How you load and off-load your forefoot bipod matters.

If you are a sprinter, how you load the forefoot bipod might be a variable for speed or injury. Tendons can change their cross sectional area, if you load them, but they don't change, if you don't.
Of course this article is not exclusive for sprinters, it pertains to any running sport, even endurance.
Maximum isometric force had increased by 49% and tendon CSA by 17% !
Tendons can change their cross sectional area, if you load them.
Here I show lateral forefoot loading in a heel raise, and a medial forefoot loading in heel raise. This has to be part of the discovery process outlined below. Forefoot types will play into the loading choice, and unequal strength of the medial or lateral calf compartment will also play into the loading choice made. Where do you need to put your strength ? And is the forefoot competent to take that loading challenge ? Meaning, do they have a forefoot valgus? A forefoot supinatus ? These things matter. If you are a sprinter, how you load the forefoot bipod might be a variable of foot type, asymmetrical posterior compartment strength, or foot strike pattern in the frontal plane (search our blog for cross over gait and glute medius targeting strategies for step width) ,or a combination of several or all of the above. These things matter, and why and where you put your strength matters, if you are even aware of where and how you are putting the loads, and why of course. Of course, then there are people like the recent Outside online article that says how you foot strike doesn’t matter, but it does matter. But of course, if you do not know the things we have just mentioned, it is easy to write such an article.
Isometrics are useful, they have their place. In a recent podcast we discussed the place and time to use isometrics, isotonics, eccentrics and concentrics.
One of the goals in a tendinopathy is to restore the tendon stiffness. Isometrics are a safe way to load the muscle tendon complex without engaging a movement that might have to go through a painful arc of movement. With isometrics here is neurologic overspill into the painful arc without having to actually go there.
The key seems to be load. More load seems to get most people further along. Remember, the tendon is often problematic because it is inflammed and cannot provide a stiffness across its expanse. Heavy isometric loading seems to be a huge key for most cases. But, we have to say it here, not everyone fits this mold. Some tendons, in some people, will respond better to eccentrics, and strangely enough, some cases like stretching (perhaps because this is a subset of an eccentric it seems or because there is a range of motion issue in the joint that is a subset of the problem). Now the literature suggests that stretching is foolish, but each case is unique all in its own way, and finding what works for a client is their medicine, regardless of what the literature and research says.
Finding the right load for a given tendon and a right frequency of loading and duraction of loading is also case by case specific. Part of finding the right loading position is a discovery process as well, as noted in the photos above. Finding the fascicles you want to load, and the ones you do not want to load (painful) can be a challenging discovery process for you and your client. Finding the right slice of the pie to load, and the ones not to load takes experimentation. When it is the achilles complex, finding the safe However, if one is looking for a rough template to build from, brief, often, heavy painfree loads is a good template recipe to start with.
Here, in this Geremia et al article, "ultrasound was used to determine Achilles tendon cross-sectional area (CSA), length and elongation as a function of plantar flexion torque during voluntary plantar flexion."
They discovered that, "At the end of the training program, maximum isometric force had increased by 49% and tendon CSA by 17%, but tendon length, maximal tendon elongation and maximal strain were unchanged. Hence, tendon stiffness had increased by 82%, and so had Young’s modulus, by 86%.
Effects of high loading by eccentric triceps surae training on Achilles tendon properties in humans. Jeam Marcel Geremia, Bruno Manfredini Baroni, Maarten Frank Bobbert, Rodrigo Rico Bini, Fabio Juner Lanferdini, Marco Aurélio Vaz
European Journal of Applied Physiology
August 2018, Volume 118, Issue 8, pp 1725–1736

Approaching hip pain differently.

You might have fewer struggles with your hip pain clients if you start approaching the hip joint as the intersection of a long pole (the leg) with a ball on the end (the femoral head) and the pelvis' acetabulm/labrum sitting/balancing on top of the ball.
The game is to get the stick (the leg) stable and stiff enough that you can control the positioning of the frontal, sagittal and rotational planes of that ball on the end, and achieve enough control/skill, strength, stability, endurance of the interface of the pelvis socket (the pelvis' acetablum/labrum) on top of this ball. The key to success in this area is the understand that the pelvis, and the body mass above it, is terribly disadvantaged to find controlled equilibrium on top of the ball (femoral head). Thus, achieving sufficient skill of the muscles bridging the two, adequate endurance in them to last the duration of the challenges, and certainly sufficient strength of those muscles to control shear, compression, stability and controlled mobility are key components to successful and pain free hip function.
One has to think of things in a closed chain, one's limb is fixed on the ground, and one needs to see that the game is to control the pelvis and the massive entire torso mass on top of this small ball in a controlled fashion, while we are moving and changing position.
This is the game.

*This is why single leg lifts and rehab are so key in the success of a client. Remember, gait and running and most sports are for the majority of the time, spent in single leg loading.

Shawn Allen, the other #gaitguys

#gait, #thegaitguys, #gaitproblems, #gaitcompensations, #gaitanalysis, #hippain, #hipbiomechanics, #Singlelegloads, #unilateraldeadlifts, #stancephase,

photo, courtesy of pixabay.com

https://pixabay.com/en/soccer-football-soccer-players-kick-1457988/?fbclid=IwAR13Laep8KM-w4KaVl8Ip9vyz7Svk6BXbGgEE_UkSYU-3eoAV1suHtsbi80

The effect of Arm swing on lumbar spine and hip joint forces.

