The Impact of Footwear and Foot Type on Injury Prevention
“Always Evolve” – one of my favourite valedictions used by esteemed physical therapist and blogger Mike Scott, DPT at the end of posts in his weekly series “Educainment.”
Running has certainly seen some evolution of thought over the last few years, much of it following the publication in May 2009 of Christopher McDougal’s best seller Born To Run, bringing with it bold claims that running barefoot (or wearing something as close as possible to barefoot while protecting you from environmental elements) can strengthen your feet, reduce running injuries, encourage proper running form, and improve performance.
Until then, the only experience many of us had of barefoot running was seeing the South African teenager Zola Budd on our television sets, running barefoot in the women’s 3000 meter race at the 1984 Los Angeles Olympics.
Whilst some runners have praised a transition to barefoot running (along with the typical shift to forefoot striking that barefoot running encourages) as a cure for an injury they were suffering, others have not been so fortunate and have seen it bring the onset of new injury, despite religiously following a slow, progressive transition period.
Clinical tests to date have also produced conflicting results. Barefoot running has been seen to reduce the risk of certain running related injuries, but increase the risk of others. It’s as if what works for some does not necessarily work for others. Sound familiar?
Regardless of personal experience, production of conclusive evidence for the benefits of barefoot running is still an ongoing project.
The increased profile and interest in barefoot running brought with it demand for less restrictive, less cushioned footwear, with the idea of allowing the foot to move and work in a more natural fashion whilst still providing a certain amount of protection.
As a result, today there is a wide spectrum of minimalistic footwear that, though not as extreme as barefoot style shoes like the Vibram FiveFingers, typically aim to provide less drop (difference between heel height and toe height), less cushioning, a wider toe box (more room for the toes) and more flexibility.
Like barefoot running, conclusive evidence for the benefits of minimalistic footwear is still a work in practice. A 2012 review in the Journal of Strength & Conditioning titled: “Running Barefoot or in Minimalist Shoes: Evidence or Conjecture?” concluded:
“Running barefoot or in minimalist footwear has become a popular trend. Whether this trend is supported by the evidence or conjecture has yet to be determined.”
Before any of you take “lack of conclusive evidence” as a reason to dismiss the possible benefits of barefoot running or minimalist shoes, I should point out – and this may come as a shock to you – that there is no evidence either that traditional running shoes can reduce injury or improve running performance.
Yes, you read that right. Though you were maybe told in the sports shop that your cushioned, stability or motion control trainer will help prevent injury, there is no evidence to support it. The problem is, the model that has been used for the last sixty years and more often than not is still used to help you select which trainers suit you is based on, well… not a lot.
If you have ever been to a sports shop to buy a pair of running shoes (or have received an “ankle-down” gait analysis), chances are you are familiar with the diagram below, or something very similar. It links three “foot types” (based on the height of the medial arch) with three corresponding types of recommended running shoe:
The origin of the idea to group feet according to the height of the medial arch is not clear. Ian Griffiths, Director of Sports Podiatry Info Ltd suggests it may stem from a method of assessing footprints devised in 1947 by Colonel Harris and Major Beath as part of an Army foot survey. The first time an image associating medial arch height with shoe type actually appeared in print could have been the 1980 “The Running Shoe Book” by Peter R Cavanagh.
What we do know is that since 1980, running shoes all over the world have been recommended and sold using the Foot Type model. Selection typically follows an “assessment” (often involving the subject stepping onto a pressure pad or being filmed from the ankle down whilst running) of how much the medial arch drops (referred to in the diagram as “pronation”) or doesn’t drop (“supination”), along with the idea that somewhere in the middle (“neutral”) is normal, healthy and necessary for injury prevention (more on that later).
- If the arch of your supporting leg drops “too much”, you are labelled an “overpronator” and assigned a motion-control shoe that will in theory reduce the “overpronation”. If your arch does not drop “enough”, you are said to be an underpronator (or supinator), and assigned a flexible, cushioned shoe to absorb some of the shock that underpronator is said to cause.
- If you are somewhere in the middle, you are said to have normal pronation and are recommended a “neutral” shoe that in theory provides just the right amount of stability and cushioning. Leaving aside the question of who decides “how much” dropping is normal, it is important at this stage to remind ourselves that both pronation and supination are natural, integral parts of foot biomechanics.
