When I first started exploring the benefits of barefoot balance training, my initial draw was to the kinematic changes that this training technique had on lower extremity alignment.  However, the more I began to apply this training technique the more I began to see other benefits.   One of the most fascinating benefits noted was in muscle recruitment and activation patterns.

From a subjective perspective, clients and athletes were associating their barefoot training with increased squat strength, faster run times and decreased low back pain.  

Were these benefits related to improved lower extremity alignment?   Or could it have been that they were recruiting more muscles fibers due to to enhanced muscle activation pathways?

As I began to investigate the concept of neuromuscular activation and muscle recruitment patterns, I came across the work of Dr Benno Nigg.   Nigg is the Co-Director of the Human Performance Laboratory and a biomechanics professor at University of Calgary in Alberta, Canada.  Has spent more than 40 years researching human locomotion as it relates to shoes, orthotics and sports surfaces.

Nigg has done numerous research studies on the concept of plantar foot sensation as it relates to muscle activation patterns during gait.   What Nigg found was that the skin on the bottom of the foot acts like a “load sensor”, providing critical information on impact patterns, joint kinematics and motor control.   

Nigg found that as pressure shifted to different parts of the foot, reflex-type activation patterns occur to the muscle of the feet and lower extremity.   One of the most fascinating of these activation patterns occurs when we shift forward onto the ball of the foot and the tibial nerve is stimulated.  This tibial nerve stimulation activated the gastrocnemius and soleus muscle.  What's cool though, is that this tibial nerve stimulation not only activated the calves - but also the extensor activity of the rectus femoris!   

This means that plantar cutaneous feedback does not only influence the muscles that surround the foot, but can activate those of the hip and thigh.  Even more so, this supports that muscle activation pathways of the human body are highly interconnected - and truly do begin from the bottom of the foot! 

So perhaps the benefit of barefoot training is more that just strengthening the muscles that maintain proper foot posture and lower extremity alignment.  Perhaps it has to do more with muscle activation patterns and pathways.  

If fitness professionals and coaches were to integrate barefoot training techniques into their client and athlete programming, would they note an increase in speed, agility and quickness?   Would they note an increase in strength?   And will they note a decrease in injuries?

It was through concepts such as this, that led to the advent of EBFA’s newest course - Bells & Bare Feet:  The Why Behind Barefoot Kettlebell Training.    

Join EBFA Saturday June 2^nd from 10am - 12:30pm in NYC as we join force with Kettlebell Concepts to explore the benefits behind two of the hottest training techniques – kettlebells & barefoot training!

Saturday June 2, 2012

10am - 12:30pm 

Bells & Bare Feet:  The Why Behind Barefoot Kettlebell Training

Lucille Roberts - NYC

Registration Fee:  $75 - includes NASM & AFAA cec's

www.ebfafitness.com

Reference:

Nurse, M. and Nigg, B.  The effect of changes in foot sensation on plantar pressure and muscle activity.  Clinic Biomech, 2001.  16: 719-727.

As fitness professionals and movement specialists we encounter a myriad of musculoskeletal issues in our clients.   Tendonitis, trigger points and joint pain are probably some of the most common complaints we treat.   But what about vascular issues?  Could there be a role for the fitness professional in the management and prevention of vascular health, namely, varicose veins?

I was first introduced to the concept of postural influences on vascular status by EBFA faculty member and Posturologist, Mat Boule’.  We were discussing a patient he had recently seen whose initial complaint was not musculoskeletal in nature, but rather vascular. 

The patient was complaining of unilateral tenderness and induration along the right great saphenous vein.  Patient states she felt relief with compressive dressings but symptoms returned with activity, such as running and cycling.  After evaluation by several medical doctors, including a vascular surgeon, the patient was left with no explanation for the venous tenderness, and sought out Mat Boule’ for his help.

Postural Influences and Vascular Health

When presented with patients experiencing unilateral varicose veins, Mat Boule’ immediately begins to consider the influence of pelvis alignment on venous flow.  Why pelvis alignment must be considered in patients with assymeitrical venous symptoms has to do with lower extremity vascular anatomy.

The Femoral Triangle

Situated in the upper thigh lies an important anatomical region called the femoral triangle. Bordered by the adductor longus and Sartorius, the femoral triangle is an area where the important femoral nerve, vein and artery cross the hip joint.   Due to the proximity of these vital structures in relation to hip musculature, it is quite apparent how pelvic posture could influence venous flow. 

