November 27, 2012 November 27, 2012/ The Gait Guys

Shoesday Tuesday:

Shoe News You Can Use: The Shank

Look at the “skeleton” in the photo on the left. Now look at the black material above the white area of the midsole (above the outsole) on the right. This is the “shank” of the shoe. The shank is the stiff area of the shoe between the heel to the transverse tarsal joint. It should correspond to the medial longitudinal arch of the foot. It is designed (along with the midsole material: see post here), to provide additional torsional rigidity to the shoe and helps to limit the amount of pronation and motion at the subtalar and mid tarsal joints. It also acts as a “plate” between the outsole and ininsole to provide protection to the foot from rocks, sticks, broken glass, shrapnel and small animals : ).

Not all shoes have a shank, so it may not always be present. We usually dissect shoes sent to us so we can see what they are all about if the manufacturer or rep is unable to provide us with an “exploded” or sectioned model. Look for our take on the new SKORA soon, complete with a dissected version!

The Gait Guys. Making sure you know what you need to so you can make more educated decisions

November 20, 2012 November 20, 2012/ The Gait Guys

Shoe News you can use….

The Midsole

Last time we talked about the outsole (see here and here if you missed it or need a review). Today we will focus on the midsole.

The Midsole, sandwiched between the outsole and the upper, provides torsional rigidity to a shoe. They can be single (uni) density (left picture) or multiple (middle picture).

Midsole material is very important, as it will accommodate to the load imposed on it from the person as well as any gear they may be carrying. It serves as the intermediary and transducer for load transfer between the ground and the person. Softer density material in the heel of the shoe, like in the blue lateral side of the shoe in the bottom picture, softens the forces acting at heel strike and is good for impact and shock absorption.

Because the midsole tranduces forces and provides torsional rigidity (picture on right). The stiffer the material, the more motion control it provides. Midsoles like the one in the center are made with materials of differing densities (white is softer, light grey more dense, dark gray, most dense) to absorb force and decrease the velocity of pronation during heel strike and mid stance, with a firmer material medially that protects against overpronation as you come through mid stance and go through toe off.

Wow. Shoe anatomy for the day. Knew this? Great! Lost? Want to know more? Download our Shoe Fit Certification program by clicking here. You can also email us for more information about becoming IFGEC certified in shoe fit: thegaitguys@gmail.com

Ivo and Shawn. Bald. Handsome. Knowledgeable. The Gait Guys!

November 07, 2012 November 07, 2012/ The Gait Guys

Shoe Facts: The Outsole (also called the “sole”)
This is the part of the shoe that comes in contact with the ground. It is often made of rubber and provides for traction and some degree of shock absorption. It can be sewn, cemented or in… — **Shoe Facts**: **The Outsole (also called the “sole”)**

This is the part of the shoe that comes in contact with the ground. It is often made of rubber and provides for traction and some degree of shock absorption. It can be sewn, cemented or integrated with the midsole.

Remember that the heel strikes the ground at approximately a 16° angle, lateral from the center of the heel. 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 (add link **see mondays post here for more on progressional forces**). This can be assisted by a “rocker” which is a “drop” put into the front portion of a shoe, to ease walking and assist in toe off (more on this in another post).

A flare to the sole of the shoe (usually at the rear, medial or lateral), can be important for stability on uneven surfaces, by providing a bigger “footprint” or surface area contacting the ground (much like Dr Allen’s new Dodge truck). A **lateral flare** provides extra stability upon heel strike by preventing too much inversion of the heel, *but it speeds up the rate of pronation*. A **medial flare** would *slow pronation* (not great for a supinator though, or folks who keep weight on the outside of the foot for extended periods of time). This flare’s placement (whether medial or lateral) will profoundly affect forces at the mid tarsal joint as the foot comes through mid stance.

The Gait Guys. Making you more “shoeliterate” each day!

*Want to know more? Email us at thegaitguys@gmail.com for information about our National Shoe Fit Certification course.*

copyright 2012 The Homunculus Group/ The Gait Guys. All rights reserved. DON’T RIP OFF OUR STUFF.

March 11, 2012 March 11, 2012/ The Gait Guys

Thinking about throwing away those old running shoes? Think again. A recent study looking at plantar pressures in new vs old shoes reveled that newer shoes had higher perssures, assumedly due to increased stiffness of the shoe.

This definitely is a fly in the ointment about changing your shoes every 500 miles and supports a slow break in for any shoe.

Ivo and Shawn. Yes, we are shoe geeks…even on a Sunday

March 10, 2012 March 10, 2012/ The Gait Guys

The Sole Truth and Nothing but the Truth

Thicker soles mean more muscle activity. Nothing new here. We have posted on the fallacy of increased cushioning and decreased impact many times. Here is another supporting study.

Here are part of the results: “Compared to the barefoot condition, there is an increase in the magnitude of muscle contraction on wearing shoes, which further increases with thickening shoe soles.”

and the conclusion...“Footwear with increasing shoe sole thickness evokes a correspondingly stronger protective eversion response from the peroneus longus to counter the increasing moment at the ankle-subtalar joint complex following sudden foot inversion. Hence, fashion footwear with thicker sole is likely to increase the risk of lateral ligament injury of the ankle when such protective response is overwhelmed. Similarly, the clinicians need to be cautious regarding the amount of shoe raise that they could provide for patients with limb length discrepancy without any detrimental untoward side effects.”

We remember the peroneus longus attaches from the upper, lateral fibula, traveling down the fibular shaft, around the lateral malleolus and attaching to the base of the 1st 1st metatarsal and lateral cunieform. It fires from just prior to heel strike to terminal stance, assisting in eversion of the foot and cuboid, locking the lateral column of the foot during supination, and plantar flexes the 1st ray (brings the medial tripod down to the ground). More sole = More activity = More potential for injury

The influence of shoe sole’s varying thickness on lower limb muscle activity.

Ramanathan AK, Parish EJ, Arnold GP, Drew TS, Wang W, Abboud RJ.

Source

Institute of Motion Analysis & Research, Department of Orthopaedic & Trauma Surgery, TORT Centre, Ninewells Hospital & Medical School, University of Dundee, Dundee, DD1 9SY, Scotland, UK.

Abstract

BACKGROUND:

The lateral ligament injury of the ankle is acknowledged to be the most common ankle injury sustained in sport. Increased peroneus longus muscle contraction in the shod population has already been documented. This study aimed to quantify the effect of shoe sole’s varying thickness on peroneus longus muscle activity.

METHODS:

Electromyographic recordings of the peroneus longus muscle activity following unanticipated inversion of the foot from 0° to 20° in a two-footplate tilting platform were collected from 38 healthy participants. The four test conditions were: barefoot, standard shoe, and shoes with 2.5 cm and 5 cm sole adaptation respectively.

RESULTS:

Compared to the barefoot condition, there is an increase in the magnitude of muscle contraction on wearing shoes, which further increases with thickening shoe soles. The peroneus longus was responding earlier in the shod conditions when compared to the barefoot, although the results were variable within the three shod conditions.

CONCLUSION:

Footwear with increasing shoe sole thickness evokes a correspondingly stronger protective eversion response from the peroneus longus to counter the increasing moment at the ankle-subtalar joint complex following sudden foot inversion. Hence, fashion footwear with thicker sole is likely to increase the risk of lateral ligament injury of the ankle when such protective response is overwhelmed. Similarly, the clinicians need to be cautious regarding the amount of shoe raise that they could provide for patients with limb length discrepancy without any detrimental untoward side effects.