Leg Stiffness

The difficulty in following this thread has not been that I don't understand the material. Rather, it has been that, between you and Michael Weber, about 100 new posts have been generated to read in the last nine days, which prevents me from reading all the posts thoroughly. Lots going on now with my lecture in Rome coming up, keeping up on the barefoot running stuff, practice, vacation, etc. What I do know is that, at this rate you will pass me as "most posts" in about 3 months here on Podiatry Arena.

Like you said, I knew somewhat of what you were talking about describing leg stiffness, but then you started asking about bending moments which I think is quite different from leg stiffness, so I was unclear what you were exactly talking about.

And finally, I am not sure of the frontal plane movement (side to side sway) of the center of mass (CoM) during running. My guess is there is less frontal plane movement of the CoM in slower running speeds and a minimal frontal plane movement of the CoM at faster running speeds due to the increased double float phase length and decreased support phase percentage of total gait cycle as running speed increases. In other words, at jogging speeds the CoM moves more side to side than during faster running speeds where it moves less side to side.

 

BTW, before anyone gets confused the vertical leg stiffness will be the same in the frontal and sagittal planes.

I started asking about bending moment because you wrote:

So I asked about the relationship between vertical leg stiffness and bone bending. Given the apparent relationship between a stiffer leg and bone pathology, does a stiffer leg result in increased bone bending?

 

I found this but just the abstract.

 

http://www.mendeley.com/research/le...relationship-with-sprint-running-performance/
http://www.mendeley.com/research/le...ss-as-ability-factors-in-100m-sprint-running/

This perhaps has implications for the barefoot running debate:

http://www.mendeley.com/research/a-...n-running-and-running-shoe-bending-stiffness/

http://www.informaworld.com/smpp/content~content=a780769753&db=all

 

I know this is a question for Kevin, But I was thinking about this and I´m not sure if I´m on the correct path but....

Stiffer leg increased compression from bone to bone ie femur to tibia, tibia to talus increased bending moments.

In the less stiff leg the knee flexes more which changes the angle of compression femur to tibia and I´m guessing reduced the load on the tibia less bending force. Also the more the knee flexes the more energy is lost which might reduce the bending moment, but I´m just thinking out load.

 

Examples of ZOOLS for different activities.

 

Example of maintaining ZOOLS as footwear stiffness properties change with wear:
http://bjsm.bmj.com/content/43/10/745.abstract

 

backs up the "less is more" new ideas in running shoes arguement.

 

http://pt2.usc.edu/labs/mbrl/pdfs/B... tibial stress fracture in female runners.pdf

"McMahon et al. (20) have shown that
running with exaggerated knee flexion (Groucho running)
reduces the effective vertical stiffness of the lower
extremity and causes the runner to attenuate more shock
between the shank and head, compared with normal
running. Conversely, if knee joint excursion is decreased,
greater lower extremity stiffness will likely result. A ‘‘stiff’’
runner has been shown to spend less time in contact with the
ground (7) and attenuate less shock (20). This may also
increase their risk of TSF [tibial stress fracture]".

 

This is the conclusion from another study by the some of the same Folks.

Thanks for putting the full paper up Ian I missed it yesterday. ( page 5 post 150 if anyone else missed it )

Are knee mechanics during early stance related to tibial stress fracture
in runners?
Clare E. Milner a,*, Joseph Hamill b, Irene Davis c,d

So it´all comes back to the initial loading phase.

 

Anyone got a full text of this please?:
http://www3.interscience.wiley.com/journal/120122878/abstract?SRETRY=0

 

in the paper (Are knee mechanics during early stance related to tibial stress fracture in runners? Clare E. Milner a,*, Joseph Hamill b, Irene Davis c,d)

that I Quote above they also had this to say about Groucho running. I still need to read it it detail.

 

This one is interesting looks at the effects of "semi-rigid devices" (whatever they are?) on leg stiffness etc.

http://people.umass.edu/jhamill/PDF/Laughton, McClay & Hamill, 2003.pdf

Decreased knee flexion, increased stiffness, yet the devices must have increased the surface stiffness beneath the foot...

