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Barefoot Running Guide

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					Breaking the Barriers: Benefits of Barefoot Running




                Terrieha L. Romer

    University of Colorado at Colorado Springs
                                    Table of Contents

I.     Section I

       a. Common Terms and Definitions

II.    Section II

       a. Summation of Benefits of Barefoot Running

               i. Impact Forces

              ii. Injuries

             iii. Running Economy/Efficiency

       b. Adaptations and Implementation Strategies

III.   Section III

       a. Foot Strike Patterns

               i. Heel Strike

              ii. Midfoot Strike

             iii. Forefoot Strike

       b. Running Kinematics

               i. Shod Running-Lateral View

              ii. Barefoot Running-Lateral View

             iii. Shod Running-Medial View

              iv. Barefoot Running-Medial View

              v. Shod vs. Barefoot Running-Aneterior and Posterior Views

       c. Relative Joint Angles

               i. Shod Running

              ii. Barefoot Running
IV.     Barefoot Run Training Program

        a. Weekly Training Guidelines

        b. General Tips

V.      Barefoot Running Workouts

        a. Weeks 1-4

        b. Weeks 4-8

VI.     Barefoot Strengthening Program

VII.    Forefoot Strike Drills

VIII.   Review of the Literature

IX.     References
                                             Section I
Terms & Definitions

      Running: a series of steps in which both feet are briefly and simultaneously off the

       ground during the flight phase

      Running Kinematics: the movements occurring about the body during running

      Running Kinetics: the relationship between the movements occurring about the body

       and the forces that cause them during running

      Three primary phases of running: support, drive, and recovery

      Three primary foot strike patterns:

           o Heel Strike: heel lands first then forefoot touches down (heel to toe running)

           o Midfoot Strike: heel and ball of the foot land simultaneously

           o Forefoot Strike: ball of the foot lands first (usually below 4th and 5th metatarsals)

               before the heel touches down (toe to heel running)

      Four phases of foot strike:

           o 1st phase: moment of impact

           o 2nd phase: flat foot

           o 3rd phase: midstance

           o 4th phase: toe off

      Dorsiflexion: movement which decreases angle between the superior (top) surface of the

       foot and leg (ie: pulling toes up); less than 90º at ankle joint

      Plantarflexion: movement which increases the angle between the superior (top) surface

       of the foot and leg (ie: pointing toes down); greater than 90º at ankle joint

      Supination/Inversion: turning the sole of the foot medially (toward the body‟s midline)
   Pronation/Eversion: turning the sole of the foot laterally (toward the body‟s outside)

   Impact Force: mass involved in the collision (ie: whatever portion of the body that

    comes to a dead stop along with the point of impact on the foot, which is the effective

    mass) times the acceleration (ie: the rate of change of the mass' velocity)

   Effective Mass: the portion of the body that comes to a complete stop with each foot

    strike
                                            Section II
Benefits of Barefoot Running:
       One of the most widely known and scientifically accepted benefits to barefoot running is

related to foot strike patterns and the reduction of impact forces due to the forefoot strike running

gait used in barefoot running. The reduction of impact forces along with a number of other

benefits and adaptations related to barefoot running has been hypothesized to lead to a reduction

in lower extremity injuries (Doud, 2009; Liberman et al., 2010; Robbins & Hanna, 1987). While

the primary benefits related to barefoot running are all intertwined, they can be grouped into

three main categories: (a) impact forces, (b) injury prevention/ reduction, and (c) running

economy/ efficiency.

      Impact Forces: Impact force has been defined as a force resulting from the collision of

       two bodies over a relatively short time period with a relatively high magnitude (Hreljac,

       2004). Heel strike running creates a collision force that leads to both a rapid (10-30

       milliseconds) and high impact force (Hreljac, 2004). Depending upon running speed this

       force has been shown to have a magnitude ranging between 1.5 to 5 times body weight

       (Hreljac, 2004; Lieberman, et al., 2010).

           o Most (80%) shod runners heel-strike, experiencing a very large and sudden

               collision force about 1,000 times per mile, while barefoot runners most likely

               forefoot strike and experience much smaller collision forces.

           o Impact forces were 7 times lower in barefoot runners with forefoot strike gait

               compared to shod runners who heel strike (Lieberman et al., 2010; Oakley &

               Pratt, 1998).
o Barefoot running results in reduced effective mass at ground contact (1.7% of

   total body mass) compared to shod running (6.8% total body mass) (Lieberman et

   al., 2010).

o Based on this research, Lieberman and colleagues (2010) formulated the

   hypothesis that the impact forces experienced every time the foot touches down

   while running plays an important role in repetitive stress injuries (ie: chronic

   running-related injuries) and that a reduction in impact forces and/or effective

   mass, will result in a reduction of the likelihood of repetitive stress injuries.

o Hreljac (2004) proposes that runners who exhibit relatively large and rapid impact

   forces while running (ie: specifically those who heel strike) are at an increased

   risk of developing an overuse injury of the lower extremity.

o Running shoes have been shown to not reduce the impact of the vertical

   component of the ground reaction force during running (Clarke, Frederick, &

   Cooper, 1983; Robbins & Gouw, 1990; Robbins, Gouw & Hanna, 1989; Robbins

   & Hanna, 1987).

          Running shoes did not reduce shock during running at 14 km/h on a

           treadmill (Robbins & Guow, 1990).

          No difference was found between standard running shoes and running

           shoes with a 50% increase in heel cushioning (Clarke, Frederick, &

           Cooper, 1983).

          Comparison of three running shoes with varying levels of cushioning

           found the shoe with the greatest amount of cushion displayed a
                   significantly higher impact loading rate during running, thus negatively

                   subjecting the body to increased forces (Aguinaldo & Mahar, 2003).

       o Barefoot running results in decreased vertical displacement, greater knee flexion,

           and ankle plantarflexion, which acts as a shock absorber by increasing the time in

           which the force is applied to the body (Burkett et al., 1985).

   Injuries: It is estimated that 50-70% of American runners will sustain an injury related to

    running during any one-year period (Hreljac, 2004; Warren & Jones, 1987). Incidence

    rates of lower extremity running injuries range from 19.4% to 79.3%, with the knee being

    the most predominant site of injury, with a specific incidence rate of 7.2% up to 50.0%.

    The other two most common sites of injury include the lower leg (shin, Achilles tendon,

    calf, and heel) and the foot, with injury rates ranging from 9.0% to 32.2% and 5.7% to

    39.3% respectively (van Gent et al., 2007). Running injuries can be broken down into two

    types of injuries: acute injuries (resulting from an accident during running) and chronic

    injuries (resulting from continual exposure to running). The vast majority of running

    injuries falls in the category of chronic injuries, with the etiology of these injuries being

    multifactorial and diverse.

       o While the ultimate cause of running-related injuries is not known, the rather

           consistent impression by coaches, sports medicine practitioners, exercise

           physiologists, and sport scientists is the sudden loading of the lower extremities

           on contact with the ground during weight-bearing activity produces an extremely

           sharp rise of vertically transmitted forces (Robbins & Hanna, 1987). These forces

           are commonly referred to as impact, and as such it is believed to be the increase in

           impact that is the basic premise of running-related injuries.
o Runners with stride patterns which involve relatively low levels of impact forces

   (ie: forefoot striking) and moderately rapid rate of pronation result in reduced risk

   of running-related injury (Hreljac et al., 2000; Hreljac, 2004).

o Barefoot running decreases the risk of ankle sprains, as foot position awareness is

   increased through increased proprioception and tactile sensitivity (Robbins,

   Waked, & Rappel, 1995).

o Barefoot running transfers the ground reaction force impact to the yielding

   musculature of the lower leg instead of the plantar fascia, resulting in a very low

   incidence of plantar fasciitis in barefoot populations (Robbins & Hanna, 1987;

   Warren & Jones, 1987).

o Research has indicated that shod running may lead to weaker feet, contributing to

   the development of various foot pathologies, including weak/ less elastic arches,

   flatter arches, and excessive pronation due to less strength in the muscles,

   ligaments and other connective tissues which stabilize the arch (Hrejlac et al.,

   2000; Rao & Joseph, 1992; Robbins & Hanna, 1987). These foot pathologies have

   been shown to generate large torques and cause unnatural lower extremity

   biomechanics in running, ultimately resulting in increased likelihood of lower

   extremity injuries (Hrejlac et al., 2000).

o Barefoot running could result in decreased patellofemoral pain syndrome due to

   the following adaptations: increased proprioception, increased responsiveness in

   the foot and the production of sensory feedback, and the ability to adapt to uneven

   surfaces (Robbins & Hanna, 1987; Warburton, 2001).
       o Barefoot populations in underdeveloped countries indicate the rarity of lower

          extremity injuries, while reports from countries with co-existing barefoot and

          shod populations indicate elevated lower extremity injuries in only the shod

          population (Robbins & Hanna, 1987). Based on the vast body of research, both

          published and personal reports, Robbins and Hanna indicate there is a very low

          frequency of lower extremity injuries in barefoot populations. Based on the afore-

          mentioned research, it is believed there are adaptations associated with barefoot

          running that provide impact absorption and protection against lower extremity

          running-related injuries.

