Original Articles

Muscles of the Shank, Movement of the Shin & Susceptibility to Lower Extremity Injury

Muscles of the Shank, Movement of the Shin & Susceptibility to Lower Extremity Injury in American Sport

Andrew Charniga

www.sportivnypress.com

 

Figures 1 & 2: Two elite (NBA) basketball players suffer Achilles rupture within days of each other in December 2019. In virtually identical circumstances; a seemingly benign step with shin shifting from a vertical disposition to leaning forward slightly towards the toes, i.e., knees bending with femur dropping towards horizontal; resulted in a catastrophic Achilles injury. A few weeks later another NBA player went down under virtually identical circumstances: untouched, another Achilles injury; aka a ‘flat tire”.

“Learn how to see.”
“Realize that everything connects to everything else”. Leonardo Da Vinci

Most if not all references in Kinesiology texts  to the function/action of ankle muscles in the rear of the shank such as soleus, gastrocnemius; likewise the muscles situated in the front of the shank, such as tibilais anterior are connected with these muscles moving the foot. Generally, there is little or no reference to shifting the shin when the foot is in a fixed position; such as flat on a surface. For instance:

“{tibialis anterior} The muscle dorsiflexes the ankle and foot, and supinates the (inverts and abducts) the tarsal joints when the foot is dorsiflexed.”Hamilton, Luttgens, 2002.

So, if one’s focus is uni – dimensional; rooted in the textbooks to be memorized in college courses; in this case, the action of shank muscle on movement of the foot; it is easy to miss what these same muscles do when the foot is fixed: move the shin:

“When the foot is bearing weight, flexion of the knee cannot take place unless the ankle is dorsiflexing at the same time . If this dorsiflexion is prevented, the weight bearing knee is unable to flex.’ (Wells, 1976)

Well then, according to Wells, 1976; the weight bearing knee cannot flex unless unless the ankle is dorsi- flexing. This means muscles acting on the shin to pull it forward such as Tibialis anterior should work alongside thigh, hip and other ankle muscles such as Gastrocnemius to bend the knee. 

The knee joint is a coupling unifying thigh (femur) and shin (tibia, fibula) bones. The movement of thigh bone directly influences movement of shin bones and vice versa; they are connected by the knee coupling. Kinesiology reference texts do not classify muscles in the front of the shin, such as the tibialis anterior, as knee flexors. Tibialis anterior (TA) muscle is referred to as uni – articular; meaning its attachments cross only one joint, i.e., generating a torque at one only.

Since TA muscle’s attachments do not cross the knee joint, the Kinesiology textbooks make no reference to any action on knee. The reason being such muscles are assumed only to  act on foot and ankle. If at all, there is usually no mention TA as a muscle synergist; active in bending the knee by pulling shin forwards towards the toes; which was indirectly referred to in the above textbook quote.

Figure 3. From V. A. Podlivayev (1975); cited by Verkhoshansky (1988). An electro – myographic (EMG) of a high class weightlifter is depicted in figure 3. Note the synergistic action of quadriceps – gastro – soleus muscles to straighten legs and in squatting under the barbell; depicted as large circles of the bursts of electrical activity of the muscles contracting. Conversely the same synergistic cooperation of hamstring – tibialis anterior is obvious to flex the legs. It is necessary to move the shins to bend knees which requires coordination of ankle and thigh muscles. Likewise, synergistic coordination of thigh and ankle muscles are necessary to straighten the knee.   

Figure 4. The disposition of the shins as a weightlifter shifts knees under the barbell. Both anterior and posterior muscles: Soleus and other plantar flexors; Tibialis Anterior are involved. Note: bulging Tibialis Anterior (TA) muscles actively pulling shins forward and of course bending knees. This re – loading of leg muscles stretches Achilles tendon increasing the power of the final extension of legs and trunk. Charniga photo.

The Role of Reciprocal Innervation for Developing Power and Shifting/Dissipating Mechanical Energy

“Reciprocal innervation is a reflexive act characteristic of all movements and is perfected quickly in the process of training.”  Y. V. Verkhoshansky, 1988

Weightlifters lift a barbell from the floor by straightening first the legs; then include the trunk as the shins approach a vertical disposition. Once the shins approach vertical a weightlifter; or any athlete for that matter, is unable to fully utilized the power of the all the leg muscles to lift, jump, and so forth. The weightlifter’s force against the support drops. 