We have discussed the arm swing issue so many times over the years that we have lost count. By many sources, arm swing is a product of lower limb action and a product of the effective, or ineffective, relationship between the shoulder "girdle" (maybe thoracic rotation component) and the pelvic girdle (lumbopelvic rhythm) during gait. This is the concept of phasic and anti-phasic limb swing. If you want to dive into that, and you should if you are unfamiliar with the concept, you can look it up on our blog using the search box. We are not to forget that the arms, and thus arm swing, is a major factor in maintaining balance. We have used the term "ballast" many times to describe the effects of arm swing, rotation, abduction, circumduction etc on assisting balance maintenance of the body during various locomotion strategies. These are largely subconscious actions, hence why we agree with the research suggesting that arm swing is secondary, compensatory, and takes its queues off of the activity of the lower limb motor actions. In essence, arm swing variants are necessary compensations to assist in maintaining things like balance, center of pressure, equilibrium and the like.

In this recent 2017 study, we have another suggesting arm swings function in assisting, even improving, dynamic stability. We are reminded of MdGill's suggestion, and the concepts of phasic and antiphasic torso-pelvis counter rotational movements, of how spinal loads can be affected by changes or differences in arm position. Even arm position changes in sitting and standing can alter spinal loads, so during movement it is a virtual guarantee.

This study looked at "how arm swing could influence the lumbar spine and hip joint forces and motions during walking." In this study, the researchers had each subject perform walking with different arm swing amplitudes and arm positions. Here is a comment from the researchers on what they found, it is pretty much what we have been writing about for several years based off of other research"

"The range of motion of the thorax with respect to the pelvis and of the pelvis with respect to the ground in the transversal plane were significantly associated with arm position and swing amplitude during gait. The hip external-internal rotation range of motion statistically varied only for non-dominant limb. Unlike hip joint reaction forces, predicted peak spinal loads at T12-L1 and L5-S1 showed significant differences at approximately the time of contralateral toe off and contralateral heel strike."

Thus, we find yet another study confirming what many will say is obvious, that being arm position and movements have notable effects on whole body kinetics and spinal loads. This study suggested that arm variations did not have an effect on spinal loads during walking. We find this curious; it is something we will be looking into, and pondering. We hope you do as well.

Effect of arm swinging on lumbar spine and hip joint forces
Lorenza Angelini et al. Journal of Biomechanics, Sept 2017
http://www.sciencedirect.com/…/article/pii/S0021929017304670

Podcast 122: Achilles problems, glutes, & feet.

Key tag words:
neuroscience, elon musk, achilles, tendonitis, tendonopathy, eccentric loading, tendon loading, gluteus maximus, gmax, glutes, abductor hallucis, foot pain, hip biomechanics, navicular drop, BEAR, ACL tear, ACL reconstruction, plantar fascitis
 

Show links:

http://traffic.libsyn.com/thegaitguys/pod_122f.mp3

http://thegaitguys.libsyn.com/podcast-122-achilles-problems-glutes-the-feet
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Interested in our stuff ? Want to buy some of our lectures or our National Shoe Fit program? Click here (thegaitguys.com or thegaitguys.tumblr.com) and you will come to our websites. In the tabs, you will find tabs for STORE, SEMINARS, BOOK etc. We also lecture every 3rd Wednesday of the month on onlineCE.com. We have an extensive catalogued library of our courses there, you can take them any time for a nominal fee (~$20).
 
Our podcast is on iTunes, Soundcloud, and just about every other podcast harbor site, just google "the gait guys podcast", you will find us.
 
Show Notes:

Stanford Develops Computer That Literally Plugs Into People's Brains

https://www.entrepreneur.com/article/289645


Elon Musk says humans must become cyborgs to stay relevant. 

https://www.theguardian.com/technology/2017/feb/15/elon-musk-cyborgs-robots-artificial-intelligence-is-he-right

1. achilles tendonopathy:

http://www.jospt.org/doi/abs/10.2519/jospt.2016.6462?platform=hootsuite&code=jospt-site

2. achilles tendinitis and tendonosis.

Ohberg L, Lorentzon R, Alfredson H, Maffulli N. Eccentric training in patients with chronic Achilles tendinosis: normalised tendon structure and decreased thickness at follow up. British Journal of Sports Medicine. 2004;38(1):8-11. doi:10.1136/bjsm.2001.000284.

link to abstract: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1724744/

3. Is Achilles tendon blood flow related to foot pronation?
 E. Wezenbeek,T. M. Willems,N. Mahieu,I. Van Caekenberghe,E. Witvrouw,D. De Clercq

http://onlinelibrary.wiley.com/doi/10.1111/sms.12834/full

4.  The effects of gluteus maximus and abductor hallucis strengthening exercises for four weeks on navicular drop and lower extremity muscle activity during gait with flatfoot

Young-Mi Goo, MS, PT,1 Tae-Ho Kim, PhD, PT,1,* and Jin-Yong Lim, MS, PT1  J Phys Ther Sci. 2016 Mar; 28(3): 911–915.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4842464/

5. BEAR
https://www.youtube.com/watch?v=k3g-CagCrZM

Bridge-Enhanced Anterior Cruciate Ligament Repair (BEAR) procedure uses stitches and a bridging scaffold (a sponge injected with the patient’s blood) to stimulate healing of the torn ACL eliminating the need tendon graft.

References:
Murray, M., Flutie, B., Kalish, L., Ecklund, K., Fleming, B., Proffen, B. and Micheli, L. (2016). The Bridge-Enhanced Anterior Cruciate Ligament Repair (BEAR) Procedure: An Early Feasibility Cohort Study. Orthopaedic Journal of Sports Medicine, 4(11).

