Biomechanical assessments for runners with midportion Achilles Tendinopathy issues

With an injury rate of 2.35 per 1000 in the adult population (de Jonge et all, 2011), the Achilles tendon is one of the most commonly injured tendons, especially in athletes involved in running and jumping sports/activities (Kvist, 1994) (Wilson, 2005)

As per studies, the loading on the Achilles tendon during running increases to 12 times the body weight. This is much higher as compared to walking (upto 3.5 times body weight), or cycling (close to body weight) (Komi, et al., 1992). Such loading rates when combined with improper running biomechanics can be detrimental to Midportion Achilles Tendinopathy issues in runners.

A gait analysis, whether observational or through a video based system, is an excellent way to identify any biomechanical faults in the runner. A biomechanical fault can be as a result of either a physical limitation in the body or a technical error in the running form.  

In this blog, we will discuss various biomechanical faults that are associate with excessive loading on the Achilles tendon.

FOOT STRIKE PATTERN

Running with a rear footstrike pattern is considered to load the Achilles tendon less than running with a forefoot-strike pattern (Komi, et al., 1992). As per recent studies, running with a midfoot- or forefoot-strike pattern, as opposed to a rearfoot-strike pattern, added an additional load of 48 times body weight for each mile (1.6 km) run. (Almonroeder, et al., 2013)

ASSESSMENT OF FOOT STRIKE PATTERN

Foot strike pattern can be determined by measuring the foot inclination angle.

The foot inclination angle is the angle between the running surface and the

sole of the runner’s shoe and allows for the determination of foot-strike 

pattern.

Heel strike

(Landing on the posterior aspect of their heel)

Rearfoot strike 

(Landing on the anterior aspect of the heel, with FIA <10 degrees)

Midfoot strike

(Rearfoot & forefoot making contact nearly simultaneously, with FIA near 0°)

Forefoot strike

(Forefoot landing with FIA <0 degrees)

Within the context of return to sport, to control for overall loading, a runner 

who runs with a forefoot-strike pattern would not be allowed to run as far as

a runner with a rearfoot-strike pattern. (SILBERNAGEL & CROSSLEY, 2015)

OVERSTRIDING

Overstriding can be picked up when reviewing the video taken in the sagittal 

plane. The term simply means that the runner is landing excessively ahead 

of the center of mass of the body (COM can be approximated at the center 

of the pelvis). Doing this often increases the stride length of the runner, 

OVERPRONATION

Recent studies have linked excessive subtalar eversion with excessive Midportion Achilles Tendinopathy. In a study comparing running mechanics of runners with Achilles Mid-Portion Tendinopathy with healthy runners, The Achilles Tendinopathy Group displayed significantly greater sub-talar joint eversion displacement during mid-stance of the running gait.  (Ryan M, 2009)
Exercise programs for arch strengthening etc along with foot orthotics can be helpful in reducing excessive calcaneal eversion and reducing the load on Achilles tendon loading.hence the name ‘overstriding’. (Souza, 2016 )

Subtalar eversion can be assessed by measuring the rearfoot angle in the 

posterior view. Rearfoot angle is defined by the midline of the heel relative to

the midline of the lower leg.

Biomechanical Faults Associated with Patellofemoral Pain Syndrome

UNDERSTANDING PATELLOFEMORAL PAIN

To manage Patellofemoral pain in runners its important to understand the
correlation between running biomechanics and  its effect on the
patellofemoral joint. 

Patellofemoral pain syndrome (PFPS), most commonly known as
‘Runner’s knee‘ or anterior knee pain syndrome, is defined as “pain occurring
around or behind the patella that is aggravated by at least one activity that loads
the patella during weight-bearing on a flexed knee.”

BIOMECHANICS LINKED WITH PATELLOFEMORAL PAIN

OVERSTRIDING

A small degree of knee flexion is required at the moment of foot strike 

(initial contact) to ensure good shock absorption. Now, imagine a case of 

an amateur runner looking to increase his running performance through an 

increase in stride length. Such amateur runners tend to achieve this goal 

through increased knee extension at foot strike.

Although the strategy of knee extension is helpful from immediate performance
point of view as it is increases the stride length. However, this increases the 
ground reaction forces at the patellofemoral joint, leading to Runner’s knee 
problems.

