Exploring the Links Between Human Movement, Biomechanics & Gait
Month: May 2011
There are 2 photos here (move your cursor over to the little triangle on the right to highlight the bar to toggle between photos)
Can you believe that an experienced runner would let a pair of shoes get this far on both sides. This person does a few marathons a year and has been a patient of our for years…..he tends to milk out every last step in a pair of shoes but we had to hog-tie him and flog him repeatedly for going overboard this time. I bet there had to be 2000 miles on these puppies ! And get this…..he had no foot or knee pain ! (his response was, i saw the wear but i was not having any issues).
Can you imagine how far out side the contact line the knees had to be ? This has the old Nike Cesium beat by a long shot (they were rear foot posted varus by about 3degrees). Heck, this could be 20-25degrees varus ! There is no question that he is avoiding and rear or mid foot pronation……the dude is fixed in supination.
OF clinical note, he has a fixed right hallux limtus (turf toe) so this likely helps him to avoid medial toe off and forcing dorsiflexion through the big toe joint……however, there are better strategies than this to avoid a hearty toe off !
It is amazing what the body can endure ! Take this as a lesson of what NOT TO DO ! keep the miles between 400-500 miles gang……there are only so many compression cycles in EVA foam before deformation occurs. In this case there was both deformation and just pure and simple friction wear !
PS: this was an easy pick up clinically……he sat in the waiting room with the 55 gallon barrel set beside him ….the one that he had been carrying around between his knees to force this much rear foot varus !
We received a great question from a doctor active on our Facebook page (Thegaitguys PAGE, not our user portfolio, make sure you are on the “PAGE”) Here was the comment:I do like the crouch gaits to help with proximal muscle activation. However I am still not sold on the long toe extensor activation. It would seem to me that the function of this muscle in close chain (ie gait) would be more to aid in pulli…ng the body over the talus (while keeping the toes fully anchored and wide) as opposed to extending the distal phalanx in an open chain fashion. While open chain exercises may ‘strengthen’ this muscle the neurological processing would seem to be different than closed chain and therefore the transfer to more dynamic exercises would be difficult.? I would think that it would not necessarily change the gait but instead allow for better compensatory strength and durability. Although I still have yet to develop a great exercise for this closed chain control. Any ideas?See More
10 hours ago · LikeUnlike
The Gait Guyswhen you activate the toe extensors the arch is increased from the windlass mechanism across the metatarsophalangeal joints. Raising the arch will help bring it to neutral since the crouched gait is a pronation challenge. give it a try…..…….try the crouch shuffles with toes down and toes up…..you will feel the increased demand on the anterior leg compartment, the greater awareness of the foot tripod esp the first metatarsal head anchor point and the improved ability to control the internal tibial spin (and pronation challenge( that occurs with shuffling with toes down. Remember, closed chain is not any more important that open chain activities……arm swing it gait is open chain but it is necessary…..leg swing is open chain but it is necessary for normal progression and pelvic/core use. also remember……we are a flexor dominant society…..look at how many of your clients toes have either a gentle flexion to them or significant…..the balance of the function across the metatarsophalangeal joint is necessary on balance of extensors and flexors……the shuffle gait with toes up is a huge challenge to the toe extensors……that feeling of the strain on the top of the foot and into the shin is confirmatory. OF course, you are right in what you said……but to get the toes optimally anchored you have to have enough long toe extensor strength to override the long flexor dominance…..otherwise you being hammering the toes and enter into the spiraling vortex of flexor dominance, lumbrical inhibition, short extensor overactivation, proximal fat pad drag etc.
If you are truly to be a shoe geek, then you must be familiar with some “shoe anatomy.” Simply put, there is the sole ( the part that contacts the ground), the midsole (the part right between the sole and the last), the shank (the stiff rear part of the midsole), the last (the part on top of the midsole and where the insert or orthotic will sit), the insole (the removable insert), the upper (the part above the last that has the sides, laces, etc)the heel counter (the part that holds the heel in place), and the toe box.
Lets discuss each in turn
The Sole (also called the outsole)
This is the part of the shoe that comes in contact with the ground. It is usually made of rubber and provides for some degree of shock absorption and traction. For running shoes, it is usually cemented to the midsole.
Remember that the heel strikes the ground at approximately a 16° angle lateral from the center of the heel (in a heel strike gait, no we aren’t condoning this, this is how shoes are designed). The force is then transmitted from the sole of the shoe, up the lateral column of the foot and across to the first metatarsal for propulsion.This can be assisted by a “rocker” which is a “drop” put into the front portion of some stiffer trail shoes, to ease walking and assist in toe off.(This is good for people with Morton’s toes or hallux rigidus).
A flare to the sole of the shoe, particularly lateral can be important for stability on uneven surfaces.A lateral flare provides extra stability upon heel strike, but it speeds up the rate of pronation.This may be a bad thing, depending on your feet. This flare must extend the length of the sole, otherwise injury can occur at the mid tarsal joint as the foot comes through mid stance. A medial flare can help to prevent overpronation, as the foot comes through mid stance. Again, it must run the length of the shoe.
