THE BIOMECHANICAL APPROACH TO

FOOTWEARKelsey Zane 8/19/15

OBJECTIVES1. Understand why running shoe knowledge is

relevant.2. Increase awareness of shoe terminology.3. Awareness of types of shoes on the market:

what you’ll see in the clinic.4. Have ideas of what shoe’s are appropriate for:

the Recreational Runner, Gym Rat (Crossfit, circuit training), Walker, Minimalist

5. Learn something new.

SO WHAT ABOUT SHOES? We are movement experts which means that we should be concerned about something a patient wears everyday…. Whether it’s helping or hurting them we should be aware of what’s out there. Research shows that it’s not only the arch height that is necessary in prescribing the correct kind of footwear.1

The incidence of LE injury in traditional running shoes is as high as 79.3 %2

HOW DO YOU BEGIN TO CHOOSE? Per “American Academy of Podiatric Sports Medicine” the correct/most beneficial approach to choosing footwear is based off gait patterns:3

According to the biomechanics research, humans do not respond in a systematic way to footwear features and since gait patterns are highly unique, it is not always possible to predict how someone will interact with a given shoe.  So instead of recommending shoes, the AAPSM advises that individuals become familiar with the structural features that work well for them and then seek out those features when replacing shoes

Don’t we analyze gait?

SHOE ANATOMY:Outsole: blown or carbon rubber

Upper: cloth of various materials, including plastic and cotton, that are stitched together then glued to the midsole of the shoe. Midsole: where it becomes highly variable among companies and can be complicated.

Cushion: closed cell foam “Ethyl vinyl acetate (EVA)” provides cushioning and is usually a white or lighter color. Some use polyurethane.

Above: Brooks cushion system and marketingBelow: Lunarlon ® Nike’s trademark cushion/support system

CONCERNS AS A PT: MIDSOLE STABILITY

Shank: designed to reduce torsion and flexion of the shoe. Benefits: assists the shoe in bending at the toes instead of the arch (required at terminal stance and heel off in order to transfer weight to ball of foot for toe off)Disadvantage: add’s weight

Medial Post: carbon fiber, dual density EVA, thermoplastic urethane (TPU), wave plate® (plastic material used by Mizuno). Varies as far as composition and amount used in midsoleBenefits: controlling excessive pronation at stance phase of gait cycle, highly variable among companiesDisadvantages: adds weight, reduces work of intrinsic foot muscles and dynamic foot control through gait cycle

Above: Mizuno Wave Plate ®

THE “LAST”Curved Semi curved straight

Type/Shape Light & less supportive25 degrees forefoot ADD

Hybrid10 degrees of forefoot ADD

Heavier & more stable0 degrees of forefoot ADD

Activity Racing flats, competition shoes, light/neutral shoes

Stability category, recreational runners, aerobic shoes

Motion control, walking specific shoes

Construction type What it looks likeBoard Piece of cardboard or plastic underneath

the insoleSlip No board; wrap fabric upper into

midsoleCombination Board in the rearfoot and slip in the

forefoot; allow for flexibility in the forefoot without sacrificing stability

Strobel Most common today; thin sheet of EVA is glued to midsole and then the upper is stitched to the midsole.

TERMINOLOGY CONTINUEDToe box: area in the front of the shoe that starts at approximately the metatarsals and extends forward. Heel counter: plastic or leather piece that reinforces the heel cup/area of the shoe and provides minimal support.Heel drop/Heel-To-Toe Offset: difference between heel height and forefoot heightZero drop: when foot is in shoe there is no difference between the heel of the foot and the ball of the foot

ALL THINGS CONSIDERED: HOW DO THEY WORK TOGETHER?