   Running Economy/ Efficiency

       o Barefoot running has resulted in decreased metabolic cost for running (Burkett et

          al., 1985; Flaherty, 1994; Fredrick, Howley, & Powers, 1980; Hayes, Smith, &

          Santopietro, 1985).

                 Oxygen consumption while running at 7.5 miles/hour was 4.7% higher in

                  shod running compared to the same subjects running barefoot (Flaherty,

                  1994).

                 Increase in oxygen consumption is directly related to the increase in mass

                  added to the foot. Absolute VO2 was significantly greater in subjects

                  running with shoes plus orthotics compared to subjects running barefoot

                  (Burkett et al., 1985).

                 Barefoot running enhances the ability of the foot to act as a spring, thereby

                  allowing a greater return of stored energy than in shod running. The

                  increase in stored energy resulting from an increased activation in the
           stretch shortening cycle increases metabolic efficiency during barefoot

           running.

o Average time for the support phase of running is significantly less in barefoot

   running compared to shod running, resulting in shorter stride length, greater stride

   frequency (turnover) and shorter ground contact time which lead to increased

   overall efficiency (Burkett, Kohrt, & Buchbinder, 1985).
Adaptations & Implementation Strategies

       Prior to beginning barefoot run training, it is recommended that individuals engage in a

4-week barefoot strengthening routine. Performing progressive strengthening exercises for the

foot and ankle, including foot inversion, toe flexion, and walking on the balls of the feet will

facilitate adaptations to barefoot training (Running Barefoot, 2010).

       There are a number of recommendations in the literature on the process of implementing

barefoot running into an individual‟s training program. The following recommendations

provided by Lieberman and colleagues (2010) are intended for individuals with no history of

barefoot running or walking. The training should be minimal initially and increased gradually

over a significant period of time, with the ideal transition involving a change of stimulus (ie:

barefoot training) at a maximum of 10% per week (Running Barefoot, 2010):

          Continuously build strength in lower leg and foot musculature.

           Begin by walking barefoot throughout normal everyday activities for no more than

           30 minutes per day.

           Utilize form/technique drills to learn forefoot strike, proper running gait, and proper

           body positioning (head and body erect; feet should be hitting the ground almost

           directly beneath body).

           Progress to jogging barefoot before, during, or after workouts.

           Start slow (Weeks 1-2: up to 800 meters every other day; Weeks 2-4: up to 1600

           meters every other day) and continue to increase intensity and duration gradually

           (10% per week).

           After 4 weeks of training, increase training to longer bouts at higher average

           velocities.
           Utilize a mix of soft and hard running surfaces to allow feet time to adjust to

           sensations and toughen up.

           Utilize static stretching 10 minutes post-activity every day.

       As forefoot strike running utilizes muscles, tendons, and ligaments of the lower leg

significantly more than heel strike running, a gradual training period and increased stretching is

necessary to run barefoot comfortably and without injury (Doud, 2009).

       Irregular contact surfaces seemed to be the main element that was present in the subjects

with greatest adaptations from barefoot training (ie: increased shock absorption and increased

activation of intrinsic musculature); as such it is recommended over time to vary the training

surface beneath the feet to produce the greatest adaptations (Robbins & Hanna, 1987; Robbins et

al., 1993). Barefoot training on uneven surfaces will also help stimulate the plantar surface and

provide increased sensory feedback (Warburton, 2001).
                                           Section III
Foot Strike Patterns

   Heel Strike (also referred to as rearfoot strike): heel lands first then forefoot touches down

    (heel to toe running).
   Midfoot Strike: heel and ball of the foot land simultaneously.
   Forefoot Strike: ball of the foot lands first (usually below 4th and 5th metatarsal heads),

    followed by the heel touching down (toe to heel running).
Shod Heel Strike Running Kinematics (Lateral View):

1st Phase: Moment of Impact




Description:
    Ankle is dorsiflexed
    Land on middle to outside of heel
    Arch is not loaded
2nd Phase: Flat Foot




Description:
    Upon landing/moment of impact, ankle begins to plantarflex
    Gastrocnemius contracts and Achilles tendon stretches
    Forefoot contacts ground


3rd Phase: Midstance




Description:
    Ankle dorsiflexes and foot everts, resulting in the entire foot being on the ground
    Medial longitudinal arch is loaded, causing it to stretch and flatten
          o This combination of ankle dorsiflexion, eversion, and arch flattening is referred to
             as pronation
4th Phase: Toe-Off




Description:
    Ankle plantarflexes
    Gastrocnemius and Achilles tendon shorten
    Heel lifts off the ground
    Medial longitudinal arch recoils and toes flex, which pushes the body upwards and
       forwards for the next stride.
Barefoot Forefoot Strike Running Kinematics (Lateral View):

1st Phase: Moment of Impact




Description:
    Ankle is plantarflexed and foot is slightly inverted
    Forefoot (just below the 4th and 5th metatarsal heads) contacts the ground
    Upon landing/impact ankle begins to dorsiflex
    Arch of the foot is loaded and begins to stretch/flatten
2nd Phase: Flat Foot




Description:
    Ankle continues to dorsiflex,
    Gastrocnemius and Achilles tendon stretch
    Heel contacts the ground
3rd Phase: Midstance




Description:
    Ankle continues to dorsiflex
    Lower leg moves forward relative to the foot
    Foot everts
    Arch continues to stretch/flatten
    Pronation occurs from forefoot to heel (opposite direction compared to heel striking)
4th Phase: Toe-off




Description:
    Ankle plantarflexes
    Gastrocnemius and Achilles tendon shorten
    Heel lifts off the ground
    Medial longitudinal arch recoils and toes flex, which pushes the body upwards and
       forwards for the next stride
Shod Heel-Strike Running Kinematics (Medial View):




       1st Phase: Moment of Impact                   2nd Phase: Flat Foot




           3rd Phase: Midstance                       4th Phase: Toe-off
Barefoot Forefoot Strike Running Kinematics (Medial View):




        1st Phase: Moment of Impact                    2nd Phase: Flat Foot




             3rd Phase: Midstance                       4th Phase: Toe-off
Shod Versus Barefoot Running Kinematics (Anterior & Posterior Views):

1st Phase: Moment of Impact




               Anterior View                            Anterior View




              Posterior View                             Posterior View
2nd Phase: Flat Foot




                 Anterior View   Anterior View




              Posterior View     Posterior View
3rd Phase: Midstance




                Anterior View    Anterior View




                Posterior View   Posterior View
4th Phase: Toe-off




                 Anterior View   Anterior View




                Posterior View   Posterior View
Relative Joint Angles during Shod Running:




                          Hip Angle:
                            149.9 º
                          Hip Flexion




                        Knee Angle:
                          156.4 º
                        Knee Flexion
Relative Joint Angles during Shod Running (Cont.):




                        Ankle Angle:
                           81.3 º
                        Dorsiflexion
Relative Joint Angles during Barefoot Running:




                         Hip Angle:
                           155.0 º
                         Hip Flexion




                        Knee Angle:
                          146.7 º
                        Knee Flexion
Relative Joint Angles during Barefoot Running (Cont.):




                        Ankle Angle:
                           113.2 º
                        Plantarflexion
                              n
                                           Section IV
Barefoot Run-Training Program:

       This program is based on an experienced recreational runner averaging ~20 miles per

week of running, with no previous barefoot running experience. This program is also based on an

individual with healthy feet, including a good, stable structure with good sensation.