L. Proffen, B., S. Perrone, G., Roberts, G. and M. Murray, M. (2015). Bridge-Enhanced ACL Repair: A Review of the Science and the Pathway Through FDA Investigational Device Approval. Annals of Biomedical Engineering, 43(3), pp.805-818.

Podcast 79: Tightness vs. Shortness, Plantar Fascitis & more.

plus, pelvic asymmetry, “wearables” and cognitive choices in movement.

This week’s show sponsors: 

www.newbalancechicago.com

www.lemsshoes.com

A. Link to our server: 

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Direct Download: 

http://thegaitguys.libsyn.com/podcast-79

B. iTunes link:

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C. Gait Guys online /download store (National Shoe Fit Certification and more !) :

http://store.payloadz.com/results/results.aspx?m=80204

D. other web based Gait Guys lectures:

www.onlinece.com   type in Dr. Waerlop or Dr. Allen,  ”Biomechanics”

______________

Today’s Show notes:

The Brain and your choices.

http://exploringthemind.com/the-mind/brain-scans-can-reveal-your-decisions-7-seconds-before-you-decide#.VCx0P8ydUK4.facebook

4 Wearables That Give You Superpowers
http://www.fastcodesign.com/3036295/4-wearables-that-give-you-superpowers?partner=rss

 

Invisibles, Not Wearables, Will Profoundly Change Health Care
http://www.fastcoexist.com/3036554/wearables-week/invisibles-not-wearables-will-profoundly-change-healthcare?partner=rss

 

Walking is the superfood of fitness, experts say

http://www.reuters.com/article/2014/09/29/us-fitness-walking-idUSKCN0HO0PV20140929

 

FB reader ,Phil

 

Hey Guys,

I have pelvis asymmetry and a snapping ankle, can you help me with … . 

 

New research on Plantar Fascitis

Plantar fasciitis – important new research by Michael Rathleff
http://blogs.bmj.com/bjsm/2014/09/15/plantar-fasciitis-important-new-research-by-michael-rathleff/

 

John from FB

Shortness vs tightness:

What protocol do you recommend for stretching ? I usually do static stretches1x2min. This article has the static stretch group doing 10x30sec. I’d have to set my alarm a half hour earlier! :-)

Hip Biomechanics: Part 6 of 6, The Conclusion (for now)

A Piece of the Functional Puzzle: Hip Rotation

As we have already mentioned, stabilization of the hip is complicated in its own right, but when we ask it to participate in balanced single limb movement and stability in the frontal/coronal, sagittal and axial planes all at once, the delicate balancing act of of these components is sheer genius.

Through our collective clinical experiences it has become apparent over time that vertical and horizontal gravity dependent postural examination can open insight into a deeper functional disturbance in patients.  For example, an externally rotated right lower limb as evidenced by an accentuated external foot flare should initiate the thought process that there is either an anatomically short right limb (external rotation increases leg length), tight right posterior hip capsule, short gluteals or other posterior hip musculature (piriformis, obterators, gemelli), weak internal hip rotators, weak stabilizers of this internal hip rotation, or possibly an over-pronating right foot which shortens the limb and hence the need for the externally rotated and lengthened right limb (ie. failed compensattion).  What we mean by this last component is that there are really two basic types of presentations, those that are compensations to an underlying problem and those that are failed compensations. In consideration of all scenarios, our traditional thinking has directed us to believe we are dealing with a limb posture that has occurred to lengthen the limb in question.  However, perhaps the compensation is deeper in its root cause.  For example, the traditional thinking in alignment restoration of this postural deviation is to stretch the piriformis, glutes and iliopsoas and perform deep soft tissue work such as myofascial release methods, stripping, post-isometric release and mobilization or manipulation to the affected tissues and associated joints to ensure normal function.  These efforts are meant to restore the limbs rotational anomaly and hopefully the cause of the leg length compensation. However, many clinicians will attest to the fact that these methods are frequently unsuccessful or at least limited in their short or long term effectiveness towards complete symptom and postural deficit resolution.  Frequently our patients enter into the cyclical office visits several times a year to address symptoms associated with the root cause.  Thus, we must delve deeper into the source of the problem, perhaps those above methods are focused at resolving the neuroprotective compensation and not the lack of strength or stability of internal hip rotation.  This approach will require the therapist to investigate the open and closed kinetic chain functions of these external and internal hip rotators and look further and more deeply for the source.

