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Irene S. Davis, PhD, PT, FAPTA, FACSM, FASB

Director, Spaulding National Running Center

The Benefits and Pitfalls of Barefoot/Minimal Footwear

Running Healthy People 2020

Exercise is MedicineTM

Up to 79% runners will sustain an injury in a given

year

46% will be recurrences

Van Ghent, 2007

The Problem

~20 million Americans run

Are we doing something wrong?

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

DysEvolution of the Runner!

Overview

Where running began History of running shoes Differences between BF and Shod Running Impacts and Injury Benefits of BF running Pitfalls of BF/Minimal Footwear

Where Running Began

Bramble and Lieberman, 2004

Australopithecus

Nuchal Ligament Larger joint surfaces Shorter femoral neck Expanded Glut Max Long Achilles Plantar Arch 5/26 Markers of Endurance Running

~ 2 Million yrs ago

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Well- Designed Feet

Medial foot

26 bones, 33 jts with 6 dof of movement

4 layers of arch muscles

Rigid Lever, Mobile Adapter, Spring

The human foot is well-suited for

walking and running locomotion

Earliest examples of footgear - sagebrush bark sandals found in caves near Fort Rock, Oregon under a layer of volcanic ash dating back 10,000 years.

The foot surface is smooth and they were held on by straps over the instep.

Prime function of the earliest sandals was protection of the sole.

SF Stewart, 1972

So why was footgear developed? History of Running Shoes

1890’s: J.W. Foster and Sons (now Reebok) introduce the first

running shoe.

1925: Adi Dasler (now Adidas) introduces customized shoes

1917: The advent of vulcanized rubber leads to the first “sneaker”,

the Keds Champion

History of Running Shoes

1972: Phil Knight leaves Asics to form Nike. Nike began producing their own version of the Tiger: the Nike Cortez.

1963: Asics Onitsuku Tiger Imported to the US by Phil Knight.

Introduced the cushioned heel.

Nearly 40 yrs later: The Modern Running Shoe – elevated cushioned heel, stiff heel counter, arch support, high medial midsole

density “Adjusts stiffness according to the time of the month”

The HORMONAL Shoe Asics GEL-KAYANO 16

Do Shoes Really Prevent Injuries?

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Conclusions

‘Assigning shoes based on the shape of the plantar foot surface had no influence on injuries’

Motion control

Stability Cushioning

2010

Do Modern Running Shoes Contribute to Injury?

Next Question…..

RFS 89%

MFS 10%

FFS 1%

Altman et al., 2009

Larson et al., 2011

Shod Running Mechanics Difference between Shod and BF Running

Reduced vertical impacts and lateral forces in BF

Significance of Impact Loads

Rabbit tibia sustains stress fractures with nontraumatic impulsive (axial impact) loads (in vivo) Radin et al, 1990

Bovine joints sustain no damage to cartilage with slow repetitive loading. However, the addition of periodic impact loading led to rapid cartilage wear (in vitro) Radin et al, 1971

Landing on your heel causes vertical impact loads!

Vertical Impact Loads in Runners

0

500

1000

1500

2000

2500

0 25 50 75 100 125 150 175 200 225

Time (ms)

ImpPk

Loadrate

X

Impact loading was greater in those with hx of stress fx and PFP

Peak Forces were not!

Milner et al, 2006 Bowser et al, 2010

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Impacts and ALL injuries (Prospective)

Davis et al., (in review)

Gait analysis

57%

Follow-up

9%

0

500

1000

1500

2000

2500

0 25 50 75 100 125 150 175 200 225

Time (ms)

Imp pk

loadrate

Higher in those who went on to an injury

Results

High Impacts may be a

Global Indicator of

Injury !!!

Effect of Reducing Vertical Impacts

Increased lateral force seen in shod running is in response to increased applied medial force

ML GRF B

F SHOD

Lat

Med

Mediolateral Forces

VGRF VGRF

Effect of Lever Arms in Traditional Shoes

Pronation is greater in shoes due to longer lever arms

LGRF

Bonacci et al, 2013

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What does typical BF running look like?

1. Gentler Landing

Benefits of BF Running

Average Loadrates reduced by 60%

Lateral Forces reduced by 55%

Lat

Med

Davis et al, 2013

…….But don’t shoes cushion our landings?

You actually land harder when you land on soft surfaces!

