Hate Running? Maybe it's because of the shoes!

by: Patrick Vaughan

Background:

Does this sound familiar? “This is pure torture! I hate how painful my legs feel after a run! Well despite the fact that there is always an adjustment period to compensate for the new stresses which result from new activities, there may be other reasons to explain your past hatred for running.

            The design of the shoe might actually be to blame! To understand the full story, let’s begin to put the history of shoes into perspective…

 A significant portion of past human existence has occurred without the use of shoes. Imagine that! People walking around barefoot in the winter, walking barefoot over stones, on hot embers, on broken sticks, you name it! It wasn’t until the mid nineteenth century [around 1850] that the first modern-day shoe became popular. This was a simple leather construct that became known as Plimsol, as it resembled the Plimsol of a ship. Traditionally is was seen and used only as a leisure-time shoe, which was mainly used in tennis and on the golf courses.

                Speed forward about a hundred years to the exercising movement in the 1960’s. This is when the popular modern-day running shoe came into existence. The science or biomechanics of running therefore is a relatively young study.

                Originally shoes were designed to protect the feet from environmental dangers such as those pesky twigs, and from extreme thermal conditions such as contracting hypothermia in the winter. Shoes were therefore NEVER meant to benefit an individual in running form such as is advertised today.

Summary:

• Shoes were designed to protect feet from environmental dangers [twigs/cold weather/etc.], not as a means to correct ones form.

•  The design and science/biomechanics of athletic shoes is still a young study [Only 50 years old]

• Plimsol, a simple leather design named after the water-line on a ship was the first popular shoe design.

Conventional Shoe Perspective:

A modern Gait analysis has shown conventional shoes increases the risk of ankle sprains and fatigue related injuries like stress fractures. This could be due to either factor listed below:

                1.) It could be caused by decreased foot awareness (Warburton)

                2.) It could be caused by an increased torque on the ankle during landings (Warburton)

Terminology to know:

•       Zero-drop = no change in stature from heel to toe [barefoot conditions] - promotes Fore Foot Strike

•       Minimalist = 6mm or less differences b/w the toes and heel

•       Conventional shod = 10mm or more [sometimes in inches like women’s heels]

•       Characterized by a softer insole, elevated heel, and potentially some motion-control device built into the shoe (Gangemi)

•       Result = natural imbalances such as rear-foot strike [RFS] as compared to a Fore foot strike [FFS]

•       Causes increased dorsiflexion of the foot

Cyclic Loading/Fatigue that results from natural running:

•       Cyclic fatigue occurs under cyclic Loading

•       Load = body weight

•       Cyclic fatigue = loading on the legs through natural processes [walking/running]

Problems occur when:

•       The cyclic loading is above current thresholds

•       This occurs when beginning to run after not running for years

·         When the frequency b/w loading is drastically increased

•       This occurs when running 2+ times a day or everyday. Basically when there is a drastic increase in one's running compared to previous levels.

Result:

•       Fatigue fractures occur when there is not enough time for bone to properly heal micro-fractures “crack initiation” after compressive loading occurs from naturally walking/running.

•       A progressive loss in strength/stiffness of the bone occurs w/ decreases in fracture toughness

•       The bone becomes increasingly brittle, compliant, overall weak

Why it happens:

• Upon loading, a mechanism called crack blunting occurs within the bones, which is a process by which the fibers act as nails that are driven by the compressive force of your body weight into the surrounding bone. On compressive release, [when the weight is removed from one of the legs] a hysteresis occurs which allows a re-sharpening of the microfractural sites within the bone. So upon the next loading cycle, the bone acts like the nail once more, and your weight acts like the hammer that allows the crack to propagate. This can be observed in the picture/diagram below.

• The Differences between the impact of a RFS vs. a FFS can be observed in the picture below.

Description of the observations:

•       Crack growth occurs at a much faster rate in RFS b/c of the double force peak; because crack blunting and re-sharpening can occur at a faster rate due to the double unloading process that occurs within a single cycle.

•       Fatigue occurs at a much faster rate in RFS than FFS, even when comparing shod to barefooted conditions due to the double force peak.

•       FFS = more of a smooth loading distribution due to an increased amount of knee flexion accompanied by less of a range of motion. This is because of the rolling effect that occurs when landing on the heel.So even when running on very stiff surfaces barefooted, there is a singular force dispersion.

As can be seen in the picture above, landing with the heel causes vertical force spikes to be sent straight up the leg. This results in the double force peak observed previously, and in the increased rate of stress fractures

•       Theory behind conventional shod = three filters; the sole the insert, the plantar surface of foot…. Still despite all of this filtration and cushioning of the force, we can see that there is still a double force spike; so from a materials perspective, all of this additional cushioning makes no difference..... 

**however if this additional stress can be avoided by running properly [FFS], why do we need all of these extra correctives to promote improper running technique!**

           

Conclusion:

•       Organic materials in the body as well as shoe design materials need to be considered in designing an effective shoe.

•       Barefoot running shows “zero-drop” and promotes a [FFS]. Barefooted shod conditions should therefore be designed over the conventional shod.

•       It is necessary to fix this issue for a healthy body, and healthy running form, so buy some zero-drop shoes like the Merrell Barefoot running shoes today! 

Embrace your feet, they were born to run naked!

Works Cited

Bramani, Marco. "One-piece Sports Sole-heel Unit with Increased Stability." Patent Number: 5768802 (Issue Date: Jun 23, 1998): n. pag. Print.

 

Bramani, Marco. "Patent US20130232820 - High Foot Mobility Shoe - Google Patents." Google Books. VIBRAM S.P.A., n.d. Web. 02 Dec. 2013.

"A Comparison of Several Barefoot Inspired Footwear Models in Relation to Barefoot and Conventional Running Footwear." Wageningen Academic Publishers (May 17, 2013): 13-21. Print.

Fliri, Robert. "Google." Google. VIBRAM S.P.A., n.d. Web. 30 Nov. 2013.

Gangemi, Stephen C., DIBAK. "Expanded Gait Assessment and Evaluation and Validation of Minimalist Footwear." N.p., n.d. Web. 2 Dec. 2013.

Gilbert, C. J., R. N. Petrany, R. O. Ritchie, R. H. Dauskardt, and R. W. Steinbrech. "Cyclic Fatigue in Monolithic Alumina: Mechanisms for Crack Advance Promoted by Frictional Wear of Grain Bridges." Journal of Materials Science 30.3 (1995): 643-54. Print.

Google.com for pictures

Kruzic, J., and R. Ritchie. "Fatigue of Mineralized Tissues: Cortical Bone and Dentin." Journal of the Mechanical Behavior of Biomedical Materials 1.1 (2008): 3-17. Print.

Lieberman, Daniel E., and Madhusudhan Venkadesan. "Foot Strike Patterns and Collision Forces in Habitually Barefoot versus Shod Runners." Nature. Nature, n.d. Web. 2 Dec. 2013.

Nakano, Kiyotaka. "Google." Google. N.p., n.d. Web. 30 Nov. 2013.

Nigg, Benno M., Matthew A. Nurse, and Darren J. Stefanyshyn. "Shoe Inserts and Orthotics for Sport and Physical Activities." Medicine & Science in Sports & Exercise 31.Supplement (1999): S421-428. Print.

Warburton, Michael. "Barefoot Running." Sportscience 5(3), 2001, n.d. Web. 2 Dec. 2013.