4/15/17. The Foot Core Paradigm. The Foot Core Concept. A Key to Healthy Feet. International Foot and Ankle Symposium, 2012

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1 The Foot Core Paradigm A Key to Healthy Feet Irene S. Davis, PhD, PT, FAPTA, FACSM, FASB Director, Spaulding National Running Center Professor, Harvard Medical School The Foot Core Concept International Foot and Ankle Symposium, 2012 Recommend: Modalities, Manual Therapy, Stretching, Taping, Orthotic Devices, Night Splints No recommendations regarding strengthening Every other Practice Guideline (knee, ankle, etc) recommend strengthening Need for awareness of the importance of foot strength for normal foot function 1

2 Lumbo-Pelvic Core Stability Lumbopelvic Core Muscles Malfunction Small X-sectional areas and small moment arms-are Stabilizes and not prime movers Hip ADD and IR Contralateral Pelvic Drop Anterior Pelvic Tilt Proposing that there is an analogy in the foot Intrinsic Foot Muscles Small X-sectional areas Short moment arms Stabilizers vs prime movers You need foot stability (intrinsics) for proper foot mobility (prime movers) and proper function Importance of foot strength highly underappreciated Pat McKeon Irene Davis Jay Hertel Explore the Concept of a Foot Core 2

3 Formation of the Arch Australopithecus ~ 2 Million yrs ago Bramble and Lieberman, 2004 Last walking man First running man Med. Long. Arch Long achilles Plantar intrinsic activity most consistent during running, least during walking Reeser et al, 1983 Well- Designed Feet Medial foot 26 bones, 33 jts with 6 dof of movement 4 layers of arch muscles Rigid Lever, Mobile Adapter, Spring Mismatch Theory We are not living the lives our bodies were designed for Food, Air, Activity level Cause of many of the illnesses today Diabetes, Obesity, CV disease Plantar fasciitis most common foot pathology 3

4 There is a high prevalence of flat feet VS Normal arches often degrade under load One can have normal RF motion. But have excessive midfoot motion 4

5 Plantar Fasciitis Often associated with pes planus Most common cause of heel pain 10% of population will experience ~32 million people! Mechanism - Repetitive Traction Injury 4 layers of intrinsic arch muscles (+extrinsics) Control the deformation with each footstrike Muscles are just one part of the core Foot Core System* *Based on Panjabi s Lumbo-pelvic Core System Model 5

6 Passive Subsystem Bony Structure 4 Arches coalesce: Med. Longitudinal Lat. Longitudinal Ant. Transverse Post. Transverse Arch Modeled as a half dome* *McKenzie, 1955 Passive Subsystem - Ligaments Active Subsystem:4 Layers of Intrinsic Muscles 1. Abd Hallicus 2. Fl Dig Brev 3. Abd Dig Min 4. Quad Plantae 5. Lumbricals 6. Fl Dig Minimi 7a. Add Hall Oblique 7b. Add Hall Transv 8. Fl Hall Brevis 9. Plantar Interossei 6

7 Extrinsic Muscles (tendons) Importance of Intrinsic Muscles Fatigue of intrinsics results in increased navicular drop Headlee et al, 2008 Tibial nerve block resulted in decreased AH activity and increased navicular drop Fiolkowski et al, 2003 Plantar Fascia Last line of defense! As tension increases in the achilles so does the plantar fascia 7

8 Neural Subsystem Plantar sensation has been shown to be critical to gait and posture Hock et al, 2012, Kavounoudias et al, 1998, 2001, McKeon et al, 2007 TTBML (s) * Increased static postural stability in BF compared with socks! Shinohara et al., 2011 Effect on Sensory Input on Dynamic Postural Stability * Bowser et al., 2017 Increased dynamic postural stability in BF Need Integration of all three for normal function Need Stability (intrinsics) and Mobility (extrinsics) 8

9 Foot Assessment Assessing the Extrinsic Foot Muscles can be done in a variety of ways Foot Core (Intrinsic ms) Assessment A recent systematic review concluded that there is no gold standard Soysa et al, 2012 Be Creative Hallux Strength Lat. Toe Strength Ridge et al, 2015 Foot Core Strength Assessment Abductor digiti minimi Quadratus plantae Flexor digitorum brevis Abductor hallucis Imaging MRI Ultrasound 9

10 Foot Core Functional Assessment Dynamic Function Multi-segment foot models Biplanar videoradiography techniques Foot Core Assessment Functionally Standing Running Normal foot function Requires strong, flexible feet 10

11 Foot Core Training Stretching Foot Core Training Extrinsic Muscles AFX Foot Core Training - Intrinsic Muscles Foundational Strength Contracted lumbosacral core Doming Stiffen toes, draw ball of foot back to heel squeeze your arches Abdominal Draw In Augment with estim McKeon et al,

12 Foot Core Training Foundational Strength Foot Core Training Functional Strength Foot Core Training Functional Strength Single leg square jumps Box Jumps Jump rope Always do exercises barefoot! 12

13 8 week strengthening Can you actually change an arch? 32 yr old runner, long hx of Plantar Fasciitis and Post. Tib. Tendinitis long hx of orthotic use Squeeze your arches while you run Weaned out of orthotics, running in minimal shoes and currently doing Crossfit Does Footwear Matter? Foot is well-designed to walk and run without assistance 13

14 Encourage foot core stability by removing support Wouldn t Rx this for life! Concept is not new Shoes of Ron Hill, 1970 Minimal Footwear Use and Foot Strengthening Running Running Walking Arch Excursion (cm) Week 0 Week 8 C FS MSW 5 months of MRS Increase in Muscle Size (MRI) 12 wk program Increase in Arch Stiffness Increase in Abd Dig Min (MRI) 8 wk program Reduced arch excursion from sit to stand Bruggemann et al, 2005 Miller et al, 2014 Ridge et al, 2016 Traditional (TRS) vs Minimal (MRS) shoes on Extrinsic and Intrinsic Ms 6 month running in Vibram 5 fingers * * * Cheung et al, 2016 Leg and foot muscles sig. increased 14

15 J Bone Joint Surg Br Jul;74(4): We analysed static footprints of 2300 children between the ages of four and 13 years to establish the influence of footwear on the prevalence of flat foot. Flat foot was most common in children who wore closed-toe shoes, less common in those who wore sandals or slippers, and least in the unshod. Our findings suggest that shoe-wearing in early childhood is detrimental to the development of a normal longitudinal arch Footwear Matters Lightweight Cushioned True Minimal Same runner, same session, only difference is footwear Other Effects of Traditional Shoes VGRF LGRF VGRF Pronation is greater in shoes due to longer lever arms Bonacci et al,

16 Are all minimal shoes the same? Partial minimal True minimal Mark Cuccuzella 17% dec in landing impacts in runners habituated to true minimal shoes! Rice et al, 2016 Minimal Shoes - not just for running Reduced knee ADD moment Improved Womac Reduced pain meds Story of a pair of feet 50+ yo F, PT, lifelong hx of foot pain, thousands of $ in orthotics Now only comfortable in minimal shoes, Just walked the 26 mile Inca trail in these shoes! Give feet a chance! 16

17 Perhaps its time for paradigm shift in thinking Rather than support and cushion the foot, We leverage the strength and cushioning we have in our feet 26 bones 33 articulations 4 layers of arch ms Courtesy of AFX Think Differently Acknowledgements Pat McKeon, PhD, ATC Jay Hertel, PhD, ATC Dennis Bramble, PhD Roy Cheung, PhD, PT Sarah Ridge, PhD William Rose, PhD Brad Bowser, PhD 17

18 Thank-you Spaulding National Running Center 18