Today’s post is a very nice follow up to the one earlier in the week entitled “Materials: do soft soles improve running shoes?”……which also commented on client perceptions of the footwear.  We hope the shoe and R&D companies are paying close attention to the work were are making available here. 

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Today…..

Perceiving is believing

What you think matters! Perception of shoe cushioning seems congruent with what you believe.  If you THINK the cushioned shoe will be softer, you will probably perceive it as so, even though there may be little to no change in ground reaction forces. Most studies show cushioned shoes actually INCREASE impact forces.

 

McCAW, STEVEN T.; HEIL, MARK E.; HAMILL, JOSEPH: The effect of comments about shoe construction on impact forces during walking

Medicine & Science in Sports & Exercise: July 2000 – Volume 32 – Issue 7 – pp 1258-1264

journal link:

http://journals.lww.com/acsm-msse/Abstract/2000/07000/The_effect_of_comments_about_shoe_construction_on.12.aspx

conclusions as quoted in their article:

Footwear designers incorporate a variety of midsole materials and mechanical systems to cushion shock while controlling rearfoot motion. To market shoes, advertising copy and the claims of salespeople often extol the benefits of the materials and design incorporated in a shoe. This marketing strategy is common, as evident from a perusal of a fitness magazine, in spite of a paucity of unbiased biomechanical testing of the validity of many of these claims, and a lack of understanding of how such claims may influence the gait behavior of a purchaser of a pair of shoes.”

It is vital to understand their next research finding from this study,

“The results indicated the impact ground reaction force varied as a function of the advertising message. When subjects were informed that a particular surface provided additional cushioning, impact ground reaction force data were higher (121% of body weight) than when subjects were provided with a warning message (110% of body weight). The results were interpreted as suggestive of subjects moderating impact in accordance with the expected cushioning of the material. That is, subjects were less inclined to use a landing strategy that would reduce impact force if they had been told that cushioning would be provided by the surface material. The study raises the question of how subjects would respond if the cushioning characteristics of a shoe, rather than a landing surface, were altered, because a shoe represents a more personalized aspect of the foot/ground interface.”

From their study they referenced Robbins and Waked:

“Robbins and Waked (15) demonstrated that subjects may be deceived into accepting higher forces during landing if provided with misleading information regarding the energy absorbing characteristics of the landing. Because of research suggesting a possible cause of lower impact peaks in harder shoes to be an intrinsic avoidance mechanism (1), it may be theorized based on expectancy theory that influencing someone to believe that one shoe can absorb more energy than another may result in different ground reaction force values. Contrary and sometimes confusing findings in the literature emphasize the need for further study in the area of perception and energy absorption. The purpose of this study was, therefore, to determine the effect of investigator comments regarding shoe construction on the ground reaction force measured during walking.”

This is an excellent article that seems to suggest that there is far more to it than the engeneering that goes into the shoe. That marketing and consumer assumptions are a part of how a shoe is used and works. 

Very interesting !  We hightly recommend you purchase this article here…..

http://journals.lww.com/acsm-msse/Abstract/2000/07000/The_effect_of_comments_about_shoe_construction_on.12.aspx

Part 2 of a case study from Northern Ireland. This video discusses the dynamic findings and how they correlate clinically with the history. Treatment recommendations are discussed as well.

Follow up question from a doctor…..

Thanks for the post. Interesting case study. Are most hernias at this point a result of overactive hip flexors? What would be your exercise dosage/prescription of the exercises mentioned in part 2?

The Gait Guys In our experience, most inguinal hernias are due to weakness of the lower abdominal wall, in this case, the external obliques, not being able to fire appropriately to guard against the load. Exercise would most likely progress along the lines of skill 1st (can he perform the exercise appropriately), endurance 2nd (increased reps to increase capillarization, myoglobin content, mitochondrial content; beginning with 8-12 reps and increasing to 5-10 sets daily) and strength last (low reps, high weight; dependent on progress)

Arm Swing privides clues to gait pathology

Arm swing provides clues to gait pathology. We always talk about arm swing as a compensation mechanism. Here arm swing is used to increase hip extension in individuals that want to limit rotation of the lumbar spine.

 

http://www.ncbi.nlm.nih.gov/pubmed/21181483

get the article !

 

Eur Spine J. 2011 Mar;20(3):491-9. Epub 2010 Dec 24.

Gait adaptations in low back pain patients with lumbar disc herniation: trunk coordination and arm swing.

Huang YP, Bruijn SM, Lin JH, Meijer OG, Wu WH, Abbasi-Bafghi H, Lin XC, van Dieën JH.

Source

Department of Orthopaedics, First Affiliated Hospital of Fujian Medical University, Fuzhou, Fujian 35005, People’s Republic of China.

