The Influence of Gravity, Normal Force and Anatomy on the Shape of the Body Lying on a Surface

Pages: 2-7
Year: 1992
Notes on S.I

Notes on S.I.


If a person lies on a surface, gravity and normal force naturally continue to act on his or her body. “To take somebody out of gravity” would demand a missile, not a bed. But gravity and normal force affect the form of the body in a different way than in standing because the blocks are differently related to each other and to the ground. The change in shape that happens when the person lies down is purely functional and not at all structural. It is for this reason that the word “structure” will rarely appear in this paper. Still, for Structural Integration the changes in shape are relevant, because some positions reinforce and augment the structural type while others diminish it. Therefore one position may be preferable to another for a certain structural type.

1. The Block Model on a Solid Surface.

For a beginning – to make things easy – the body is looked upon as a collection of solid blocks like the building blocks children play with. Head, neck, thorax, lumbar area, pelvis, thighs, lower legs, and feet are considered as separate and unconnected blocks with total mobility against each other.

In this simplified model lying on a horizontal surface, through the center of gravity of each block passes a vertical line, an isolated “line”, along which gravity and normal force are thought to act. While in a standing human body they ideally form the vertical line called the “Line”, they are disconnected and parallel in the body here. Each block is separately supported by normal force and behaves as a unit independent of the others.

The contour of this block-model body would be horizontal on the underside. On the upper side the contour would depend on the diameter of the blocks. There are no rotations or tilts.

A line connecting the gravity centers of all blocks would approximate the “midline” and would run somewhat parallel to the upper contour of the blocks.

2. The Structural Types in Standing.

In order to compare the block model to the four structural types, it seems necessary to review them with a view on shifts and midline only:

The regular internal has bent knees, and its structure is therefore tension dominated. The centers of gravity of the lower legs and thighs are shifted posteriorly in relationship to the axis of the knees. The pelvis is even more posteriorly shifted. The lumbar segment is shifted anteriorly in relation to the pelvis and thorax. The thorax therefore tends to be less forward but still is anterior to the overall center of gravity and the pelvic center of gravity. The center of gravity of the cervical segment is also forward but the segment is curved back, so that the posterior contour is strongly concave. Usually the center of gravity of the head is anterior to that of the neck.

The block model of a person lying on his or her belly on a hard solid surface in Fig.1 looks very much like a regular internal. Only the legs are out of order, because in this model the feet have nothing to hold them in position against the legs. In a real person lying on her belly the knees are either functionally bent because the forfoot and toes are on the bed, or when these hang over the edge the knees are functionally in a locked-knee position.

<img src=’https://novo.pedroprado.com.br/imgs/1993/1043-1.jpg’>
Fig.1 – Simple model (of unconnected blocks) of a person lying on a hard surface on the back or the front.

Thus the block model supports the hypothesis that for the regular internal the position lying on the belly will augment the shape that is typical for this structure.

If you look at the illustration and imagine it to be a person lying on his or her back, then the knees are brought into a straighter position and the lumbar and cervical segments are brought back in a way that is very similar to the “integrated” little boy in the Rolfing logo. In the “traditional recipe” that I was taught one rule was: “never put a person on her belly before the sixth session”. Such a rule would make sense for a regular internal and could be taken as another clue that the whole series was developed by Ida Rolf with the structure of regular internals in mind.

Naturally if the person has a large belly all this will no longer be true (Fig.2). Then the upper contour of a person lying on such a belly will resemble that of symmetrical external.

<img src=’https://novo.pedroprado.com.br/imgs/1993/1043-2.jpg’>
Fig.2 – Pot-bellied block-model on the back or the front.

The regular external in standing is a compressional type with straight knees and shows stick-like legs that support the body. The center of gravity of the pelvic segment is shifted anteriorly in relation to the overall center of gravity and to that of the thighs with the pelvis sitting deadpan on the straight legs. The back is straight. The lumbar segment sits straight above the pelvic block. Thorax, cervical segment, and head are balanced more back again above the pelvic block. The posterior contour from head to feet tends to be markedly concave.

