hyperextended knee.

Free Stance

In a broad sense the term “free stance” designates any kind of stance which is not sleeve-supported. It is characterized by the absence of a stable equilibrium and the presence of some active tension which is essential for maintaining it. If the tonus of the muscles contributing to hold a given free stance is reduced, the body will change its spatial arrangement. It will sink and not come back up to its original configuration by itself, without the aid of muscular activity.

Stable equilibrium is demonstrated by a ball placed in a bowl. Any translational movement of the ball requires energy, mainly because in all directions the ball has to go up. It always comes back down to the lowest point on its own by virtue of its potential energy provided by gravity. Similarly, free stance resembles a ball placed on a slope. It must actively be held there constantly. Downward movement is passive, by just letting go. Taking the ball up again to its original place requires energy. Movement to the other side, upwards, is the same as in stable equilibrium. It takes energy to move the ball up but it will return back down passively. Free stance is a sort of “mixed-type” equilibrium. With disturbances to one side, upward, the system behaves like a stable equilibrium. With disturbances to the other side, downward, it acts like an unstable or labile equilibrium.

True labile equilibrium is present hypothetically if an ideally normal structure is in neutral stance. Any disturbance in whatever direction will cause the parts of the body to sink. An example would be a ball placed at the top of a bowl turned upside down. Such a virtual point of labile equilibrium seems to exist for any structure, at least if only the pelvic segment is considered. It is generally close to neutral, with just a small anterior or posterior shift, where gravity and the elastic force resulting from imbalances in passive tissue tension just cancel out.

From the point of view of “neurological economy”, the stable equilibrium of sleeve-supported stance is preferable to the others. In principle, it can manage itself without needing any muscular involvement, and therefore not requiring any activity of the nervous system, as long as its limited range to one side is not exceeded. This usually seems to be the case for the knees if they are able to hyperextend easily. At the level of the pelvis there often is some active tension in the front of the sleeve which is “unnecessary”. This is perhaps to safeguard the pelvis against being pushed forward too much, maybe because the compression in the lumbars which is inevitable in sleeve-supported stance is too uncomfortable. It may also just be due to the body’s tendency to establish a clear bias.

Free stance requires active muscle tension. It is preferable to labile equilibrium “neurologically”, because the direction of collapse is unambiguous and clear. It is the same muscles which must exert tension all the time while others do not become involved. Stance is monitored by adapting their tonus adequately.

Labile equilibrium which cannot be attained absolutely is extremely demanding on the nervous system. It is not possible to anticipate the direction of collapse and therefore different tones patterns involving completely different muscle groups must always be ready to become activated. One gets a sense of it when standing close to “exact extension” at the knees. It can become quite uncomfortable as one is not able to tell whether the knees will jut out forward or back at any moment. It is far more relaxing to select a clearly felt preference.

<img src=’https://novo.pedroprado.com.br/imgs/1991/1041-11.jpg’>
Fig.11 – Locked-knee internal in collapsed sleeve supported stance (1), erect sleeve-supported stance (2),

<img src=’https://novo.pedroprado.com.br/imgs/1991/1041-12.jpg’>
standing near neutral stance (3), and in internal free stance (4).

Problems of Standing

To understand the ramifications of stance is extremely important because structure is usually assessed with the client standing. Stance does not show structure. This is demonstrated almost trivially when one changes one’s kind of stance from one moment to the next. The spatial relationships of the parts of the body will be visibly different, the pattern of tension and pressure in the body will change noticeably, but the structure is of course still the same.

For regular internals and symmetrical externals standing in free stance, even near the structural point, is often not very easy. This seems to be the case especially for the majority of them whose fasciae are rather rigid and short. Typically, their musculature is well developed. For a minority with soft fasciae this is not true.

When they are asked to stand for observation or photographs, or when they get ready to stand still for a prolonged period of time, they tend to also resort to a kind of sleeve-supported arrangement which could be called “quasi-locked-knee stance”. Since they cannot hyperextend their knees, or at least not easily so, they contract their quadriceps forcefully. The knees are so firmly locked between muscle tension which pushes back, and the fasciae in back which resist it. This is not favorable energetically of course, but the excess tension of the knee extensors secures the knees and relieves the brain from having to monitor the knees constantly. The typical sign of this happening is the knee caps jutting up. At the same time the pelvis is pushed forward so it leans into the sleeve in front by contraction of the hip extensors.

The difference to true locked-knee stance is that the lock for the knees is not between gravity and fascial resistance, which balance each other, but between active muscle tension and fascial tension. This arrangement demands a certain constant effort but has the clear advantage for the nervous system that it can be controlled easily. Muscle tension is preferably fairly high, a considerable amount of excess tension is essential. Then, small variances in tonus do not matter and must not be corrected actively. The system is in a way self-regulated like true “structural” sleeve-supported stance.

At the pelvis most people can go into true sleeve support. For structural reasons the range of stable equilibrium in the posterior direction is very limited and narrow, however. So it is often secured additionally by contraction of the hip extensors (and the “rotators”).

Sleeve-support at knees and pelvis seem to go together strongly. It is almost impossible not to well extend the knees when one lets the pelvis sink or presses it forward into the sleeve in front. However, sometimes one sees symmetrical externals who manage to press the pelvis forward into sleeve-support but who stand with clearly flexed knees. The knee extensors work hard, not so much against fascial restraints but against gravity’s anterior thrust. This stance is not economical or easy at all.

Many regular internals choose “quasi-locked-knee” stance when asked to stand still. In movement, most of posterior them will go into the typical “zig-zag line” of Folding or flexed at least more in its direction. Knees and shoulders are anterior, ankles and hips posterior to the Line. If this is not taken into consideration, errors are easily made in structural analysis.