Consequently, the weightlifter’s reaction to the unavoidable drop in force against the support as the shins shift to vertical; is to “re – introduce” (Zhekov, 1976; Roman, 1968;74,86; Podlivayev, 1975) the muscles which straighten the legs: quadriceps and gastro – soleus (figure 3). The knees bend shifting forward under the barbell (figure 4.) This bending of knees which of course means tilting the shins, stretches the Achilles tendon, the largest, strongest spring in the human body. A weightlifter’s lifting power is greatly enhanced the faster the shins tilt (knees bend) and subsequently the faster the knees straighten, i.e., shins shift towards vertical (Frolov, 1977).

The action of the TA pulling shin towards the toes reduces the tension in soleus and other plantar flexors; creating optimum conditions, such that the soleus and Achilles stretch without undue internal resistance. Considering the serious injuries depicted the figures 1 & 2 resulting from such benign, ordinary movements of the lower extremities; something is clearly amiss with the gastro – soleus – tibialis anterior, agonist – antagonist synergy of these athletes. That lacking of synergy is part of and/or a combination of lack of mobility in the ankle; compliance of tendons and ligaments of the lower extremities.

Although the synergistic action of the shin muscles is the same for everyone; the unique feature of the weightlifter in comparison with the basketball players is the multiple re – introduction of the ankles muscles in the classic exercises: first to straighten the legs at the start, second to re – introduce the same muscles once the shins are vertical and third to rapidly flex the legs into the squat (figures 3,4,5).

This involves a high speed reciprocal innervation of agonist contracting as antagonists relax: quadriceps and gastro – soleus contract as hamstring and TA relax and vice versa. Without question the speed of the relaxing muscles must exceed that of the contracting to produce smooth, rapid movements. And, a faster relaxation of muscles than contraction of muscles sequence is a characteristic of elite athletes (Matveyev, 1977).

Dynamic Correspondence of Thigh and Shank Muscles

One factor not considered when one compares lower extremity injury susceptibility of weightlifters; especially relative to an Achilles tendon rupture; to those lower extremity injuries common in American football, basketball and others; is an optimal dynamic between the anterior and posterior ankle muscles. An optimal dynamic empowers weightlifters with the ability to generate the great power expressed from the rapid displacement of shins, i.e., a high speed loading and recoil of a catapult mechanism. 

A prevailing bias, without substantiation, common to all in the community involved in the strength training of athletes, athletic trainers, physical therapists, personal trainers; or, indirectly academics, physicians,  and the like; is the belief deep knee bends will stretch ligaments and lead to injury (Charniga, 2014 – 2019). Half – squats limiting knee angle to about 90°, until thighs are parallel or just below parallel are considered safe even though this technique is connected with the largest stress on the knee joint and ligaments (Hartman, 2013).

Furthermore, tilting of the shin towards the toes (away from the vertical) is restricted in athletes’ exercise regimes because it is believed; likewise without substantiation; the tilting shin creates a unjustifiable shear force on the knee. Yet, the fluidity of this very high speed tilting of the shin is the principle source of a weightlifter’s power; and this, sans the lower extremity injury plague common to athletes who learn to restrict these motions.

For instance:

“….instruc­tions about a restriction of the forward knee displacement have to be strictly avoided. This recommendation is based on a misinterpretation of existing data and should be removed in future practical literature.” Hartman, 2013

The unfortunate circumstances leading up to the catastrophic injuries depicted in figures 1&2 are a testimonial to the ignorance of the coaches, trainers, therapists and so forth who espouse half bends and minimal displacement of shins in bending lower extremity exercises. 

For example, foot injuries such as Lisfranc, Jones fracture, even foot pedal injuries are common in football and professional basketball. So common the problem, a go – to physician to fix the myriad of foot and ankle injuries in the National football league (NFL) has a special clinic in Green Bay, Wisconsin. The ubiquitous nature of four lower extremity injuries in just the NFL are presented in table 1.