In the open kinetic chain (swing phase of gait) the primary and secondary external rotators turn the lower limb outwards in relation to a fixed pelvis established by a sound core; this is late swing phase. This external rotation is, at this point, largely assistive in driving foot supination to gain a rigid foot lever to toe off from.  In the closed kinetic chain scenario, with the foot engaged with the ground, the activation of these same muscles will cause the same movement at the hip-pelvis interface but in this case the pelvis/torso will rotate.  For example, in observance of a closed chain right lower limb, upon activation of the glutes, piriformis and accessory external hip rotators the client’s pelvis and thus torso will rotate to the left (counterclockwise rotation) along the vertical body axis about the fixed right limb.  With this functional thinking we must now embrace the fact that our traditional perspectives of body function assessment in the frontal and sagittal planes must be largely discarded.  It is a rare occurrence that we move in a single plane of motion without any component of rotation.  This being accepted, we must return to our client’s left pelvis rotation and understand that torso rotation must occur in the opposite direction if gait is to be normal with proper arm swing and propulsion.  This rotation can occur from activation of not only component muscles at the hip-pelvis interval but also from the abdominal obliques, thoracic spine and rib cage.  Therefore, one could hypothesize that a client’s external rotation of the right lower limb in stance or gait might not be a primary problem with the piriformis, glutes or accessory muscles rather it could be a compensation for either a one sided over-active or  weak abdominal oblique system/sling/chain or abnormal thoracic rotation, or a combination of both.  Assessment of a patient’s passive and active torso and thoracic/rib rotation might open a window into one of a range-driven deficit or weakness/inhibition. Shoulder mobility assessment is going to be necessary as well because it can and will effect torso/rib cage mobility, arm swing is a huge predictor and indicator in faulty gait assessment and it is one frequently overlooked (type in “arm swing” into our blog SEARCH box and you will be excited to read the research on arm swing in gait). The practitioner must always embrace the thought that the client’s core might not only present as weak but to a higher level that of imbalanced, which is a combination of weakness, stretch weakness, strength, over-activation, inhibition and impaired movement patterns (including breathing).  This imbalance can come from such parameters as pain, handed dominance activities, lower limb dominance issues, occupational demands or others as discussed below.

What we continue to find as our clinical experiences expand is that many deficits in the body are driven by a functional core weakness/imbalance or forces not dampened across a weak core and from impaired gait biomechanics.  In this case, the absence of balanced core abdominal strength and torso rotation renders a weaker or inhibited core rotation/lateral bend on one side and it is this deficit that is often compensated in the pelvis as a tight hip/pelvis soft tissues unilaterally (expressed perhaps as the unilateral externally rotated limb). This will often alter function, strength and mobility in single leg stance during the gait cycle and enable a compensatory cheat into one or several of the cardinal planes of motion. This is of course but just one scenario. Taking the example above, a right externally rotated lower limb with associated tight and/or painful right piriformis muscle, we frequently (but yes, not always) see a loss of rotation range or strength into left torso rotation.  This can be seen on supine rolling patterns looking for upper or lower limb driver deficits. This scenario might be showing little to no progress with therapy but may do so with focused work on supine rolling patterns.  Therapeutically facilitating oblique abdominal strength to improve range and strength into left thoracic/rib cage rotation over time may reflexively reduce the piriformis spasm and rotational deficit in the right lower limb without even applying much direct therapy to this area.  In other words, our experience shows that improving the thoracic rotation into the side of limitation can have some neurologic response of inhibition/relaxation on the tight posterior hip compartment.  We would be remiss if we were to neglect that this oblique abdominal weakness could coincide with a slight anterior pelvic tilt in the sagittal plane on that side (which promotes weakness of the internal hip rotators since the lower abdominals help anchor them).  We would see a slight bellowing of the left abdominal group and a slight increased anterior pelvic tilt on the same side.  This asymmetrical pelvis posture would load the superior aspect of the right piriformis and force it into spasm due to the sustained pelvic obliquity and slight drop in the anterior direction.  This spasm can inhibit the gluteal group and further complicate the problem.  Keep in mind that a weak left oblique abdominal system would facilitate a tendency towards a sway back position, stretch weak left iliopsoas, and the anterior femoral glide syndrome of the hip (not to mention weak internal hip rotators).  As previously touched upon, activities of daily living such as sleep, stance and sit positions, driving style, handedness, respiration,  functional and anatomical leg length differences, unidirectional floor transfers and simply imbalances in the hip rotators can all cause this imbalance and thus piriformis dysfunction.  In summary, the key to the body in the above scenario is in its ability to create and control rotation.  The ribs, thoracic spine, foot and hips are the most important rotators of the body and their relationship is well established.  Even something as simple as respiration mechanics can be dysfunctional as a result of excessive computer use, reading, driving, sedentary lifestyle and sporting history (one sided dominant sports).  For these reasons, most individuals will be unable to rotate effectively and without compensation patterns so the rotational deficits frequently are expressed either upwards into the thoracic spine, ribs and shoulders (one way to see these problems is to look at shoulder posture and arm swing during gait) or they are expressed caudally into the pelvis at the hips. 

We are sure there is more in us on hip biomechanics but for now this 6 part series will have to suffice. We are putting it aside for now and will move back to some other issues on gait and  human movement so we do not get stale.  We hope you enjoyed our 6 part series.

Shawn and Ivo  (not just your average gait analysis doctors)

Hip Biomechanics: Part 5 of 6

Sagittal Plane Functional Biomechanics

Thus far we have discussed the hip biomechanics mostly in the frontal plane.  The sagittal plane mechanics are much less complex since the axis of movement is in the frontal plane (the axis is directed horizontally through the femoral heads and pelvis) and the body weight for the most part rests on this same plane (unlike the frontal plane mechanics where the body weight is a moment arm away from the center of the hip rotation).  One of the main reasons the mechanics are a little less complicated for the most part is due to the fact that even with the pelvic obliquity that occurs during gait cycles of swing and stance, the body weight still remains largely over this trans-femoral head axis. 

In the sagittal plane the prime movers are the abdominas and gluteals (flexion and extension of the hip respectively) with some help from the ilopsoas for hip flexion perpetuation. The calf compartment is also  helpful as is arm swing.  The hip flexor synergistic muscles are the quadriceps and abdominals while the hip extensor synergist is mainly the hamstring group.  This is certainly simplified since transaxial rotation through a vertical oriented axis does occur as a coupled motion and thus we cannot talk about sagittal plane movements, or even frontal plane movements for that matter, without at least considering the effects of movement generation or stabilization by the hip intrinsics (gemelli, oburators, quadratus femoris, piriformis). 