4-Weeks Pre-Barefoot Running:

      Continue regular running and lifting training program

      Perform everyday activities at home barefoot (ie: walking around house and yard,

       checking mail, walking dog around the block, etc)

      Perform barefoot strengthening program at least once a day, three days per week

      Stretch (static stretching) 10 minutes post-activity every day



2-Weeks Pre-Barefoot Running:

      Continue regular running and lifting training program

      Perform everyday activities at home barefoot for at least 30 minutes per day (ie: walking

       around house and yard, checking mail, walking dog around the block, etc)

      Perform barefoot strengthening program at least twice a day, four days per week

      Begin working on form/technique drills to learn forefoot strike and proper body

       positioning

      Stretch (static stretching) 10 minutes post-activity every day
Weeks 1-2 Barefoot Running:

      Continue regular running and lifting training program

      Incorporate barefoot jogging into workouts for either warm-up, cool-down, or active

       recovery (no more than 800 meters total volume, every other day) on grass or sand

      Continue performing everyday activities at home barefoot for at least 30 minutes per day

      Continue performing barefoot strengthening program twice a day, four days per week

      Continue working on form/technique drills to learn forefoot strike and proper body

       positioning

      Stretch (static stretching) 10 minutes post-activity every day (hamstrings, calves and

       arches will need special attention)



Weeks 2-4 Barefoot Running:

      Continue regular running and lifting training program

      Incorporate barefoot jogging into workouts for either warm-up, cool-down, or active

       recovery (no more than 1600 meters total volume, every other day) on varied terrain

      Continue performing everyday activities at home barefoot for at least 30 minutes per day

       (ie: walking around house and yard, checking mail, walking dog around the block, etc)

      Maintain barefoot strengthening program at least three days per week

      Continue working on form/technique drills to learn forefoot strike and proper body

       positioning

      Stretch (static stretching) 10 minutes post-activity every day (hamstrings, calves and

       arches will need special attention)
Weeks 4-8 Barefoot Running:

      Incorporate barefoot running into regular training program

      Gradually increase intensity of barefoot running along with duration (eg: good rule of

       thumb is 10% increase in barefoot running volume per week)

      Continue to utilize a variety of terrain and introduce harder training surfaces (ie: asphalt)

      Ensure correct technique (foot placement/ foot strike) and posture is used in all running

      Maintain barefoot strengthening program at least two-three days per week

      Stretch (static stretching) 10 minutes post-activity every day (hamstrings, calves and

       arches will need special attention)

      Massage claves and arches frequently to break up scar tissue

      Ice baths will aid in recovery




Key Notes:

      The information provided is for educational and informational purposes only. It is

       strongly encouraged to consult a physician before implementing any exercise program.

      This program is not recommended for individuals with diabetes, due to the risk of

       peripheral neuropathy.
Tips for Barefoot Running:

      If pain develops, cease training and let the body heal. Sore, tired muscles are normal, but

       bone, joint, or soft-tissue pain is a signal of injury. Arch and foot pain may occur due to

       landing with the feet too far forward relative to the hips or from landing with too rigid a

       foot and not letting the heel drop gently.

      With proper footstrike the landing should feel gentle, relaxed and compliant, landing on

       the ball of the foot towards the lateral side.

      Do not over stride (landing with the foot too far in front of the hips). Over striding will

       cause excessive plantarflexion, thus adding stress to the calf muscles, Achilles tendon,

       and the arch of the foot.

      Transition slowly, it will take time and effort to switch from heel striking to forefoot

       striking

      Another option for training is utilizing minimalist shoes (ie: Vibram Five Fingers, Nike

       Free, etc.) The minimal shoes will allow development of proper form while also allowing

       the feet to adjust to the new stimulus and terrain. Minimal shoes should incorporate:

           o Flexible sole

           o No arch support

           o No built up heel
                                          Section VI

Barefoot Strengthening Program:

       Complete 3 sets of 25 repetitions per exercise for each exercise. Follow the barefoot

training program guidelines to determine number of sessions per day/week.

      Toe Crunches:

          o Place towel flat on ground

          o Assume seated position on ground with knees at 45º angle and feet flat on ground

          o Using toe flexion, scrunch the towel towards the body

      Toe Fans:

          o Laying down or seated with legs straight out spread toes as wide as possible

      ABC’s:

          o Laying down or seated with legs straight out form letters of alphabet

          o Do only 1 set per leg

      Marble Pick-ups:

          o Place 50 marbles and jar on ground

          o Seated or standing pick up marbles (25 per leg) using toe flexion and put in jar

      Tippy-Toe Walk:

          o Raise up onto balls of both feet

          o Walk for 30 seconds

      Barefoot Calf Raises

      Thera-Band Work:

          o Inversion/Eversion

          o Dorsiflexion/Plantar Flexion
                                         Section VII

Forefoot Strike Drills:

       All drills should be completed as part of the warm-up activity.

          Pawing Drill:

              o Standing in grass with proper posture (head erect, hips at neutral) and using a

                  supporting structure for balance

              o Lift one leg to form ~90º angle at hip and knee (thigh parallel with ground)

                  with slight dorsiflexion at ankle

              o With rapid hip extension, forcefully attack the ground with the suspended leg,

                  striking under the center of mass (ie: under the hips) with the forefoot

              o Following through the contact, allow the heel to touch the butt

              o Quickly bring leg back up to starting position with rapid hip flexion (do not

                  allow torso to collapse)

              o Complete 20 reps on one leg then switch legs

              o Look at grass to ensure foot is striking directly under body
   ‘A’ Drill: Perform each drill twice over 20 meters.

       o Beginner: ‘A’-March

                  With the head erect and torso upright, lift one leg to form ~90º angle at

                   hip (thigh parallel with ground), knee fully flexed (heel close to butt)

                   and foot dorsiflexed

                  March by forcefully attacking the ground with the forefoot striking

                   directly under the center of mass

                  As one leg makes ground contact the other leg should be starting the

                   sequence

       o Intermediate/Advanced: ‘A’-Skip

                  Skip using the same mechanics as in the A-March

                  Emphasize quiet, explosive foot strike and minimize ground contact

                   time

   ‘B’ Drill: Perform each drill twice over 20 meters.

       o Beginner: ‘B’-March

                  Begin with same form as used in A-March (lift one leg to form ~90º

                   angle at hip (thigh parallel with ground), knee fully flexed (heel close

                   to butt) and foot dorsiflexed)

                  Extend knee of suspended leg in front of body

                  Forcefully contact the ground with the forefoot striking directly under

                   the center of mass with quick hip extension

                  As one leg makes ground contact the other leg should be starting the

                   sequence
       o Intermediate/Advanced: ‘B’-Skip

                 Skip using the same mechanics as in the B-March

                 Emphasize quick knee extension, followed by explosive hip extension

   Straight Leg Skips: Perform drill twice over 20 meters

       o With body in proper running position, run keeping legs straight and feet

           dorsiflexed

       o Contact ground with the ball of the foot directly under the center of mass

       o As one leg makes ground contact the other leg should be in the air with the

           body upright and pelvis in neutral position

   Quick Cycle Drills

       o Begin running (75% - 80% intensity) with proper body alignment

       o While running, randomly (~ every 3-4 strides) perform pawing drill motions

       o Complete at least 15 cycles over a distance of approximately 50 meters

       o Beginner: Complete on one leg at a time (right leg only then left leg only)

       o Intermediate: Complete cycles alternating legs

                            Right leg Left leg

                            Left leg Right leg

       o Advanced: Complete cycles alternating legs

                            Right leg Left leg Right leg

                            Left leg Right leg Left leg
Breaking the Barriers: The Benefits of Barefoot Running

                  Terrieha L. Romer

      University of Colorado at Colorado Springs
                  Breaking the Barriers: The Benefits of Barefoot Running

       “The human foot is a work of art and a masterpiece of engineering.”- Leonardo Da Vinci

The human foot is an anatomical marvel of evolution with 26 bones, 33 joints, 20 muscles, and

hundreds of sensory receptors, tendons and ligaments. Like the rest of the body, the feet must be

stimulated and exercised to remain healthy. However, in today‟s American society, the foot is

crammed into a shoe from the time an infant can walk until an old man can no longer walk. The

modern athletic shoe does not allow the foot to work in the manner it was designed, but instead

considers it a delicate, rigid structure which is used only for propulsion (Lieberman, 2010;

Robbins & Hanna, 1987). The external support provided by running shoes cannot match the

support provided by a well functioning foot (Warburton, 2001)

       Running has become one of the most popular means of exercise throughout the United

States, with more than 35 million Americans (estimated to be greater than 10% of the

population) participating in endurance running as a form of exercise in 2007 (National Sporting

Goods Association, 2008). Of those 35 million, over 12 million Americans were actively

engaged and participating in the sport at least 100 days of the year in 2002 (USA Track & Field

[USATF], 2003). With the increased popularity in the sport, the number of developments in

equipment design (ie: running shoes), training philosophies and strategies, and scientific research

related to the kinematic and kinetic variables, which has been linked to injury reduction and

performance enhancement, have also increased.