If you add to the block model a big belly and imagine that it represents a person lying on his or her back, then you get the contour of a mild regular external, especially in the legs and their relationship to the pelvis.

Thus the hypothesis may be ventured that for regular externals lying on the back is neutral or even diminishes the shape typical for their type, since it diminishes their posterior concavity. This is only true, however, when the surface is solid and does not give way. Even on a slightly soft surface the posterior contour becomes convex and the shape becomes that of a symmetrical external.

Lying on the front, the shape typical for the regular external is extremely diminished and is functionally taken towards that of a regular internal.

A person with a big belly will even be more like a regular external in the position on the back, while when lying on the front the shape will turn into that of a symmetrical external (Fig.2).

The symmetrical external has bent knees and is therefore a tension dominated structural type in standing. In the trunk the pelvis is shifted posteriorly in relation to the. legs. The lumbar segment is shifted posteriorly even further. The thorax comes forward together with the neck. The trunk is anteriorly held in a shortened position to keep it from falling off backwards from the femora. Often that looks like an anterior concavity in the trunk.

Thus the hypothesis can be formulated that symmetrical externals lying on the back on a hard surface will have a shape that is taken more towards normal. If the surface is soft, their structural shape is reinforced.

Lying on the front the shape of their body becomes even more that of a symmetrical external especially if they have a belly. When lying on the back the big-bellied symmetrical external looks more like a regular external (Fig.2)

The locked-knee internal is partly a compressional system with hyperextended legs. They are like sticks held in place by ligamentous structures. The pelvis is shifted anteriorly. The lumbar segment is on top of the pelvis and curves back toward the posteriorly shifted thorax. The neck comes forward together with the head.

In lying similarities to that shape can only be detected in the leg and pelvic arrangement if the block model representing a person lies on the back. The hyperextended knees and the anteriorly shifted pelvis conform more or less to the typical arrangement of this type in standing. But the relationships of the segments above the pelvis are not similar any more

Thus the hypothesis can be ventured that lockedknee internals get the shape of their pelvic and leg arrangement augmented when they ly on their back (Fig.1 ).

This seems to be true for big-bellied persons as well (Fig.2).

3. The Block Model on a Soft Surface.

If instead of assuming a solid suface a soft mattress is introduced into the model, the unconnected blocks sink into the soft surface and lower their center of gravity. The extent of this displacement depends on the weight per square centimeter and the displacement factor of the mattress. If the mattress is assumed point elastic, which means that a displaced part moves independently of the neighbouring parts, and if in addition the blocks are assumed homogenous, of equal density, then the big blocks would sink in deeper than the small ones. This would straighten out the midline and take it closer to what would be normal in standing. However only if the elasticity of the mattress would be just “right”, meaning exactly adjusted to the varying properties of the body, the midline would be exactly straight in whatever position the block-model would be lying on the table.

Unfortunately real mattresses never are ideally elastic nor ideally point elastic. They always form troughs that extend to the neighbouring blocks. The softer the mattress, the deeper and larger the trough.

The trough phenomenon is important because it introduces rotations into the model which correspond to segmental tilts in standing: the trough formed by the heavy segments (thorax and pelvis) takes the lumbar segment along. The heaviest part of the body near the center of gravity will sink deepest and pull along the neighbouring areas. In this way a trough is formed with its deepest point in the lumbar area. This segment is therefore lower than it would be on a hard surface. Legs and neck are in contrast higher. The softer the mattress the stronger therefore the trough-effect and the deeper the lumbar segment would have to go. The sloping upwards of the trough towards the neck and the legs would then rotate the thoracic and pelvic blocks towards the lumbar segment. The more pronounced the trough effect the more pronounced would also be this functional anterior shift of the lumbar segment and the rotations of the thoracic and pelvic segments in its direction.

Lying on the back, the model would look like a symmetrical external in standing because the trunk would be posteriorly convex and the legs would be shifted forward in relationship to the pelvic segment and slightly flexed in the knees.

