Internal-External Is a Perception of the Nature of Structure: A Post-Rolf Point of View

By Jan H. Sultan, Advanced Rolfing® Instructor, and Lina Amy Hack, Certified Advanced Rolfer®
July 2022

ABSTRACT The internal-external model, originally published in Notes on Structural Integration, titled “Towards a Structural Logic,” in 1986 by Jan H. Sultan, is a foundational understanding of the nature of the human structure. Sultan has written a second edition of this model, informed by more than fifty years of practice and teaching. He describes the inspiration for and the history of the internal-external model and the value of the structural types – congruent internal, congruent external, and incongruent-mixed types. The internal-external model is a structural language that was early to identify lines of force transmission. It is a structural description of the inherited direction of growth and adaptations visible in the fascial network. 


Authors’ note: This article is written in the voice of Jan H. Sultan. It is a consolidation of many conversations between the two co-authors, putting to the page the Sultan legacy teachings for the Dr. Ida Rolf Institute® (DIRI).

It has been thirty-six years since I first published the internal-external model in Notes on Structural Integration under the title “Towards a Structural Logic"  (Sultan 1986) and I want to re-open this discussion, to infuse it with my decades of experience teaching and practicing. Internal-external (I-E) is a perception of the nature of human structure and how people adapt their inherited form (genotype) to the demands of their lives (phenotype). It is a way to understand and coherently describe both form and function from a morphological perspective. I-E is concerned with the biology of form and the relationships between the segmental elements of body structure. While the anatomy of humans is similar throughout the range of our genetic types, there are some functional differences in the forms that we exhibit. I-E is a body-reading tool in the Rolfing® Structural Integration (SI) paradigm that follows our Principles of Intervention (Sultan and Hack 2021) and gives us information about patterns of how the body manages the forces of movement, incongruencies, and interruptions of fluid flow, and places where manual interventions can be targeted to increase intersegmental alignment in gravity. I-E provides a client-centered approach. This is the bridge to Rolfing SI after Rolf. The I-E perspective uses the geometric consideration of the body in gravity and takes it a step further by describing a range of spatial structural patterns that are innate to human biology. 

The History of the Internal-External Model

Ida P. Rolf, PhD (1896-1979) taught the SI ‘Recipe’ as a sequential pattern of interventions. Some of the elements of this Recipe were expressed as general goals for each session. For example, lengthen the front of the body, lengthen the back, lengthen the sides, differentiate the function of the adductors from the hamstrings and quadriceps, and in her fifth-session Recipe the mandate was to organize the relationships of the psoas, diaphragm, and the rectus abdominus. She wanted to see legs that moved as if they came from the diaphragm, not just the hip joint. 

Each unit of her Recipe has a directive. Rolf would insist that her newly trained partitioners stay with doing her Recipe for five years, “or until we knew what we were doing.” Even as I stayed loyal to that directive when I moved to New Mexico in 1970, the demands of the rural community into which I moved often bade me to use the elements of the Recipe in response to the needs of people who came for help. I was a thousand miles from any other Rolfer, and because Rolfing SI was so new and unfamiliar, literally no one knew what Rolfing SI was; I became the guy who lives in the valley who “works on people.”

Certain truths emerged for me as I observed and worked with hundreds of clients over those years. Rolf’s Recipe was more than a set of goals but also had process directives. For example, if you observed ten people receiving the third session of the Recipe, you would see a session that looked more or less the same, even as any ten clients would have a lot of variation in their individual forms. This discrepancy between the Recipe and the variations of structure I was seeing in my private practice led me to consider the ultimate validity of applying a universal template: What about the legs? It seemed to me that some folks had very pronounced genuvalgum (knock-knees, X-legs), while others had very pronounced genuvarum (bow legs, O-legs). And there are many people that present variations between these extremes. Did all these people need the same second session of the Recipe? It was discrepancies like these that awakened my curiosity about wider applications of the method Rolf taught us.  

