The hallux plays a key role within dynamic and static activities. For example, without a correctly functioning hallux, static balance is compromised, as seen in an experiment using a specially designed splint to restrict the function of the hallux.¹ During movement, this becomes more pronounced and more dangerous if one doesn’t possess adequate foot structure or strength.

The Role of the Big Toe in Running and Walking

Starting with a walk, human walking gait is described as an inverted pendulum.² Walking is low impact, meaning that a human may use a heel strike at the onset of each step. Body weight travels from the heel, across the outside of the foot as the center of mass passes in a sagittal direction over the foot.³ Bodyweight continues and falls inward (or pronates in) over distal ends of the metatarsals, and here is a critical point. The hallux needs to control this pronation to guide bodyweight forward, and it does this by pressing into the ground. The hallux controls pronation of the foot.

Pronation is sometimes described as destructive or an injury risk factor. However, you need some degree of pronation in order to fully utilize the foot. Pronation causes the foot to deform and absorb kinetic energy in each step. It’s even stated that this ‘windlass mechanism’ returns as much as 17% of the energy generated with each step.² During human running gait, the forefoot will land first, as the impact would be too high for a heel strike, and more suited to a wider base of support.³ Now the hallux must continue to control pronation to allow the correct loading of the plantar fascia, or ‘windlass mechanism,’ as the heel touches down onto the ground.

It is when the hallux becomes misaligned, termed hallux valgus, that we see over-pronation of the foot which can shift the direction of bodyweight from the sagital plane onto the frontal or transverse plane,³ leading to a host of injuries, specifically ACL damage in female athletes and runners. In order to reduce these outcomes, the hallux must be abducted away from the second toe (see Fig. 1 right). Here, the hallux is at a much stronger mechanical position to halt this pronation and direct bodyweight in the correct plane. This function is unlikely with hallux valgus, also seen in Fig. 1 (left side).

Fig. 1: Hallux valgus versus the correct position.⁴

For sports which are running-based, it may be advised to take this into consideration within the context of the sport. For example, asking basketball players to train barefoot on the court may not be optimal, as they play in shoes. However, including a barefoot warm up along with specific foot strength and structure training may be enough to decrease the numbers of ACL injuries within the sport. 

How can you wake up your weak feet?

Unlock Power and Performance With a Golf Ball

References:

1. Chou, Shih?Wei, Hsin?Yi Kathy Cheng, Jen?Hua Chen, Yan?Ying Ju, Yin?Chou Lin, and May?Kuen Alice Wong. “The role of the great toe in balance performance.” Journal of Orthopaedic Research 27, no. 4 (2009): 549-554.

2. Bramble, Dennis M., and Daniel E. Lieberman. “Endurance running and the evolution of Homo.” Nature 432, no. 7015 (2004): 345-352.

3. Wilkinson, Mick, and Lee Saxby. “Form determines function: Forgotten application to the human foot?” The Foot and Ankle Online Journal 9, no. 2 (2016): 5.

4. Shu, Yang, Qichang Mei, Justin Fernandez, Zhiyong Li, Neng Feng, and Yaodong Gu. “Foot morphological difference between habitually shod and unshod runners.” PloS One 10, no. 7 (2015): e0131385.

The post The Real Function of the Big Toe appeared first on Breaking Muscle.

‘The shape of the foot conforms to that of the shoe’

-Dr. Phil Hoffman, 1905¹

Modern footwear is largely focused on style, rather than the function of the human foot. Choice of shoe is a hugely important task, as this determines how our feet will function both in and out of them.

‘The shape of the foot conforms to that of the shoe’

-Dr. Phil Hoffman, 1905¹

Modern footwear is largely focused on style, rather than the function of the human foot. Choice of shoe is a hugely important task, as this determines how our feet will function both in and out of them.

Foot Anatomy vs. Footwear

To understand what makes a good shoe, we must first understand the shape and function of the human foot. In humans, the foot supports us during locomotion and usually directs our bodyweight forwards. Therefore, the wider and flatter the foot, the more support.²

When walking, the gait cycle usually begins with a heel strike, then travelling through the foot ending with the toe-off phase, with an inverted pendulum mechanism. During running, a spring mechanism takes over,^{3, 4}with forefoot or mid-foot landing, followed by the toe-off phase.⁵

During this toe-off phase is when the hallux (big toe) must press into the ground, halt foot pronation and direct the body in the sagittal plane. Any valgus of the hallux may compromise this function and shift the load elsewhere, usually out to the sides.²

This can potentially cause knee valgus, pelvic twisting and additional pressure on other joints, and is usually seen in the foot of the trail leg splaying out to the sides.