 

My firewall won´t let me see the Abstract, I did try and look. Maybe cut and paste in the abstract ?

 

Here you go Mike:
Review
A review of research on the mechanical stiffness in running and jumping: methodology and implications
M. Brughelli 1 , J. Cronin 1,2
1 School of Exercise, Biomedical and Health Sciences, Edith Cowan University, Joondalup, WA 6027, Australia, 2 Institute of Sport and Recreation Research New Zealand, Auckland University of Technology, Auckland 1020, New Zealand
Corresponding author: M. Brughelli, School of Exercise, Biomedical and Health Sciences, Edith Cowan University, 100 Joondalup Drive, Joondalup, Western Australia 6027. Tel: 0061 86304 5152, Fax: 0061 86304 5036, E-mail: m.brughelli@ecu.edu.au
KEYWORDS
stiffness • spring • running • jumping
ABSTRACT
Mechanical stiffness (vertical, leg and joint stiffness) can be calculated during normal human movements, such as running and hopping. Mechanical stiffness is thought to influence several athletic variables, including rate of force development, elastic energy storage and utilization and sprint kinematics. Consequently, the relationship between mechanical stiffness and athletic performance is of great interest to the sport and research communities. Unfortunately, these relationships are relatively unexplored by researchers. For example, there are no longitudinal studies that have investigated the effects of strength or power training on mechanical stiffness levels (calculated during human running). In addition to reviewing the available literature on the relationships between mechanical stiffness (calculated during human running) and functional performance, this review focuses its discussion on the various equipment and methods used to calculate leg-spring stiffness during human running. Furthermore, future implications are presented for practitioners and researchers based on both the limitations and the gaps in the literature reviewed. It is our hope that a better understanding of mechanical stiffness will aid in improving the methodological quality of research in this area and its subsequent effect on athletic performance.

 

No orthosis versus soft orthosis versus rigid orthosis = no difference in leg stiffness.
Foot Ankle Int. 2003 May;24(5):410-4.
Dual-function foot orthosis: effect on shock and control of rearfoot motion.
Butler RJ, Davis IM, Laughton CM, Hughes M.

Department of Physical Therapy, University of Delaware, Newark, DE 19716-2591, USA. rbutler@udel.edu
Orthoses have been designed that claim to both reduce shock and control rearfoot motion. It was hypothesized that the dual-purpose soft orthosis would reduce shock and control rearfoot motion greater than a no-orthotic condition. Three-dimensional kinematic and kinetic data were collected along with tibial acceleration while subjects ran in no-orthotic, the dual-purpose orthotic, and a rigid orthotic condition. Variables of interest were eversion excursion, peak eversion, eversion velocity, peak positive acceleration, loading rate, and leg stiffness. None of the evaluated variables were significantly different (p = .05) between the three conditions. These data suggest that shock attenuation and rearfoot motion cannot be controlled by the orthoses used in this study for a group of healthy runners.

Yet:
Interaction of Arch Type and Footwear on Running Mechanics
Robert J. Butler, PhD*,†, Irene S. Davis, PT, PhD‡,§, and Joseph Hamill, PhD||
+ Author Affiliations

From the †Department of Exercise and Sport Science, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, ‡Department of Physical Therapy, University of Delaware, Newark, Delaware, §Drayer Physical Therapy Institute, Hummelstown, Pennsylvania, and ||Department of Exercise Science, University of Massachusetts, Amherst, Massachusetts
Address correspondence to Robert J. Butler, PhD, University of Evansville, Department of Physical Therapy, 1800 Lincoln Ave, Evansville, IN 47722 (e-mail: robertjbutler@lycos.com).
Abstract

Background: Running shoes are designed to accommodate various arch types to reduce the risk of lower extremity injuries sustained during running. Yet little is known about the biomechanical changes of running in the recommended footwear that may allow for a reduction in injuries.

Purpose: To evaluate the effects of motion control and cushion trainer shoes on running mechanics in low- and high-arched runners.

Study Design: Controlled laboratory study.