On the front, the stronger the trough-effect the more the midline would resemble that of the locked-knee internal in standing: the pelvis tilted forward and shifted anteriorly in relationship to the thigh segment. The midline of the thigh segment would go up from the trough towards the knee. This would tend to produce an obtuse angle of more than 180° on the posterior side of the knee which would constitute hyperextension.

The thoracic segment would also be tilted posteriorly in relationship to the lumbar segment. The cervical segment will go with the head bridging the ridge between the troughs of the head and trunk.

<img src=’https://novo.pedroprado.com.br/imgs/1993/1043-3.jpg’>
Fig.3 – Block-model on an ideally point-elastic surface.

4. The Hydrostatic Model without Bones.

In a body made of fluid-filled bags inside bags inside bags, the fillings exert pressure while the bags hold the form by the tension in their tissue. Without bones as spacers the body would flatten somewhat and the tensile element would be more important to keep the shape. On a solid surface the body would go wide and flat depending on the tension – or its lack – in the bags. The higher the tension the rounder the shape of the body would be. But still the shape would remain flattened out.

In a lying body muscular activity is not relevant except to keep up the bodily functions. It is the resting tonus of the muscles and the tension of connective tissue in the bags that keeps the body from going all over the place.

In such a hydrostatic boneless zombie lying on a surface the pressure gradient rises from bottom to top according to the height of the fluid column no matter how many bags are interspersed. Higher columns tend to spread and distribute their pressure so that the upper contour tends to equalize and become parallel to the lower contour except for places with much higher tension.

Areas of secondary shortness in the fascial net are always muscularly reinforced. Since muscle action is reduced to a minimum in lying, they become less pronounced than in standing. Primary shortness which is predominantly fascial would therefore become more pronounced.

The pressure is highest on the underside of such a hydroystatic structure. Tensions in the surface of the bag therefore are more obvious on the upper side where they are less flattened out by the pressure of the fluid. Since primary shortness is more of a tension-in-the-bag-phenomenon and much less a matter of muscular holding, it becomes most obvious when positioned on the upper side of a lying body. Whatever the structural type, the primary shortness in the concavities (that he presents in standing) present themselves more strongly in the lying body than the convexities. They appear as shortenings in the tissue. Yet while they are more flattened out on the bottom of the body lying on a surface they are especially prominent on the upper side of the body.

On a soft surface the body gets additional support from the sides curving up from the heaviest and lowest point. Therefore there is less tension on the top surface. This additional slack allows shortenings in the tensional structures to become even more obvious. Primary shortness therefore tends to become more prominent in a soft body lying on a soft surface than they are in standing. Since in the lying body convex contours of the trunk become even more convex when in contact with soft surfaces, the structural types keep their respective shapes more clearly on a soft surface than on a hard surface.

Because of the friction-resistance of the surface, the way a person is made to lie down considerably influences the resulting shape. This becomes most obvious in the hydrostatic boneless model: the waterfilled bag can be stretched on its underside like dough by rolling it out on the surface with as long an underside as possible. Then just like dough any pressure applied to the upper side makes the underside longer and wider. The body will be kept long by the surface friction of the surface unless it is contracted by muscles. The result is the intended lengthening of the midline. Without that stretching in the positioning of the body the “bag” will form folds and crumples on its underside which will be kept in place by the same surface-friction, and the desirable lengthening of the underside will not happen. On the opposite: If the upper side is lengthened, the folds on the underside will even increase and the midline will not lengthen. Thus the surface friction can be used as a gigantic “third hand” in working that reaches most of the underside of the person. It can therefore become an important consideration whether and how much the underside of the body should be stretched in positioning a client on the table.

<img src=’https://novo.pedroprado.com.br/imgs/1993/1043-4.jpg’>
Fig.4 – Trough-effect on a block-model on a soft surface.

5. The Hydrostatic Model with Bones.

In lying on a horizontal surface the bones undoubtedly function as spacers since the gravitational load is almost negligible. If bones are introduced into the hydrostatic model, some of the properties of the block-model are reintroduced into the system. These non-compressible, solid elements make the body-segments behave like blocks and not any more like the columns of liquid in the “hydrostatic balloons”.

