Tag: COGBOS

Experimenting with the Berg – 9. Component 7

Submitted by: Jeremy Nelson PT

7.0 Standing Unsupported with Feet Together

This component is challenging the body’s ability to increase the control of the center of gravity given that the base support has now narrowed. As the base of support is narrowed that increases the strain on the core musculature particularly those of the hip. The goal of this component is to be “able to place feet together independently and stand 1 minute safely”. In addition to the static control tasks of maintaining the position, there is required weight shifting within the component itself to attain the test position. This includes a lateral weight shift and step of the non-stance limb towards midline on the frontal plane. This is the first peek at the capacity of the body to perform the single limb pattern and its associated critical tasks. Specifically the hip abductors are tested to control the adduction moment produced by the lateral weight shift in the frontal plane.

When the patient “needs help to attain position and unable to hold for 15 seconds” there exists limited core stability and inability to control the weight shifting required to change the BOS to the narrow position. “Needs help to attain position but able to stand 15 seconds feet together” is also a comment on the capacity to lateral weight shift. The first place to observe is the position of the hip joint. Is there a positive Trendelenburg sign indicating abductor weakness? If so, what is causing the weakness? From a problem solving perspective the approach would be to begin abduction strengthening using an open kinetic chain to isolate the gluteus medius. As the gluteus medius performs abduction it must be the offending element, and requires correction through strengthening. With enough repetition the goal would be to build the strength of the abductor to counter the adductor moment.

However within the context of the critical tasks that support increasing complexity of the COG BOS relationship, the first step would be to step down to the sit to stand to sit critical tasks. Do the hip adductors have adequate length to complete the sit to stand? Does the hip abductors have adequate strength to control the ascending and descending of the COG? What about the core strength during the anterior weight shift? By stepping down a level to examine the completeness of the critical tasks, the foundation of movement is verified. If there are abhorrent movements as this level, they will need to be completed first before the direct approach is attempted. Within the context of the hierarchies of movements, the direct approach would seek to be consistent with the critical task demands. In this case, the lateral weight shift is preceded by hip abduction and extension and internal rotation in the closed kinetic chain. At no time does this task require an open kinetic chain.

“Able to place feet together independently but unable to hold for 30 seconds” and “able to place feet together independently and stand 1 minute with supervision” verifies that a weight shift has taken place in order for the narrowing of the BOS. This may look like small, quick steps towards midline as the body weight is supported by the stance LE for only short periods of time. This pattern is evidence that the current capacity is inadequate when compared with the goal of maintaining standing for extended periods. Further examination of contributing body segments is also completed to determine the readiness to support the increasing complexity of movement during upcoming Berg components.

A final note on the importance of understanding the critical tasks within a functional movement as data points to organize the change effort. This test component could be observed to be a test of balance capacity in a narrow symmetrical BOS. If this was the case, with a low score, the place to go would be to organize around the BOS and challenge the body to hold this position. Perturbations could be included to challenge the cores ability to maintain the COG over the BOS. Different surfaces would be added to impart on the body forces that it must learn to deal with. A focus on increasing lower extremity strength could also be included.

However without a solid support of the lower level critical tasks the body segments will produce compensatory movements. Repetition of the compensations produced while the body is being “trained” to handle these forces produces learning for the nervous system. As a result, instead of the desired flexible nervous system that has mastered the coordination of muscles to produce critical tasks, the available movements are limited circumstance. In addition, without completion of the critical tasks of the performance skills of symmetrical stance and single limb positions, the nervous system will have a more difficult time in completing the tasks that are upcoming.

Experimenting with the Berg – 4. Component 2

Submitted by: Jeremy Nelson PT

Component 2.0 – Standing Unsupported

This component is seeking to learn more about how well the patient is able to maintain the center of gravity over their base support in an elevated position. As the center of gravity rises above the base of support there is an increase in the kinetic energy. New forces are imposed on the structure of the body, and the body needs to respond to control the dynamics. So the static standing is more challenging for the neuromuscular system than being seated. In the seated position, control of the center of gravity is enhanced by a larger BOS, within the base of support that includes the pelvis, femurs and feet.