Methods: Twenty high-arched and 20 low-arched recreational runners (>10 miles per week) were recruited for the study. Three-dimensional kinematic and kinetics were collected as subjects ran at 3.5 ms−1 ± 5% along a 25-m runway. The motion control shoe evaluated was the New Balance 1122, and the cushioning shoe evaluated was the New Balance 1022. Repeated-measures analyses of variance were used to determine if low- and high-arched runners responded differently to motion control and cushion trainer shoes.

Results: A significant interaction was observed in the instantaneous loading rate such that the low-arched runners had a lower instantaneous loading rate in the motion control condition, and the high-arched runners had a lower instantaneous loading rate in the cushion trainer condition. Significant main effects for shoe were observed for peak positive tibial acceleration, peak-to-peak tibial acceleration, mean loading rate, peak eversion, and eversion excursion.

Conclusion: These results suggest that motion control shoes control rearfoot motion better than do cushion trainer shoes. In addition, cushion trainer shoes attenuate shock better than motion control shoes do. However, with the exception of instantaneous loading rate, these benefits do not differ between arch type.

Clinical Relevance: Running footwear recommendations should be based on an individual’s running mechanics. If a mechanical analysis is not available, footwear recommendations can be based empirically on the individual’s arch type.

 

I get this journal so have hard copy in my hand now. I ring tomorrow and find out how to get a pdf off the net.

 

Foot type determines leg stiffness-
Foot Ankle Int. 1998 Nov;19(11):761-5.
Leg stiffness and foot orientations during running.
Viale F, Dalleau G, Freychat P, Lacour JR, Belli A.

Laboratoire de Physiologie de l' Exercice, Faculté de Médecine Lyon-Sud, Oullins, France.
This study was done to determine whether leg stiffness (Kleg) during running was related to rearfoot-to-forefoot angle in standing (RFAst) and running (RFArun). Footprints obtained from 32 subjects were used to calculate RFAst and RFArun, defined as positive when forefoot axis was abducted from rearfoot axis. A spring-mass model was used to calculate Kleg in running from ground reaction forces, measured by a force platform. The Kleg of runners (13.0 +/- 2.7 kN x m(-1)) was negatively correlated with RFAst (-8.4 degrees +/- 6.4 degrees) and RFArun (-0.4 degrees +/- 7.2 degrees). When runners were divided into opened foot (RFArun > 0; N = 19) and closed foot (RFArun < 0; N = 12) groups, the Kleg of opened foot runners was less than that of the closed runners. We suggest that foot structure is a factor responsible for the differences in leg stiffness observed in runners.

If they performed regression analysis, it should be possible to predict leg stiffness based on this simple measure of foot type.

 

Kevin's post got me thinking, If we calculate vertical leg stiffness as load / vertical displacement of the CoM it will be the same in the sagittal and frontal planes because the vertical displacement of the CoM will be the same whether we look at it from the front or the side. But while the net stiffness of the lower limb will be the same, the segmental stiffness will be variable between planes and between segments.

The vast majority of the research we have reviewed has looked at the net vertical leg stiffness, perhaps by looking at the big picture we are missing the detail, and that detail may be significant.

I spoke about this earlier, but perhaps worth a revisit: lets say we are looking at sagittal plane segmental stiffness (stiffness = load / displacement) if the stiffness of one segment increases, the stiffness of another segment must decrease in order to maintain the net leg stiffness- this is evidenced by the classical postural changes reported by Howard Dananberg. Looking at frontal plane stiffness: decreased rearfoot stiffness (increased rearfoot pronation) should mean that the frontal plane stiffness of other segments is increased- evidenced by? Any thoughts Kevin?

A medially deviated subtalar joint axis will result in a decrease in pronation stiffness at the subtalar joint, increased subtalar joint pronation results in increased tension in the plantar fascia, increasing midfoot pronation stiffness? Increasing 1st MTP pronation stiffness? More or less knee flexion with more pronation?

 

Question: how does each joint/ segment reduce its contribution to the net leg stiffness in each plane?
So we know that in the sagittal plane that increased hip flexion will reduce net leg stiffness, but does internal or external rotation in the transverse plane alter the net limb stiffness too? What about frontal plane position of the hip? What position would result in the net least stiffness that the hip contributes to the total leg stiffness?