CORRECTIONS: Typical overstriders hugely benefit from cadence retraining,

 a method that promotes shorter and faster steps instead of longer steps.

This ensures the same performance and better shock absorption at the knee

 joint.

Additionally, Refer to this link by Stanford Health for some drills. 

EXCESSIVE KNEE FLEXION AT MID STANCE

Knee flexion angle is highly predictive of peak patellofemoral joint force, such that peak force increases as knee flexion angle increases (Wille CM et al 2014). Running with excessive knee flexion at Mid Stance (a moment when both knees are adjacent to each other) increases the patellofemoral joint stress & may require intervention. 

Alternatively, some data exists suggesting that lower knee flexion (<40 degrees) may be associated with certain subgroups of patients with patellofemoral pain due to increased ground reaction forces (Dierks TA et al 2011). So ideally, this angle should revolve around 40 degrees at mid stance.

CORRECTIONS: Along with a rehab program, Runners with excessive knee flexion at mid stance benefit from cadence retraining, a method that promotes shorter and faster steps instead of longer steps. 

Moreover, Verbal cues to promote a softer landing are also helpful.

EXCESSIVE CONTRALATERAL PELVIC DROP

The event of mid stance (both knees are adjacent to each other) is accompanied by a small contralateral pelvic drop, generally greater in women as compared to men. 

An excessive contralateral pelvic drop, increased hip adduction & internal rotation increases lateral stress on the patellofemoral joint, resulting in maltracking of the patella. (Dierks TA et al 2008)

CORRECTIONS: In addition to a rehab program, visual feedback to ask the runner to maintain a level pelvis is very helpful to prevent excessive contralateral pelvic drop.

SUBTALAR OVER PRONATION

Excessive pronation of subtalar joint in the midstance phase of the gait cycle can be a contributing factor to anterior knee pain associated with PFPS.

CORRECTIONS: 

In addition to a rehab program, studies also recommend the use of orthotics (Kannus VP,1992) or higher level of support shoes to correct subtalar overpronation.

Can running gait retraining improve running efficiency

We’re asking ourselves if the individual’s gait may place more stress on sensitive tissue and whether we can modified it. I also often wonder though what impact such changes may have on performance. This new study went some way to answering that question and exploring the interplay between gait, loading and efficiency…

Step Frequency Training Improves Running Economy in Well-Trained Female Runners – Quinn et al. (2019)

                                                  Resource : Running Physio

Runners with good economy use less oxygen than runners with poor economy at the same steady state speed (Barnes and Kilding 2015 – a great open access paper if you’d like to find out more).

• Quinn et al. (2019) report that step rate increased by approximately 7.5% which is also how much Willy et al. (2015) aimed to increase step rate by in their study which saw reductions in impact force, hip adduction and knee load.

• A recent study (Pizzuto et al. 2019) found that knee flexion/ extension and hip adduction during stance were associated with running economy, with hip adduction explaining as much as 43% of the variance in economy. In a nutshell increased knee flexion or hip adduction during stance appear likely to have a negative effect on economy. They’re also thought to increase load on several tissues, especially the patellofemoral joint (Lenhart et al. 2014, Neal et al. 2016).

• Increasing step rate by 10% has been found to reduce peak knee flexion and hip adduction (Schubert et al. 2014) and reduce patellofemoral load and peak muscle forces for the calf, quads and glutes (Lenhart et al. 2014). 

• An increase in step rate has also been reported to reduce peak achilles load, (Lyght et al. 2016) tibial load (Edwards et al. 2009) and plantar fascial load (Wellenkotter et al. 2014)

•  Luedke et al. (2016) found those with a low step rate (164 or less) were more likely to develop shin pain that those with a higher step rate (174 or above).

Resource : Running Physio

Key Note to remember:

• If step rate is already high or we increase it too much it can have a negative effect on running economy and lead to a high number of loading cycles.
• It’s important to recognize that increasing cadence is far from a cure all and should be based on an individual’s need and goals.
• Step rate is influenced by speed and height and tends to be higher in more experienced athletes (Luedke et al. 2018). There’s no single approach to it (such as aiming for a cadence of 180) that will suit everyone.