Causes of Pelvic Obliquity

All three planes of movement should be considered when assessing a client’s pelvis posture.   Unilateral tightness of the anterior hip musculature can pull the pelvis into either a sagittal or transverse plane rotation. By addressing the imbalance between overactive anterior hip rotators and weak posterior musculature, a movement specialist can restore proper alignment in the pelvis.  

Another cause of pelvis obliquity which must be considered in a client with assymetrical venous symptoms is limb length discrepancy.   Our body must compensation for variances in limb length.  Whether this compensation is observed as unilateral foot pronation or a frontal plane hip hike, obliquity in the pelvis is often noted.  In this case, adequate correction of the pelvis obliquity cannot be achieved without addressing the limb length discrepancy.   

To learn more about how you can better assess your client’s lower extremity alignment and the influence of limb length discrepancy on posture, please visit www.ebfafitness.com

To learn more about Mat Boule’ and his experience as a posturologist, please visit his website www.matboule.com

It is believed that many factors play a role in the development of athletic performance.  From cardiorespiratory capacity to skeletal muscle function, can our genetic and musculoskeletal makeup predict our talent as an athlete?  

With many sports performed in closed chain environments our foot is highly integrated in lower extremity kinematics, postural stability and force production.   Exactly how important is the foot type in determining athletic skill?

With most attention on the association between foot types and risk of injury, what if instead we took a moment to look at certain foot variances and the advantages each may have on athletic performance?

Foot-Typing

Due to the variances in foot type and arch height we need to begin with a classification system that is reliable and consistent. Simply classifying a foot as a high arch or low arch does that reflect the dynamic biomechanics of an athlete's foot-type.

One such foot-typing system that does provide validity and reproducibility is the Foot Posture Index. The Foot Posture Index is a 6 point static foot assessment performed in multiple planes which is used to classify foot-type and degree of severity (Cornwall 2011).

A 2011 study by Cornwall et al. evaluated the reliability of the Foot Posture Index to predict dynamic foot function. After evaluating 203 subjects it was concluded that the Foot Posture Index can predict dynamic foot mobility. Those subjects with the greatest foot mobility correlated with the over-pronated or low arch foot type.  Conversely those with decreased foot mobility were associated with a more supinated or high arch foot type.

Over-Supinated Foot Type

In the over-supinated foot-type the heel and subtalar joint are in an inverted position with a lateral shift in body weight and slight adduction of the forefoot on the rearfoot. 

Typically we think of an over-supinated foot type as more rigid with an increased risk for stress fractures, tendonitis and plantar fasciitis.   But could there be any advantages to this supinated foot position? 

Advantage #1 - Rapid Re-Supination

In sports such as soccer, changes in direction and cutting maneuvers require rapid activation of the posterior tibialis in order to create a rigid foot lever and push off. Although it is purely anecdotal, perhaps a more supinated foot type allows the athlete to quickly change direction and push off of the ground.  

Advantage #2 - Decreased Contact Time

For a runner or athlete the ability to decrease contact time, not only makes them faster but also decreases the risk of injury.   In endurance sports, time spent in contact with the ground is when the athlete gets injured.   

A 2007 study by Hasegawa et al. found that when comparing different foot strike patterns, running speed and contact time, those runners with a midfoot and forefoot strike had a shorter contact time when compared to runners with a rearfoot strike.

In addition it was observed that regardless of foot strike pattern, those runners who had the greatest degree heel inversion at foot strike also had the shortest contact time.   Because an over-supinated foot type has increased calcaneal inversion this may provide an advantage in reducing contact time when running (Hasegawa 2007).

Over-Pronated Foot Type

In the over-pronated foot-type the heel and subtalar joint are in an everted position with a medial shift in body weight and abduction of the forefoot on the rearfoot. This foot type is typically associated with increased plantar pressures and force distribution over the plantar foot.

Typically we think of an over-pronated foot type as more mobile with an increased risk for posterior tibial tendonitis, knee pain and bunions.   But could there be any advantages to this pronated foot position? 

Advantage #1 - Improved Balance

A 2002 study by Hertel et al. compared balance and stability in different foot types.  Interestingly it was found that the over-pronated foot type had better balance when compared to the over-supinated foot type.  It was hypothesized that eue to the increased plantar contact in an over-pronated foot type there was an increase in plantar cutaneous feedback which is critical in stabilization.  Sports requiring balance, such as karate, boxing or gymnastics may benefit from this foot type.