Overall: the offset is a min of 12 mm and can variable between brand and model

- Neutral shoe: primary goal is to cushion and absorb shock, allow the foot and LE to flow through it’s gait cycle without correction. Properties: curved last, no medial post, lightweight

- Support shoe: primary goal is to provide medial support to reduce slight to moderate over pronation at the ankle during the foot flat to mid stance phase of the gait cycle, also provide shock absorption Properties: curved or straight last, medial post, shank of some sort, high variability in this category, medial STJ control

-Motion control shoe: primary goal is to limit moderate to severe over pronation throughout single limb support phase of gait cycle Properties: straight last, larger medial post with incorporated plastic shank, heavier weight, medial/lateral STJ control

POPULAR SHOES/BRANDS -Top 5 Best Sellers According to… -Personal Experience: Brooks: Defyance/Glycerin, Adrenaline & Beast/Ariel Asics: Nimbus/Cumulus, 2100 Series & Kayano Mizuno: Rider, Inspire & Alchemy Adidas: Supernova Nike: Pegasus, Free Run, Structure Saucony: Kinvara, Guide

RECENT RESEARCH FINDINGS: Shu et al (2015): Found morphological differences in foot shape amongst groups that wore shoes and those that didn’t. Supported other research associated with the long term effects of ill fitting shoes.4

Fredericks et al (2014): Footwear influences foot strike pattern.5

Goss et al (2015): Runners cannot properly assess their footstrike pattern (only 68.3% properly).6

Jones et al Lateral wedge insoles (supported and lateral) helped to reduce the medial knee pressure in stance phase of gait cycle.7

Two types of lateral wedge insoles: one with only lateral support and the other with medial and lateral support

Both had 5 degree’s of support

COMMON GAIT CYCLE DEVIATIONS:

*Disclaimer about pronation: some amount is necessary. Joint motions: combination of DF TC, Eversion & ABD STJ

-over pronation potential causes:Ligamentous laxity on medial side of footMidfoot joint capsule laxity in response to decreased capsular motion at hindfoot (“stuck hindfoot”)

Decreased dynamic control at muscles that cross the ankle

Peroneal tightness

Other: reduced foot mobility due to immobilization, plantar fascia inflammation, rigid foot (supinator), knee or hip OA that causes variable deviations

CLINICAL SITUATIONS: -Summer footwear advice: wearing stable shoes if appropriate for your foot type is important regardless of whether it’s freezing or 100 degrees outside. Brands to trust: Rainbows, Montrail Molokai/Molokini, Teva, Chaco, Superfeet

- Weekend warrior who has plantar fasciitis: typically increase support in their shoe via insole or stability level of shoe in conjunction with PT

- Gym Rat (Crossfit, circuit training) with ankle tendinopathy who feels like this is the easiest way to stay fit: typically minimalist shoe; lower profile decreases potential for turning ankle during workout, adding light Superfeet insole

- Daily Walker recently diagnosed with knee OA: typically a running shoe is warranted with neutral cushioning and roomy toe box to provide comfort. Specific “walking” shoes are made of leather, heavy and limited in support options.

- (Transition to) Minimalist shoes: typically require training on form before getting a zero drop shoe.

RESOURCES FOR THE CLINIC -Online: -Bartold Biomechanics (requires fee)

-Harvard Univ. Skeletal Biology Lab

-Superfeet insoles -Stores: -Snail’s Pace in Huntington Beach

REFERENCES1. Knapik et al. 2014. Injury reduction effectiveness of prescribing shoes on the basis of foot arch

height: summary of military investigations. Journ Ortho Sports Ther. 2. Van Gent et al. 2007. Incidence and determinants of lower extremity running injuries in long

distance runners: a systematic review. Brit Journ of Sports Med.3. American Academy of Podiatric Sports Medicine. “Footwear: Running Shoe Anatomy”.

Accessed August 15th, 2015. http://www.aapsm.org/runshoe-running-anatomy.html.4. Shu et al. 2015. Foot morphological differences between shod and unshod runners. PLoS One.5. Fredericks et al. 2014. Lower extremity biomechanical relationships with different speeds in

traditional, minimalist, and barefoot footwear. Journ Sports Sci and Medicine.6. Goss et al. 2015. Lower extremity biomechanics and self reported foot-strike patterns among

runners in traditional and minimalist shoes. Jour of Athl Train.7. Jones et al. 2015. The effects of different types of insoles or shoe modifications on medial

loading of the knee in persons with medial knee osteoarthritis: a randomized trial. Journ Orthop Res.