The Genesis of an Idea

I had been puzzling over the dramatic difference between genu varus and genu valgus, and the different stresses inherent in each type. I noticed that some of the patterns were rotationally congruent with femur, tibia, and foot being either internally or externally rotated. Others had an incongruent pattern with internally rotated femur, and an externally rotated tibia and foot. Also I saw people with an external femur rotation and an internal lower leg and foot, taken together I started to think that there were structural 'types'. As I worked to understand each type, I postulated that there would be a 'line of transmission' of kinetic energy as each person moved. Assuming a theoretical line of force existed as each leg came through the weight bearing phase of the gait, it would follow that each of the different types would have their own musculofascial shape that was adapted to the way the limb was oriented. Further reflection showed that the line of transmission of kinetic force went all the way through the body and where it traversed, it created predictable structural responses in the way the musculofascial tissues developed.

In the early 1980s, John Upledger, DO (1932-2012) [founder of the Upledger Institute International], provided me with a stunning perceptual leap. Upledger came in person to the then Rolf Institute® (now Dr. Ida Rolf Institute®) and presented his craniosacral osteopathy observations and methods to a group of our faculty members. His teachings elaborated on the physiologic circulation of cerebrospinal fluid, and how those pressure changes were reflected in the cranium, spine, and sacrum as part of a whole-body response. He observed that when the cranium is going into ‘flexion’, it will be reflected in a patterned expansion of the cranial bones. This flexion is due to pressure changes in the cerebrospinal fluid circulation. In this cranial expansion, the whole body displays a subtle external rotation away from the midline. And when the cranium is going into what he called ‘extension’, which is a retraction of cerebrospinal fluid pressure, the whole body would internally rotate toward the midline. 

Upledger noted that some people would present with whole-body fixations in these rotational extremes, “Flexion-lesion heads, in general, belong to externally rotated bodies,” which correlated with the person’s head being “wider and proportionately shorter in its anterior-posterior dimension” (Upledger and Vredevoogd 1983, 108). And he described how the body extremities intrinsically rotate internally during cerebrospinal fluid retraction, with their heads trending toward being long and narrow in the transverse plane. 

This information about the interface between structure and physiology was the missing piece that helped explain the variations I saw in my practice that did not always match Rolf’s Recipe and its directives. In Craniosacral Therapy (1983), there are a pair of line drawings of Upledger himself in both external and internal rotation. The first drawing showed his body in the expansion phase (cranial flexion), with his arms and legs turned out, in external rotation, and his chest raised, as if in inhalation (Upledger and Vredevoogd 1983, 108). The contrasting drawing was Upledger demonstrating how the body internally rotates on cranial extension (retraction) toward the midline. Here, the legs and arms rotate in, and the rib cage was lowered (Upledger and Vredevoogd 1983, 110). I was thunderstruck when I saw that. 

Now, while Upledger’s illustration was to dramatize the whole-body response to the fluctuation of pressure in the cerebrospinal fluid system, his illustration had a secondary meaning to me that I’m not sure he intended. What I learned from this, that there are body types that exhibit a genetically driven preference for internal (see Figure 1) or external (see Figure 2) rotation, as an expression of their inherited form, and prior to the subtle shape changes driven by the craniosacral movement fluctuations. 

Figure 1: Four different people with the internal presentation.
Figure 2: Two different women and one man, front and back, who present as having external structures.  

Once I got the idea that there were expansion types as well as retraction types, I couldn’t see anything but this range of types. I realized that the design of Stetson hats being available in two different head shapes, rounds and ovals, was an accommodation for external and internal cranial shapes, respectively. Levi’s original jeans fit nicely on people with internally rotated legs and anteriorly tilted pelvises, while they slide right off the buns of an external whose differently proportioned buttocks lack the contour to hold them up. 

These are some of the searchings that led to finding the I-E model, it was inspired by cranial osteopathy, yet I took it a step further to the realm of structural types. Using the I-E model entails the systematic observation of the contours of the body. It is a tool to observe whole-body’s structural patterns, and a language to describe them. In part, it is a reflection of the craniosacral rhythm generating form as it is transmitted through the fascia. And yet these patterns are also tied to our ancestral lineage. People from regional gene pools have particular shapes and characteristics, and each member carries those characteristics to some degree. 