Outside of increased plantar distribution, the over-pronated foot type may not be as advantageous when it comes to athletic performance.  Since many athletics are dependent on force, speed and agility - all of which relate to rapid foot contact time - the delayed strength and activation of the posterior tibialis may put this foot type at a disadvantage.

Conclusion

Although much of this information is anecdotal due to the lack of research, it does provide important considerations for the coach or parent of an athlete.  

We are all born with a specific foot type, so it is up to us to understand our foot type and use it to our advantage whether it be for agility or balance & stabilization!

***

Normal gait requires at least 10 degrees of ankle dorsiflexion, with maximum dorsiflexion occurring closed chain during late midstance. Limited ankle dorsiflexion can result in a myriad of compensations both proximally and distally.

From knee hyperextension to midfoot over-pronation, the deforming forces caused by tight calves is enough to make any Movement Specialist cringe. I refer to this lack of ankle joint dorsiflexion as a "Podiatric Epidemic" as a majority of people assessed lack adequate ankle joint range of motion.

In last week's EBFA Blog article  I reference the correlation between proximal pelvic influences on ankle joint range of motion and calf flexibility.   In the case of a client or athlete with an anterior pelvic tilt position and over-active hip flexors, integrating hip flexors stretches will often relax the tight calves.

However for those clients or athletes who have adequate pelvic flexibility but demonstrate decreased gastrocnemius range of motion, we want to integrate posterior group stretches.

When recommending posterior group stretches some classic stretches include the wall stretch, downward facing dog and dropping a heel off of the step. When performing theses stretches have you ever considered the role rearfoot position may have on the effectiveness of each stretch?  

Impact of Rearfoot Position on Stretching

A 2009 study by Jung et al. evaluated the impact of rearfoot position on the effectiveness of gastroc stretching. Due to the prevalence of tight gastrocs in an over-pronated foot type, Jung et al. wanted to determine if the everted calcaneal position altered the effectiveness of the stretch. 

Jung et al. evaluated 30 patients with both a neutral foot type and an over-pronated foot type with increased calcaneal eversion (average 4 degrees).  Subjects performed a gastrocnemius wall stretch both in their relaxed calcaneal stance position and while wearing orthotics which placed the calcaneus in a neutral position.

Ultrasound technology was used to evaluate the degree of stretch as determined by the change in myotendinous length.   It was observed that rearfoot position had a significant impact on the effectiveness of posterior group stretching.   A 3mm difference in gastroc lengthening was achieved while stretching with the everted rearfoot shifted into a neutral position.

Considerations for the Movement Specialist

When considering articles to review and share on the EBFA Blog, I like the above study for several reasons:

1.  It emphasizes the impact subtle adjustments in body positioning can have on stretching effectiveness.   As evidence-based fitness professionals, if we can apply research studies such as this into our client's programming we may begin to see better results.

2.  It re-emphasizes the concept of foot-specific programming which I integrate into my Barefoot Training Specialist workshops.  In an over-pronated foot type with increased calcaneal eversion you want to consider the impact ankle stretching may have on the weakened posterior tibilais tendon.

3.  When the calcaneus is brought out of the excessive eversion the stretch becomes more isolated to the Achilles tendon and gastrocnemius/soleus - with little stress to the posterior tibialis.       

Want to integrate this evidence into your client's programming?

1.  For any clients with an over-pronated foot type, isolated gastroc stretching should be performed preferably non-weight bearing to minimize the impact of rearfoot position during the stretch. 

2.  If a client uses orthotics that control rearfoot motion, perform closed chain gastroc stretches while wearing the orthotics and then remove the shoes for the barefoot training exercises. 

3.  For any clients with an over-pronated foot type and wear Vibrams or minimal footwear for daily use and training, frequent evaluation of the posterior tibialis tendon should be performed. 

***

Learn more about the Barefoot Training Specialist program, please visit our website - www.ebfafitness.com 

Dr Emily Splichal

Founder EBFA

On February 8^th, the NY Times published an article on the different injury rates between rearfoot and midfoot runners.  The article references a 2012 research study that compared 52 endurance runners for injury rates.  Among the runners 59% were rearfoot strikers while the remaining were midfoot strikers.   It was found that the average injury rate was 74%, with the rearfoot strikers reporting an injury rate twice that of the midfoot strikers.  This study concluded that foot strike pattern can predict injury rate among runners. 

***

As a Podiatrist and Fitness Educator on barefoot programming, I am frequently asked my opinion on barefoot running and if I think it is beneficial and appropriate for all runners.  

My response is always the same.  