Bonus: Download free Running Assessment Sheet by clicking the link below

https://drive.google.com/open?id=1i66OtYrOvZHy5siRDL61_qiZlDfTQXgo

Fundamental of Running Form & Cadence Retraining

Understand your foot and choose footwear wisely

Before get in to the topic, I would like to enlighten the facts of foot functions in natural way and humans are not suppose to halt it for the shake of  name of fashion footwear!

The foot core system

The foot is a complex and dynamic body part. The feet play a pivotal role in balance, gait, and overall stability when you’re on your feet

The foot core is a crucial part of foot function:

The ‘foot core’ primarily refers to the plantar intrinsic musculature

There are 4 layers of plantar intrinsic musculature in the foot. By definition, the intrinsic muscles originate and insert within the foot itself. They therefore serve to stabilize support the structure of the foot/arch both statically and dynamically

Strength of the intrinsic foot musculature is a big component of foot health and function. The feet can and should be trained for strength, just like anywhere else in the body

The foot also gets stability from extrinsic muscles which originate in the lower leg and insert into the foot. They help with stability by contributing to arch rigidity and foot stiffness when needed (think propulsion, power etc.) and absorption/ground adaptation when needed (walking, running, landing etc.)

The foot core can be strengthened and trained in many ways:

One popular introductory exercise is called ‘short foot’ and involves activating the intrinsic musculature by pushing into/grasping the ground

That being said, the any given exercise can be thought of as a foot exercise if attention is paid to foot function throughout. This is best done barefoot, as more attention and sensory feedback can be attained

Simply spending more time walking barefoot or with minimalist shoes puts more demand in the foot musculature, leading to increases in strength and natural arch support
.
Train your foot core and get your feet working more!

The importance of a strong and functional FIRST RAY

The first ray is the inside segment of the foot that ends at the big toe (consisting of the first cuneiform bone and first metatarsal)

This functional unit of bones and tissues is an important part of what makes the ARCH a strong and stable structure. The first ray is an integral part of the medial longitudinal arch, and its function during walking, running, balance/stability and many human movements is crucial

The first ray functions as a pillar for the arch

- Integrity and strength of the first ray is important for PROPULSION when pushing off during walking. It acts as the primary lever which transfers a lot of load and energy/force through the ground

- Running, jumping, and athletic movements also require a strong and functional first ray to transmit force and keep the arch intact

The arch, balance, and stability:

- When standing on one foot, the integrity of your arch depends on good first ray strength. The musculature that connects into the first ray turns this structure into a strong ground stabilizer

- It allows you to keep your foot planted and ‘rooted’ to the ground when stability/balance is required. It creates rigidity and control and maintains your arch

Pay attention to inside part of your foot when you walk, stand, balance etc. Developing strength through the first ray will improve function and performance

Footwear: Biomechanics and Injury aspects

Advances in the design of such shoes have occurred in recent years, particularly for running shoes. To obtain best compatibility with the human performer in sport or exercise, shoes should, ideally, be designed for specific sports and exercises and for the relevant surface qualities.Sports shoes can change the forces in certain biological tissues by over 100% (Nigg, 1993). The wrong footwear is a major factor in causing running injury; the use of a good running shoe is one of the best ways such injuries can be avoided.Furthermore, running shoes appear in general to lose around 30% of their impact attenuation properties a modest mileage.

BIOMECHANICAL REQUIREMENTS OF A RUNNING SHOE

A running shoe should provide the following (for example: Cavanagh, 1980;

Frederick, 1986; Nigg, 1986a):

1. Attenuation of the repetitive impact forces
2. Maintenance of foot stability (rearfoot control) with no exacerbation of movement at the subtalar joint (supination-pronation)
3. Friction-traction at the shoe-surface interface
4. No exacerbation of any structural irregularities of the arches of the foot
5. Allowance for different footstrike pressure distributions
6. Dissipation of heat generated, particularly when the shoe incorporates synthetic materials and artificial surfaces are involved.
7. Comfort for the wearer. 