In addition were looking at the quality of the passive range of motion within the skeletal structure to attain extension as well as the extensors of the body to resist the pull of gravity. The human skeleton has a few tricks to assist with maintain full extension; however it requires adequate passive range of motion into extension and adequate length of the flexors to attain this. Thus an assessment of posture is worth adding to these observations. Knees that are unable to meet full extension and take advantage of the screw home mechanism may be caused by knee flexion contracture or hip flexion contracture. Being that the scoring is time dependent, the endurance factor also leads to a better understanding of the conditioning of LE and posture efficiencies.

This component BOS is a symmetrical stance. Within the component the sub-components allow for an opportunity to change the amount of support in order to up towards the ability to stand safely for two minutes. To score 0 you must unable to stand for 30 seconds unsupported. And to score one point there is a need for several tries to stand 30 seconds unsupported. Although not part of the scoring, the clinician may investigate within this score to see what impact single upper extremity support going from bilateral upper extremity support has on the standing balance.

There are a number of reasons why patient would not be able to stand unsupported. The most common is the position of the knees and hips remaining in a flexed position which increase the amount of mechanical strain on the system. 0° hip extension and knee extension allow for the joints and bones to support the standing. When the hips are flexed and unable to extend to neutral the internal rotation of the femur is lost. As a result the screw home mechanism in the knees is not available, thus reducing stability of the knee. This also burdens the patient as they must to do a lot more work during standing. Instead of the skeletal structure contributing to maintaining the COG above the symmetrical base of support, instead anterior chain is excessively used as this puts the COG near the posterior aspect of the BOS.

The symmetrical standing posture is not typically used in most functional activities, as the body is better positioned in an asymmetrical stance to move. With this component asymmetrical stance can be enhanced and the overall function of the patient improved.

Experimenting with the Berg – 3. Component one

Submitted by: Jeremy Nelson PT

Component One- Sitting to Standing

Another way to say that a person cannot stand up on their own is that they can successfully, repetitively fall back into the chair. Although this is not desirable we can ask the question, how do they do this? To find the answer consider the COG BOS relationship as primary. Everything else such as strength, mobility, and coordination is secondary, that is in support the dominant task of organizing the COG and BOS relationship. Beginning with this primary components, each can be investigated and evaluated as being supported by their component parts.

A person, who requires their hands to stand up needing several tries for success, typically has the center of gravity posterior to the base of support. This is evidenced by the observation of when they go to stand up they fall backwards, not forwards. The center of gravity is not supported by the base and as a result the person is falling back into the chair repetitively. It is not a function of leg strength, although that may be contributory. Instead it is a fault of position.

To investigate this claim, try to stand without first shifting your body weight forward between your separated feet. It will seem impossible, because it is. What must first occur is an anterior weight shift of the COG into the BOS. This is called the critical task. What strategy is employed to create this critical task is the choice of the clinician.

As the article series progresses each component of the Berg will also identify one of the critical task. Understanding the critical tasks for each movement supports the establishment of goals and sub goals. An interesting experiment is to examine how the scoring of each component can be the beginning consideration for each set of goals. Here is a deeper look at this first component of the Berg.

To score 0 on this component the patient needs moderate or maximal assist to stand. Whatever you call it, moderate or max, it’s not functional, and instead points to inadequate foundation for movement at both the COG and BOS levels. Here is a person who cannot generate the force required to counter the forces that are experienced during the sitting process, let alone the forces part of transitioning to standing. Typical reasons for why someone would need this type of assistance from going from sitting to standing posture are varied; however they all share the same elements of the two data points that produce structural tension.

The center of gravity/base of support relationship is the starting point when working with someone who has a moderate to maximal assist for sitting to standing. The goal will be to improve the body’s capacity to establish and maintain this relationship, and change the positions of each element to support functional movement. Bringing this relationship together decreases the amount of strain on the neuromuscular system. By simply rearranging those elemental parts, rapid changes in function can occur.

It’s not uncommon after using some of the establishing the base support techniques as well as teaching a hip hinge can a person go from a moderate to Max or Max to requiring a minimal to contact guard assist with utilization of bilateral upper extremities. Not in weeks, but in a few sessions. So the lesson here is to learn how to do anterior weight shift where the center of gravity is controlled and moved anterior within the base support moving from the posterior aspect of the day space support towards anterior aspect while maintaining control. In this way, the patient will complete the sitting to standing component and be well positioned to complete the more difficult tasks ahead.