       Marketing efforts and the creation of “the most advanced performance technology” has

led to a multi-billion dollar athletic footwear industry, with running shoes contributing the largest

percentage to the industry with a value of $2.71 billion dollars in 2002 and steadily increasing

each year (USATF, 2003). However, with the high frequency, up to 70% of American runners,
of running-related injuries each year, the use of running shoes, training methodologies, and

running mechanics are all being questioned to determine the best way to reduce the likelihood of

injury and enhance performance.

       From the ancient Greek Olympics to the 20th century, elite athletes and coaches have

successfully incorporated barefoot running and racing into their training programs, citing a

number of reasons and sources to validate their training ideologies. As such, it has been stated

that barefoot running is not a barrier to performance at even the highest of levels (Warburton,

2001). With Olympic coaches touting the phrase, “Athletes that train barefoot run faster”, the old

adage “All you need to run is a pair of shoes.” just may not be true anymore.

                                   History of Barefoot Running

       Before the invention of the modern running shoe in the 1970‟s, humans were running in

flat leather shoes, thin sandals, moccasins, or in no shoes at all (Lieberman et al., 2010). The first

form of running shoes in the 1950‟s were just simple running flats with little cushioning, no arch

support, and no built-up heel; shoes not even close to mimicking the design and construction of

the modern running shoe.

       Humans and our ancestors have been accomplished endurance runners for more than a

million years (Bramble & Lieberman, 2004). It has been suggested that human endurance

running abilities may have evolved to enable our ancestors to engage in persistence hunting as a

means of gathering food for survival. Due to the evolutionary principle of survival of the fittest,

it has been proposed that our ancestors who engaged in barefoot running did not suffer from the

running-related injuries that are present in today‟s society (Lieberman et al., 2010). Though it is

not known exactly how early humans began running, research indicates that humans were able to

run comfortably and safely when barefoot or in minimal footwear by landing with a flat foot,
defined as midfoot strike, or by landing on the ball of the foot before bringing down the heel,

defined as forefoot strike (Running Barefoot, 2010). Due to Darwin‟s evolutionary principles,

the human foot is likely to be so well adapted to running long distances while barefoot, the

modern heavily cushioned, high arched running shoes may not be necessary.

       Not only was barefoot running utilized in persistence hunting for survival, but it has also

been present at the highest levels of athletic performance. In the ancient Greek Olympics both

men and women competed barefoot. This practice of barefoot running was still present in the

20th century, as Abebe Bikla, previous world record holder and two-time Olympic gold medalist

in the 1960 and 1964 marathon, along with Zola Budd, Olympic distance runner and previous

world record holder in the woman‟s 5000 meters in the mid 1980‟s, were both barefoot runners

who set world records while racing barefoot. Even in the 21st century, elite athletes and coaches

incorporate barefoot running into their training programs. As such, it has been stated that

barefoot running is not a barrier to performance at the highest levels, but may actually enhance

performance (Warburton, 2001).

                                      Review of Literature

Running Kinematics and Foot Strike Patterns

       By simple definition, running is defined as a series of steps with three primary phases:

support, drive, and recovery; and an activity in which both feet are simultaneously off the ground

for a brief time during the flight phase. Running, which has also been described as a series of

leaps, can be expressed as a spring-mass model, in which the stance leg acts as a linear spring,

when compressed under the mass of the body (Doud, 2009). This model allows transfer between

potential and kinetic energy. During the first half of the stance phase, the stance leg compresses

which stretches the tendons, ligaments, and muscles of the leg and foot and allows the storage of
elastic energy. The stretched tendons, ligaments, and muscles recoil and return elastic energy,

which provides a significant percentage of the energy required to extend the leg during the

second half of the stance phase (Cavagna, Saibene, & Margaria, 1964; Cavagna, Heglund, &

Taylor, 1977; Farley & Ferris, 1998). The exchange of energy reduces the metabolic cost per

foot strike, thus leading to an increase in running economy (Ker, Bennett, Bibby, Kester, &

Alexander, 1987). To produce the exchange of energy in the spring-mass system of running,

muscles, tendons, and ligaments must first lengthen and then shorten while the foot is on the

ground (Alexander & Bennet-Clark, 1977). For example, the medial longitudinal arch recoils

and returns approximately 17% of the total energy required during each stance phase, while the

Achilles tendon stores approximately 35% of the energy required during running (Ker et al.,

1987). The elastic recoil provided by these muscles and tendons contribute a significant

proportion of the energy for propulsion in endurance running, and reduce the metabolic cost of

running by approximately 50% (Alexander, 1991; Ker et al., 1987).

       Lieberman and colleagues (2010) have defined three primary foot strike classifications

for endurance running: heel strike, midfoot strike, and forefoot strike. The following

classifications are simply defined as:

               Heel Strike (also referred to as rearfoot strike): heel lands first then forefoot

                touches down (heel to toe running).

               Midfoot Strike: heel and ball of the foot land simultaneously.

               Forefoot Strike: ball of the foot lands first (usually below 4th and 5th metatarsals)

                before the heel touches down (toe to heel running).

       The Running Barefoot website, based on the research of Lieberman and colleagues

(2010), provides a description of the kinematic sequencing of both heel strike and forefoot strike
running. When examining the kinematics related to running for all foot strikes patterns, there are

four phases: moment of impact, flat foot, midstance and toe off. The most common foot strike

pattern is heel striking, with more than 80% of the estimated 35 million Americans running with

a heel strike gait. As such, heel strike running has been considered to be normative by

researchers and runners alike, despite research findings related to the increased impact noted in

heel strike running (Doud, 2009).

       Lieberman and colleagues (2010) describe the following actions at the foot, ankle, and

knee for all four phases of heel strike running. At the moment of impact, defined as the first

phase, the lateral aspect of the heel contacts the ground and the ankle plantarflexes from an

initial dorsiflexed position. Between the first and second phase, controlled ankle plantarflexion

occurs, which contracts the gastrocnemius and allows the Achilles tendon to stretch, while

simultaneously flexing the knee, and allowing the forefoot to contact the ground. Between the

second (flat foot) and third (midstance) phases the ankle dorsiflexes and the foot everts, resulting

in the entire foot being on the ground and the medial longitudinal arch being loaded, causing it to

stretch and flatten. This combination of ankle dorsiflexion, eversion, and arch flattening is

referred to as pronation. The final (toe off) phase of heel strike running begins as the ankle

plantar flexes, causing the gastrocnemius and Achilles tendon to shorten resulting in bringing the

heel off the ground. The recoiling of the arch along with toe flexion pushes the body upwards

and forwards for the next stride.

       Forefoot strike running has been noted as the running gait most commonly seen in

runners who train barefoot. Lieberman and colleagues (2010) describe the kinematics for

forefoot strike running related to the foot, ankle, and knee as follows. During the first phase, the

forefoot (just below the 4th and 5th metatarsal heads) contacts the ground, with the ankle being
plantarflexed and the foot slightly inverted. Upon contact, the ankle begins to dorsiflex and the

medial longitudinal arch is loaded. Between the first and second phase, the ankle continues to

dorsiflex, allowing the heel to contact the ground through the controlled stretching of the

gastrocnemius and Achilles tendon. Between the second and third phase, pronation occurs from

the forefoot to the rearfoot (opposite direction of heel strike running) and the final phase of

forefoot strike running kinematics is identical to the final phase for heel strike running.

Furthermore, the kinematics of midfoot strike running indicate a continuum between heel strike

and forefoot strike running and is dependent upon where the center of pressure is at impact.

       At the moment of impact the foot should be moving backwards, matching the speed of

the ground beneath the runner to allow the body to move forward. This can only be achieved

with a forefoot or midfoot strike as a heel strike landing results in the heel pushing against the

ground in the opposite direction, causing the foot to move forward while the ground is moving

backwards beneath the foot. In performance settings, heel strike running is often referred to as

„braking‟. This „braking‟ phenomenon is a result of the rapid change in momentum by the foot

coming to a complete stop upon contact with the ground (Doud, 2009).

