Retail Focus: The Midsole

The Midsole is the area sandwiched between the out sole and the upper (or vamp, as we have learned).

The two jobs of the midsole are to provide some degree of shock absorption as well as torsional rigidity to a shoe.

Midsole material (usually EVA or similar 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 serves to soften the forces acting at heel strike (hopefully NOT when running) and “feels” good for impact and shock absorption. We know from studies we (and you) have read (and posts we have posted) that this is largely perception, as softer midsole materails generally INCREASE impact forces.

The stiffer or denser the midsole material, the more motion control it will provide. This is one of many “motion control features” put into shoes.  Some shoes have two different density foams (called dual density midsoles (see pictures above)), to provide a more graduated resistance. The midsole is softer on its lateral aspect, to absorb force and decrease the velocity of pronation during heel strike and midstance (ie. it keeps you supinated a bit longer), with a firmer material medially that protects against overpronation as you come through mid stance and go through toe off.

Air is an excellent shock absorber, however it does not deform, it displaces. This creates an unstable surface for the foot, promoting ankle injuries. It is great for tires, but we feel does not have a place in shoes. Can you think of any shoes that have Air in the midsole? We can, we have all heard that brilliant marketing campaign.  Foam and gel seem to be much better as they transduce the force and dissipate it.

What’s the bottom line? Materials determine the flex and to some degree, the shock absorbing characteristics of the shoe. More rigid midsoles provide more motion control, less rigid ones less. Not everyone can go into minimalist shoes, and not all need control. But we all need educated.

Want to know more? Take our soon to be released course “Proper Shoe Selection” or better yet, our entire shoe fit course, so you too can be a Shoe Jedi!

Shoe Jedi Masters….The Gait Guys

Make sure you visit our Youtube channel: The Gait Guys, or follow us on Facebook and Twitter

Retail Focus Thursday: The Lateral Flare

We recall that The lateral flare is part of the outsole, where it is elongated laterally (as opposed to medially, as in a medially flared shoe), to create stability.

Look at the above example (left above). Notice how the cushioning is different at the lateral aspect of the outsole; in this case: two densities. In this case, Nike Cesium, there is no lateral flare but plenty of entry zone cushion !  In this case this is to “ease the foot into pronation” (keep the foot longer in supination) and is considered a motion control feature (along with dual density midsoles and torsional rigidity, among others).

The typical lateral flare however, as seen in the middle picture drawing, can be a good thing and acts differently than the soft lateral entry zone of the Cesium above. The typical lateral flare will help to pronate the rearfoot, helping minimize the risk for ankle inversion; something you do not want especially when trail running where heel strike is sometimes more pronounced. The Nike above on the other hand, without the lateral flare, will keep the foot in supination longer, and tends to increase stresses to the lateral column of the foot.  Not a good trail running shoe example !

Typical lateral flares, speed up initial pronation (when walking we usually strike on the outside of the heel, as do some heel strike runners.  The flare creates a greater distance to travel in the same amount of time; again; see center pic above). It does not appear to increase total pronation or affect impact forces. It is a good idea for one problem, but often creates another. Not everyone can handle an increased speed of pronation effectively: these folks need to suddenly decelerate the medially spinning leg. What will do that? Most likely the glutes (max and medius); the vastus medialis (contracting eccentrically) and the anterior leg muscles (like the tibialis anterior, extensor digitiorum longus, extensor hallucis longus). You have probably been reading our posts for some time now. How many individuals have competency in these muscles? Not many.

Regarding the lack of lateral flare in the Nike shoe above, this feature has a tendency to “close” the knee medially and “open “it laterally. On the other hand, a typical laterally flared shoe will open the medial knee joint line and close the lateral but this does depend on the degree of tibial torsion and varum.  These lateral flare issues need to be strongly thought out when prescribing a shoe for a client.  This can be a double edged sword. Arthritis is most likely going to effect the medial (inside) knee 1^st so you will want to chose a shoe that does not compress that medial knee.  

The bottom line? Proceed with caution with ANY shoe that has a motion control feature and know what you are recommending.

A little lost? Have no fear;  the complete shoe fit program (with IFGEC certification if desired) is coming in the next few months. Watch here, on Facebook or Twitter for the announcement. What is the IFGEC you ask ? “The International Foot & Gait Education Council” , a group of experts brought together from around the world in a combined braintrust to further foot, gait, running form and shoe forward thinking.

The Gait Guys…Shoe Geeks Extroidinaire. Helping you help your clients make better shoe choices

Retail Focus Thursday: The Heel Counter/ Heel box

Let’s differentiate between the heel counter and a lateral flare of the out sole.

The heel counter refers to the back part of the upper of a shoe that actually holds the heel in place (see left above).

The lateral flare is part of the outsole, where it is enlarged laterally, to create stability to a shoe. (see right above). It does this at the expense of speeding up pronation (we usually strike on the outside of the heel, creating a greater sidtance to travel in the same amount of time; again, another post for another time). Good idea for one problem, but often creates another.

The heel counter is necessary, because as the foot pronates from its initial contact with the ground through midstance, the calcaneus moves laterally (or as shoe pro’s say “it everts”).  If the calcaneus does not encounter something to abut up against (like the heel counter), to stop rearfoot pronation at the appropriate time, it will continue to evert and the medial arch will collapse.

“So what” you say? Excessive rearfoot motion, like this can not only cause prolonged midfoot pronation (remember it pronates to absorb shock to midstance, then supinates to create a rigid lever to push off of. Click here if you need a pronation review), but is a common cause of heel blisters. How many times do you remove a clients shoe (hopefully you are removing their shoes and looking at their feet before selling them some shoes) and you notice a “bump” (and sometimes a blister) on the back of the heel (see above) and the outer portion of the heel box is worn on the inside of the shoe? Hmm, sounds like too much room in the heel box.

What causes too much room in a heel box? Narrow heels (or calcaneii , as we like to say) or literally, too much room. The “too much room” scenario often happens when you put a woman’s heel (usually narrow) in a men’s shoe (often wide)

A little lost? Have no fear;  the complete shoe fit program (with IFGEC certification if desired) is coming in the next few months. Watch here, on Facebook or Twitter for the announcement.

The Gait Guys…Shoe afficianado’s. Bringing you the facts so you can make better decisions….

heel counter image from: www.hughston.com