What about the knee, rearfoot, midfoot, and forefoot segments? If we were designing a limb to have the least vertical stiffness what position should we place all of the joints/ segments in?

 

I´ll go with more knee flexion with pronation from our weekend school of silly walks discussion.

All good questions which I´ve no idea. Ive only read compair and contrast type papers. ie these people have stiffer legs than those . Thats looks think 1000´s hours of research there alone.

 

.....

 

All but one the 2nd one attached (its not available online)

 

This is one used in the barefoot debate a lot

 

Thanks, Ian.

 

Nice one Ian . Some sort of information overload at the min.

 

Simon:

Once the maximally pronated position of the subtalar joint (STJ) has been reached, then STJ pronation stiffness will increase significantly due to interosseous compression forces within the sinus tarsi. Since most patients with medially deviated STJ axes spend much of stance phase maximally pronated at the STJ, and therefore will have increased STJ pronation stiffness during stance phase, these individuals may suffer from the effects of increased STJ pronation stiffness since they will have decreased STJ pronation motion during contact phase to help absorb the impact shock of walking. Whether this causes any effect on sagittal plane stiffness of the knee and ankle, I couldn't say.

 

Thanks, Kevin. You are right of course. So is the increased STJ pronation stiffness an attempt to stiffen the limb due to increased compliance further up the chain?

Craig seems to think the tibia drives the foot, not the other way around. Knee flexion seems to be coupled with internal tibial rotation, increased knee flexion = reduced leg stiffness. Increased knee flexion = increased tibial internal rotation resulting in increased STJ pronation and with that, medial deviation of the STJ axis, STJ maximally pronated = increase in STJ stiffness = increase in net leg stiffness to compensate for the decrease due to the knee?

SO if we have decreased leg stiffness due to increased knee flexion, is the body trying to increase stiffness at heel strike via stiffening the STJ by driving it toward its end of range?

 

or is the body trying to further reduce the leg stiffness but runs out of ROM =pathology

 

Nice!

 

Simon:

Leg stiffness is simply a measure of the load versus deformation characteritics of the lower extremity and may not be directly related to subtalar joint (STJ) pronation/supination moments.

The end range of STJ pronation, the maximally pronated rotational position, will cause more STJ pronation stiffness since the STJ will pronate less with increasing magnitudes of STJ pronation moment when the STJ is in the maximally pronated position. On the other hand, for example, the STJ neutral position, is a relatively compliant STJ rotational position so that there will be less required external STJ pronation or STJ supination moments necessary to cause a given angular rotation of the STJ joint, all others factors being equal.

Midtarsal joint (MTJ) stiffness is, I think, is very interesting and quite different from the STJ in regard to its load vs. deformation characteristics. The MTJ becomes much more stiff with increasing weigthbearing loads on the forefoot due to the large increases in tensile forces within the plantar fascia and plantar ligaments and large increases in interosseous compression forces within the joints of the MTJ and midfoot.

Very important is the fact that stiffness of the MTJ/midfoot joints within the sagittal plane (i.e. forefoot dorsiflexion stiffness)will increase with a more normal STJ axis spatial location when compared to a medially deviated STJ axis spatial location since in a normal STJ axis location, the talus head and neck are aligned more superior to the anterior calcaneus. This increased "stacking" of the talar head/neck on top of the anterior calcaneus results in a greater vertical distance from the dorsal compression forces acting at the talo-navicular joint and the plantar tensile forces within the plantar fascia , thereby giving a greater resistance to bending moments at these joints than if the STJ axis was medially located which would, in turn, result in the talar head/neck being more plantarly located relative to the anterior calcaneus so that the vertical distance from the talo-navicular joint to the plantar fascia was reduced.