According to this doctor there are various reason for the NFL’s ubiquitous foot problem. The players feet get stuck in the turf. Not likely as the cleats are a maximum of 0.2 cm (0.5 inches) in length. Furthermore, the artificial turf used in football stadiums consists of carpet infused with rubber pellets. The ‘non – stick’ properties of this surface are evident even on Tv; in the form of a dark cloud (of rubber pellets) pulled up as a player cuts or slides moving about or in the act of being tackled.

However, according to the foot doctor improper fitting shoes cause the injuries: 

“So now you’ve got a shoe that’s not functioning right, that’s not bending the way it should, and they’re potentially placing themselves at more risk for fractures, turf toe and Lisfranc injuries,” he said. Anderson said many foot injuries are the result of players wearing the wrong shoes and cleats, especially when paired with artificial surfaces.”Demovvsky, 2017

Table 1. Some lower extremity Injuries in the NFL.

Injury Achilles Foot Ankle Calf Knee
9/02/2018 18 47 65 12 180*
11/12/2018 10 27 44 9 123
1/02/2019 16** 32 58 7 143
9/05/2019 13 19 40 6 68
11/07/2019 8 22 37 5 71
1/02/2020 17*** 35 75 7 119
  • * knee injuries are inclusive ACL being the most common; followed by PCl and MCL;
  • ** Sixteen Achilles injuries on 1/02/2019 became 18 by 1/15/2019;
  • *** Seventeen Achilles injuries 1/2/2020 was actually 19 if two NFL head coaches are counted.

Although obtaining a precise accounting of lower extremity injuries in the NFL (let alone collegiate football) is an opaque enterprise; consider the following:

Between 2012 – 2019 NFL seasons the following injuries were reported: MCL (medial collateral ligament) – 1,076 cases; ACL (anterior cruciate ligament) tears – 445 cases; or, an average of approximately 190 injuries per season over the eight year span of just those two structures!

A Technological Answer?

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

The NFL had an average of 30 foot afflictions at various stages of the 2018 & 2019 seasons; with as many as 47 by the first week of the 2018 season (table 1). The solution outlined below of players subjected to computerized 3Ds scans of their feet; which “all 32 NFL teams have”; so that shoes can be customized as a “protective piece of equipment”  does not jive with data in the table; let alone with the entirety of the injury conundrum:

“Among them is the “FitStation Powered by HP.” All 32 NFL teams have them at their facilities, but when players come to Green Bay, they go through it with Anderson’s help.

The device takes a 3D scan of a player’s foot — width, height, length and girth — and then comes up with the proper shoe match for the player. “We’re trying to do a paradigm shift with the players and the manufacturers to look at the shoe as a protective piece of equipment, not apparel,” Anderson said. Anderson said most players come to the NFL with the wrong shoes.”https://www.espn.com/blog/green-bay-packers/post/_/id/39159/renowned-surgeon-dr-robert-anderson-joins-packers-medical-team

For instance, 19 foot injuries were reported by the first week of the 2019 season along with 40 ankle injuries. By playoff time in January of 2020 there were 35 foot and 75 ankle injuries. On 01/10/2019 there were NFL 399 players on the injured reserve (IR) list; with a reported 18 Achilles injuries by 01/15/2019. On 01/02/2020 there were a reported 412 NFL players on IR and 17 Achilles injuries; nineteen if you include the two head coaches (Green Bay and Detroit).

Were 3D scans and specialized footwear the answer to foot injuries; since all 32 teams have this technology; the lower extremity injury rate should reflect this. Even if one can show the foot injuries have declined; which they haven’t; the problem inevitably shifted to the ankle and knee.

Indeed, the hip – to – knee – to – shin – to – foot kinematic chain is called the human body’s (likewise many animals) leg spring. Movement of one joint in the leg spring is interdependent, inter-conditional and interconnected to all in the chain. Training an athlete and/or restricting movement of the shin has consequences. The proliferation of knee, foot and ankle injuries attests to this. Merely adjusting shoes cannot and obviously does not address the scope of the problem.   