Abstract

Patients with chronic non-specific low back pain (LBP) walk with more synchronous (in-phase) horizontal pelvis and thorax rotations than controls. Low thorax-pelvis relative phase in these patients appears to result from in-phase motion of the thorax with the legs, which was hypothesized to affect arm swing. In the present study, gait kinematics were compared between LBP patients with lumbar disc herniation and healthy controls during treadmill walking at different speeds and with different step lengths. Movements of legs, arms, and trunk were recorded. The patients walked with larger pelvis rotations than healthy controls, and with lower relative phase between pelvis and thorax horizontal rotations, specifically when taking large steps. They did so by rotating the thorax more in-phase with the pendular movements of the legs, thereby limiting the amplitudes of spine rotation. In the patients, arm swing was out-of phase with the leg, as in controls. Consequently, the phase relationship between thorax rotations and arm swing was altered in the patients.

It pays, metabolically and biomechanically, to swing your arms! “Experimental measurements of humans (n = 10) showed that normal arm swinging required minimal shoulder torque, while volitionally holding the arms still required 12 per cent more metabolic energy. Among measures of gait mechanics, vertical ground reaction moment was most affected by arm swinging and increased by 63 per cent without it.” Get the article ! http://www.ncbi.nlm.nih.gov/pubmed/19640879Proc Biol Sci. 2009 Oct 22;276(1673):3679-88. Epub 2009 Jul 29. Dynamic arm swinging in human walking.Collins SH, Adamczyk PG, Kuo AD. Source Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109-2125, USA. shc@umich.edu Abstract Humans tend to swing their arms when they walk, a curious behaviour since the arms play no obvious role in bipedal gait. It might be costly to use muscles to swing the arms, and it is unclear whether potential benefits elsewhere in the body would justify such costs. To examine these costs and benefits, we developed a passive dynamic walking model with free-swinging arms. Even with no torques driving the arms or legs, the model produced walking gaits with arm swinging similar to humans. Passive gaits with arm phasing opposite to normal were also found, but these induced a much greater reaction moment from the ground, which could require muscular effort in humans. We therefore hypothesized that the reduction of this moment may explain the physiological benefit of arm swinging. Experimental measurements of humans (n = 10) showed that normal arm swinging required minimal shoulder torque, while volitionally holding the arms still required 12 per cent more metabolic energy. Among measures of gait mechanics, vertical ground reaction moment was most affected by arm swinging and increased by 63 per cent without it. Walking with opposite-to-normal arm phasing required minimal shoulder effort but magnified the ground reaction moment, causing metabolic rate to increase by 26 per cent. Passive dynamics appear to make arm swinging easy, while indirect benefits from reduced vertical moments make it worthwhile overall. 

Dynamic arm swinging in human walking.

We came across this video on Youtube. Look at the obvious deficiency on the right limb with the amount of internal spin of the foot.  Much can be gleaned from this information. remind you that making assumptions of what is wrong or what the treatment is from what you see on a treadmill or in a person walking or running may not be their actual problem, rather it is quite often their compensation pattern. 

In this case, we see an aggressive negative foot progression angle on the right. Normal foot progression angle is anywhere from zero degress (see this persons left foot) up to 15 degrees depending on their given anatomy. 

This is likely from internal tibial torsion on the right but femoral torsion would need to be looked at. What is interesting is taking the concepts of what are seen here and projecting some other thoughts and considerations, as The Gait Guys always do.  This person is “toeing off” the lateral column of the foot (3rd-5th digits).  This will enforce a supinatory toe off, it is always nice to toe off a rigid lever but in time running in this case could eventually lead to some osseous stress reaction/response into these lesser metatarsals and could “couch” this person for a period. To gain more stability (plantar purchase of the foot on the ground) these clients frequently have over activity of their long toe flexors (FDL) and some toe hammering in the lateral digits is not uncommon.  Be sure to look for this phenomenon in your clients.

Toe off from the lateral foot is not uncommonly seen pairing up with a shortened step length on that side and same side knee hyperextension, reduction in ankle rocker (dorsiflexion through the tibial-talar joint) which can lead to anterior impingement at this interval as the ankle dorsiflexion is prematurely terminated,

We also frequently see a reduction in strength of the anterior compartment musculature; the ankle dorsiflexors (primarily the tibialis anterior) and toe extensors which further impairs any chance of normal ankle rocker range.  Additionally, these folks typically have weak lower abdominals on the affected side and tend to strategize through their quadriceps instead of the more effective glute-abdominal core stabilizing unit.In this case here, the more internal tibial torsion or internal spin a limb has, the less likely the client is able to engage the external hip rotators of which the gluteus maximus (iliac division) and gluteus medius (posterior division) are powerful proponents.

Lastly, for now, although this is likely a case of internal tibial torsion, it brings up the considerations in other cases that an internally rotated limb is typically shorter functionally and thus this can lead to an apparent leg length discrepancy.

These are all great “mental exercises” to keep your eyes and brain keen. But as we always say, what you may see may not be so.  Be sure to test your muscles and motor patterns to see if what they are displaying is their deficiency or their compensation pattern, or a bit of both. 

The Gait Guys , Shawn and Ivo