Experimenting with the Berg- 2. Choices of Structures

Submitted by: Jeremy Nelson PT

The key to building tangible results over time is described by Robert Fritz as first establishing structural tension. He describes this tension as not stress or anxiety but instead the state of two complementary and different points in relation to each other. Generally it is the relationship between the desired end result, the outcome that is wanted, and the current reality as it is defined in relation to the outcome. By first establishing the relationship a dynamic is generated that supports the choices and actions on a strategic basis. Other structures are available, such as a problem solving structure in which the intensity of the problem drives the actions. Which structure the clinician chooses to use will influence the interventions selected as well as the impact on functional outcomes.

Starting with the first element, a desired end result is required. As mentioned before, each component part of the Berg has within it sub elements. These observational descriptions for that movement are organized from unable (score of 0) to fully capable (score of 4) with each score providing a defined task to complete. Used primarily as a scoring matrix, this could also be a framework for goals of towards progression of the patient through that component. So an example would be 1.2 able to stand using hands after several tries the goal would be 1.3 able to stand independently using hands and so the treatment plan would be then to move towards that goal.

The cause of poor function is absent in the testing tool, and is the domain of the clinician to evaluate the contributing body segments that are required to support the center of gravity relationship in the test component. Which interventions, and the success of progressing through a component and then into higher levels of complexity depends on the overall structure of the plan of care.

Problem solving structure will seek to eliminate the restriction that is stopping the movement to the next level. Interventions applied will be utilizing therapeutic exercises, may be soft tissue mobilization, maybe neuromuscular reeducation, to get rid of the problem. As the intensity of the problem decreases, for example pain is reduced; the motivation for further action also decreases. Now the patient can stand up independently. However the cause of the problem is left unaddressed and the physical capacity to support the transitional movement has not changed, and as a result the patient is prone to recidivism.

A plan of care that is composed using the establishment of structural tension as a strategy will promote specific exercises that are related to each individual component and subcomponents as well as change over longer periods of time. The individual exercises focused on the critical tasks that are found within each component. So again an example borrow 1.2 able to stand hand-in-hand using hands actual tries and then 1.3 able to stand independently using hands. Employing the sitting hip hinge exercise in which the patient goes from hands-on knees slightly hands down inside of the tibia’s towards the medially malleoli supports the critical task at hand.

Enhancing the anterior weight shift is the goal, to move the COG over the BOS. Using this specific exercise mobility of the hip joint is enhanced. And it is enhanced in a closed chain, providing needed learning for the surrounding musculature to improve timing. The adequate hip hinge also supports the stability of the core in order to control of the change of the center of gravity within the base of support.

It could go another way. That the person who is learning the motion has adequate hip hinge ability an adequate core strength however the base of support that they’re establishing is too far forward from their ability to transfer their center of gravity over their base support so this may include working on ankle and knee mobility in order to increase flexion of the knee increased dorsi flexion of the ankle. This brings the base of support closer to the center of gravity thus facilitating their ability to successfully transfer the center of gravity on top of the base support. In this example the person still needs to utilize their hands in order to develop the force are developed to control however there now able to do that without concern of falling.

With a composed plan of care, the related motions and component segments are included in the in the clinical decision making process. From here the change effort can proceed. Using a problem solving structure will be inadequate, resulting in a limited improvement in function primarily focused on putting out the fire, not designing and constructing a new building. Over the series of articles we will examine each component of the Berg as an experiment in application of different structures as part of the clinical decision making process.

Structured Motion Approach – 6. Critical Tasks

In the previous article, the question was asked “How often today do PTs, OTs and other providers asses a person’s ability to stand up from a seated position as poor and then make the conclusion that what is needed is more lower extremity strength?” In a problems solving structure, the clinical decision making lead to exercises prescribed to improve strength. It would likely include some open kinetic chain exercises as well as Continue reading Structured Motion Approach – 6. Critical Tasks

Structured Motion Approach – 5. COG BOS and Imposed Demands

We ended the previous installment with an introduction of the star of the show, the COG and BOS relationship. The article also introduced the notion that this relationship was determinant, in other words it would be the most influential on function. This article continues to develop the point and sets the stage for the change efforts in upcoming installments.