The greatest body function in the sagittal plane is gait and many of the body’s compensations and conditions stem from alterations in hip joint function through this movement negotiation through the sagittal space.  For the therapist, clinician or trainer the greatest problem can be the body’s numerous back-up systems which compensate and share normal or abnormal loading.

The basis of gait evaluation needs to be based from a holistic perspective.  Gait cannot be evaluated without consideration of the entire organism. A minor functional limitation in the first metatarsophalangeal (MTP) joint can significantly impact hip, pelvic and spinal biomechanics.  The best and simplest example of this is the clinical scenario of hallux limitus.  We will entertain the equally devastating functional hallux limitus later on in the chapter but the point to note here is that a minor loss of the last few degrees of the normal MTP joint dorsiflexion (45-60 degrees is necessary, patient specific) can be devastating to sagittal plane motion of the body.  Even a loss of the last 5 degrees of this normal range, although appearing relatively normal on an examination and possibly without symptoms (ie. early stages of progression into a more noticable hallux limitus), can impact normal and efficient toe off.  If toe off is early, even to a small degree, then the stance phase will be abbreviated via early heel rise.  If heel rise is early this creates a functional change in the kinetic chain, both open chain and closed chain.  There are many closed chain changes that will occur. One such change might be toe off propulsion forces being imparted through a more flexed tibiofemoral joint (knee) which will impart both translatory shear forces in the sagittal plane and torsional forces through the joint, both causing potential maceration effects on the menisci.  However, perhaps the easiest functional changes to understand are the changes at the hip.  It is well known on EMG studies that hip flexion is both an active and passive motion during gait.  The active flexion of the hip is generated largely by iliopsoas concentric contraction.  However, this is not the first mechanism to generate hip flexion.  In fact, hip flexion is first generated passively through engagement of the kinetic chain.  The first movement of the swing phase is rotational or torsional activation of the oblique pelvis through core activiation of the abdominal muscle group.  Through activation of the internal and external abdominal obliques and transversus abdominus, in addition to activation of their synergists and cocontration of their antagonistic stabilizers, the obliqued pelvis is rotated.  Better said, the trailing leg’s lagging pelvis is moved forward by contract of the synergistic oblique activation.  This forward movement generates a sagittal momentum and movement of the toe off leg.  Once movement is generated then the iliopsoas activates concentrically to perpetuate hip flexion.  In other words, the ilopsoas is not an initiator of hip flexion, rather, a perpetuator.  When hallux limitus limits the stride length via early generation of heel rise the pelvic obliquity is limited.  As a result, the degree of initial swing phase leg movement is less from the generation of pelvis de-rotation via abdominal activation and more through ill-directed iliopsoas hip flexion.  Thus, as hip flexion still needs to occur, the iliopsoas is called upon to compensate; it now becomes a hip flexion initiator as well as its previous function of hip flexion perpetuator.  This demand is minimal but with repetitive demand thousands of steps per day, the iliopsoas eventually looses its ability to continue these compensations, as does its now over burdened synergists.  The result is either hypertrophy, inhibition, hypertonicity, spasm, shortening, insertional tendonitis, origin tendonitis or a combination thereof but make no mistake, such burden will eventually cause dysfunction within the muscle itself or within its synergists or antagonistic pair.  The scenario may result in either joint dysfunction at the lumbar spine near the muscle’s origin, at the sacroiliac joint over which it crosses, or at the hip joint proper.  The ensuing joint derangement or dysfunction is complex and creates numerous compensation patterns locally and globally since the main function of the muscle is to create hip flexion, external rotation, and abduction in the open kinetic chain and trunk flexion and trunk internal rotation in the closed kinetic chain. In a nutshell, the loss of dorsiflexion of the hallux, even to a minor degree, must be made up somewhere in the sagittal plane.  If it is not immediately made up for at the more proximal joints (1st metatarsal-midfoot joint, talo-navicular, ankle mortise-tibiotalar, or knee) the hip will undoubtedly change its function as described above to compensate, it is well suited to do so.  Keep in mind that such compensations may be better suited at the ankle, knee or hip depending on the degree of hip ante/retrotorsion or tibial internal/external torsion if present but none the less these compensations have consequences to changes in function of muscles either eccentrically, isometrically or concentrically or by recruiting assistance from synergists or antagonistic groups.  Additionally, a person with a very flexible midtarsal joint may stop the more proximal compensations via restoration of the necessary first ray (first toe) complex dorsiflexion at that more immediately proximal joint complex. 

Shawn and Ivo (yup, that is Dr. Allen thinking he is a bad ass in the picture above, clay pigeon shooting and a cubano……. thinks he is Clint Eastwood or something. Regardless, don’t mess with The Gait Guys !).

Hip Biomechanics: Part 4 of 6

This diagram (Figure 4) also shows a balanced equation; HAM x D1 = D2 x BW.  (where HAM=hip abductor/g.medius, D1 and D1 are lever arms, BW= body weight). This is not exactly a desirable scenario or strategy to obtain when it comes to joint compression mechanics however it is close to representing what is accurate in the human hip.  Since the gluteus medius muscle is the primary joint compressor in the frontal plane (it applies two thirds of the compressive forces across the joint) we would ideally never want such a large HAM force.  Typically the internal to external moment arm ration is 2:1 thus this model would require a HAM force twice the body weight to maintain a balanced system.  None the less, we would want to offset these forces somehow.  The only way to offset the large HAM would be to move the pivot point closer to the BW thereby increasing the D1 (increase D1 and you can reduce HAM and thus joint compression load).  In a physical person the pivot point, the joint axis of movement, is fixed so there is no real strategy to improve the situation without surgery.  These patients are unlucky and have no strategies to improve their high compression forces unless they loose weight; due to the fact of the 2:1 ratio, for every pound of body weight loss there is a 2 pound force decrease in the HAM.  Obesity is going to wreak havoc on our populations hips.

