Imagine you’re back in high school chemistry. You take 5 units of compound A and mix it with 5 units of compound B. You knew exactly what chemical reaction you were going to get. Unfortunately, the consistency that exists in a chemistry lab does not exist when you are dealing with people.
That’s a problem when you are a healthcare provider. Nobody ever knows for sure how a person is going to react to a drug, a surgery or a rehabilitation exercise protocol. Give the same rehab protocol to 10 different people with Achilles tendinopathy and you will not get the same outcome. More likely, you will get 10 different outcomes. The reason we don’t know is because there are so many variables – acute vs chronic, what part of the tendon, nutritional status, stress, genetics, occupation, mobility, stability/motor control, psychosocial fear about their condition, daily postural habits, medications etc., etc.
This brings me to the topic of this post: Footwear.
The same rules about not knowing how people react to a therapy are the same for prescribing footwear. Making generalized statements about what people should wear on their feet is unreasonable, yet that’s what has been going on in research papers, running shoe stores, doctor’s offices and even in runners telling other runners what they should wear or how they should run.
We can pretty much break down shoe choice based on these typical categories:
- Foot type
- Minimalist vs Standard
- Foot Orthoses (footbeds, orthotics)
1) Foot Type:
I hear of, and see people choosing their shoe based on their foot type (high arched vs .flat foot). While this notion seems to fit into a nice little package, it simply doesn’t work that way. Using a shoe type based on the shape of your foot has been studied a few times with less than desirable results. The so called “wet-footprint test” has been the basis for shoe prescription for the past 3 decades, despite the evidence showing its inappropriateness. Unfortunately, many shoe retailers and clinicians continue to look at the shape of a client’s/patient’s arch and use this shape as a basis for prescribing a “motion control”, “stability” or “neutral” shoe.
There are two well designed, prospective studies that have disproven this notion of prescribing shoes based on foot type (Ryan et al, 2011 and Knapik et al, 2010). Despite what some people would have you believe, if you have flat feet you don’t need high arched shoes and if you have high arches, you don’t need cushioning. You might, you might not. There are no sweeping, universal rules that apply. Trying to teach this to people when they have preconceived notions is very difficult.
Pronation is the inward rolling of the foot and ankle during the weight bearing part of walking or running. I have previously written extensively on the essence of the problem with pronation. We can’t define what pronation is, let alone what “over”pronation is. Since there is no consensus on what “over”pronation is, and if there are multiple factors that cause it (whatever “it” is), and if research is conflicting on “its” association with injury, how can you expect to tell everyone that “it” is bad?
If there is merit in choosing a shoe based on the amount that you pronate, there should be a few things established: a) that pronation is important and linked to injury, b) Trying to reduce pronation is advantageous and c) That shoe choice consistently influences the amount of pronation.
Let’s look at each of these individually
- Pronation is linked to injury: Results are conflicting and inconsistent. There are studies showing that “over”pronation is associated with injury (Messier et al. 1988, Willems et al. 2006). However, there are also many studies that show no association (Hestroni et al. 2006, Reinking et al. 2010, Nielson et al. 2013) There are also studies showing that reduced pronation is associated with more injury (Thijs et al. 2007), and that excessive pronation is protective of injury (Hreljac et al. 2000). This lead to a recent review of the literature to conclude, “Based on the review of literature, there is no definitive link between atypical foot mechanics and running injury mechanisms.” (Ferber et al. 2009). So, the issue of pronation and “over”pronation is inconsistent with injury in the research. That is not to say that it doesn’t exist. I’m merely pointing out that assigning a shoe solely based on the amount of pronation is tenuous at best. I will repeat this ad nauseum: we are all individuals and you can’t make general statements like “pronation is bad” or “pronation is not bad”.
- Trying to reduce pronation is advantageous: When someone is observed “over”pronating (too much, too fast or too long), there is seldom any thought as to “why” this is happening, or even if efforts “should” be made to reduce it. “Over”pronation can be caused by many different issues. For example, limited ankle dorsiflexion mobility can cause increased compensatory pronation (Karas et a. 2002, Blackman et al. 2009, Whitting et al. 2011). If the excess pronation is merely a compensation for limited ankle mobility, why wouldn’t you just fix the ankle mobility instead of trying to stop the compensation? (see a detailed explanation of that concept here). I would argue that if the excessive pronation is compensatory for limited ankle mobility and you try and take away the compensatory pronation, you are asking for an injury. Another reason could be higher up the kinetic chain. Another cause may be poor motor control in the hip – less force generated by the gluteal muscles can result in the thigh moving toward midline and internally rotating, which moves the knee with it and possibly, the foot and ankle into pronation (Delp et al. 1998, Zeller et al. 2003) The gluteus maximus plays a large role in decelerating internal rotation of the thigh and shin and thus decelerating pronation early in the stance phace of gait (Preece et al. 2008) and there is another study that suggests that during the latter stage of the stance phase of gait, the ankle and foot are controlled by the leg, not the leg being controlled by the foot and ankle (Bellchamber et al 2000). In other words, pronation is highly influenced by structures higher in the leg. It would be a backwards approach to try and “fix” the pronation with a shoe if there is faulty motor control higher in the leg.
- Shoe choice consistently influences the amount of pronation: I will not bore you and talk about all the different studies on this topic. Suffice it to say that the results are all over the map. Rather, I will rely on a 2011 study (Cheung et al, 2011) which took a review of the literature regarding motion control shoes and their ability to control pronation (thanks to @Rway810 for the article). While they concluded that overall, there was some effectiveness for motion control shoes to reduce pronation, they also stated, “Studies on the efficacy of motion control shoe are equivocal with different results being reported on the effectiveness of motion control shoes for controlling foot pronation.” In addition, they concluded that the data did not support the idea that motion control footwear can influence movement in the segments of the leg higher than the foot. They stated, “the relationship between tibial and foot movements is not uniform across individuals and there is likely to be high inter-subject variability.” High inter-subject variability is really saying – “we don’t know what will happen when we use motion control shoes”. This is because there are many influences to foot mechanics higher up in the leg. I went over this in the paragraph above.