Kinematics and Foot Strike Patterns Related to Barefoot Running Benefits

       From an evolutionary perspective, it has been suggested that heel strike running is not a

normal mode of foot contact during endurance running, but instead may be a recent phenomenon

brought about by the invention of the modern running shoe (Doud, 2009). It has been proposed

that forefoot strike, the noted foot strike pattern in barefoot running, is the most efficient and

most economical running gait (Warburton, 2001). Research has noted that habitually barefoot

runners, including American runners who switched to running barefoot or in minimalist shoes,

forefoot strike, even when wearing running shoes (Barefoot Running, 2010; Doud, 2009). The
forefoot strike produced by barefoot runners increases the work of the foot‟s soft tissue support

structures and intrinsic musculature of the lower leg, resulting in increased strength, which has

been hypothesized to reduce the risk of injury (Warburton, 2001). Furthermore, the average time

for the support phase of running, in which the heel is on the ground, is significantly less in

barefoot running compared to shod running. During shod running, the heel is on the ground for

80% of the stance phase, while the heel is only briefly in contact with the ground for forefoot

strike running. The reduction in time of support noted in barefoot running results in shorter

stride length, greater stride frequency (turnover), and shorter ground contact time, all variables

which lead to increased overall efficiency (Burkett, Kohrt, & Buchbinder, 1985).

       The degree of ankle plantarflexion is higher in barefoot runners compared to shod

runners in both neutral running shoes and minimal running shoes (Griffin, Mercer, & Dufek,

2007; Warburton, 2001). This increased ankle angle has been related to the lack of cushioning

underfoot, as the ankle plantarflexes to produce a softer landing (Aguinaldo & Mahar, 2003).

The foot of shod runners has been described as rigid and is a fragile and delicate structure

comprised of unyielding connective tissues. However, based on the concept of natural selection,

it has been proposed that the natural foot is a yielding structure responsive to the stress placed

upon it, producing sensory feedback and absorbing shock (Robbins & Hanna, 1987; Robbins,

Gouw, McClaran, Waked, 1993).

Running Forces and Kinetics

       To understand the biomechanical differences between different foot strike patterns both

running kinematics and running kinetics must be understood. Simply defined, running kinetics is

the relationship between movements and the forces that cause them (Running Barefoot, 2010).
       The impact of the body with the ground generates an impact force. This force equals the

mass involved in the collision (ie: whatever portion of the body that comes to a dead stop along

with the point of impact on the foot, which is the effective mass) times the acceleration (ie: the

rate of change of the mass' velocity) (Lieberman et al., 2010). This principle is Newton‟s 2nd Law

(F=ma).

       The Running Barefoot website, based on Lieberman and colleagues (2010) work,

provides a description of the kinetic variables presented below for both heel strike and forefoot

strike running. The three main kinetic variables which have been examined and compared by

Lieberman and colleagues between forefoot strike and heel strike running are: (a) effective mass

at impact, (b) conversion of vertical momentum at impact, and (c) impact force. The effective

mass differs greatly between forefoot striking and heel striking. For heel strike runners, the

effective mass is the foot plus the lower leg, as both come to a complete stop at impact.

However, forefoot strike runners have an effective mass that is equal to only the forefoot and a

small portion of the rearfoot and leg, as only the forefoot comes to a complete stop, as the lower

leg and rearfoot continue to fall after foot strike, thus the effective mass involved in a forefoot

strike is just a portion of the foot. The value for the effective mass for heel strike running is 6.8%

of total body mass and only 1.7% of total body mass for forefoot strike running in the runners

measured by Lieberman and colleagues. The second kinetic variable examined, conversion of

vertical momentum at impact, is also different between foot strike patterns. In heel strike

running, the vertical momentum of the lower leg is mostly absorbed by the vertical component of

the collision force, whereas the vertical momentum in forefoot strike running is converted into

rotational momentum. The third and final kinetic variable studied by Lieberman and colleagues

is the impact force and is also notably different between the two foot strike patterns.
       Impact force has been defined as a force resulting from the collision of two bodies over a

relatively short time period with a relatively high magnitude. Heel strike running creates a

collision force that leads to both a rapid (10-30 milliseconds) and high impact transient force

(Hreljac, 2004). Depending upon running speed the collision force experienced in heel strike

running has been shown to have a magnitude ranging between 1.5 to 5 times body weight

(Hreljac, 2004; Lieberman, et al., 2010). This impact force sends a shockwave through the body,

transmitting the force along the lower limb to the upper body via the skeletal system (Aguinaldo

& Mahar, 2003; Doud, 2009).

       However, the collision produced by forefoot strike running and most midfoot strike

running results in a very slow rise in force with no distinct impact transient force. By landing on

the forefoot, runners are able to reduce the magnitude of the collision between the foot and

ground at impact by reducing the effective mass involved in the collision (Doud, 2009). Research

has shown that runners with a forefoot strike gait tend to have much lower impact forces

compared to shod runners who heel strike (Lieberman et al., 2010; Oakley & Pratt, 1998).

Lieberman and colleagues (2010) found that impact forces were seven times lower in barefoot

runners compared to shod runners. Furthermore, rates of loading in forefoot strike runners are

equal to or less than rates of loading for shod runners. In forefoot striking, the collision of the

forefoot with the ground generates a very minimal impact force with no impact transient. Based

on the research related to foot strike patterns and impact forces, Lieberman and colleagues

propose that the large impact forces during running can be avoided by forefoot striking properly.

       Similar to forefoot strike landing, most midfoot strike runners will land softly, resulting

in low impact forces. However, depending upon the location of the center of pressure, some

midfoot strikes can generate impact forces similar to heel strike running; though these forces are
distributed over larger surface areas and as such reduces the stress on the foot (Lieberman et al.,

2010).

Running Forces and Kinetics Related to Barefoot Running Benefits

         A number of studies investigating the vertical component of ground reaction force during

running do not support the notion that running shoes reduce the impact (Clarke, Frederick, &

Cooper, 1983; Robbins & Hanna, 1987; Robbins, Gouw & Hanna, 1989; Robbins & Gouw,

1990). Robbins and Gouw (1990) reported that running shoes did not reduce shock during

running at 14 km/h on a treadmill, while Clarke, Frederick, and Cooper (1983) found no

significant differences in impact forces between standard running shoes and running shoes that

contained a 50% increase in heel cushioning. Furthermore, Robbins and Gouw (1990) argued

that the plantar sensation created during barefoot running creates a plantar surface protective

response causing runners to alter their foot strike patterns to reduce shock. Conversely, footwear

with greater cushioning caused a sharp reduction in shock-moderating mechanics, thus resulting

in increased impact force (Robbins & Hanna, 1987; Robbins, Gouw, & Hanna, 1989; Robbins &

Gouw, 1990).

         Lieberman and colleagues (2010) examined the running gaits of (a) habitual barefoot

runners (those who trained at least 20km/week barefoot or in minimalist shoes for at least 6

months, (b) habitual shod runners, and (c) those who had converted to barefoot running from

shod running. The results showed that most shod runners heel-strike, experiencing a very large

and sudden collision force about 1,000 times per mile, while barefoot runners were more likely

to forefoot strike. The difference in foot strike patterns generated profoundly different impact

forces with forefoot strikers generating much less severe impact forces than heel strikers. Based

on this research, Lieberman and colleagues formulated the hypothesis that the impact forces
experienced every time the foot touches down while running plays an important role in repetitive

stress injuries and that a reduction in impact forces, will result in a reduction of the likelihood of

repetitive stress injuries.

Running Injuries

        It is estimated that 50-70% of American runners will sustain an injury related to running

during any one-year period (Hreljac, 2004; Warren & Jones, 1987). An overview of published

reports on the incidence rates of lower extremity running injuries in long distance runners

indicate ranges from 19.4% to 79.3%, with the knee being the most predominant site of injury,

with a specific incidence rate of 7.2% up to 50.0%. The other two most common sites of injury

include the lower leg (shin, Achilles tendon, calf, and heel) and the foot, with injury rates

ranging from 9.0% to 32.2% and 5.7% to 39.3% respectively (van Gent et al., 2007). Running

injuries can be broken down into two types of injuries: acute injuries (resulting from an accident

during running) and chronic injuries (resulting from continual exposure to running). The vast

majority of running injuries falls in the category of chronic injuries and has previously been

termed over-use injuries. By definition, these injuries are musculoskeletal ailments that result in

a restriction of running speed, distance, duration, or frequency for at least one week (Hreljac,

2004). However, due to the frequency and prevalence of these injuries among recreational

runners who are running very modest mileages (19 miles for women and 27 miles for men) and

reasonable amounts of time, the term „running-related injuries‟ is often used as opposed to over-

use injuries (Robbins & Hanna, 1987).

