ARE YOUR RUNNING SHOES HELPING OR HURTING YOU?

There are so many different running shoes available on the market today, and there are hundreds (if not thousands) of websites offering advice on which shoes are right for YOU.  The goal of this article is to inform readers of shoe anatomy, things to consider when purchasing running shoes, and to offer practical information regarding shoe care and replacement. Experienced runners know that running shoes can make or break a training regimen.  Running shoes also play an integral role in the prevention or predisposition to overuse injuries such as stress fractures, plantar fasciitis, shin splints, and achilles tendinopathies.

SHOE ANATOMY

Upper: this is the part of the shoe above the midsole.  It consists of the toe box, tongue, insole, lacing system, and heel counter (a motion control device).  This part of the shoe is typically made from lightweight nylon mesh and other synthetic materials.  The upper should be flexible, durable, and breathable.

Midsole: this is the MOST IMPORTANT PART OF THE SHOE!  The midsole provides cushioning, stability, and motion control.  It is usually composed of ethyl-vinyl acetate (EVA), which provides lightweight, foam-based cushioning or polyurethane (PU), which is more durable but weighs more.  The density of the cushioning varies throughout the midsole to reinforce particular regions of the shoe, such as the medial arch.  This increased support is often referred to as dual-density EVA.  Other components of the midsole include air, gel, or liquid to offer additional shock absorbtion, and additional motion control devices.

Last:  this refers to the configuration and overall shape of the shoe.  Lasts can be straight or curved.  Most people do not have feet that are perfectly straight.  The forefoot (front of the foot) often curves inwards in relation to the hindfoot (back of the foot).  The shape of the shoe should match the shape of your foot.  Generally, people with a higher arch will need more of a curved last, whereas people with lower arches (people who tend to pronate) will need a straighter last.

Outsole: this is the part of the shoe that contacts the ground.  It is often composed of carbon rubber, blown rubber, or a combination of the two.  Because the outsole makes contact with the ground, it provides varying degrees of traction, and can also be modified to enhance particular aspects of the running cycle (for example, an elevated toe box to increase push-off).  People often wait until the outsole is worn out to buy new shoes, but the integrity of the outsole will remain long after the midsole has worn out.  Don’t make this mistake!

THINGS TO CONSIDER WHEN PURCHASING RUNNING SHOES

Foot Type: Do you have a flat arch, high arch, or something in between?  If you have a flat arch you may need a shoe that provides for support (dual density EVA) in the midsole under the medial arch.  Is your foot more straight or curved?  This will determine the type of last that you look for in a shoe.  How wide is your forefoot?  Different brands of shoes have wider/narrower toe boxes.  Try a couple of different brands.

Body Weight: bigger/heavier runners will require more support and durability from their shoes.  These people also tend to have flatter arches.  A motion control shoe is often recommended for heavier people.

Type of Training: how far will you be running?  How frequently will you be running?  What kind of terrain will you be running on (trail running)?  Different shoes are better for different distances, frequencies, and terrains.

Brand of Shoe: everybody has there favorite brand, but if you are experiencing foot/ankle pain, think about trying a different one.  Ask a representative about the benefits of different brands when purchasing your shoes.

Type of Shoe: each brand makes different styles of shoes.  There are cushioned shoes, motion controlled shoes, racing shoes, stability shoes, trail shoes, etc…  Click here for a simple article describing the different types of running shoes and which one may be right for you!

Manufacturing Defects: manufacturing defects can cause overuse injuries such as the four we named in the introduction.  Click here for more information on how to treat shin splints! Make sure that the shoe is balanced by pushing down on the center of the toe box and letting the heel of the shoe come down onto the surface.  If the heel lands off-center, towards one side, this may predispose a person to an ankle sprain in that direction.  Also, feel for the bend in the shoe by squeezing the toe box and heel of the shoe towards each other.  The shoe should bend in the same area that your feet bend when you raise onto your toes.

When You Purchase Your Shoes: feet tend to swell throughout the day.  Keep this in mind.  It may not be a smart choice to purchase shoes in the morning, only to find that by 5 PM they don’t quite fit!

Where You Purchase Your Shoes: perhaps most importantly, go to a store with a knowledgeable staff regarding running mechanics, that can provide good advice for your specific situation.

TIPS FOR RUNNING SHOE CARE

• Only wear your running shoes for running!  Every step you take wears down the midsole.  The heat that is generated when you run also adds to the deformation of the shoe materials.
• Untie your shoes before taking them off!  The all-too-popular method of using one foot to pry the other foot loose is very detrimental to the integrity of the midsole.  Do yourself and your shoes a favor and untie the shoes before taking them off AND before putting them on (cramming your feet into shoes that are already tied is even worse!)
• Avoid running in wet shoes!  Running in wet shoes will decrease shock absorption by about 40-50%!
• Don’t put your shoes in the washer or dryer!  This will decrease the lifespan of the shoe by degrading the materials.
• Give your shoes a break!  Just as you need to recover after a long run, so do your shoes.  The EVA or PU in the midsole of the shoes takes about 24 hours to rebound from the forces absorbed during running.

WHEN YOU SHOULD REPLACE YOUR SHOES

There is a correlation between infrequent shoe replacement and injury.  Most people wait too long to replace their running shoes.  As we said before, the midsole wears out before the outsole.  So if the outsole looks worn down, the shoes should have already been replaced.  Keep these facts in mind:

• There is a 25-30% loss of cushioning during one 3 mile run (remember that it takes 24 hours for the EVA and PU to recover)
• Shoes lose 30-50% of shock absorption capability after 250 miles or 1-2 years on the shelf

You should replace your running shoes every 400-600 miles or every 6 months.  Increase the life of your shoes by alternating between two pairs of shoes and by providing at least 24 hours of recovery for your shoes between runs.

This information was modified from a lecture given by Crista Osio, MS, PT, and Linda Wanek, PT, PhD at the University of California, San Francisco/San Francisco State University Graduate Program in Physical Therapy.