In biomechanics and in medicine, it is difficult to classify every athlete or patient into the same category.   Due to different foot types, some runners will respond well to barefoot running while others have more difficulty and find barefoot running awkward and unnatural.  

So I cannot fully say that all runners should throw away their traditional running shoes and opt to go barefoot or minimalist.  Instead I prefer to address these injury rates by encouraging effective recovery and preventive techniques integrated with barefoot training to increase intrinsic muscle strength eccentric eccentric endurance of the foot stabilizers. 

Runners & Overuse Injury

The high injury rate among runners as demonstrated in this 2012 study is not new research.  Previous studies have reported an injury rate averaging 34 – 70% with the most common injuries being directly related to overuse or inadequate dissipation of ground reaction forces. 

By taking a closer look at the body’s mechanism for attenuating ground reaction forces we can better design barefoot training programs to improve a runner's foot strength and therefore reduce their risk of injury. 

 Innate Loading Response

Beginning with foot strike, ground reaction forces are initially attenuated through the contraction and deceleration of the posterior tibialis and soleus muscle. As the foot continues to push-off, the intrinsic foot musculature contracts and the knee begins to flex to absorb the remainder of ground reaction forces.  

The effectiveness of this innate loading response is dependent upon the eccentric strength of the extrinsic musculature and the concentric strength of the intrinsic musculature.  This means that to optimize the foot’s ability to attenuate ground reactions forces, these muscles should be trained for the phase in which they used during running. 

Recovery is Key 

In addition, adequate recovery is a key component in the reduction of overuse injuries among runners.  Studies have shown that eccentric muscle contractions crease adhesions and trigger points at a higher rate when compared to concentric or isometric contractions.   This means that runners exposed to increased levels of ground reaction forces require daily muscle recovery that will specifically address adhesion or trigger point formation. 

The technique I recommend in my programming and to my patients is myofascial compression technique (MCT) with the Foot Baller by Trigger Point Performance (www.tptherapy.com) The effectiveness of MCT is found both before running (Pre-Gen) and after running (Re-Gen).  

Barefoot Training & Injury Prevention 

Through proper barefoot programming we are better able to reduce overuse injuries observed in both the rearfoot and midfoot striker.  Unfortunately there is no perfect way to strike the ground to reduce all ground reaction forces.  So instead, encourage your client or athlete to choose the running technique that is most natural for their body’s biomechanics.  

Supplement their running technique with barefoot training and recovery techniques that will improve their eccentric strength and reduce their risk of overuse injury. 

Dr Emily Splichal, DPM, MS, CES

***

For more information on eccentric training and how to design the most effective eccentric programming, please check out last week’s EBFA Blog Post –

“Can eccentric training reduce overuse injuries among runners?"

***

For more information on the Barefoot Training Specialist Program from EBFA, please visit our website - www.ebfafitness.com

From cardiovascular benefits to weight loss, running is one of the most common forms of exercise.  One of the negative consequences of prolonged running is the increased risk of overuse injuries, namely tendonopathy, shin splints and plantar fasciitis.  In fact, a 2007 review study by Wen et al. found the overuse injury rate to be as high as 79% in endurance runners.  With such a high rate of overuse injuries associated with running, how can runners reduce their injury risk?

GRF’s and Risk of Injury

With every step we take, a ground reaction force averaging 1 to 1.5 times body weight is translated through the body.  Pick up the pace to a running cadence and ground reaction forces increase up to three times our body weight (Nilsson 1998).

From midfoot pronation to knee flexion, controlled eccentric contractions and deceleration plays an important role in the dissipation and attenuation of these ground reaction forces.  The exact role of eccentric contractile strength, or more specifically endurance, is evident when a runner begins to experience fatigue. 

Previous studies have suggested that as a runner begins to fatigue, the effectiveness of the musculoskeletal system to reduce ground reaction forces becomes impaired.  A great example of this would be an endurance runner who complains of shin pain or plantar fasciitis pain always at a certain mile marker. 

Exactly how much does fatigue impact the level of GRFs on the body?  A 1998 study by Voloshin found that after 30 minutes of running those runners who experienced fatigue demonstrated a 60% increase in forces to the tibial tuberosity and 35% to the sacrum.  The marked increase of high frequency ground reaction forces specifically to the tibial tuberosity can be suggestive of an increased risk of tibial stress fractures and patellar tendonitis. 

Eccentric training and Risk of Injury

In my Barefoot Training Specialist®  course I speak about the role of eccentric training for optimizing foot function.  As we look at the mechanism of midfoot pronation, this key step in the attenuation of ground reaction forces is dependent on eccentric strength of the posterior tibialis. 