McNitt-Gray et al, 2006 Bishop et al, 2006

$10 $65

Ferris et al, 1988, 1999 –running

Stiff mat – Soft Landing Soft mat – Stiff Landing More cushioning – Stiffer knee

Questionnaire to 5026 Runners

Ht, Wt, Age, Sex Training mileage

Motivation Injury History

Footwear Runners who wore shoes >$95 were twice as likely to be

injured compared to those in shoes <$40

Marti et al, 1989

Even when corrected for previous injury and training mileage!!

May help explain this…….

2. Shorter Stride

89% Shod - RFS Longer Stride

Most Barefoot - MFS/FFS Shorter Stride

Benefits of Shorter Strides

1. Effects of Stride Length and Running Mileage on a Probabilistic Stress Fracture Model Edwards et al, 2009

Conclusions: Injury risk is reduced when taking shorter strides despite the fact that you are taking more steps!

2. Effects of Step Rate Manipulation on Joint Mechanics during Running Heiderscheidt et al, 2010

Conclusions: Hip and knee loads are reduced when taking shorter strides.

Also Hip ADD reduced (Inc. Hip ADD related to ITBS, PFP, Stress fx, FAI

3. Barefoot Running Reduces Patellofemoral Stress Bonacci et al, 2010

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Effect on knee injuries?? Figure 6

Identify the site of previous injuries that have gone away once you began barefoot running:

0%

5%

10%

15%

20%

25%

30%

35%

40%

45%

50%

Foot Ankle Knee Hip Low Back Previouslyun-injured

BF: Reduced Loading Rates – less impulsive loading

Early stance, Force is less, knee is more flexed, greater contact area – Reduced PFJ Stress

Increased static postural stability in BF compared with socks!

Shinohara et al., 2011

TTB

ML

(s) *

3. Greater Sensory Input

*

*

Rose et. al., 2013

Increased dynamic postural stability in BF

Effect on Sensory Input on Dynamic Postural Stability

Running-Related Injury Prevention through Barefoot Adaptations (Robbins and Hanna, 1987)

BF Group: Dec. Foot Length Indicates Raising of Arch and Strengthening

4. Increased Foot Strength

17 BF, 10 Controls Studied for 4 months

Measured foot length radiographically

Increase in Muscle Size

25 Nike Free, 25 Normal Warm up only 5 months Tested strength, balance, agility and x-sectional area of the muscle

Bruggemann et al, 2005

Improved Strength of Foot and Ankle muscles Improved Balance and Agility tests

Effect of Reducing Footwear on Foot Strength

Increase in ADM and FDB and foot stiffness following 12 week transition to minimal footwear Miller et al, 2014

J Bone Joint Surg Br. 1992 Jul;74(4):525-7. 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

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Plantar Fasciitis – up to 25% foot injuries!!

Medial foot

Strong Feet are Healthy Feet !!

Permanent Tx For Neck Pain?

Permanent Tx For Foot Pain

We decondition them with chronic support!

The Arch is the Foot Core!!*

Small X-sectional areas Short moment arms Stabilizers vs prime movers

You need foot stability for proper foot mobility!

* McKeon et al, 2014

Intrinsic Foot Muscles

Summary: Benefits of Barefoot Running

1.  Less impact, softer landing

2.  Shorter stride lengths, reduced joint loads

3.  Greater sensory input – Static and dynamic stability

4.  Greater strength

Pitfalls of BF/Minimal Footwear Running

Barefoot

Minimal Footwear

Injure plantar surface*

*sensory impairment contraindication !!

Injure soft tissue (arch, calf)

Injure bones (metatarsals)

Cold/Heat Dark Trails

Protect your Feet !!!!

Avoiding the Pitfalls

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Transition Carefully !!

Not weeks, but months!

A New Normal ?

Reduced vertical impacts Reduced lateral forces

Reduced eversion Reduced stride length Reduced hip adduction

Reduced hip and knee loading Stronger feet and lower legs

Billy Rodgers circa 1970

Or Old Normal?

You can not out-engineer Nature

Nothing in Biology Makes Sense Except in the Light of Evolution

Special Issue: Barefoot and Minimal Footwear Running, June, 2014

Special Issue: Running October, 2014

Resources If we evolved to run, why do we get so injured doing it??

We were not built for the speeds we are running (we push ourselves too hard)

We were not meant to land on our heels (impacts are related to injury)

We have taken away the function of the foot (Feet are deconditioned, places greater demands on other structures)

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Acknowledgements

Thank  You  

Spaulding  Na1onal  Running  Center  www.runsnrc.org