As mentioned previously, the model presented is very much incomplete.  Muscular forces surround the joint, movement occurs in every cardinal plane and there is acceleration of body segments which requires even greater muscular contraction isometrically, concentrically and eccentrically.  These factors all considered, it has been calculated that the total hip force crossing the joint can reach 3 times the body weight during walking.   This force is welcomed for maintaining joint stability but it can be an unwelcome force in a degenerative arthritic joint where the cartilage is less pliable and flexible.  The loading forces in an arthritic joint rhythmically pass into the acetabulum and femoral head as a result of the compromised cartilage necessitating increased bone mass and sclerosis within them.  This compromised arthritic joint will have some minor laxity due to the loss of the cartilage bulk and thinning of the acetabular labrum.  Thus the joint will have a slight increase in translatory/accessory movement and require greater muscular contraction to minimize/stabilize these movements.  These increased forces will be unwelcomed as they will generate more pain.  Additionally, the increased movements and degenerative debris within the joint will cause irritation and inflammation of the joint capsule and synovial lining causing further pain.  This entire scenario will cause the patient to investigate conscious and subconscious gait strategies to reduce the compression across the joint, in other words, they will essentially seek gait strategies that will reduce HAM (gluteus medius contraction) and increase the D1 internal moment arm.  These strategies will reduce the perpendicular joint compression forces that likely will be causing pain but if performed well they will be devastating to the normal frontal plane equilibrium since the gluteus medius muscle will be essentially shut down and inhibited.  Thus, the patient’s gait strategy will give us the compensated Trendelenburg gait pattern.  The uncompensated Trendelenburg gait will show a dropping of the contralateral hemipelvis on the swing side during gait, this is the pathologic gait pattern we see when the patient has not implemented strategies to reduce their pain but it is more likely seen when the patient is not yet at the painful stage in which they need to implore strategies to avoid the movement.  Comparatively, compensated Trendelenburg gait pattern will display a lifting of the contralateral hemipelvis.  This strategy is not implemented by activation of the gluteus medius on the side in question, rather it is a compensation move performed by shifting the patient’s body weight over the pathologic hip thus causing the hip that is dropping to be passively raised into a more normal range in the frontal plane.  This passive frontal plane move by the patient over the painful hip is at first difficult to embrace logically as one does not expect to want to load their body weight further over top of the painful hip.  However, upon investigation of the mathematical equation one will see that the shift of body weight (BW) over the affected hip will significantly reduce the D2 external moment arm, significantly increase the D1 internal moment arm and thus deliver us the desirable significant reduction in the HAM gluteus medius compressive contraction across the painful hip.  Thus, the pathologic compensation gait pattern in the frontal plane will markedly reduce the patient’s hip pain.  From a kinetic chain perspective however, there is always a price to pay.  This implemented strategy of ipsilateral trunk lateral flexion is performed by utilization of the thoracolumbar paraspinals and quadratus lumborum on the painful hip side. The resulting abnormal muscular and joint strategies now imparted on the lumbar spine and pelvis interface frequently begins a cascade of muscular and joint pain in the low back and abnormal loading of the lumbar discs.  The strategy also begins an unwelcome increased loading of the non-painful hip as the patient is loading the hip greater than normal due to the height from which the hip and pelvis drop from the compensated Trendelenburg position.  In other words, by protecting the painful arthritic hip from increased loads we sacrifice the healthy hip for a period of years until the forced finally amount to enough damage that pain begins here as well.  Fortunately, we have the ability to mediate some of these dramatic movements and forces by using logic and a cane.  By placing a walking cane in the hand opposite to the painful hip and by asking the patient to contact the cane with the ground when they initiate contact with the painful limb we can offset some of the excessive compensations and forces.  When the cane contacts the ground the patient is to apply a mild to moderate downward force through the cane via arm contraction.  This downward force will afford us a resultant upward ground reactive force through the cane delivering us a lifting effect on the dropped hemipelvis side (dipping hip side/non-painful side).  This strategy will allow us a more passive shifting of the body weight (BW) over the painful hip side without having to lift or pull the body weight (BW) over the painful hip with the hip abductor muscles (HAM).  These passive forces (which can be more than  half of those normally needed to be generated by the HAM) will help to markedly reduce the muscular forces needed by the spinal and quadratus muscles while also rendering the desired marked reduction in HAM compressive forces across the painful joint.  It is interesting to note that the further the cane is placed from the body, the longer its moment arm and thus the less downward force necessary by the patient’s arm.  It is quite possible, that if used correctly, a cane can almost completely offset the required contralateral HAM force.  Another passive strategy would be to carry objects (purses, books, grocery bags, etc) on the affected hip side.  This action will also balance the teeter-totter  in favor and thus reduce the muscular forced necessary to perform the same task.  It must be noted however that increasing any body load is undesirable and should be avoided not so much because of issues pertaining to the painful degenerative hip but because of the increased load on the healthier hip.