        While the ultimate cause of running-related injuries is not known, the rather consistent

impression by coaches, sports medicine practitioners and exercise physiologists is the sudden

loading of the lower extremities on contact with weight-bearing activity produces an extremely
sharp rise of vertically transmitted forces (Robbins & Hanna, 1987). These forces are commonly

referred to as impact, and as such it is believed to be the increase in impact that is the basic

premise of chronic running-related injuries. Research has indicated that runners with stride

patterns which involve relatively low levels of impact forces (ie: forefoot striking) and

moderately rapid rate of pronation result in reduced risk of running-related injury (Hreljac,

Marshall, & Hume, 2000; Hreljac, 2004). Furthermore, foot pathologies, including weak arches

and excessive pronation have been shown to generate large torques and cause unnatural lower

extremity biomechanics in running, which has also been attributed to result in lower extremity

injuries (Hreljac et al., 2000).

        Commonly reported running-related chronic injuries include: ilio-tibial (IT) band

syndrome, patellofemoral pain syndrome, patellar tendinitis, shin splints, stress fractures,

Achilles tendinitis, and plantar fasciitis (Hreljac et al., 2000; Robbins & Hanna, 1987). The

etiology of these running-related injuries is unknown, but has been stated to be multifactorial and

diverse. The majority of the factors identified as causes of running-related injuries could be

placed into three general categories: training, anatomical, and biomechanical variables (Hreljac

et al., 2000; Hreljac, 2004). Furthermore, the kinetic and kinematic variables which have been

related to the cause of running-related injuries include: magnitude of impact forces, rate of

impact loading, magnitude of active (propulsive) forces, magnitude of joint forces and moments,

along with the magnitude and rate of foot pronation (Hreljac, 2004). Hreljac has hypothesized

that runners who exhibit relatively large and rapid impact forces while running (ie: specifically

those who heel strike) are at an increased risk of developing an overuse injury of the lower

extremity. Furthermore, studies have indicated that shod running may lead to weaker feet, thus

contributing to the development of various foot pathologies such as less elastic arches, flatter
arches, and excessive pronation due to less strength in the muscles, ligaments and other

connective tissues which stabilize the arch (Hrejlac et al., 2000; Rao & Joseph, 1992; Robbins &

Hanna, 1987).

       Plantar fasciitis, the most commonly occurring running-related injury at the foot, is an

inflammation in the plantar fascia and presents itself as heel or arch pain during or after running

(Warren & Jones, 1987). Plantar fasciitis can be attributed to the plantar fascia acting as the

support for the medial longitudinal arch which creates a strain on the proximal fascial attachment

during foot strike in shod populations (Robbins & Hanna, 1987). However, Robbins & Hanna‟s

research has revealed barefoot running transfers the impact to the yielding musculature of the

lower leg, sparing the fascia and resulting in a very low incidence of plantar fasciitis in barefoot

populations.

       While there are a number of theories as to the etiology of patellofemoral pain syndrome,

research studies have attributed patellofemoral pain syndrome to the loss of the capability of the

lower extremity to adapt to the variability of the surface beneath the foot (Ryan, MacLean, &

Taunton, 2006; van Gent et al., 2007). Key adaptations to barefoot running which could result in

decreased patellofemoral pain syndrome include: increased proprioception, increased

responsiveness in the foot and the production of sensory feedback, and the ability to adapt to

uneven surfaces (Robbins & Hanna, 1987; Warburton, 2001).

       Ankle sprains, one of the most commonly reported acute injuries across all sports, are

also the most common acute injury in running. Due to the decreased proprioception and overall

lack of feedback from the plantar cutaneous mechanoreceptors, Robbins and colleagues

hypothesize the risk of ankle sprains is increased in shod runners (Robbins, Waked, & Rappel,

1995). However, barefoot running has been reported to increase proprioception and tactile
sensitivity, both of which have been described as key elements in the reduction of ankle sprains

(Warburton, 2001).

       Observation of barefoot populations in underdeveloped countries indicate the rarity of

lower extremity injuries, while reports from countries with co-existing barefoot and shod

populations indicate elevated lower extremity injuries in only the shod population (Robbins &

Hanna, 1987). Based on the vast body of research, both published and personal reports, Robbins

and Hanna indicate there is a very low frequency of lower extremity injuries in barefoot

populations. It is believed the adaptations associated with barefoot running provide impact

absorption and protection against lower extremity running-related injuries.

       Research has been conducted studying common anthropometric and biomechanical

variables which have been attributed to chronic running-related injuries. From this research,

Hreljac and colleagues (2000) determined increased vertical impact forces experienced and

increased rate of loading are the most commonly occurring variables among injured runners.

Hreljac and colleagues compared two groups of recreational runners to identify biomechanical

and anthropometric variables that contribute to chronic running-related injuries. The study

consisted of a group of 12 participants who had never sustained a running-related injury and a

group of 12 participants who had suffered at least one at or below the knee running-related

injury, though the majority of the group had suffered multiple injuries. All participants had been

running on a regular basis for a minimum of three years, and the previously injured participants

had returned to training regularly for at least three months. Training history, including weekly

running distance, average training pace, running surfaces, footwear, stretching, and cross-

training habits along with anthropometric and anatomical data was collected and recorded for all

participants. Biomechanical data including contact time, vertical force impact peak, maximal
vertical loading rate, maximum active force peak, maximum push-off force, Achilles tendon

angle at touchdown, maximal angle of pronation, total change in Achilles tendon angle, and

maximal pronation velocity was acquired by subjects running over a floor-mounted force

platform at a speed of 4m·s-1. All tests were completed under shod conditions and all variables

were normalized to body weight to allow for comparison between subjects of different mass.

There were no significant differences between the groups for any of the training variables and

the only anatomical variable which was significantly different between groups was the non-

injured group demonstrated greater hamstring flexibility, 3.2 ± 10.2 cm compared to -3.7 ± 11.5

cm for the previously injured group (p<0.05). The vertical force impact peak was significantly

lower (p<0.004) in the non-injured group 2.13 ± 0.42 BW, compared to 2.40 ±0.41 BW for the

previously injured group. The only other biomechanical variable which exhibited significant

difference between groups was the maximal vertical loading rate, with the non-injured group

(76.6 ± 19.5 BW·s -1) being significantly lower (p>0.01) compared to the previously injured

group (93.1 ± 23.8 BW·s -1). Hreljac and colleagues suggest the results of this study indicate

runners who utilize a stride characterized by low impact forces, as noted in barefoot running, are

at a reduced risk of incurring chronic running-related injuries.

       Furthermore, another study investigating variables related to running injuries, specifically

predictors of plantar fasciitis, utilized 91 runners, a control group of 46 runners with no history

of plantar fasciitis, a group of 31 runners currently diagnosed with plantar fasciitis, and a group

of 14 runners who had previously been diagnosed with plantar fasciitis. The purpose of Warren

and Jones (1987) study was to determine if anatomical and biomechanical variables could be

predictors of runners who had suffered with plantar fasciitis, either presently or formerly, versus

runners who had never suffered with plantar fasciitis. All subjects completed a training history
and were measured on several anatomical variables (leg length, plantar and dorsiflexion at the

ankle, degree of pronation/ supination during standing in a loaded stance, mid-tarsal joint

abduction/ adduction, and arch height). Biomechanical variables (contact time, foot strike, and

pronation) were obtained for each participant while running in both barefoot and shod conditions

on a treadmill. The control group exhibited the least difference in leg length, least ability to

dorsiflex, greatest degree of plantar flexion, lowest amount of pronation during standing, lowest

arches, and the longest contact time during shod running. The currently diagnosed group

exhibited the greatest ability to dorsiflex, greater pronation while standing, highest arches, and

the greatest degree of pronation on the left foot and least degree of pronation on the right foot

while running during both barefoot and shod conditions. The previously diagnosed group