Although we often think of muscles for their concentric function, the dynamic nature of the foot and ankle requires eccentric contractions with every step we take.  Whether a runner is a midfoot or rearfoot striker, eccentric endurance of the posterior tibialis is vital to the prevention of shin splints, plantar fasciitis, stress fractures and posterior tibialis tendonitis. 

Three of my favorite eccentric exercises for the foot and ankle - I like to perform all barefoot!

 1.     Eccentric calf raises

       Standing on a step with heels off the edge, use both feet to press up onto your toes. Lift one foot and slowly (3 - 4 seconds) lower the opposite heel down below the edge of the step.  Again use both feet to press back up onto the toes.  Repeat 6 - 12 repetitions on each side.

  2.     Walking backwards

        On a tredmill at a controlled speed, walk backwards. Ensure proper foot placement from toe to heel contact.  As eccentric strength increases, add weighted vest or backpack to increase load. Perform 5 minute intervals increasing to 10 minutes.

  3.   Parellel or plie' squat jumps

A more advanced exercise that incorporates higher eccentric loads is a squat jump.  During a squat jump, the focus should be on decelerating the foot as it returns to the ground.  Proper foot placement should be from toe to heel contact.  Due to the high eccentric loads in squat jumps ensure adequate ankle flexibility before integrating this in your client's program. Perform 6 - 12 repetitions.

***

Tips to successful eccentric training

1.     Perform 4 sets of 6 – 10 repetitions 3 -4 times a week.  

Do not do eccentric training everyday as there is increased muscle damage associated with eccentric training.  

2.  Perform eccentric exercises before concentric exercises

Studies have shown decreased muscle soreness if eccentric training is followed by concentric training.

3.  Do not perform eccentric training before a run or cardio. 

Eccentric training can cause a transient disruption in sarcomere length following eccentric training. Although this disruption decreases with increases eccentric training, the risk of injury is not worth running after an eccentric workout.

***

To learn more about the eccentric training and the Barefoot Training Specialist®  course from EBFA, please visit www.ebfafitness.com

Dr Emily Splichal

Founder Evidence Based Fitness Academy (EBFA)

www.ebfafitness.com

References:

 Nilsson, J.  Ground reaction forces at different speeds of human walking and running. Acta Physiol Scand, 1989.  136(2):  217-227

Voloshin, A.  Dynamic loading of the human musculoskeletal system  - effect of fatigue.  Clinic Biomech, 1998.  13:  515- 520

Wen, Dennis.  Risk factors for overuse injuries in runners. Current sports medicine reports, 2007. 6(5): 307-313. 

The human gait cycle involves a rhythmic shift of center of mass from one base of support to another.  From stride length to contact time, symmetrical running kinematics has been associated with increased energy efficiency, faster race times and a decreased risk of injury (Blustein 1985). 

If we look at the impact of limb length discrepancy (LLD) on lower extremity kinematics and compensation patterns could subtle differences in limb length impact injury risk and athletic performance?   And if so, should runners and athletes frequently be assessed for asymmetrical loading patterns secondary to LLD?

Types of Limb Length Discrepancy

   - Structural LLD

In children the most common LLD is structural with unequal development being a contributing factor.   A study by Gross et al. found that in structural cases of LLD, the left leg is most commonly affected.  This is due to the in utero position with the left leg crossed over the right leg and the left leg compressed against the mother’s vertebrae.  Proper management of structural LLD is typically through heel lifts and shoe modifications

   -       Functional LLD

Functional LLD can be associated with unilateral foot imbalance, inflexibility of the pelvis and tightness of spinal stabilizers.  A careful biomechanical exam and movement assessment is important in the diagnosis of functional LLD.

  - Environmental LLD

Environmental LLD is common in runners who train on banked surfaces, indoor running tracks and uneven wear patterns of shoes.  Environmental factors can either accentuate or correct structural and functional LLD (Caselli 2002).

What is a Significant Limb Length Discrepancy?

Although the studies are varied, there are some general guidelines coaches and trainers can follow for predicting if a LLD will result in compensation and the severity of these compensation patterns.

 A 1997 study by Song et al. looked at LLD as a percent of vertical displacement to determine predictable compensation patterns as it relates to severity of LLD.  Song et al. concluded that a LLD of 5.5% or greater induced movement compensations in subjects.   Some of the most common movement compensations observed included toe-walking on the short limb, excessive pronation in the long limb and pelvic obliquity on the short limb. 