Another occurrence which can regularly be observed also tends to obscure the structural picture. When going into locked-knee stance or “quasi-locked-knee” stance, the center of gravity of the whole body shifts forward. The weight is then borne more forward on the forefoot. The Line which in free stance passes into the ground in the area of the ankles also shifts forward. The apparent anterior shifting of the pelvis is so less marked in reality than it may seem, because shift relates to the Line and the gravity center of the whole body, not some fixed line of space or anatomy.

Regular externals present a special picture of their own. At the knees they tend to extend strongly, but rarely do they go into marked hyperextension. Knee extension is close to “exact extension” on either side if fascia is soft(6). With more rigid fasciae the knees are often slightly flexed for structural reasons but kept in a sort of “quasi-locked knee stance” with some excess tension in the quadriceps. The pelvis, which is shifted anterior and tilted posteriorly, leans a little into the sleeve in front. The impression one has is generally that they “orient” themselves more on the fasciae in front, which also hold some active tension, not so much of letting the pelvis be pushed forward into it. This apparent reluctance to let the body go into full sleeve-support, including locked knees, is perhaps due to the concomitant and inevitable loss of their specific compressional support from the ground (Notes on S.I. 89/1, p.31).

Locked-knee internals are especially apt to demonstrate the mechanics of sleeve-supported and free stance. It must always be shown to them because they cannot be integrated from their habitual locked-knee stance. One goes best from locked-knee stance toward internal free stance(7) slowly (Fig.12). in truly “easy” sleeve-support most locked-knee internals don’t feel very comfortable. Collapse is all too apparent. They feel “easy” and erect a little closer to neutral with active tension in the front of the sleeve. The closer to neutral their stance is, the less they feel supported by the sleeve. They soon come to a point where they don’t sense any of it anymore but notice that they hold themselves up by using their musculature. At the same time they begin to sense support from the ground, however. They become grounded in a physical sense.

<img src=’https://novo.pedroprado.com.br/imgs/1991/1041-13.jpg’>
Fig.12 – Graph relating the stances of Fig.11 to the energy necessary to hold them. The dotted line indicates the degree of sleeve-support, the dashed line that of “ground-support”.

Sleeve-support and ground-support” seem to be mutually exclusive. This is also easily experienced by other structural types when going from sleeve-support to free stance and back. Ground-support is only present in free stance. Its degree or strength is partly dependent on the vertical arrangement of the body. The closer to vertical the midline is, the stronger ground-support appears. Another factor intervenes, however. The degree of ground-support seems to be determined even more strongly by the amount of overall muscle tension. Muscle tension takes one “away from the ground”, relaxation lets the body settle down more. This can be experienced when in some sort of free stance, one pulls up the shoulders and lets them drop down again. So ground support is felt maximally at the Structural Point with overall tonus as close to base tension as possible

<img src=’https://novo.pedroprado.com.br/imgs/1991/1041-14.jpg’>
Fig.13 – Regular internal in quasi-locked-knee stance and in free stance.

<img src=’https://novo.pedroprado.com.br/imgs/1991/1041-15.jpg’>
Fig.14 – Symmetrical external in quasi-locked-knee stance and in free stance.


The concept of the Line is developed. The Line is defined as the vertical line which goes through the center of gravity of the whole body. It is a property of the gravity field and expresses the main effect of the force of gravity on the body as a whole.

The midline is composed of the centers of gravity of extremely thin horizontal slices, cross-sections through the body. At any level above ground the midline shows where the weight of left and right side, front and back is balanced. the Line and the midline together demonstrate gravity’s effect on the pliable body. Some examples are given.

If the midline is straight and vertical, it coincides with the Line. This “neutral stance” is not disturbed by gravity in the ideal sense. Structure comes in when economy, the basic premise of the field, is considered This leads to examine fasciae and their tensional inequalities. They must be cancelled by active muscle tension. Gravity’s effect, when the midline is curved, must also be neutralized by muscle activity.

The Postural Curve relates the energy necessary for a succession of stances along a certain line of collapse, starting from neutral stance. The stance which requires the least effort is called the Structural Point. It is anywhere between neutral stance and total collapse. It is suggested that the Structural Point expresses best the degree of integrity of a given structure.

Stance is generally used to diagnose structure. Stance is function, however, obeying its own, functional laws. It does not express structure directly. But knowledge about the Structural Point allows to find truly easy stance which then can be used to determine the direction of structural aberrations and therefore structural types. It is necessary to be aware of sleeve-supported stance which is chosen habitually by a large majority of persons but which is often not expressive of the spatial arrangement of the body in movement and of structure. The Structural Point must be determined in free stance. Some problems about the function of standing are discussed which may lead one to false conclusions about structure if they are not analyzed consciously.


1. This is not exactly true because weight distribution along the “line” is not homogenous.

2. Earlier the term “normal stance” has been used for this ideally vertical arrangement. It is changed to “neutral stance” in order to avoid confusion with the terms “normal structure” and “normal function”, where “normal” has a different meaning.

3. it is not mentioned especially that all this goes from the further unrealistic assumption that the bones are perfectly “normal”, whatever that means with them, and that they therefore don’t limit the extent of potential integration, which they do in reality of course.

4. This is not to be taken as a recommendation for sleeve-supported stance, of course!

5. This revises the earlier statement that there should exist more external than internal sleeve-supported structures (Notes on S.I.,88/1, “The Tilt of the Pelvis”).

6. The midline through the whole leg is slanted anteriorly slightly!

7. “Internal free stances is new hart in a narrower sense meaning near the Structural Point of free stance which is in minimal Folding for both locked-knee and regular internals.

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