exhibited the greatest difference in leg length, the least ability to plantar flex, greater pronation

than the control group while standing, lowest amount of foot adduction and greatest amount of

foot abduction, least degree of pronation on the left foot and greatest degree of pronation on the

right foot while running during both barefoot and shod conditions, and the shortest foot contact

time during running. The following nine variables were determined through factor analysis to be

predictors for the plantar fasciitis groups (control, currently injured, and previously injured): leg

length inequality/barefoot pronation, dorsiflexion ability, ankle flexibility, arch height, pronation

while running in shoes, time of foot contact while running, and type of footstrike. The analysis

correctly predicted 76% of the control group, 55% of the currently injured, and 36% of the

previously injured group, thus 63% of the runners were correctly assigned to their respective

groups. The authors concluded that the factors were good predictors of the control group (no

history of plantar fasciitis), but were not good predictors of those currently or previously

diagnosed with plantar fasciitis.
Benefits and Adaptations of Barefoot Running

       One of the most widely known and scientifically accepted benefits to barefoot running is

related to foot strike patterns and the reduction of impact forces due to the forefoot strike running

gait. As previously discussed, the reduction of impact forces along with a number of other

benefits and adaptations to barefoot running has been hypothesized to lead to a reduction in

lower extremity injuries (Doud, 2009; Hreljac et al., 2000; Hreljac, 2004; Liberman et al., 2010;

Robbins & Hanna, 1987).

       Additionally, a number of studies has shown barefoot running has resulted in decreased

metabolic cost for running (Burkett et al., 1985; Flaherty, 1994; Fredrick, Howley, & Powers,

1980; Hayes, Smith, & Santopietro, 1985). A report by Flaherty (1994) determined oxygen

consumption while running at 7.5 miles/hour was 4.7% higher in shod running (weight of shoes

= 700 grams) compared to the same subjects running barefoot. Furthermore, Burkett and

colleagues (1985) found there was a linear increase in oxygen consumption directly related to the

increase in mass (ie: shoes) added to the foot. Absolute VO2 was significantly greater in subjects

running with shoes plus orthotics compared to subjects running barefoot. One possibility for the

increased energy cost during shod running has been attributed to the continual accelerating and

decelerating mass of the shoe along with the required external work in compressing, flexing, and

rotating the sole of the shoe against the ground with each stride (Warburton, 2001). Furthermore,

barefoot running enhances the ability of the foot to act as a spring, thereby allowing a greater

return of stored energy than is present in shod running. As a result the increase in stored energy

resulting from an increased activation in the stretch shortening cycle increases metabolic

efficiency during barefoot running.
       Barefoot running results in decreased vertical displacement and greater flexion at the

knee, with the latter helping to act as a shock absorber by increasing the time in which the force

is applied to the body (Burkett et al., 1985). Research has shown a loss of shock absorbing

capacity in older runners, thus barefoot running could be regarded as very beneficial to this select

population, due to the decrease in impact forces and rate of loading.

       Additionally, there are a number of benefits and adaptations of barefoot training which

occur within the musculature of the foot and lower leg. Based on reports indicating a low

running-related injury frequency in barefoot populations, Robbins and Hanna (1987)

hypothesized that barefoot running produces adaptations, specifically deflection of the medial

longitudinal arch, which provides impact absorption, resulting in protection against running-

related injuries. Robbins and Hanna‟s second hypothesis was the rigidity of the shod foot is

responsible for the high injury rates in recreational runners. Their 1987 study analyzed the

adaptive pattern of the medial longitudinal arch due to increased barefoot weight-bearing activity

in recreational runners over a period of four months. The study consisted of an experimental

group, 10 participants who increased weight-bearing activity (greater than one-hour per day), and

a control group, 7 participants who did not increase weight-bearing activity. All subjects

recorded a detailed running history and maintained a training log for the duration of the study.

Foot imprints and x-rays were taken both prior to the commencement of the study as well as at

monthly intervals in both a relaxed weight-bearing state and a loaded state. A positive change in

the medial longitudinal arch span is indicated by significant (1mm) shortening of the arch with

increased weight bearing activity. The experimental group resulted in 72% changed positively,

11% changed negatively and 17% saw no change (p<0.05) in the arch span. However, 91% of

the control group changed negatively (p<0.05). The mean change in the medial longitudinal arch
span for the experimental group was +4.7 mm and -4.9 mm for the control group. The shortening

of the medial longitudinal arch allows the foot to act as an impact dampener and not merely a

lever for propulsion. Robbins and Hanna concluded this adaptation appears capable of

preventing the most common running-related injuries. Furthermore, the electromyographic

studies conducted by Robbins and Hanna have shown there is no tonic activity of the intrinsic

muscles of the shod foot during weight-bearing activity. However, after four months of

progressively increasing barefoot running, the medial longitudinal arch was shortened and the

load was redistributed to the digits during weight-bearing activity. As such, Robbins & Hanna

attribute this change to the activation of the intrinsic musculature of the foot and lower leg which

is inactive in the shod population studied. Furthermore, this study demonstrates the foot and

lower leg musculature of shod populations can be rehabilitated to mimic the active musculature

which is present in barefoot training populations.

       When training barefoot, the mechanoreceptors produce plantar sensory feedback which

increases intrinsic foot shock absorption (Robbins et al., 1993). Barefoot running, with a

forefoot strike, results in a flatter foot placement, which has been theorized to be a protection

mechanism, protecting the heel of the foot and lower leg from high impact forces and allowing

the gastrocnemius and Achilles tendon to control the lowering of the heel to the ground, thus

increasing the time in which the force is applied to the body (De Wit, DeClarcq, & Aerts, 2000).

Furthermore, excessive pronation, which has been attributed to resulting in unnatural lower

extremity biomechanics, is not present during barefoot running, with research showing the

degree and speed at which pronation occurs being lowest when running barefoot (Stacoff, Kalin,

& Stussi, 1991).
Current Trends in Running Shoes and Barefoot Running

       Though the research is limited examining the effect of minimalist shoes, there are a

number of studies that have examined the effect of modern running shoes in relation to impact

absorption, foot strike patterns, and overall running kinematics (Aguinaldo & Mahar, 2003;

Doud, 2009; Griffin et al;, 2007; Hreljac et al., 2000; Hreljac, 2004; Lieberman et al., 2010;

Oakley & Pratt, 1988; Robbins & Hanna, 1987; Robbins et al., 1989; van Gent et al., 2007;

Warburton, 2001; Warren & Jones, 1987; Willy & Davis, 2009). Also, research is becoming

more prevalent regarding the effects of barefoot running specifically concerning its relationship

to injury prevention through reduction in impact forces and performance enhancement through

improved running economy (Aguinaldo & Mahar, 2003; Doud, 2009; Flaherty, 1994; Griffin et

al;, 2007; Hreljac et al., 2000; Hreljac, 2004; Lieberman et al., 2010; van Gent et al., 2007;

Warburton, 2001; Warren & Jones, 1987; Willy & Davis, 2009).

       Running shoes have progressed from flat, thin shoes with no cushion to ultra thick

cushioned motion resistant shoes, to minimalist shoes developed to mimic barefoot running. The

$13 billion dollar athletic shoe industry is continuously designing and developing new shoes

with the „latest and greatest technology‟ but there are few if any scientific studies conducted on

this „newest and greatest technology‟ before production begins (National Sporting Goods

Association, 2008).

       In the simplest terms, running shoes should be regarded as devices to protect the feet

from dangerous objects and extreme temperatures, rather than the corrective devices they have

been marketed as for the last two decades (Warburton, 2001). The external support provided by

running shoes does not match the support provided by a well functioning foot. Research has

indicated runners wearing expensive highly cushioned and/or motion control running shoes have
a greater prevalence, more than double, of running-related injuries than runners wearing cheaper

non-cushioning shoes. Aguinaldo and Mahar (2003) evaluated the effect of running shoes on

impact force patterns during running. Kinematic and ground reaction force data was collected on

10 participants running in two shoes with varying levels of extra cushion and a traditional

running shoe. The shoe with the least cushion/ most stiffness of the two extra cushioned shoes

produced significantly lower (p =0.02) impact force (1.84 ± 0.24 BW) compared to (1.94 ± 0.18

BW) and significantly lower (p = 0.005) loading rates (45.6 ± 11.6 BW·s -1) compared to (57.9 ±

12.1 BW·s -1). Both of the extra cushioned shoes showed impact force characteristics similar to

the traditional running shoe. The study also noted that increased stiffness of a shoe resulted in

altered landing patterns which were attributed to the lower impact forces.