All that being said, there are some people that will do great in motion control shoes and some people will not. Some people will do great in neutral shoes and some people will not. This is partly because the amount of pronation an individual has is controlled by many different factors. Sometimes it’s the anatomy of the foot, but other times it’s due to anatomy or motor control somewhere else. That is probably why orthotics and motion control shoes have such high variability in their results.
My point is that prescribing shoes based on the amount of pronation for no reason other than a philosophy of “overpronation is bad” is a philosophy without merit. If you base your shoe choice on this philosophy you are doing so without any scientific basis and worse, you may get injured. Unfortunately, that is the basis for most shoe prescription in today’s world. However, to repeat…trying to convey this message to people who have preconceived ideas is very difficult.
3) Minimal vs. Standard Shoes:
The last 7 years have seen an upheaval in the running shoe industry with the “minimalist” movement. I’m not going to explain it all here. If you’ve read this blog before, you know all about it. Unfortunately, there are fanatics on both sides of this argument. Who is correct? Well, it depends….
There are no good studies that show minimalist shoes are more economical or prevent injury better than standard shoes. On the other hand, there are no studies showing that standard shoes are more economical or better at injury prevention than minimalist shoes. We are all different and we all will respond differently. For Pete’s sake, that’s the whole point of this article!
The most applicable research paper on this topic came out last year. In this 2012 study, researchers looked at runners wearing a “standard” shoe (Asics GEL-Cumulus 10i) and a “minimalist” shoe (Vibram FiveFingers) and compared the running economy with them using either shoe. After tallying all the data, the researchers concluded that runners wearing minimalist shoes, “are modestly but significantly more economical than traditionally shod runners regardless of strike type, after controlling for shoe mass and stride frequency.” So the researchers concluded that minimalist shoes were more economical, however when you get into the details of the study, not everyone was more economical in the minimalist shoes. In fact, “within-subject differences in cost ranged from being 9.66% more economical to 7.32% more costly.” Yes, you read that correctly…when wearing minimalist shoes, some subjects were 9.66% MORE efficient while others were 7.32% LESS efficient. What a surprise…we all react differently!
The researchers took a statistical average to make the “minimalist is more economical” conclusion, but that doesn’t pertain to everyone. So will a minimalist shoe more economical for you? Well…it depends!
4) Orthoses (footbeds, orthotics)
Keeping with the theme of high variability when applying the same treatment to different people, we see the same thing with foot orthoses – whether they are prescription or over the counter. Liu et al., (2012)used intracortical markers (pins embedded in subjects foot bones) to measure kinematic changes associated with orthotics but unfortunately, it only involved 5 subjects (I’d imagine people aren’t lining up to have pins stuck in their bones). The authors found that, “Changes in calcaneus-tibia motion were comparable with those described in the literature (1°-3°)… However, the nature and scale of changes were highly variable between subjects.” They found that sometimes, the changes were in the subtalar joint and sometimes in the ankle joint. In other words, subjects reacted differently.
That is not to say that foot orthoses don’t help some people. There is some research that shows they do help reduce pain in many people…but not consistently. However, the mechanism is more likely through alterations in muscle control rather than consistent changes in mechanics.
Summary and Recommendations
Here is a summary up to here: We are all different. There are no universal recommendations for shoes for everyone, nor is there a universal recommendation for subgroups (pronators, forefoot strikers, ultramarathoners, females, fat people, caucasions, people with tight hamstrings, redheads, people with yellow hats or whatever sub-category you want to make up).
Can individual shoe recommendations be made? Yes, but with caution. Shoe choice depends on comfort, injury location, injury history, evaluation of movement patterns, joint ranges of motion, training load and overall style of running. For example: a person with an arthritic big toe should propbably have a shoe with a forefoot rocker, a person with anterior ankle impingement should probably have a higher heel to forefoot angle and a person with a history of tibialis posterior tendinopathy should probably be in something that controls pronation. However, these recommendations should be part of an overall biomechanical assessment of their kinetic chain, rather than looking at their foot as an isolated segment that isn’t influenced by other segments of the body.
So if there are no universal recommendations, how do you pick your shoe?
Well, there are a few different scenarios here:
- You have been running for a while and have a history of injuries and shoe selection and currently injury free. You should know what works for you and stick to it. Don’t buy into the hype of new technology, or if you do, incorporate those newer shoes slowly into your weekly mileage and only as an occasional change of pace from the shoes that have worked for you in the past.
- You are new to running without a history of injuries or shoe choices. Go with what feels comfortable to you and be judicious with adding weekly mileage. The body is great at adapting to new loads you place on it, but it does so gradually. Don’t be sold by the minimalist crowd and don’t be sold by the anti-pronation crowds. Don’t buy into the upselling of orthotics either. My personal viewpoint is that we should try and run in as little shoe as we can get away with – no more and no less. There is no research that says minimalist shoes reduce injuries and no research that says pronation control, elevated heel, cushioned shoes reduce injury. Go with what feels comfortable to you.
- You are currently and repeatedly injured despite different shoe types. Well, this is what I see in my office quite often. We have to realize that the shoes play a small role in injury and your body mechanics and training errors play a much larger role. You need to have a serious discussion with someone who understands running injuries and can look at your movement patterns, running biomechanics, training patterns and maybe even order blood work or imaging. If you go to a healthcare provider with pain somewhere and all they focus on is treating the spot that hurts, they are probably missing the boat.