Restricting the hallux using a splint has been observed to reduce single leg performance.⁶ Considering that running is a single leg activity, this finding is rather significant.

Poor footwear essentially mimics the effect of a splint, creating a dysfunctional foot that is no longer capable of support or directing bodyweight during locomotion.

Even during standing, the hallux presses into the floor and exerts twice the pressure of the remaining four toes, if it functions correctly.⁶

Distance between the hallux and second toe is also key in optimal human foot function (see Fig. 1). Shod runners have been shown to possess a 6.28mm and 5.39mm distance in men and women respectively, while barefoot runners displays distances of 23.73mm and 19.38mm in men and women.⁷

This hallux adduction helps give the foot width, and provides an optimal angle to function correctly by providing greater leverage to halt foot pronation. Simple observation shows that the barefoot runner’s feet provider a wider base of support than that of shod runners.

Diagram from:Foot Morphological Difference between Habitually Shod and Unshod Runners⁷

What Makes Running Shoes So Bad?

Many running shoes now have features that work the polar opposite of anatomy: narrow toe boxes, high toe/heel drops, thick and cushioned soles, and a toe spring.

Narrow toe boxes do not allow correct hallux function, squeezing the toes together and essentially shutting down the foot’s ability to direct bodyweight. When this happens, other tissues will have to compensate for the ineffective hallux.²Fig. 1 beautifully shows the differences between shod and barefoot runners for a visualisation.

Toe springs, identified by elevated toes of the shoe, take away the foot’s natural ability to absorb, store and release energy. The naked foot’s spring action returns about 17% of the energy from each step.⁴

When that mechanism is hindered, other tissues are once again needed to compensate, and the next available spring is the Achilles tendon. Toe springs in shoes might sound like an advantage, like these shoes are helping us run faster and for longer.

However, due to shoes taking away these functions, our feet are becoming unable to perform their natural roles, causing muscles to atrophy and connective tissue to become fibrotic.

Cushioned shoes are thought to interfere with the body’s ability to change from an inverted pendulum (walking) gait to a spring gait (running), and create rear foot striking.⁵

During walking, the heel lands first. Ground reaction forces (GRF) travel through the first point of contact and provide information as to how hard the heel is striking the ground. Once these GRFs increase, the risk for injury increases, and the body reacts by changing to a running gait.

Adding cushioning to the heel dampens this feedback, increasing the speed at which you can run with a heel strike. Again, the effect is that additional tissues come in and compensate for this alien running technique.

Reversing the effects of years of anatomically incorrect shoes is not an easy task. [Photo credit: Pixabay]

The Problem with Poor Footwear

The whole kinematics of shod runners appears different to barefoot populations.⁸

Shod runners experience increases in stride length, stride time and ground contact time compared to barefoot running. Shoes also seem to enable higher hip flexion, which may be tied to the increased stride length and time.⁵

The biomechanical differences between shoes with different toe/sole drop are substantial. Comparing shoes of 0mm and 8mm drop, a 4.2° increase in foot-ground angle (the acute angle of the foot relative to the ground) was observed during the touchdown phase of running.⁹

In other words, the more the heel is elevated, the more one will land heel-first during running. This tendency to land on the rear foot or heel strike may also explain the decreased knee angle at touchdown.

The negative effects of shoes can also be observed in a very short amount of time. Hallux valgus and deformation has been observed in habitually barefoot teenagers in a mere 6 weeks after wearing shoes. In adults, hallux valgus may take as long as two years to correct with barefoot shoe use.^2,10

The feet appear to quickly morph to the shoes they are encased in, and these effects may be easier to resolve at a young age.

What You Can Do About It

As previously stated, a cushioned sole is likely to interfere with the foot’s natural function and sensory feedback,²as well as contribute to this increase in heel striking tendencies.⁵

Due to the vast biomechanical differences between conventional running shoes and barefoot, it is advisable to ease into barefoot running. A transition shoe or multiple transition shoes, depending your starting point, would be optimal to prepare your body for barefoot running.

This transition shoe(s) should slowly move in the direction of barefoot running by featuring a reduced heel/toe drop or wider toe box.

Reversing the effects of years of anatomically incorrect shoes is not an easy task, but the younger you start this process, the easier and faster it will be. An ideal place to start could be a barefoot policy in your home. The end goal is to achieve a foot similar to Fig. 1B rather than 1A.