It is a common observation that bending stiffness in lumber is also increased when the bending force is applied along the thinner side of the board so that the thicker side of the board is resisting the bending forces. In other words, walking on the 1.5" side of a 2 x 4 board will bend the board less than when walking on the 3.5" side of the same board, with both examples being done with the board being supported by bricks at its ends. The same mechanical principles may be applied to the midtarsal/midfoot joints to help explain the common observation that pes planus deformities have reduced forefoot dorsiflexion stiffness when compared to the pes cavus deformities.

Sounds like a topic for another paper, Simon.:drinks

 

Kevin,
Thanks for your reply. I'll perhaps come to rest later, but for now:

But foot type is related to leg stiffness:


Foot Ankle Int. 1998 Nov;19(11):761-5.
Leg stiffness and foot orientations during running.
Viale F, Dalleau G, Freychat P, Lacour JR, Belli A.

Laboratoire de Physiologie de l' Exercice, Faculté de Médecine Lyon-Sud, Oullins, France.
This study was done to determine whether leg stiffness (Kleg) during running was related to rearfoot-to-forefoot angle in standing (RFAst) and running (RFArun). Footprints obtained from 32 subjects were used to calculate RFAst and RFArun, defined as positive when forefoot axis was abducted from rearfoot axis. A spring-mass model was used to calculate Kleg in running from ground reaction forces, measured by a force platform. The Kleg of runners (13.0 +/- 2.7 kN x m(-1)) was negatively correlated with RFAst (-8.4 degrees +/- 6.4 degrees) and RFArun (-0.4 degrees +/- 7.2 degrees). When runners were divided into opened foot (RFArun > 0; N = 19) and closed foot (RFArun < 0; N = 12) groups, the Kleg of opened foot runners was less than that of the closed runners. We suggest that foot structure is a factor responsible for the differences in leg stiffness observed in runners.

We also have the observation of William's et al. that high-arched feet are associated with stiffer legs than low arched feet:

Gait and Posture 19 (2004) 263–269
High-arched runners exhibit increased leg stiffness
compared to low-arched runners
Dorsey S. Williams III a,∗, Irene McClay Davis b,c, John P. Scholz c,e,
Joseph Hamill d, Thomas S. Buchanan e
a Department of Physical Therapy, East Carolina University, Greenville, NC 27858-4353, USA
b Joyner Sportsmedicine Institute, Harrisburg, PA 17111, USA
c Department of Physical Therapy, University of Delaware, Newark, DE 19716, USA
d Department of Exercise Science, University of Massachusetts, Amherst, MA 01003, USA
e Center for Biomedical Engineering Research, University of Delaware, Newark, DE 19716, USA
Accepted 14 May 2003
Abstract
Leg stiffness between high-arched (HA) and low-arched (LA) runners was compared. It was hypothesized that high-arched runners would exhibit increased leg stiffness, increased sagittal plane support moment, greater vertical loading rates, decreased knee flexion excursion and increased activation of the knee extensor musculature. Twenty high-arched and 20 low-arched subjects were included in this study. Leg stiffness, knee stiffness, vertical loading rate and lower extremity support moment were compared between groups. Electromyographic data were collected in an attempt to explain differences in leg stiffness between groups. High-arched subjects were found to have increased leg stiffness and vertical loading rate compared to low-arched runners. Support moment at the impact peak of the vertical ground reaction force was related to leg stiffness across all subjects. High-arched subjects demonstrated decreased knee flexion excursion during stance. Finally,
high-arched subjects exhibited a significantly earlier onset of the vastus lateralis (VL) than the low-arched runners. Differences exist in leg stiffness and vertical loading rate between runners with different foot types.

Since STJ position will in part determine both the forefoot to rearfoot ab/ adduction and the height of the arch, I don't think we can ignore the role of the STJ moments in leg stiffness.

I think so.

 

You could be right.:drinks

 

So, if foot type is in part related to leg stiffness, and when running barefoot we reduce leg stiffness due to the lack of shoe cushioning, we have a situation where the decrease in leg stiffness required for the harder surface should be fine for those functioning at the upper to mid end of the zone of optimal leg stiffness (ZOOLS) but running barefoot may place those with a lower leg stiffness to begin with (more pronated foot/ lower arch height) at a greater risk of dropping below the (ZOOLS) and experiencing pathology. Unless, they can change their foot-type. Interestingly, the barefoot running proponents report an increase in arch height with barefoot running. If this is real, this is very interesting. We need a prospective study of arch height in barefoot runners. Is this what this shows - full text if you can please Mr Griffiths?:

Med Sci Sports Exerc. 1987 Apr;19(2):148-56.
Running-related injury prevention through barefoot adaptations.
Robbins SE, Hanna AM.