Look at the lugs on the sole. Are they beveled or straight? A straight lug or cleat will hold on to mud, whereas a beveled one will shed it. This is an important consideration if running off road. How about the cleat pattern (front vs. back and side to side)? Are they symmetrical or opposing? Opposing patterns will enable you to ascend and descend easier at the expense of a slight amount of speed.
The Midsole (sandwiched between the sole and upper)
Midsole material is very important, as it will accommodate to the load imposed on it from the person and their body weight. It serves as the intermediary for load transfer between the ground and the person.Softer density material in the heel of the shoe softens the forces acting at heel strike and is good for impact and shock absorption. The stiffer the material, the more motion control.Air is an excellent shock absorber, however it does not deform, it displaces. This creates and unstable surface for the foot, promoting ankle injuries. Foam and gel are much better as they transduce the force and dissipate it. Often midsoles are made with something called “dual density”.This means that the midsole is softer on its lateral aspect, to absorb force and decrease the velocity of pronation during heel strike and midstance, with a firmer material medially that protects against overpronation as you come through mid stance and go through toe off.
The Shank (this can be within the midsole)
The shank is the stiff area of the shoe between the heel to the transverse tarsal joint. It corresponds to the medial longitudinal arch of the foot, provides torsional rigidity to this shoe and helps to limit the amount of pronation and motion at the subtalar and mid tarsal joints.
The Last (the part between the midsole and insole)
The last (look inside the shoe on top of the shank) is the surface that the insole of the shoe lays on, where the sole and upper are attached).Shoes are board lasted, slip lasted or combination lasted. A board lasted shoe is very stiff and has a piece of cardboard or fiber overlying the shank and sole (sometimes the shank is incorporated into the midsole or last) .It is very effective for motion control (pronation) but can be uncomfortable for somebody who does not have this problem.A slip lasted shoe is made like a slipper and is sewn up the middle.It allows great amounts of flexibility, which is better for people with more rigid feet.A combination lasted shoe has a board lasted heel and slip lasted front portion, giving you the best of both worlds.
When evaluating a shoe, you want to look at the shape of the last (or sole).Bisecting the heel and drawing an imaginary line along the sole of the shoe determines the last shape.This line should pass between the second and third metatarsal.Drawing this imaginary line, you are looking for equal amounts of shoe to be on either side of this line. Shoes have either a straight or curved last.The original idea of a curved last (banana shaped shoe) was to help with pronation.A curved last puts more motion into the foot and may force the foot through mechanics that is not accustomed to. Most people should have a straight last shoe.
The Upper (the sides and top of the shoe)
This is the part above the midsole that holds your foot on the sole. It is usually made of nylon, Gore-Tex or some other man made material. Pick something light and breathable.
The Heel Counter (the back of the upper)
This is part of the upper. A strong, deep heel counter with medial and lateral support is also important for motion control; lateral support especially for people who invert a great deal or when you’re going to place an orthotic in the shoe which inverts the foot a great deal.The lateral counter provides the foot something to give resistance against.This needs to extend at least to the base of the fifth metatarsal, otherwise it can affect the foot during propulsion. A deep heel pocket helps to limit the motion of the calcaneus and will also allow space for an orthotic. The heel counter should grip right above the calcaneus, hugging the Achilles tendon.
The Toe Box
The toe box should be generous enough to prevent crowding and pressure on the metatarsal heads.The widest portion of the shoe should parallel a line bisecting the metatarsal heads.Excessive pressure can result in bunions and/or hammertoes.The shoe may soften and break down laterally, but it will not increase in length.
When measuring feet and determining shoe sizes, do it both sitting and standing, because the laxity of ligaments can become very evident, especially when the foot is weight bearing or you have the weight of a pack on your back.If the person has greater than one size of splaying in both length and width when going from one position to the other, go for the bigger size.Always use ball length rather than sole length. People usually buy smaller shoes because when you pronate, there is less volume in the mid foot and a smaller size shoe will feel better.
The Insole (the removable inner footbed)
This is the part of the shoe that most people remove to put in an orthotic. They have come a long way in construction and make a big difference in shoe fit. They are usually made of some type of foam or EVA material. Some of the newer ones are even dual density foam.
Well, if you made it through this, you are officially as nerdy as us. We’ll see you in the shoe isle…..
horse: walk, trot, canter, gallop man: walk, jog, run, sprint….very similar ….amble…..well that is another story……horse “ambling” gaits, a collection of several other smooth footfall patterns that may appear naturally in some individuals but which usually occur only in certain breeds, and often require special training…….as for humans? hummm. time for some homework
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.
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
“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…..
Varations of this crouch style gait (we call them shuffles) are a major staple in our gait and core and lower limb rehab and exercise progressions……after dozens of emails already in just an hour of this posting……we can see that we need to do a DVD on our gait progressions and Shuffle Gait variants…..as there are multiple variants to correct various problems…..we will do our best to get it out soon……it is now in the hopper.