THE STRUCTURE OF A RUNNING SHOE

Heel counter

This is an important part of the shoe as it contributes to shoe and rearfoot stability, cradling the calcaneus and limiting excessive pronation; Rigid, materials are needed for this purpose and a sheet of thermoplastic is normally incorporated in the heel counter. External counter stabilisers are also used to reduce excessive rearfoot movement (Easterling, 1993). The design of the heel counter has a profound effect on the stiffness of the fatty heel pad and, therefore, on impact attenuation. The nearby ‘Achilles tendon protector’ (or heel tab) is somewhat misnamed—hard or high heel tabs can cause

inflammation of the tendon or peritendon (Dunning, 1996).

Uppers or Toe Box

A compound structure is the most common. Usually, a foam layer provides good perspiration absorption and a comfortable feel, woven nylon taffeta supplies most of the strength, while a cotton weave backing helps to prevent the nylon from tearing or snagging.

Human foot is designed to splay wide at the forefeet to distribute load of our body and be the widest at the tips of the toes.

The vast majority of  the footwear gets narrower and tappers to a point at the very place our foot should be widest.  and we wonder why our feet cave inwards, why they hurt, why we get bunions. It's a really quite obvious - most shoes aren't made in the shape of feet and it's deforming our foundation.

WOMEN DITCHED THE STAYS AND CORSETS – ISNT’ IT TIME WE DID THE SAME WITH NARROW, POINTY SHOES??

This image shows how feet can be pushed and pinched into the shape of shoes. And for women and girls this shoe shape is more than likely to be slim and pointy

So what happens to slim and pointy feet? When we consider adult women are FOUR TIMES as likely as men to have debilitating, painful foot problems, it’s pretty clear WOMEN’S SHOES are a problem

Isn’t it time fashion stopped constricting our bodies into painful submission? This mother is making sure her daughter DOESN’T follow in her pointy-shoe footsteps, literally

While Mum has uncomfortable, unhealthy and unhappy feet, she’s making sure Daughter’s footsteps stay FOOT-SHAPED: she goes barefoot where possible and when shoes are necessary makes sure those shoes are foot-shaped: FLEXIBLE, WIDE and BENDY so her daughter’s feet can grow strong and healthy

VivoKids are all created to be as close to barefoot as possible; protecting only from climate and terrain so feet can do their natural, healthy thing as they grow

We don’t believe in corsets: for bodies - or feet!

Midsoles and wedges

These are the critical parts of the shoes for shock absorption, the most commonly used material being a closed-cell polymeric foam (EVA—ethylene vinyl acetate) (Easterling, 1993). 

This absorbs energy mainly by compression of the pockets of air entrapped in the cells and secondarily by deformation of the cell walls. These foams are 80% gaseous with thin (<10μm) walls. Closedcell foams regain their original dimensions more quickly than open-cell foam. 

The long-term durability of these foams is unknown, but all foams form a ‘compression set’—a permanent deformation—because of repetitive stress. This reduces the ability of the material to absorb energy substantially, although the shoes may otherwise look as good as new. Cook et al. (1985) found a loss of about 30% of shock absorbency across a wide range of top class running shoes after only 500 miles (800km) of running. More recent developments have included various pneumatic and liquidfilled devices, the claims for which have not always been substantiated by rigorous scientific research.

Outsoles

Polyurethane rubbers are generally used here because of their durability and abrasion resistance; EVA compounds fail on the last property, wearing through in 200 miles (320 km). Treading removes to some extent the poor traction of polyurethane soles when wet, and changes in tread configuration can affect both the shock attenuation and traction.

It’s time to rethink footwear. This picture seems ridiculous but go to a typical shoe store and you will see tons of footwear that isn’t that far off

It’s pretty simple: the further a shoe brings your foot away from the ground, the less your foot can act like a foot
.
Thinner sole = more sensory feedback and more flexibility

Insole board

In modern running shoes a fibre-board, composed of cellulose fibres embedded in an elastomeric matrix with additives to prevent fungal and bacterial growths, is usual. Other shoes, known as ‘slip-lasted’ shoes, do not have an insole board and the upper is fitted directly to the last giving flexibility but with limited stability. Combination-lasted shoes have the rear part of the shoe board-lasted and the forefoot part slip-lasted: this represents a good compromise between rearfoot stability and shoe flexibility (Easterling, 1993).