The bony parts of the body will behave more like the block-model, while body segments with only one bone will behave more like the boneless hydrostatic model. Therefore the neck, the lumbar segment and the legs will flatten out and show their areas of primary shortness more strongly on the upper than on the underside. Head, thorax and pelvis behave more like blocks and therefore look like a regular external if the body is lying on its back and like a regular internal when lying on the front.

Lying on the side, in the block-model the segments of pelvis, thorax, and head would be shifted to one side, while the segments of feet, legs, lumbar area, and neck are shifted to the opposite side. This relative position resembles the augmented side-curve on the side of the shorter leg in standing. The thoracic segment is shifted over towards the longer leg, while the pelvis is shifted away from the longer leg. In the position on the side the mixture of hydrostatic and block model reinforces this augmented side curve. Thus the whole side of the shorter leg is straighter in contour while the side of the longer leg shows augmented curves (Notes on S.I. 90/1).

<img src=’https://novo.pedroprado.com.br/imgs/1993/1043-5.jpg’>
Fig.5 – Block-model on the side on a hard surface.

6. Practical Conclusions.

From these considerations the following conclusions can be drawn for the practical work with clients on the table.

For lying on the side, structural types are irrelevant. But differences emerge according to whether one lies on the side of the shorter or longer leg. Lying on the side the curves in the upper contour are always augmented as if it was the side of the longer leg. The side on the table flattens out or is stretched into a convex contour like that of the shorter leg depending on the softness of the surface and its trough-effect. Conscious positioning of the body can increase this stretch or decrease it. This effect can therefore be employed in planning the strategy for a session: if the side with the longer leg is known, it must be laid out on the underside with as much lengthening as possible. Then the work of lengthening the upper side will straighten out the whole body and bring the desired gain in length of the midline of the body. The side with the shorter leg should not be put under such stretch when it is on the underside because that would augment the already existing shift.

The four structural types become relevant when working with clients in a supine or prone position on the table. For each type the situation is different according to whether the person lies on the front or on the back.

Regular external.

Lying on the front always reverses the anterior pelvic shift if the surface is hard and often reverses the posterior pelvic tilt. Depending on the softness of the surface the reversal will vary greatly. With a soft mattress the tilt will more often become anterior because of the trough-effect. The shift will not reverse and remain anterior. Since the pelvis is also anterior to the thighs, the body will approach the locked-knee internal arrangement. But a very big belly will create the shape of a symmetrical external.

Primary shortness in this type is mainly in the back. It will tend to keep the back short and in this way will inhibit the anterior tilt and the relative posterior shifting of the pelvis. Working in this position, a change of shape in the direction of a regular internal should be taken as a sign of integration.

Lying on the back the shape characteristic for regular externals is augmented if the surface is hard. On a very soft surface with a strong trough-effect the pelvic shift is reversed and the shape of a symmetrical external is produced. Primary shortness in the back will impede that change in shape, while primary shortness just above the pubes will augment it. So in working with regular externals in that position, care should be taken to keep the front long especially in the pubic area while the back is lengthened from below by applying the technique of the “third hand”.

Regular Internal.

Lying on the front, the pattern tends to be augmented. On a soft mattress with a lot of trough-effect the pelvis can sink in so far that it is shifted forward in relation to the thighs. If the fasciae in back of the legs are soft enough, this situation can result in the shape of a locked-knee internal – especially if the feet are allowed to hang over the end of the table. But with regular internals whose popliteal fasciae are very rigid and make proper extension of the knee impossible that position can be used to extend these fasciae. In a person with a big belly the position on the front can reverse the pattern into that of a symmetrical external.

Primary shortness in the lumbar area and in the neck will increase this tendency to produce the augmented appearance of a regular internal especially if the front is kept long in lying down. (This is naturally not true for a pot-bellied regular internal).