Another study by Pertunnen et al. concluded that movement compensations in a LLD averaging 1.7cm are associated with asymmetrical load patterns and pelvic obliquity.  Although the musculoskeletal system can absorb many of these shifts in loading patterns, eventually chronic pain and injury can result. 

Impact of Limb Length Discrepancy

1.  Greater impact forces and prolonged loading phases on the longer limb, which overtime can lead to overuse injuries such as tendonitis and stress fractures. 

2.  Greater knee extensor torque, increased ground reaction forces and increased peak plantar pressures in the longer limb.

3.  Frontal plane pelvic obliquity on the side of the shorter limb.  This is often further complicated by jamming of the femoral head into the acetabulum on the side of the longer limb (Blustein 1985).

Pelvic Obliquity and LLD

            Pelvic obliquity secondary to LLD should be assessed in all runners complaining of unilateral hip, knee or foot pain.  Pelvic obliquity often presents in a runner through a hyperactive iliopsoas on the longer limb side. 

Blustein et al. demonstrated that due to the attachments of the iliopoas to the anterior vertebrae, the muscle will contract to try and correct the pelvic shift.  This eventually leads to iliopsoas spasm and shortening of the iliopsoas muscle. 

            Chronic iliopsoas tightness has been associated with vertebral shearing forces and low back pain in athletes who participate in sports that require excessive hip flexor activity.         

Management of Functional LLD

            After understanding the compensations and movement imbalances associated with functional LLD, it is important to know how effectively reverse the imbalance. 

Step 1 – Confirm it is functional LLD

            The first step must be determining whether a LLD is structural versus functional.  Typically structural LLDs are treated through orthotic and shoe modifications and must be referred out to a qualified professional.  

On the other hand, functional LLD requires more soft tissue work.   Although some argue that the body adapts to LLD and that it should be left alone, Gofton et al. recommends treatment of even the slightest LLD due to the increased rate of osteoarthritis seen in the longer limb knee and hip.

Step 2 - Terminate the aggravating activity

            If the functional LLD is associated with an environmental factor, the aggravating activity should be terminated.   Often times in the case of runners, running terrain is a common cause of functional LLD and must always be considered.  

Step 3 - Create a stretching & strengthening program

A specific stretching and postural strengthening program is necessary with care being taken to address the specific needs of each limb.  Remember that each limb will present with very unique compensations which must both be equally addressed.  All comprehensive stretching and strengthening programs must consider imbalance from the foot up to the hip and lower back.

Step 4 – Build strength within the new alignment

            All too often reversal of postural imbalances are prescribed with an oversight to address the possible instability within the new range of motion and alignment.  I like to integrate positional isometrics to the stabilizing muscles of the foot, knee and hip after all recommended stretches and myofascial release. 

To learn more about the impact of LLD as it relates to low back pain, please check out EBFA's Biomechanics of Low Back Pain course available both online and by educational DVD!

 - Dr Emily Splichal,  CEO/Founder Evidence Based Fitness Academy

***

References:

Beal, M. et al. The short leg problem. J Am Osteopath Assoc, 1977. 76: 745.

 Bloedel, P. et al. The effects of limb length discrepancy on subtalar joint kinematics

during running.  J Ortho Sports Physical Therapy, 1995.  22(2): 60-64.

 Blustein, Steven et al.   Limb length discrepancy.  J Am Pod Med Assoc, 1985. 75(4):

200-206.

 Caselli, Mark et al. Detecting and treating limb length discrepancies.  Podiatry Today,

2002.  15(12): 65-68.

 Fields, KB et al.  Biomechanics of running and gait.  Essentials of Sports Med, 1996. 

478-486.

 Gofton, J.P et al. Studies in osteoarthritis of the hip: Biomechanical considerations.

Can Med Assoc, 1971. 104: 791

 Pertunnen, J.R.  et al.  Gait asymmetry in patients with limb length discrepancy.  Med

& Science in Sports, 2004.  14: 49-56.

 Sadeghi, H. et al.  Symmetry and limb dominance in able-bodied gait: a review. Gait

Posture, 2000.  12: 34-45.

 Schuit, D. et al. Effects of heel lifts on ground reaction force patterns in subjects with

structural leg-length discrepancies.  Phys Ther, 1989. 69: 663-670

 Song, Kit et al. The effect of limb-length discrepancy on gait.  J Bone Jt Surgery, 1997. 

79(11): 1690-1697.