Self-myofascial release of the foot spring can be beneficial, specifically the plantar aponeurosis, Achilles tendon, tibialis anterior and soleus. Any tissue that is compensating for another is likely locked in a shortened position.

Coaxing these tissues to full function and increasing the neural pathways to lesser active (locked long) tissues of the foot may improve the overall function, strength and movement of your feet.

Strength training of the intrinsic foot muscles is also key, specifically flexor/extensor hallucis longus, flexor/extensor digitorum longus, and abductor halluces. Howevers this shouldn’t take a priority in your rehabilitation. Achieving a structurally robust foot must accompany strength gains of these intrinsic muscles.

Pick the Right Shoe

Proper running shoes must have a wide toe box to allow the toes to splay out and encourage distance between the hallux and second toe. They should have zero toe/heel drop to allow the feet to function correctly, and feature a thin, non–cushioned sole that will not dampen feedback from the ground.

While no shoe compares to the effects of barefoot running,^8,11a shoe that interferes as little as possible with the natural form and function of the human foot while providing plantar protection against puncture injury is the most beneficial.

This article has been written regarding running shoes. But this information can also be applied to nearly every type of shoe for every occasion from running to black tie events.

All modern shoes appear to feature similar defects to running shoes, such as narrow toe box, elevated heels, toe springs, and so on. Barefoot shoes, though they are an oxymoron if there ever was one, are increasing in popularity, which means an increase in availability. Take these points into your next shoe purchase may just put you on the path to getting your feet back to full strength.

More on anatomy and impact forces:

Impact Forces, Shoes, and Lower Leg Injuries: Part 1

References:

1. Hoffmann, Phil. “Conclusions drawn from a comparative study of the feet of barefooted and shoe-wearing peoples.” American Journal of Orthopedic Surgery 2, no. 2 (1905): 105-136.

2. Wilkinson, M., & Saxby, L. Form determines function: Forgotten application to the human foot?. The Foot and Ankle Online Journal, 9 (2):5.

3. Bolgla, L. A., & Malone, T. R.Plantar fasciitis and the windlass mechanism: a biomechanical link to clinical practice.Journal of athletic training,39(1), 77.

4. Bramble, Dennis M., and Daniel E. Lieberman. “Endurance Running and the Evolution of Homo.” Nature 432, no. 7015 (2004): 345-52. doi:10.1038/nature03052.

5. Mei, Qichang, Justin Fernandez, Weijie Fu, Neng Feng, and Yaodong Gu. “A Comparative Biomechanical Analysis of Habitually Unshod and Shod Runners Based on a Foot Morphological Difference.” Human Movement Science 42 (2015): 38-53. doi:10.1016/j.humov.2015.04.007.

6. Chou, Shih-Wei, Hsin-Yi Kathy Cheng, Jen-Hua Chen, Yan-Ying Ju, Yin-Chou Lin, and May-Kuen Alice Wong. “The Role of the Great Toe in Balance Performance.” Journal of Orthopaedic Research 27, no. 4 (2009): 549-54. doi:10.1002/jor.20661.

7. Shu, Yang, Qichang Mei, Justin Fernandez, Zhiyong Li, Neng Feng, and Yaodong Gu. “Foot Morphological Difference between Habitually Shod and Unshod Runners.” PLoS ONE 10, no. 7 (2015). doi:10.1371/journal.pone.0131385.

8. Bonacci, Jason, Philo U. Saunders, Amy Hicks, Timo Rantalainen, Bill (Guglielmo) T Vicenzino, and Wayne Spratford. “Running in a Minimalist and Lightweight Shoe Is Not the Same as Running Barefoot: A Biomechanical Study.” British Journal of Sports Medicine 47, no. 6 (2013): 387-92. doi:10.1136/bjsports-2012-091837.

9. Chambon, Nicolas, Nicolas Delattre, Nils Guéguen, Eric Berton, and Guillaume Rao. “Shoe Drop Has opposite Influence on Running Pattern When Running Overground or on a Treadmill.” European Journal of Applied Physiology Eur J Appl Physiol 115, no. 5 (2014): 911-18. doi:10.1007/s00421-014-3072-x.

10.Knowles, F. W. “Effects of shoes on foot form: an anatomical experiment.”The Medical Journal of Australia1, no. 17 (1953): 579.

11. Lieberman, Daniel E., Madhusudhan Venkadesan, William A. Werbel, Adam I. Daoud, Susan D’Andrea, Irene S. Davis, Robert Ojiambo Mang’Eni, and Yannis Pitsiladis. “Foot Strike Patterns and Collision Forces in Habitually Barefoot versus Shod Runners.” Nature 463, no. 7280 (2010): 531-35. doi:10.1038/nature08723.