Lying on the back, the regular internal shape tends to go towards that of the regular external if the surface is soft. The trough-effect will reverse the pelvic tilt into the slight posterior tilt of the regular external. The weight of the legs and the primary shortness in the groin will keep that tilt and shift from going all they way into the shape of the symmetrical external. On a hard surface the weight of the legs and the primary shortness in the groin will keep the pelvic tilt in its anterior position while the table will shift the pelvis upwards into an anterior position relative to the thighs, which then creates the relationship exhibited by the locked-knee internal in standing. Thus the weight of the legs can help against the posterior pelvic tilt. They should therefore be kept down and stretched out most of the time, lengthening the groin which is in primary shortness.

If the regular internal is positioned with maximal length in the lumbar area (an area of primary shortness in this type), the primary shortness in the groin and upper chest will become more apparent and keep the shape from going into the direction of a regular external. Therefore, while working, any change of shape (that does not stem from a lengthening of the belly-wall) towards a regular external can be taken as a sign of integration.

Symmetrical External.

Lying on the front will switch the shape of the symmetrical external into that of a regular internal if the belly is not too big and if the lumbar segment can sink forward enough. This is even more so if the front of the body is placed on the surface as long as possible. Primary shortness in the gluteals and hamstrings down to the popliteal area can impede the pelvis from going towards normal, in the direction of an anterior tilt. This can serve as a landmark for integration in this position. Primary shortness in the popliteal area can be lengthened by allowing the feet to hang out over the edge, if that does not pull the pelvis into a posterior tilt, which must be avoided by all means.

In pot-bellied symmetrical externals lying on the front augments their shape-pattern and should therefore be avoided.

Lying on the back shifts symmetrical externals into the regular external arrangement, if the surface is hard. The pelvis is shifted anterior relative to the thighs and the lumbar area. On a soft surface the symmetrical external pattern is usually augmented. Stretching the back would therefore make primary shortness in front more apparent. It can be decreased by lengthening the front while keeping the pelvis from tilting posteriorly with a controlling hand in the lower back. Such a decrease can be taken as a sign of integration.

The major difficulty – especially with a soft surface is the posterior tilt of the pelvis which is augmented by lying on the back. It is partly checked by the weight of the legs. They should therefore be kept stretched out as much as possible. They should be bent for relaxing the belly wall or for working the hamstrings only one at a time. They can even be allowed to hang out over the end of the table, at least with the heels.

Locked-knee internal.

Putting a locked-knee internal on the front onto a solid surface will shift the pelvic segment posteriorly. It will also pull long the upper chest which is in primary shortness. The feet should not be allowed to hang over the end, because they would drag the knees into their habitual hyperextension (Notes on S.I. 91/ 1). Primary shortness in the gluteal and lumbar area will then be more pronounced than in free stance. If it can be lessened and length is brought to the area, it could be taken as a sign of integration.

On a soft surface the softness of the mattress will increase the anterior tilt of the pelvis and will allow an additional anterior shift in relation to the thighs. Thus only a sufficiently pot-bellied locked-knee internal can benefit from the position on the front. Without a sufficient belly the position on the front would augment the pattern of the locked-knee internal in free stance. This is even more true when pressure is applied to the back of the legs, pelvis, or lumbar area.

Downward pressure should therefore be avoided. Instead one hand should keep the front long while the other lengthens the back. The hamstrings which tend to go out and forward in hyperextension could be brought back and together with one hand while the other hand brings length to the primary shortness in the vastus fascia just above the patellar area.

Lying on the back, the anterior pelvic shift in relationship to the thighs is augmented if the surface is hard. But the lumbar area will fall back and often take the pelvis into a posterior tilt if the downward pull from the legs allows this. Sometimes a pillow can be placed under the knees to keep this pull minimal and to keep them from going into hyperextension. For the same reasons the back should be made as long as possible in lying down on the table. This will make the primary shortness in the upper chest more apparent even though the weight of the head will somewhat obscure this. If one hand keeps the lumbar area long by checking on the pelvic tilt, the other can lengthen this primary shortness.

If the surface is soft the position on the back will tend to give the locked-knee internal the shape of a symmetrical external. The advantages of the position on the back for primary shortness in the upper chest will be lost by the trough-effect. But primary shortness in the back is less marked this way. And if the front can be kept long, this is a possibility to give that area the length that it needs.

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