Each of the different COG BOS relationships is imposing a new demand on the neuromuscular system as the kinetic energy is increased as the COG moves away from the BOS and the need for the production of internal stability is increased as the BOS changes to a less stable form. Within each of these snap shots in time of the COGBOS relationship, there are Continue reading Structured Motion Approach – 5. COG BOS and Imposed Demands

Structured Motion Approach – 4. Performance Skills

In the previous installments, a number of introductory components of the Structured Motion approach have been described. Starting with a focus on making specific results, the client or patient is then engaged to ensure that the result being made is really what is wanted by the patient or client. As part of being an expert in the field, it is easy to decide for the patient or client what they should want. It is also important, given that these processes and actions are expressions of the value of freedom, that the patient be a collaborator in the outcome. This is an active process of collaboration in which the client or patient identifies what they want and the professional organizes around that outcome. Included in this is the freedom of the patient to not accept the intervention by the rehab professional. It is essential that the client or patient is choosing to be involved, and choosing to act on behalf of their involvement in life. If the client or patient refuses service, then further referrals to the appropriate professional can be made. It has been our experience that there are different levels of desired involvement in life. This is different than depression or a withdrawing which again would require a referral to the appropriate provider. It is this initial process of organization by the professional that will be introduced in this article.

At this point a report that presents the comparison of the desired level of function as identified by the client and the current levels of ability is generated to assist in the assessment process. Each specific activity identified will have one or more performance skills category which includes those movements that observable. These are typically what is referred as functional movements. These movements are often tested using standardized testing such as the berg test. Examples include: sitting and standing, turning in a circle, reaching for something on the floor and a host of many more functional activities. These movements become the entry point into the assessment of the person’s ability to perform the desired specific activities identified earlier. These performance skills are more than just movements on a macro scale, but are really movement strategies of the brain in orchestrating the body to manipulate the COG BOS relationship. All motion includes the controlling of the COG either statically or dynamically in an ever changing BOS.

The movement skills are further defined in terms of the COG and BOS relationship within the observable Performance skill category. For example within the category of bridging, the COG will start out in the BOS which is the length of the body as the person is resting in supine. The BOS will then change to a 3 point of both feet on the ground and the trunk as the person attains hook lying position. The COG then is dynamic as the body raises the COG above the 3 point BOS and the BOS further changes from the trunk to only the upper spine, scapulae, neck and head in contact. After attaining maximal rise, the lowering begins, requiring a different muscle contraction and level of control, until the beginning level is returned to.

This clarification of the functional movement as it relates to the desired specific activity and its related definition of COG and BOS relationship provides a framework in which the COG and BOS relationship will be present throughout the assessment, evaluation, and change effort. In this way questions regarding the impact of an intervention on body movement or posture can be compared with its result on the COG BOS relationship as it will determine the functional involvement in the desired activity.

Planes, Boats, Bicycles and Bodies

Submitted by: Jeremy Nelson MPT

I was reading a book on engineering and design of bicycles not too long ago. Cycling had been a very big part of my life and I was interested in what gave a bike a certain “feel”.  Another way to say was how the bicycle behaved over different circumstances, cornering, climbing, descending, sprinting.  In other words why it functioned as it did. The more I read about the design process and the goal of changing the COG over the BOS of the bicycle with the addition of a rider, I recognized many of the same considerations in the practice of PT.

It’s as if the therapist is playing the role of the engineer, working on behalf of the brain, which is seeking to balance the forces created by the COG BOS relationship. The cerebral captain of the corporeal ship is always changing course, ordering the crew with an ongoing changes in the position of sails and rudder to stay the course, or react to changes in the environment. In a presentation, Robert Fritz describes the thoughts of Peter Senge who writes about the interaction of design and performance. Mr Fritz and Mr. Senge ask “Who has more influence on the ship, the captain or the ships designer?”  After consideration of the role of cause and effect in how something behaves, they provide the answer: “It’s the ships designer as the design of the ship will determine how the ship moves through the water. ”

The role of the designer is to organize the ships form to create a distinct COM/COG and a BOS relationship that takes advantage of the natural forces of buoyancy. This is not a trivial task.   Have you ever seen or been on a aircraft carrier? Every time I am looking over San Diego bay I see the aircraft carriers based in Coronado and wonder, how it is that these huge masses of metal float like corks in the water. And as a result provides a distinct functional capability that the captain organizes his decisions around.