Shawn and Ivo, The Gait Guys

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Hip Biomechanics: Frontal Plane Part 3

This diagram (Figure 3)  also shows a balanced HAM x D1 = D2 x BW equation.  The BW is larger than the HAM but this is offset in the rules of the teeter-totter.  Shifting the pivot point towards the larger mass is offset by the smaller D2 and larger D1 moment arms.  This is a typical compensatory mechanism used by obese patients to ambulate effectively.  It does render significant frontal plane movement of the pelvis instead of the more desirable silent frontal plane pelvis.  In this compensation, even large body weights can be somewhat offset by the degree of contralateral hip hiking to reduce the D2 moment arm and increase the D1 moment arm however this compensation has its limits.  When the limits of alteration of moment arm length are reached the body’s only compensation at that point is to increase the HAM forces which increases joint compression and thus cartilage wear since the cyclical loading and unloading of the cartilage is much less.  This is also the same mechanism used by patients with a osteoarthritic painful hip joint.  We are not referring to increasing BW, rather we are suggesting that to reduce pain the patient will want less joint compression and thus a reduced HAM.  To do this we want to increase the D1 moment arm. The only way other than surgery to achieve this increase in D1 is to take the existing body weight and shift it closer to the pivot point. Ideally you would want to lean so far over the affected painful hip as to get your body weight (BW) immediately over the pivot point. This is what is done with a walking cane in the opposite hand of the stance leg, to help lift the swing phase leg and pelvis and to push the body mass over the hip WITHOUT using more HAM (glute medius contraction generated compression, which would generate pain). This would effectively reduce D2 to nil and significantly increase D1 thus allowing HAM to be minimal; thus reducing painful joint compression.  (In teeter-totter verbiage, put the small child on the long part of the teeter-totter arm and you can move large forces with little effort at the pivot point.) 

Hip Biomechanics Part 2

Figure 1 shows the condensed version of the parameters (forces and moment arms) affecting movement and stability of the femur-acetabulum complex in the frontal plane during the closed kinetic chain.  (A moment arm such as D1 and D2 is defined as the length of a line that extends from the axis of rotation to a point of right angle intersection with a respective force, in this case HAM or BW.)

In Figure 1 above we see several parameters.  HAM represents the Hip Abductor Muscles, D1 represents the internal moment arm, D2 represents the external moment arm and BW represents the Body Weight of the individual.  These factors all come into play when considering the frontal plane equilibrium of the hip joint.  The equation representing the interaction of all of these parameters is HAM x D1 = D2 x BW.  Both sides of this equation must be equal and balanced in order for the pelvis to remain stable and without movement when in the closed chain stance phase of gait. In this diagram, if the left side of the equation is greater than the right the net effect will be a counterclockwise hip moment and the patient will move their torso over the hip creating a hiking or lifting of the contralateral hip.  This net movement will create abduction at the hip joint.  If the right side of the equation is greater than the left the net effect will be a clockwise hip moment and the patient will move their torso away from the hip creating a dropping of the contralateral hip.  This net movement will create adduction at the hip joint seen here and thus the classic Trendelenberg gait.  We need to keep in mind that this is not a perfect model presented here since we are ignoring acceleration of the body in the forward sagittal plane and rotational planes.  Investigating the equation further should bring the reader to further realization that if the body weight (BW) were to increase, mathematically the D2 external moment arm could decrease to keep the equation balanced.  However, since the length of this D2 moment arm is rather fixed (unless the pelvis were to go through a counterclockwise  rotation which would draw the body weight center closer to the hip joint center effectually abducting the stance hip, thus reducing the D2 moment arm) this is not a more likely scenario. Rather, the response would be to attempt to increase the left side of the mathematical equation thus increasing the HAM forces to attempt to keep the pelvis level and the equation from changing.  In other words, when body weight increases we must increase the gain or contraction in the HAM group during each step to keep the pelvis level and balanced.  Unfortunately the HAM strength has its limits of maximal contraction, sometimes far below any major increases in body weight.  One must keep in mind that with increased HAM contraction there is a corresponding increase in joint compression across the hip articular surfaces which at reasonable levels is well embraced but at unreasonable levels can damage articular cartilage.  One should thus conclude that maintaining a reasonable body weight for one’s bone structure keeps the right and left sides of the mathematical equation at tolerable levels, both for movement, stability and cartilage longevity.  Fortunately the equation has a built in safety mechanism for these counterclockwise hip moments, one that is beneficial.  In such scenarios, as the body is brought over the hip thus decreasing the D2 moment arm, the D1-internal moment arm increases in length and since the equation must be balanced the HAM force can decrease.  Thus, the magnitude of the HAM force is inversely proportional to the length of the D1-internal moment arm.  The whole equation can better be visualized and conceptualized by a teeter totter diagram with a sliding pivot point.

Shawn and Ivo,  The Gait (and biomechanics) Guys

Fundamental Hip Biomechanics: Part 1

Hip Biomechanics

The following excerpted text is copywrited from the textbook; “Form and Function: The Scientific Basis of Movement and Movement Impairment” (Dr. S. Allen, Dr. E. Osar)


Frontal Plane Functional Biomechanics

The hip is a very complex joint.  It is a ball and socket joint with great stability and potentially great mobility.  One of the most critical and essential planes of motion and stability is the frontal plane of hip joint motion.  This plane (coronal/frontal) of motion and stability is largely determined by the hip abductor muscle (HAM) group through an axis of oriented in the anterior-posterior direction through the head of the femur.  The most obvious and simple function of the hip abductor muscles is to produce a movement or moment of abduction of the femur in the acetabulum in the frontal/coronal plane (as in a side lying leg lift).  As mentioned, this is a simple way to determine open kinetic chain range and open chain strength in this range but it is neither true nor transferable in theory or practicality when the foot is on the group.  When the foot engages the ground the typically usable functional range is much less and the muscular function is now to move the pelvis on the stable and somewhat static femoral head in the frontal plane.  Explained in another way, in this closed chain, the insertion of many muscles remains static and the force generated through the muscle will pull at the origin and generate movement at the joint in this manner.  In a nutshell, the hip abductor muscles (HAM) will produce either leg motion to the side (abduction) or it will produce a lateral bending or lateral flexing of the pelvis-torso into the same range of motion (abduction). 