Dr Shawn Allen, Diplomate of American Board of Chiropractic Orthopaedists explains:
“The foot is a biomechanical marvel. 26 bones and 31 joints, working together in concert to provide balance, stability, and locomotion. As we walk or run, the foot is supposed to go through a series of biomechanical changes, so that it can either adapt to the environment or become a rigid lever for propulsion. When these mechanisms fail, problems usually arise. When the heel hits the ground, the arch of the foot is supposed to partially collapse (pronation), so that the foot can adapt to the ground; in this position, it is flexible and “unlocked”. After the weight of the body passes over the foot, the arch is supposed to retract, and the foot becomes more rigid or “locked” (supination), so that you can use it to propel yourself forward. If the foot remains in pronation for too long, or does not supinate correctly, problems will develop over time.”
Problems with assigning shoes according to degree of pronation
So, the running shoe recommendation model is based on the idea that at midstance, just before the full weight of the body passes over the foot, the best position of the subtalar joint is “neutral”, i.e. the foot perpendicular to the horizontal ground.
The argument is that this “neutral” position signifies optimum functioning of the foot, optimum pronation and supination. One problem with this is the fact that the subtalar joint has variable anatomy. In other words, function will vary from person to person, so the ‘optimum’ position to be in will also vary. Ian Griffiths explains:
“Studies have shown that the structural anatomy of the human subtalar joint varies from person to person and it has also been shown that the location of the axis of the joint can and does vary from person to person; this will of course directly influence the magnitude of pronation and supination seen. In light of this sort of evidence it seems odd that there would be an expectation that all individuals could or should function similarly or identically.”
Taking the above into consideration, it should come as no surprise that there is no data or evidence that suggests “neutral” STJ alignment is linked with injury and/or pain free running. One study examined 120 healthy individuals both non weight-bearing and weight-bearing. Not one subject conformed to the criteria of “neutral” alignment.
Is there any evidence that “over-pronation” increases injury?
Almost all studies to date on “over-pronation” have found no evidence that it increases the risk of injury. A 2010 study concluded that the prescription of shoes with elevated cushioned heels and pronation control systems tailored to an individual’s foot type was not evidence based.
Another piece of research suggested the running shoe model was overly simplistic and potentially injurious. In fact, in this research, every ‘overpronated’ runner put into a motion control shoe during a 13 week half marathon training programme reported an injury.
Craig Payne, DipPod MPH, University lecturer and famed Running Research Junkie points out that lack of evidence for linking overpronation to injury may well be down to the methods used to measure pronation:
“The weakness of many of those studies is how they measured “pronation”; for example, some measure calcaneal eversion; some measure navicular drop; some do a footprint analysis; and some use a dynamic 3D kinematic analysis. The problem with that is that someone may be ‘overpronated’ on the measurement of one parameter and not ‘overpronated’ on another parameter.”
A study published this month by Teyhen DS. titled “Impact of Foot Type on Cost of Lower Extremity Injury” set out to determine the relationship between foot type and medical costs associated with lower extremity musculoskeletal injury, using a population of 668 healthy U.S. military healthcare beneficiaries in active military service for at least 18 months of the 31 month study.
It quantified level of pronation using the Foot Posture Index, a measurement of static foot posture that takes into account not one but multiple components that go into “overpronation”, devised by Dr Anthony Redmond, Arthritis Research Campaign Lecturer at the University of Leeds.
Whether static foot posture has much to do with foot posture whilst moving (e.g. running) is a discussion for another day. What the study did show is that of the 336 participants (out of the total 668) who sought medical care for lower extremity musculoskeletal injuries, a high percentage (no exact value available at this time) were those who had been listed as “extreme pronated feet” via the Foot Posture Index.
Future research will be needed to help see if degree of pronation via multiple component assessment (e.g. the Foot Posture Index) can be linked to injury. In the meantime, using just one component of “over-pronation” (e.g. medial arch height) to assign suitable footwear will continue to be a game of hit and miss.
- Is the whole running shoe recommendation model based on misconception?
- If it is, what model should be used, if any?
- There are certifications out there teaching shop staff how to sell running shoes. What are they based on?
- As a result of this debate, some are suggesting that runners should buy trainers based on “comfort” alone. Hard to imagine?
As I see it, just because an injury is present on someone with an “excessive” level of pronation (whatever that is…), it does necessarily mean that the level of pronation is the cause of the injury (correlation vs. causation).
It is imperative to consider and understand the biomechanics of the rest of the body (as well as foot posture) before reaching any conclusions. And even with all of that knowledge, it will still be a daunting task to be able to say “this is the running shoe you need!”
So, what should we base trainer recommendation on? A tricky question that we will consider next week. In the meantime, I am keen to know of your personal experience. What you are currently running in? What made you buy them? Have you managed to reduce injury via a change in footwear? Maybe a change in your footwear has led to an increase in injury? As always, I look forward to your comments!