In my practice, I begin my initial interview by observing the client’s whole-body structure: sitting, standing, and walking. I consider it the representation of a lineage, or the end point of an evolutionary line. In working with an injury or postural problems, the tissue’s matrix is the genetic blueprint and the context in which the client’s current events are happening. Environment and experience are organized around this ancestral baseline. In biology, they evaluate the ‘nature/nurture’ equation. When we see a femur has a preference for external rotation or perhaps the pelvis with a preference for posterior tilt positioning, it may be a part of this genetic legacy and not an aberration of normal structure. 

In application, then, these structural elements are not problems to be solved, but rather elements of blood- and gene-driven patterns. When we begin to talk about posture, we need to keep in mind that much of what we see is foundation organization. It is within this fascial matrix that we work to provide the possibility to ‘behave’ differently. And if there are injuries and adaptive patterns, they are happening in this preexisting matrix. So, we are working to organize around the segmental arrangements we were born with. Consider the injury of whiplash, people experience this same injury, but the ramifications differ between individuals depending on the general typology of their structure, one element being whether they tend toward internal or external structures. When we do our Rolfing SI body readings, we hold this context in mind while we assess the body segment relationships with the symbolic vertical ‘Line’ as a template, and from there we observe limb rotations, the amplitude of the spinal curves, and pelvis position. This gives us a lot of information to work with. 

Towards a Structural Logic

Rolf’s premise that gravity is a major environmental factor in the well-being of every human body is compatible with the internal-external mode of seeing patterns of human structure and function. She observed that when a person’s form was geometrically organized around gravity’s influence, they would be relatively free of compression and could gain support and even acceleration from the gravity dynamic. To visualize this, think of someone walking fast. As they lean into their gait, the body is effectively falling part of the time. This is like free energy to move oneself forward quicker. Rolf’s mastery was her ability to see and intervene manually with the body’s segmental organization, especially individual segments that were displaced away from that same central vertical axis. People who have pain and limitations in their movement often have what Rolf described as compressional loading and an adversarial relationship with gravity. Rolf’s teachings made this visible. 

The I-E model gives us a language to describe these patterns of strain in the three-dimensional web of connective tissue. This lens of viewing whole-body physiology makes the body reading before the interventions, both manual and with movement, work really efficiently. It makes the selection of interventions simpler. Rolf told us that fascia is the organ of form and adaptation. The first adaptation is the genetic blueprint that executes the production of form from embryo to adulthood. Relationships between the major segments of the body begin at this point, as every person is born as an end point of evolution and is a structural blend of inheritance from our mother’s people and our father’s people. The second adaptation is what happens from that conception point forward, both the factors for growth and accumulation of injuries. Connective tissue “can change the direction and density of its fibers with changing demands on the body” (Sultan 1986, 12). People who display a preponderance toward the internal structural type have different working patterns in the fascial web than people who present as an external type.

Figure 3: Features a congruent external and a congruent internal.

At first, this post-Rolf thinking led me to realize that there could be two Recipes, one for internals and one for externals. Then I realized it went beyond that because ‘pure’ internals and ‘pure’ externals are rare. They are theoretical structural patterns to be found in describing the extreme of a spectrum (see Figure 3). While there are people that have a congruent pattern of an internal or congruent pattern of an external, it is rare to see a pure type. More common is the third possibility that describes a lot of people – incongruent-mixed type. These people present a unique mix of internal and external segments. Those transition points of the incongruent segments are often motion restricted and are the structural stress points. The incongruent shift is a useful place for Rolfers to do their manual and movement work, to release the motion restrictions that accompany counterrotations. Viewing the body through the I-E lens gives information about the strain and the direction to promote ease in the client’s spatial organization. Being able to identify the dominant structural type of internal or external will determine the nature of the compensations for incongruent-mixed types (see Figure 4). 

Figure 4: Woman with internal presentation as well as scoliosis.

