Biomechanical Approach to Footwear KZ
- 1. THE BIOMECHANICAL APPROACH TO FOOTWEAR Kelsey Zane 8/19/15
- 2. OBJECTIVES 1. 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.
- 3. 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
- 4. 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?
- 6. 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 marketing Below: Lunarlon ® Nike’s trademark cushion/suppo
- 7. CONCERNS AS A PT: MIDSOLE STABILITYShank: 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 midsole Benefits: controlling excessive pronation at stance phase of gait cycle, highly variable among companies Disadvantages: adds weight, reduces work of intrinsic foot muscles and dynamic foot control through gait cycle Above: Mizuno Wave
- 8. THE “LAST” Curved Semi curved straight Type/Shape Light & less supportive 25 degrees forefoot ADD Hybrid 10 degrees of forefoot ADD Heavier & more stable 0 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 like Board Piece of cardboard or plastic underneath the insole Slip No board; wrap fabric upper into midsole Combination 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.
- 9. TERMINOLOGY CONTINUED Toe 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 height Zero drop: when foot is in shoe there is no difference between the heel of the foot and the ball of the foot
- 10. 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
- 11. 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
- 12. 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
- 13. 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 foot Midfoot 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
- 14. 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.
- 15. RESOURCES FOR THE CLINIC -Online: -Bartold Biomechanics (requires fee) -Harvard Univ. Skeletal Biology Lab -Superfeet insoles -Stores: -Snail’s Pace in Huntington Beach
- 16. REFERENCES 1. 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
Editor's Notes
- #4: The foot is the distal end of a powerful kinetic chain responsible for supporting us and moving us from one place to another. Lamens terms, everything is connected! Our own health and wellness is also key, we spend a majority of our work day standing or squatting.
- #7: Upper: This is where a majority of the issues with the perfect fit come into play. Every person’s foot is so differently shaped and responds to exercise differently (ie amount of swelling) which can create a barrier to finding the best shoe for their mode of exercise. Cushioning: Cushioning systems are used as well that range from closed gel, air or other material
- #8: Shank: It can be coupled with the medial post which improves the stability of the overall shoe. Medial Post:
- #10: Toe Box: Generally wider in athletic shoes but important to be aware of for certain types of pathologies like diabetic neuropathy, Rheumatoid Arthritis (RA), hallux valgus or recently fracture foot bones.
- #14: Disclaimer about foot pronation: necessary in order to provide a soft landing as the foot conforms to the ground at foot flat and through mid stance. The issue is if the foot isn’t able to become a rigid lever to propel the body throughout heel off and the transition to the swing phase of the gait cycle.
- #15: Weekend Warrior: Questions to ask: what other shoes are they wearing during their day? What’s their goal? Did they go through a gait analysis for their shoe selection? Gym Rat: Questions to ask: is this their main source of exercise? History of ankle instability/sprains? Daily Walker: Questions to ask: what kind of surfaces are you normally on (trail or street)? Barefoot Runner: Questions to ask: what is your training plan? Is there a race that you want to run using the minimalist technique?