One has only to look to basketball which has many of the same injuries to feet, ankles and knees; sans the NFL’s excuses of artificial turf, cleats and the wrong shoes. Just consider the severity of the consequences of the rather benign bending depicted in figures 1&2. If the shoes were the problem and not the mobility of the athlete; the ubiquity of 3D scanning of feet to create customized shoes would manifest in lower injury rates; which of course it does not.

Furthermore,  the incongruity of professionals listed above, evidently don’t realize the shin bones form half the knee joint; yet virtually all agree the shins should not move beyond the toes or worse yet, if even that far; when performing half or just below parallel squats. Yet it is this very tilting of the shin where the knee flexion synergist TA is very active pulling shin forward towards the toes.

Consequently, athletes who practice most any strength training movement such as squats, lunges and so forth learn to restrict tilting the shin forward. This would seem logical to them as textbooks refer to the function of TA as moving the foot; not moving the shin with foot flat on floor or otherwise fixed; so, presumably this muscle has no useful function with feet on the floor.

Consider the two circumstances depicted above of elite (NBA) basketball players. Both suffered an Achilles rupture stepping forward with injury occurring when knee angle approached 90°. Bending further past this angle would entail shin tilting towards the toes; which means tibialis anterior would actively pull shin towards the toes, i.e., bending knee and hip.

Now contrast those injury producing moments to the EMG in figure 3 and the movements depicted in figures 4 & 5. The weightlifter shifting knees under the bar with shins tilting forward in figure 4 and the weightlifter in a low squat with huge lean forward in shins serve as a prerequisite to generate great power (figure 4) and amortize the forces on (figure 5) the athlete flexing under the barbell: i.e., facilitating power and re – distribution of mechanical energy. 

The muscles of the weightlifter’s shank are very active in all phases of bending. The shoes are not that specialized, certainly not individually customized with 3D scanning; they offer no protection for ankle, foot or knee. The surface is hard wood. The forces on the weightlifter’s lower extremities are far greater than one encounters in football or basketball; ankle injuries are rare; Achilles ruptures virtually unheard of and rate of knee injury low.

Figure 5. The weightlifter  in the figure lifting more than 250% of bodyweight sits in a full squat position with shins tilted far forward of toes with large development of tibialis anterior muscle in left shin. Charniga photo

A Peculiarity of Rapidly Switching Directions

Figure 7. Super elite weightlifter switching from straightening (figure on left) the legs to bending: with rapid inversion of ankles (figure on right). An example of the extraordinary complexity of the functions of shank muscles with the rapid switch from straightening shin and with it the knee and hip to flexing feet and bending shin. Charniga photos.

With lower extremity injuries; especially ankle and knee, the plague of American athletics; a curious feature often overlooked is the role of shank muscles such as TA and Tibialis Posterior (TP) in high speed switching of direction. The legs shown in figure 7 belong to the world’s strongest man OM Yun Chol (PRK) lifting 166 kg or 302% of his body weight. An integral element of this extraordinary feat is the speed with which the athlete drops under the barbell which barely reaches the height of his waist.

The super elite athlete’s shank muscles execute this extremely fast flexing of lower extremities; curiously, initially by inversion of ankles; followed by the same action as feet begin to leave the floor (figure 7). Contrast this natural functioning of shank muscles under extreme conditions of human performance; to the ubiquity of inversion sprains in sports like football and basketball; so dreaded in the USA, many athletes have ankles and feet taped; even spatting (show in figure 8).

So,  there is a dialectical contradiction in philosophy. On the one hand the people who train and rehab the athletes with the most frequent ankle injuries deign to protect the feet and ankle joint from inversion movements and the shin from tilting forward, with special shoes, taping and so forth; purposely marginalizing the muscles; which perform complex synergistic actions of bending and straightening lower extremities. While on the other hand, weightlifters who experience the lowest incidence of these problems; conveniently use these muscles in synergistic harmony to produce great power and speed of movement.  

Binding Feet to Ankles {taping, spatting, bracing) Reminiscent of Chinese Foot-binding?

A salient point missed in all the talk about 3D technology to create shoes which are protective is what happens when the trainer fastens those 3D designed/customized shoes to ankles (see figure 8): tapes shoes to ankles; as is so commonplace in American sport?