The most critical and commonly considered hip abductor muscles (HAM) are the gluteus medius, gluteus minimus and tensor fascia lata-iliotibial band complex.  These muscles have the most favorable line of pull and all have a femur and pelvis attachment.  We will call these muscles collectively the HAM group.  In the stance phase of gait the body’s center of gravity (COG) is medial to the hip joint axis of motion.  Thus, in this single leg support phase of gait the tendency will be for the body mass above the hip to rotate or drop towards the swing leg side.  This gravitational movement should be offset by the concentric, isometric and eccentric muscular activation of the HAM group through the anterior-posterior oriented axis through the head of the femur.  Any functional strength deficits (concentric, isometric or eccentric) of the HAM group and/or neighboring synergistic stabilizers will result in an altered joint stability challenge because not only do the HAM and surrounding muscles product movement but they also generated joint compression and thus stability.  The possible undesirable outcome may be an altered movement patterning characterized by inappropriate muscle or muscle group activation in either timing, force, speed or coordination with typically coupled muscles.  These challenges to the joint and its normally expected movement patterns will result in the body’s search for more stable positions in the frontal, sagittal or oblique planes.  These newly established, yet less efficient, positions and patterns of movement are initially welcomed compensations but in time as the new accommodations become rooted in pattern the synergists and other recruitments become overburdened and further demand compensations from other neighboring muscles eventually resulting in pain, joint derangement and dysfunction.  These compensations in recruitment and movement eventually will lead to non-contractile soft tissue changes such as hip capsule pattern changes in tension and length. These non-contractile soft tissue changes can not only dictate or perpetuate the newly established aberrant joint movements but help engrain the abnormal movement patterns and their new neurologic patterns.  

Gait Video Analysis: Olympian Carl Lewis.

Carl Lewis: arguably one of the great runners of the 20th century, especially in form.

Today we are going to use this video to look at a few specific components.

First, lets compare his front on technique to Lauren’s from yesterday.  Notice the total lack of limb cross over? Lauren showed almost a “running on a line” where as Carl is running on two lines. This requires more gluteal strength, and if you can get to a position to train it you can make it stronger.  You will also notice that with Carl’s reduced cross over the tibia are vertical and the degree of foot pronation is minimized thus affording less time in the dampening pronation contact phase in comparison to Lauren. 

Now lets talk about the gluteus maximus for a minute.  The function of the G.Maximus is multifactorial. The G.Max is mostly silent at low activity levels such as level and uphill walking, but it increases substantially in activity and alters its timing with respect to speed during running.

The G.Max controls trunk flexion on the stance-side and it contracts in the late swing phase (when the leg is finishing it’s swing in front of our body) through early stance phase to decelerate hip flexion and initiate hip extension. There is lessening gluteal contraction at toe off but the medial bundle (more sacral divisions) offer a brief burst of force. So, if you look at its activity levels and the timing of them, you will get the distinct sense that the gluteus maximus function is to pull the leg through hip extension. The key word here is PULL.  Remember, the foot is fixed to the ground in the stance phase. So as the glute fires in the early half of stance phase, when the hip is still in relative flexion, it pulls us through the stance phase thus driving us forward. Mind you, the core must be strong enough to hold the pelvis static so that the extension can occur through the hip and not travel upwards to create lumbar extension. You can get a great sense of this in Carl Lewis’ video above.  Many people see the G.Max as a push off muscle but this is not true. It is more of a pull muscle, pulling us forward on the ground as opposed to pushing us forward .

Want to do some precision work to focus on the feeling of the glutes “pulling you through”, then try some hip-glute extension pull throughs (click) with a cable crossover on the bottom setting or heavy kettlebell or sandbag swings (click). Best of all to get the feel of what the glute max does …… grab a skateboard and plant one foot on the board and begin pulling yourself through the stance phase with the leg…..after all that is what you are doing, pulling yourself through.  Of course form is everything, so be careful and focus on slow movements that are clean and precise. Just do one thing when you do either of these.  Feel the foot contact and imagine the hips and glutes driving forward on a stiff protected core while you feel the posterior drive through the foot.  This is likely the feeling Carl would be aware of in his feet at the 10-15 second mark in the video. 

Some readers will jump at the opportunity to say “hey, Carl is a sprinter, Lauren is a distance runner…… you cannot compare apples and oranges !"  Our response here is , yes that is correct.  But they are not that different, look at the kick in the end of close a distance race…..are they really that much different ?"  But what we really need to say here on that question is, "That was not the point of this exercise. We are looking at flaws here."  If we asked Lauren to sprint, we would see the same pattern as in her video here.

Shawn and Ivo………. just a couple of nerds always wondering why everyone else is in the box and we are standing outside of it.  It’s not fair.

Dr. Shawn Allen discusses Gait Biomechanics again, this time pure hip biomechanics and how it applies to gait and running and compensation patterns. This is Part 1 of 2 of the Hip Biomechanics. This is essentially applied biomechanics.