Congruent Internal Structure

I-E model has become part of Rolfing SI’s Principles of Intervention, it is embedded within wholism, the way of seeing that has everything to do with shape and especially trait (Sultan and Hack 2021). When looking at the congruence or incongruence of a person’s structure, we are looking at the dominant traits this person has inherited and been moving with for their lifetime. Congruence is a quality where the relationship between the major segments are showing the same trends. An organized structure is one that has neither extremes of internal nor external, and is also congruent from head to toe with itself. Structures like this exhibit a graceful flow in movement, ease with themselves, and optimal adaptive capacity to stress and insult. 

As already mentioned, the congruent internal is a cranial retraction structural type first described by Upledger (Upledger and Vredevoogd 1983). This is when the whole body is rotating into the midline, that is to say, the arms and legs are turned in, the rib cage comes down, and the pelvis is anterior tilted. In general, the internal pelvis has a soft tissue pear shape, where the person appears narrow at the crest of the pelvis and wider between the tuberosities. In motion, a congruent internal person’s knees point inward on the swing phase of the gait. They will have a characteristic rolling gait, with strong contralateral movement. In standing with feet together, the legs show as genu varum (O-legs, bow legs). The lateral view of the spine will present with relatively high amplitude spinal curves. This is seen as a deeper lumbar curve, a more pronounced kyphotic curve, and a significant cervical curve. The profile of their sacrum will appear almost as part of an arc of a circle – a crescent sacrum. Internally rotated femurs are fairly easy to spot and a good place to start, then lead your inquiry systematically through each segment. If a client presents with most of the qualities of the internal structure, they are a congruent internal type. 

Transmission lines for a person who is congruent internal has a relatively flexor dominant, ventrally oriented body. Palpation of the craniosacral rhythm will reveal a longer excursion with the extension phase, and the circumference of the head will be more ovoid, long in the anterior/posterior direction. In viewing the body from the side, the congruent internal fascial line of transmission can be found at the posterior cervical compartment, crossing from back to front along the clavicles, the ventral ribs are relatively exhalation dominant, the transmission line follows to traverse the abdominal obliques, to the iliacus. At this point, the force transmission line that found the iliac crest and the iliacus also traverses the inside of the pelvis and continues into the medial hamstrings. From the iliac crest, the transmission line also goes into the tensor fascia latae and vastus lateralis, and into the lower leg, the lateral gastrocnemius, behind the fibula, and then reaches the plantar fascia by way of the lateral arch (see Figure 5). The congruent internal has low flexible arches in the feet. As Rolfers, we take in this pattern as one event happening in the tissue. That means that intervention along any part of the line of transmission affects the whole line. 

Figure 5: Lines of fascial force transmission for congruent internal type.

As the differences in I-E types emerged, I realized that Rolf’s Recipe was biased in her perception of what Upledger called the cranial extension or retraction-type of body, what I came to call the internal. From the design of her Recipe, it seems that Rolf just didn’t see people with external structural traits as a counterpoint (see Figure 6). All her primary directives of posture were for people with internal structural traits – addressing high amplitude spines, collapsed rib cages, and pelvises anteriorly tilted. The objective of her intervention was to bring that ‘flexed’ body into an upright posture. And for this type of structure, her Recipe is brilliant. 

Figure 6: Profile comparisons of four different people, internal and external types, side by side. 

Congruent External Structure

The congruent external structure has predictable lines of transmission in comparison to the congruent internal structure (see Figure 7). As viewed from the side, the external line involves the anterior cervical compartment and then crosses from anterior to posterior at the thoracic outlet to focus on the relatively flat mid-thoracic region. It then traverses into the prevertebral space from posterior to anterior and finds the crura of the diaphragm and the psoas. Following the psoas, it crosses the groin and into the femoral triangle. From there, the transmission line follows the pelvic rotators out from the pelvic basin, down the lateral hamstrings, crosses behind the knee, traverses to the deep posterior compartment of the lower leg, to emerge on the medial tibia distally, and then goes through the medial arch to the plantar foot (see Figure 8).

Figure 7: Lines of transmission of the legs for the congruent external compared to the congruent internal, while standing.