As clinicians we have a role as a designer, an architect and engineer of a plan and actions to produce new relationships for the brain to utilitze.  Each body, whose structural proportions are fixed, have interrelated components that move in relationship to each other to provide function. Change the relationships of COG and BOS relationships and new levels of performance are made available.

Likewise the re-structuring of the segments of the human form such that there is greater efficiencies in controlling the COG over a wider variety of BOS configurations. Each different organization of the COG and BOS imposes new demands on the brain to position the extremities and core in ways that maximize there capacities. If one area is inadequate to task, others are called upon to take more of the strain. This lack of component capacity limits the effectiveness of all the other parts of the neuromuscular structure.

Our body has proportions that also work to guide and direct forces, like the ship or the plane. Our body creates a tension, as does the planes structure. Based on the form of a ship or plane there is a zone of most efficiency when piloting these crafts, a path of least resistance for the operation of the ship. The structure of the vehicle creates a 3D zone of most available motions that are most efficient, that due to the structure of the vehicle can attenuate forces the best. Pilot these vehicles out of the zone and the structure are tested as shearing forces are created that can damage the structure and lead to failure.

Our human form has a path of least resistance that is seen in beauty of the spiral form, curves of motions, and ballet type moves of gracefulness. We are not linear in nature, robotic, prone to 2 degrees of freedom. Robots move with extremities acting in support themselves, while the human body is a continuous form, with all motion emanating from the core. When the brain is trying to shift the COG anteriorly over the BOS from an upright seated position in the sitting pattern what is going on under the hood is a changing of force. to maximize the kinetic energy such that the muscles can work efficiently to change the position of COG relative to the BOS.

When seen in this way, therapeutic exercise is no longer a focus on just correcting malposition’s, but become intensifications of the functional movements that are required to perform the functional task. In order to sit and stand, the hip hinge is used to translate the COG over the BOS to the position of most efficiency before standing up. The approach that thinks of the body as a summation of the strength and flexibility could conclude that the problem is inadequate LE strength and begin the process of LE ther ex to improve sit to stand ability. Returning to our ship analogy, if the COG is to high and the BOS is to narrow, the ship will be unsteady, and likely capsize because of the force of buoyancy. Planes need to have their wings positioned in relation to their COG to produce adequate lift to fly. If we though that the lack of flying was a strength issue, we would add a bigger engine creating greater forces on the frame of the plane and stressing the wings even more, possible to the point of failure. See, it’s not a strength issue, but an issue of COG and BOS.

One more, returning to the bike example we started with. By placing the COG of the bicycle and rider towards the rear of the bike, stability is increased and the bike has a smoother more relaxing ride. This is the type of bike that even a novice could ride with their hands off of the handle bars and safely cruise around. A rider participating in a race with many turns and need for fast acceleration would find this type of bike working against her. It would be difficult to make the turns and the rider would have to work extra to accelerate.

Now take the same rider, and put them on a bicycle which has a COG towards the front of the bike in relation and the rider will find themselves quickly cornering and accelerating out of each corner with ease. Now keep in mind, same rider, same strengths, and different bikes with all things equal other than the COG BOS relationship different. The point is that the COG BOS relationship is imposing different demands, and as a result the brain will have to reorganize its coordinated efforts to complete the tasks at hand.

As rehabilitation and performance professionals we often see our clients and patients performing awkward patterns of movement when trying to complete a task. As professionals we can misinterpret these compensations as areas of weakness, thinking it is the compensatory part that is to blame. We then go to work to correct the compensating area. However, if we ask what is happening at the COG BOS level to impose the demand on the body, we may then see that the area is attempting to make the COGBOS relationship work. Other areas are resulting in the inadequacies. Start with the COG and BOS relationship as dominant data points when organizing your change effort and you will find it is easier to understand what is causing the patients difficulty in being involved in their life as they desire.