       Despite the increased popularity of minimalist running shoes, research regarding the

effect of these shoes is mixed. Willy and Davis (2009) examined five subjects to determine if

running in a minimal shoe (Nike Free 3.0, Beaverton, OR) reduced ground reaction forces and

mimicked footstrike patterns of barefoot running, compared to running in a traditional running

shoe (Nike Pegasus, Beaverton, OR). The study is on-going, but at date of publish had examined

the following variables: average vertical load rate, tibial shock, leg stiffness, ankle dorsiflexion at

heel strike, and horizontal angle of the foot at heel strike of recreational runners while running on

an instrumented treadmill at 3.35 m·s-1. The results of the study thus far have shown all variables

of interest were greater when running in the minimalist shoes. However, Willy and Davis suggest

the positive kinematic adaptations experienced from barefoot running may occur over time when

running in minimalist shoes, and as such a study of runners who habitually run in minimalist

shoes is underway.
       Another study examining the kinematic effects of a minimal running shoe (Nike Free 5.0,

Beaverton, OR) found very few kinematic differences in barefoot running compared to running

with minimalist shoes (Griffin et al., 2007). The purpose of Griffin and colleagues study was to

determine if knee and ankle kinematics were similar when running with bare feet and when

running in a minimalist shoe. Nine subjects ran on a treadmill for 8 minutes, with ten footfalls

per subject for each condition (barefoot and wearing minimalist test shoes) being used to

evaluate knee and ankle angle at impact, knee angular velocity at impact, peak knee angle at

midstance, and peak knee angular velocity at midstance. Barefoot running resulted in the ankle

being significantly more plantar flexed at contact (7.4 ± 6.1º), compared to shod running (15.9 ±

3.6º); peak knee angle was significantly more extended when barefoot (45.8 ± 1.6º) than when

shod (49.5 ± 2.0º); and peak knee angular velocity was significantly slower when barefoot

(357.55 ± 42.9º) than when shod (421.9 ± 82.2º) (p<0.05). The authors concluded there were

very few differences between running in the test shoes and running with bare feet. Furthermore,

research examining the effect of warming up in minimalist running shoes found that musculature

in the toe and foot responsible for plantar and dorsiflexion was increased by 4-5% over a five

month training period. It has been hypothesized that this increased foot strength may assist in

controlling excessive motion in the foot. Additionally, research conducted by Lieberman and

colleagues (2010) noted that after training in a minimalist shoe, specifically Vibram FiveFingers

(Concord, MA), habitually shod heel strike runners begin to either midfoot or forefoot strike.

Implementation of Barefoot Running

       As the modern running shoe has successfully diminished sensory feedback without

diminishing the injury inducing impact, the arch support has interfered with the body‟s natural

downward deflection of the medial longitudinal arch upon loading, and the shoes were designed
to use the foot as an inflexible lever; Americans are utilizing barefoot running as a means of

correcting running kinematics, improving running performance, reducing the impact forces, and

reducing the likelihood of running-related injuries (Lieberman et al., 2010; Robbins & Hanna,

1987). Based on a review of literature concerning the incidence of injuries in long distance

runners, the overall recommendation is runners to not exceed 39 miles per week to aid in the

reduction of running-related injuries (van Gent et al., 2007).

   Prior to beginning barefoot run training, it is recommended that individuals engage in a 4-

week barefoot strengthening routine. Performing progressive strengthening exercises for the foot

and ankle, including foot inversion, toe flexion, and walking on the balls of the feet will facilitate

adaptations to barefoot training (Running Barefoot, 2010). As forefoot strike running utilizes

muscles, tendons, and ligaments of the lower leg significantly more than heel strike running, a

gradual training period and increased stretching is also necessary to run barefoot comfortably

and without injury (Doud, 2009).

       There are a number of recommendations in the literature on the process of implementing

barefoot running into an individual‟s training program. The following recommendations

provided by Lieberman and colleagues (2010) are intended for individuals with no history of

barefoot running or walking. The training should be minimal initially and increased gradually

over a significant period of time, with the ideal transition involving a change of stimulus (ie:

barefoot training) at a maximum of 10% per week (Running Barefoot, 2010):

          Continuously build strength in lower leg and foot musculature.

           Begin by walking barefoot throughout normal everyday activities for no more than

           30 minutes per day.
           Utilize form/technique drills to learn forefoot strike, proper running gait, and proper

           body positioning (head and body erect; feet should be hitting the ground almost

           directly beneath body).

           Progress to jogging barefoot before, during, or after workouts.

           Start slow (Weeks 1-2: up to 800 meters every other day; Weeks 2-4: up to 1600

           meters every other day) and continue to increase intensity and duration gradually

           (10% per week).

           After 4 weeks of training, increase training to longer bouts at higher average

           velocities.

           Utilize a mix of soft and hard running surfaces to allow feet time to adjust to

           sensations and toughen up.

           Utilize static stretching 10 minutes post-activity every day.

       Irregular contact surfaces seemed to be the main element that was present in the subjects

with greatest adaptations from barefoot training (ie: increased shock absorption and increased

activation of intrinsic musculature); as such, it is recommended over time to vary the training

surface beneath the feet to produce the greatest adaptations (Robbins & Hanna, 1987; Robbins et

al., 1993). Barefoot training on uneven surfaces will also help stimulate the plantar surface and

provide increased sensory feedback (Warburton, 2001). Changes to the feet and lower leg

produced by barefoot running include: thickening of the sole of the foot, activation of small and

weak intrinsic muscles, and development of calloused plantar skin. However, running shoes

should not be completely disregarded as they play an important role in extreme weather

conditions and on some courses which may present dangerous or painful objects (ie: glass, sharp

objects, etc). Furthermore, the only contraindication to barefoot running provided in the research
is for individuals with peripheral neuropathy (loss of sensation in the feet), which is a common

complication of diabetes mellitus (Lieberman et al., 2010; Robbins & Hanna, 1987; Robbins et

al., 1993).

        Research studies have shown that subjects are able to make technique changes with very

limited adaptation time (Lieberman et al., 2010, Robbins & Hanna, 1987). As such, a runner

does not have to be exposed to barefoot running for long periods of time to unconsciously make

changes; however, longer periods of barefoot training time may be required for those changes to

become permanent when the stimulus is removed (ie: when training in shoes). A conclusion

drawn from Willy & Davis‟ (2009) study comparing running kinematics in a neutral running

shoe (Nike Pegasus) and a minimal running shoe (Nike Free 3.0) supports Lieberman and

colleagues claim that the changes and adaptations/benefits related to barefoot running take time

when training with shoes, even minimal shoes.

                                             Conclusion

        Based on the research, it is known and not debated that barefoot running changes foot

strike patterns, leading to either a forefoot strike or midfoot strike running gait. It is also known

and not debated that the ankle is more plantarflexed and the knee is more flexed during barefoot

running. While the majority of research has shown barefoot running with a forefoot strike

reduces the impact force and loading rates experienced, thereby leading to a decrease in the

likelihood of chronic running-related injuries; it is still debated by a few researchers in the field.

Furthermore, there have been no long-term research studies investigating the injury incidence

rates for shod versus barefoot running nor have there been any studies which have directly

shown that heel striking contributes more to injury than forefoot striking.
       In the future, Lieberman and colleagues hope their research on barefoot running and foot

strike patterns can not only further investigate the adaptations and benefits related to barefoot

running, but can also provide insight into how to better prevent the repetitive-stress injuries that

afflict a high percentage of runners in today‟s American society. As such, controlled prospective

studies are needed to test the hypothesis that individuals who do not predominantly heel strike

while running barefoot or in minimalist shoes, as the foot apparently evolved to do, have reduced

injury rates (Lieberman et al., 2010).

       As there has been a number of research studies showing benefits related to barefoot

running, in regards to reduced impact forces, reduction in the likelihood of injury, as well as

improved running economy, and there has been no research showing any negative health or

performance markers related to barefoot training, the decision to utilize barefoot training will be

left in the hands of the coaches and athletes to make the decision they see best fitting into their

training methodologies, principles, and ideologies. The old adage “All you need to run is a pair

of shoes.” just may stick around for the time being until more concrete research is produced.
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