Insole (or sockliner)

Usually made from a moulded polyethylene foam with a laminated fabric cover, this should help to reduce impact shock, absorb perspiration and provide comfort. It should provide good friction with the foot or sock to prevent sliding and consequent blistering (Easterling, 1993).

Can foot wear cause Back Pain ??

Back pain has become an epidemic, with many people turning to the quick fix of pain medication — which can actually make things worse —  rather than finding ways to alleviate or stop the physical causes of the pain in the first place

But this comes as no surprise, as many of us sit down for countless hours during the day, at home, at work, in our cars or public transport, all hunched over in a position that creates an inward curve in our lower back —  a position which our bodies were not evolved to be in for long periods of time

This issue is also connected to our footwear. Wearing shoes that have a heel has a knock-on effect across our entire posture. It pushes the hips forward and forces our upper body to compensate for balance, creating that same inward curve in our back, which can over time be the cause of chronic back pain

Shoes with zero lift and zero heel keep our feet flat on the ground, re-aligning the back and allowing us to “stand tall” with a straight posture

Resources

1. McKeon PO, Hertel J, Bramble D, Davis I. The foot core system: a new paradigm for understanding intrinsic foot muscle function. BJSM. 2015
2. Sports Biomechanics: Reducing Injury and Improving Performance by Roger Bartlett Sport Science Research Institute, Sheffield Hallam University, UK

RUNNING GAIT CYCLE

RUNNING GAIT CYCLE

Understanding the running gait cycle is imperative for proper clinical gait analysis and communication with runners. 

Just like walking, it is a standard to begin the running gait cycle from the initial contact of a leg till the next initial contact of this same leg. Unlike walking, there is no double support phase during the running gait cycle.

Important Phases of Running Cycle

  Initial contact

Instant at which the foot first makes contact with the ground and is best identified in the sagittal plane.

This is the moment when the foot just hits the ground. At this moment, forces approaching 2.5 times the body weight are suddenly exerted on the body. Hence, efficient shock absorption is important to minimize excessive joint loading at initial contact.

KNEE ANGLE: Knee angle is the measure of knee flexion/extension present in the stance phase leg during initial contact. Knee flexion angles near 20° are generally recommended for effective shock absorption

LEG INCLINATION ANGLE (LIA): The leg inclination angle is the angle of the tibia with the true vertical. This angle plays a role in the amount of stress and loading at the tibia during running, a common problem found in runners with a history of ‘Tibial stress fracture’

REARFOOT VS FOREFOOT STRIKE

There is no universal agreement on which foot-strike pattern is the best suitable for all runners. According to recent studies (Click here to read the research), Forefoot Strike seems favourable for patients with unstable knee joints in the AP axis and Rear Foot Strike may be recommended for runners with unstable ankle joints.

A number of studies have investigated the effect of shift from a rearfoot to a forefoot strike pattern. One such study by Roper et. all monitored the transition process in a group of runners. The study reported no significant adverse events in the experimental group. The experimental group however complained of calf soreness during the retraining phase which subsided by the 6th retraining session for all subjects.

Two subjects in the experimental group (25%) reported ankle soreness associated with the new running gait at the one-month follow-up. Subjects described it as an ache that quickly subsided after they discontinued running

Mid Stance

Instant when the greater trochanter of the femur lines up directly over the mid-point of the foot. This can be easily identified in the sagittal plane.

In the posterior view/anterior view, mid stance can be identified as the moment when the pelvis is at its lowest vertical position.

At this point in the gait cycle, the entire weight of the body is on a single leg. Hence, the parameters measured at this point are useful in assessing the stability and weight bearing strength of the stance phase leg.

Push OFF

Instant at which the foot just leaves the ground and is best identified in the sagittal plane.

During the push-off phase, the major role of the stance phase leg is to propel the body into the next stride

RESOURCES FOR FURTHER READING

1. Gallow, A. & Heiderscheit, B., 2016. Clinical Aspects of Running Gait Analysis. In: T. L. Miller, ed. Endurance Sports Medicine. s.l.:s.n., p. 336.

2. Souza, R. . B., 2016 . An Evidence-Based Videotaped Running Biomechanics Analysis. Phys Med Rehabil Clin N Am, 27(1), p. 217–236.