In those early days of training with Rolf, Judith Aston [founder of the Aston® Kinetics] and I were chatting, and she asked, “So when Ida tells you to get your waistline back, what happens to you?” I responded, “Well I try and get my waistline back.” And she said, “Your back already has a diminished lumbar curve. You have no ass. Where is your back?” She went on to say, “If I were directing you, I would have you bring your tail up a little bit and get a better lumbar curve, and have some more resilience because of the curve.” Aston saw what Rolf did not, but Dr. Rolf was my teacher, so what did I say? “Thanks, Judith, but I’m still going to keep my waistline back because Ida was very adamant about it.” In the course of getting my Rolfing sessions, my back went from achy to acute pain. I endured years of that. On reflection, it’s amazing to me that I persisted even as both sensation and logic pointed to the obvious. Judith Aston had already predicted the I-E range of structural types in 1974, and I had denied it. 

Figure 8: Lines of fascial force transmission for congruent external type.

After Rolf died, I was teaching and working with a lot of people, and I was struggling with all this information. I’d look at somebody prior to a first session and think, I don’t want to lengthen the front for this person, they are already long in the front in a banana-like posture. Finally, seeing the expansion body type by Upledger, this congruent external structure opened my eyes (see Figure 9). This is post-Rolf technology, to see and work with people according to how their genetically determined structure presents in terms of the internal-external perception of their form. This is client-centered structural integration. 

Figure 9: A congruent external woman walking. 

Fairly early in this internal-external conception, I realized that, as there was a Recipe for internals (see Figure 10), which Rolf had given us, there was also a Recipe for externals. There are further distinctions to be made for people who are the incongruent-mixed type of the I-E model. What are we to do when a person presents with internally rotated legs and an externally lifted rib cage? Or vice versa? Or a person with externally rotated femurs, the genu valgus knee pattern, and an internal thorax? These possibilities are mixes of the segment types, and clients will present with any blend of presentations from both columns in Figure 3. The chances are that those transition points where external meets internal are most likely where the structure would be motion restricted. These places are called the incongruent shift. These regions will have high-fascia strain and often match the self-report of pain from the client. These crossovers are also where injuries are likely to happen. To some extent, these relationships also predict where adaptations and compensations for a local injury will land in the body. 

Figure 10: Legs of a person with an internal structural type lying on a practitioner’s table.

Knowing the baseline congruent types gives the SI practitioner insight when faced with a client who is an incongruent-mixed type. Then the work becomes client-centered instead of recipe-centered. This is the bridge to Rolfing SI after Rolf. 

Jan H. Sultan’s initial encounter with Dr. Rolf was in 1967 as her client. In 1969 he trained with her. In 1975, after assisting several classes, Rolf invited him to become an instructor. After further apprenticeship, she invited him to take on the Advanced Training. Over the next ten years, Sultan taught several Advanced Trainings with Peter Melchior, Emmett Hutchins, Michael Salveson, and other faculty members, collaborating on refinements to the Advanced Training. Sultan currently teaches Basic Trainings, continuing education, and Advanced Trainings for the Dr. Ida Rolf Institute and continuing education to the extended SI community. He feels strongly that his responsibility as an instructor goes beyond simply passing on what he was taught, but also includes the development of the ideas and methodology taught by Rolf. 

Lina Amy Hack, BS, BA, SEP, became a Rolfer® in 2004 and is now a Certified Advanced Rolfer (2016) practicing in Canada. She has an honors biochemistry degree from Simon Fraser University (2000) and a high-honors psychology degree from the University of Saskatchewan (2013), as well as a Somatic Experiencing® Practitioner (2015) certification. Hack is the Editor-in-Chief of Structure, Function, Integration


Sultan, Jan H. 1986. Towards a structural logic. Notes on Structural Integration 1:12-16.

Sultan, Jan H. and Lina Amy Hack. 2021. The Rolfing SI Principles of Intervention: An integrated concept. Structure, Function, Integration 49(3):16-24. Upledger, John E. and Jon D. Vredevoogd. 1983. Craniosacral therapy. Seattle, WA: Eastland Press.

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