A Chinese practice of binding the feet of females lasted for a thousand years; until the early 19th century Christian missionaries coerced the government to outlaw this custom. Binding feet beginning in childhood prevented natural growth of the foot;  effectively crippling half the population. There were several reasons for the practice including:

“Why are feet bound? It is not because they are good looking with their bowed arch, but rather because men feared that women might easily leave their quarters and therefore have their feet bound tightly in order to prevent this.”Fan Hong, 1997

Be that as it may, one sure way to cripple feet is to restrict motion. Today’s binding of feet an ankles with tape and braces, purportedly to protect structures which have evolved over countless millennia to produce in the words of DaVinci “a masterpiece of engineering and a work of art”; are now somehow or other, in need man made intervention for protection. 

Figure 8. Professional football player leaves the practice field with serious knee injury “suffered on the third snap of the team’s first organized team activity session”. Note: right foot with shoe heavily taped to ankle. Is this an example in the modern day of the Chinese practice of ‘foot binding”, i.e, an inadvertent crippling resulting from restriction of the hip/thigh/shin/ankle/foot synergy?  

Conclusions

“it is hard to see how things work by looking at single parts.” Nasim Taleb 2012

/ attempts to apply a simplistic “single parts” (Nasim Taleb, 2012) approach gleaned from anatomy courses to the extraordinary complexity of human movement cannot have a positive outcome;

/ all the parts of the body make up the whole entity; none of which can be marginalized without consequences for rest; 

/ technology is no substitute for experience and common sense:

For example, another ‘tech answer’ to the proliferation of lower extremity injuries in the  NFL (https://www.cnbc.com/2020/02/29/tech-company-sparta-science-combats-nfl-injuries-with-ai.html)  purports to “identify foot and knee issues”, “to identify soft tissue problems usually blamed for hamstring injuries in sports”; with computer analysis of vertical jumps and so forth. Teams can pay tens of thousands of dollars for this information.

The NFL alone began the 2018 season on 9-2-2018 with a reported 74 hamstring injuries. In 2019 the NFL had a reported 43 hamstring injuries by August 2, 2019; 41 on October 12, 2019 and 36 on January 2, 2020. At any given time throughout the 2018 & 2019 seasons there are at least 25 hamstring injuries.  Go figure!

References

/ Hamilton, N., ., Kinesiology, McGraw Hill, 2002

/ Wells, K., Luttgerns, N., Kinesiology, McGraw Hill, 1976

/ Charniga, A., “Achilles tendon ruptures and the NFL”, www.sportivnypress.com

/ Charniga, A., “The foot. the Ankle Joint and Asian Pull”, www.sportivnypress.com

/ Charniga, A., “Variations of the Jump Under the Barbell in the Snatch and the Clean”. www.sportivnypress.com

/ Charniga, A., “Of Flat Tires and Brittle and Basketball Players”, ww.sportivnypress.com

/ Charniga, A., “Ankle Breakers and Glasket – ball”, www.sportivnypress.com

/ Charniga, A., “Why Safe is Unsafe”, ww.sportivnypress.com

/ Zhekov, I.P., BIomechanics of the Weightlifting Exercises, FIS, Moscow, 1976. Sportivnypress, Livonia, MI 48152 English translation.

/ Roman, R.A., The Training of the Weightlifter, Moscow, FIS, 1968;1974; 1986. English Translation Sportivny Press, Livonia, Michigan

/ Frolov, V.I., “The optimal phasic structure of the snatch of highly qualified weightlifters”, Tiiazhelaya Atletika Ezhegodnik, 1977:52-55, FIS, Moscow. Translated by Andrew Charniga

/ Robinson, J., “Liverpool is Throwing Load Management Out the Window”, The New York Times, posted 1-26-20

5/ Matveyev, L.P., Fundamentals of Sport Training, FIS, Moscow, 1977

/ Fan Hong,  “Footbinding, Feminism and Freedom”, Frank Cass, Portland, OR 1997

 / Demovsky, R. https://www.espn.com/blog/green-bay-packers/post/_/id/39159/renowned-surgeon-dr-robert-anderson-joins-packers-medical-team, 2017

/ https://www.cnbc.com/2020/02/29/tech-company-sparta-science-combats-nfl-injuries-with-ai.html

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