A number of reports indicate an extremely low running-related injury frequency in barefoot populations in contrast to reports about shod populations. It is hypothesized that the adaptations which produce shock absorption, an inherent consequence of barefoot activity and a mechanism responsible for the low injury frequency in unshod populations, are related to deflection of the medial longitudinal arch of the foot on loading. It is also hypothesized that the known inability of this arch of the shod foot to deflect without failure (foot rigidity) is responsible for the high injury frequency in shod populations. To evaluate these hypotheses, 17 recreational runners were analyzed to study the adaptive pattern of the medial longitudinal arch of the foot due to increased barefoot weight-bearing activity. Changes occurred in the medial longitudinal arch which allowed deflection of this arch on loading which substantiated the hypotheses. Other evidence suggests that sensory feedback largely from the glabrous epithelium of the foot is the element of barefoot activity which induced these adaptations. The sensory insulation inherent in the modern running shoe appears responsible for the high injury frequency associated with running. The injuries are considered "pseudo-neuropathic" in nature.

Question: if I had a low arched foot, what changes in muscle function could turn it into a higher arched foot?

 

Sorry sir - sadly my subscription only gets me full pdfs from 1996 to present.

 

Craig is aways talking about the neuropathic changes of Diabetic patients with weakened foot intrinsics muscles getting a higher arch, so there is one reason the other way thru muscle use that I can think of would be increased strength of the Tib Ant possibly having greater effect over navicular drop, but I recon it´s pretty iffy.

 

To quote directly from the article:
Practical implications​

•

To maximiseVforward during the last stage of a 400msprint,

maintaining a faster ​

fstride through retaining a higher Kvert

​

​

would be necessary.
•

Increases in muscle activation levels and changes in touchdown

joint angles might be a key to retain a higher ​

Kvert.

​

​

•

When runners feel fatigue, they might benefit from paying

more attention to the maintenance of ​

fstride, rather than
focusing on maintaining Lstride.​

 

I went looking for this thread, they discuss foot intrisic muscle,

http://www.podiatry-arena.com/podiatry-forum/showthread.php?t=395

The point that Craig and Kevin were making at the start were that the plantar intrinsic don´t begin to work until the heel begins to unload from the ground but in ff striking the heel does not come incontact with the ground 1st- this In my thinking would load up the plantar intrinsic muscle alot. They may then get stronger with increased load- training effect. If the plantar intrinsic muscles help to support the arch and they are now stronger maybe there could be an increase in arch height when standing in midstance. the big question increased arch height is that a good thing? as increased arch height population was shown to have increased leg stiffness Williams et al.

 

Depends where they are in the ZOOLS before they take up barefoot running. If they are already at the upper end of the ZOOLS, increasing arch height could push them into the too stiff range = pathology. If they start out lower down in the ZOOLS, then it could be a good thing.

 

A good point.

2 points that Ive been considering over the last 2 days on this subject.

1 clinically how do we determine leg stiffness and when is a patient in ZOOLS or not at the moment I´m thinking linked to pathology.

2 When or how to determine when changes in leg stiffness are mechancial or CNS driven ?

ie in the discussion Simon and Kevin were having last night about STJ axis and pronation moments.

if we take a person will a medially deviated axis- RF striker . When the heel comes incontact with the ground the GRF lateral to the STJ axis will cause a external stj moment, being a heel striker the CNS system will it seems reduce the leg stiffness which is seesm lead to STJ pronation moments as well. So am questioning from the 2 eggs which one becomes a chicken.
ps maybe the example is not the best as both lead to stj pronation, but I guess thats the point of some of Niggs work, It is just been a sticking point, thought I would share.