The post Why Modern Running Shoes Are Terrible appeared first on Breaking Muscle.

“It doesn’t matter how beautiful your theory is, it doesn’t matter how smart you are. If it doesn’t agree with experiment, it’s wrong.”

A very common notion in training athletes who want to improve speed that one must press into the ground. In fact, this is so engrained in how we train people that we never, ever question it. It is a method employed by a huge number of coaches and trainers when trying to increase speed. It seems to follow Newton’s 3rd law of motion, in that when one body exerts a force on another body, the second body experiences a force equal in magnitude in the opposite direction. Basically, if you press back and down into the floor, then you move forwards and up, sounds completely logical.

The problem here is that sprinting doesn’t work like that.

The Myth of Triple Extension in Sprinting

Science has dealt a fatal blow to the triple extension theory. The triple extension or push off simply does not occur. It has been observed since the 1980’s that, during sprinting, the extensor muscle groups of the lower extremities (gluteus maximus, quadriceps, gastrocnemius, etc.) associated with this so-called triple extension are silent during the period of the stance phase in which they are supposed to be active.¹ The musculature of the leg has been observed using intramuscular and surface electromyographical (EMG) electrodes, and Figure 1 below displays a visual representation of muscle activity during running.

Fig. 1: Muscular activity during each phase of running. The darker the muscle, the more activity. Reproduced with permission from Dr. Mick Wilkinson and Lee Saxby.

Calves 

The gastrocnemius (calf muscle) is active during the foot descent, foot contact, and mid-support phases, but appears to shut down shortly after plantar flexion begins, just after mid-support. It is likely that the gastrocnemius is active to aid in foot stability in preparation for ground contact, and to control dorsiflexion during the mid-support phase by eccentrically contracting. A mere 6° of ankle plantar flexion from an available 33° is caused by a concentric contraction; simply not enough to create forward locomotion.

Quadriceps

The quadriceps become active about 50msecs after maximum hip flexion, yet knee extension begins 100msecs before maximal hip flexion. The higher the speed of gait, the more degrees of knee extension are achieved by the quadriceps. The quadriceps continue to contract concentrically until foot contact. Then, just as the gastrocnemius performed, the quadriceps eccentrically contract. This is to resist the maximal ground reaction forces and gravity, which at mid-support are applying force from below and above, squashing the runner. Once the mid-support phase is over, the quadriceps shut down.

Hamstrings

The hamstrings are by nature a biaxial muscle, crossing the knee and hip, and therefore create movement at both. Both groups of hamstrings are largely identical in terms of activity.¹ The hamstrings likely undergo an eccentric contraction to control the rapid hip flexion during the forward swing phase as well as rapid knee extension during foot descent and foot contact. This could also explain why hamstring eccentric strength training plays such an important role in reducing hamstring injury risk factors.² A lack of eccentric strength appears such a strong indicator of hamstring injury that even age and previous injury risk factors are decreased with increases in hamstring eccentric strength.³

Glutes

The gluteus maximus is assumed to play a vital role in sprinting, with most seeing this as a big part of the engine that drives us forward. Another blow to the triple extension or push off theory is that as the speed of running increases, the gluteus maximus shuts down earlier. The gluteus maximus is actually the first of the tested muscles to switch off on the stance leg after foot contact during sprinting. The magnitude of activity of the gluteus maximus increases during foot descent as the speed of running increases. It is therefore likely that the gluteus maximus controls the rapid hip flexion during the forward swing phase with an eccentric contraction, then a concentric contraction during the foot descent. In addition, it brings the pelvis back from a posterior tilt to neutral after the toe off phase. It should be noted that this control of torso angle during running is probably why humans have such highly developed gluteal muscles in comparison to other primates.⁴

How Sprinting Actually Works

Previously it was mentioned that the ‘push off’ theory involving triple extension seems a logical thought process when considering Newton’s 3rd law that each action has an equal and opposite reaction. Such reactions are visually represented in Figure 2, below. Ground reaction forces upon foot contact travel up and back in line with the virtual pivot point (see Figure 3), not the center of mass.⁵ The greatest ground reaction forces are seen during the mid-support phase, where the runner is squashed between the ground reaction force and gravity. But once the runner passes this midpoint, the ground reaction force rapidly drops, and thus creates insufficient force to propel the body forward. 

Fig. 2: Ground reaction forces magnitude and direction. Runner is running left to right; greatest forces are applied at mid-support phase, and rapidly decrease as the runner falls forward. Reproduced with permission from Dr. Mick Wilkinson and Lee Saxby.

By now, the lack of a ‘push off’ is clear from the scientific literature. The extensor muscle groups switch off well before any triple extension can increase linear speed. In addition, ground reaction forces again provide insufficient force to propel the body forwards.

So what exactly is the driving force behind sprinting or indeed any forward locomotion? 

The mechanism behind locomotion is all around us. You have interacted with it every second of your life—unless you have a habit of leaving the atmosphere. It’s gravity. Gravity is the driving force behind locomotion, via a rotational movement. Stand a pen up on your desk, let go. It fell over, and its center of mass fell in a certain direction. A rotational movement using gravity. An oversimplification in which lies a problem: the higher the angle of forward lean, the faster the center of mass will accelerate towards the ground, causing constant-acceleration running. This of course is not possible, and will certainly involve the runner picking themselves up off the ground.

The current leading theory regarding how forward locomotion works without constant acceleration is the virtual pivot point model. This model suggests a virtual, not physical, pivot point located above the center of mass. The exact location differs from person to person and can range from 5-70cm above the center of mass.⁵ As stated earlier, ground reaction forces travel back and up through this pivot point. During the mid-support phase, the ground reaction force is vertically aligned with the hip, center of mass and virtual pivot point. As the runner is squashed between gravity and the ground reaction force, some of this energy is stored in elastic tissues such as the foot spring and Achilles tendon.⁶ A gravitational rotation then occurs, with the passive release of stored energy from the connective tissues, creating forward locomotion. The virtual pivot point and center of mass form a pendulum, allowing the center of mass to swing underneath the virtual pivot point, creating a virtual pendulum. This creates a stable method of moving for an upright biped, stopping us becoming ‘top heavy’ by having most of the mass under this pivot point.

Fig. 3: A visualization of the virtual pivot point.⁵ 

What to Train Instead of Triple Extension

The research base provides evidence that sprint training involving triple extension drills by pressing into the ground may be ineffective due to a lack of push off phase in running. From muscle activity during varying speeds of sprinting, emphasis on rapid hip flexion from the psoas and iliacus should be placed as a priority. In addition, ankle complex training should mimic that which is observed during sprinting, i.e. to minimize vertical displacement of the center of mass and create joint stiffness. The ankle flexion angle changes only 8° in upon foot contact in sprinting, compared to 18° in jogging.¹ Skipping with a rope could be such an activity.⁷ In addition, since eccentric contractions were observed in muscles previously thought to push off, ensuring eccentric strength, force absorption, and tendon elasticity is essential, using exercises such as Nordic hamstring curls, improving landing mechanics, and as previously mentioned, skipping with a rope.

Could your pre-race breakfast ruin your stride?

You Move as Well as You Eat: The LInk Between Food and Gait

References:

1. Mann, R. A., Moran, G. T., & Dougherty, S. E. (1986). Comparative electromyography of the lower extremity in jogging, running, and sprinting. The American Journal of Sports Medicine, 14(6), 501-510.

2. Opar, D., Williams, M., Timmins, R., Hickey, J., Duhig, S., & Shield, A. (2014). Eccentric hamstring strength during the Nordic hamstring exercises is a risk factor for hamstring strain injury in elite Australian football: a prospective cohort study. British Journal of Sports Medicine, 48(7), 647-648.

3. Opar, M. D. A., Williams, M. D., & Shield, A. J. (2012). Hamstring strain injuries. Sports Medicine, 42(3), 209-226.

4. Lieberman, D. E., Raichlen, D. A., Pontzer, H., Bramble, D. M., & Cutright-Smith, E. (2006). The human gluteus maximus and its role in running. Journal of Experimental Biology, 209(11), 2143-2155.

5. Maus, H. M., Lipfert, S. W., Gross, M., Rummel, J., & Seyfarth, A. (2010). Upright human gait did not provide a major mechanical challenge for our ancestors. Nature Communications, 1, 70.

6. Bramble, D. M., & Lieberman, D. E. (2004). Endurance running and the evolution of Homo. Nature, 432(7015), 345-352.

7. Brown, T. D., & Vescovi, J. D. (2012). Maximum speed: Misconceptions of sprinting. Strength & Conditioning Journal, 34(2), 37-41.

The post Sprinting Biomechanics and the Myth of Triple Extension appeared first on Breaking Muscle.