Shoes: Evidence and Anecdotes

 Shoes: Evidence and Anecdotes

With the cost of shoes being what it is and the huge variety available in today’s market, it is absolutely imperative that you get yourself into something that suits 1st time round. There is little guidance in this regard from an evidence perspective. 40 odd years of shoe research, including the recent large number of studies into the barefoot phenomenon, have not shown any shoes to be causative or preventative in terms of injury. This makes perfect sense due to the host of confounding variables present including: training history and training errors (good evidence in terms of injury), age, biomechanics, previous injuries etc. This was highlighted recently with Vibram FiveFingers being slapped with a class action in the USA for claiming amongst others that their shoes helped prevent injuries (over 150000 claimants). Shoe fitting (and scarily enough – design) is thus far from a scientific process. Nevertheless with the advent of readily available and inexpensive hardware and software, filming and biomechanical analysis of the running gait is in the hands of most practitioners and shoe shop employees. This combined with knowledge of the running gait and a solid dash of common sense, although not infallible, removes a lot of the guess work. If new to running or contemplating a shoe change it is often a good idea to either visit a specialist running shop or health practitioner who deals with runners and knows shoes. The following aims to give you an insight into what’s out there and the basic thought process you can follow when selecting a shoe.

Basic shoe types

Terrain

 

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The first subdivision comes with terrain. Road and Trail shoes. This is fairly self explanatory and with the popularity of trail running exploding over the past few years there has been an increased divergence of the shoe types. Trail shoes have more rugged and grippy outsoles, are often stiffer in the midsole (unless very minimalist) and have hard wearing uppers in comparison to their road counterparts.

Stability

The next is the stability of the shoe. Road shoes are divided roughly into neutral and motion control or stability shoes (anti probation). Stability shoes will typically have a different colored, high density material inbuilt on the inside (arch) of the shoe. The thought process behind this is to prevent excessive inward motion or pronation of the mid foot. There are different levels of stability from mild motion control to more intense stability.

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As the name suggests a ‘neutral’ shoe will allow for a more natural motion of the foot. However, not all neutral shoes are created equal with numerous of the high end ‘cushioned’ neutral shoes being very stiff through the midsole.

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Often, due to the material utilized in construction, a stock standard trail shoe will be stiffer in the midsole than most neutral road shoes. By road standards they could be considered mild motion control shoes. This imparts more durability and a degree of stability on the varied terrain of the trail.

Heel to toe drop

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The relatively recent explosion of the barefoot movement, assisted greatly by the barefoot bible ‘Born To Run’ has confused matters further! To avoid being left behind all shoe manufacturers have changed up their offers. The reasoning behind will be discussed in greater detail later.
Barefoot shoes: Vibram FiveFingers, Vivo barefoot etc all offer ultra minimalist shoes that supposedly replicate the action of running barefoot

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Zero drop: brands such as Altra have created shoes that like the ‘barefoot’ shoe have a zero mm drop but have various levels of cushioning or padding underneath from a thin strip to a large chunk.

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The in betweens: most popular brands in both trail and road derivatives offer a variety of drops from 2mm, 4mm (popular) up to the 8mm mark.

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The High End: typically the flagship ‘cushioned’ models especially in the road market have a 10 – 12mm drop.

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Guiding your selection

Terrain

As mentioned earlier, trail and road shoes differ markedly in terms of construction. With their stiffer mid soles and grippy outsoles trail shoes are typically ill suited to road running despite the claims of numerous manufacturers that certain models are road and trail shoes.

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A regular trail shoe could generally be consider to be mild motion control road shoe. As a neutral runner being over corrected could potentially cause a host of problems including ITB and anterior knee issues. This relative increase in stability is largely nullified by the variety of trail terrain and decreased repetitive action as a result. Typically a safer bet if you want a single shoe for both pursuits go the road option, particularly if you are not running very technical trails. You obviously loose the grip and durability (trail destroys road shoes!) but you will at least not have the issues that come with being ‘over corrected’ on the road. However, if finances allow and if you are doing sufficient mileage on both buy a road and a trail shoe.

Stability

A 2015 article traced the history of the running shoe and examined whether selecting running shoes based on foot arch height influenced injuries. It also examined historical data on injury rates when physical training amongst military personal was performed in boots versus running shoes. ‘In the 1980s and into the 2000s, running shoe companies were advertising specialized shoes with “motion control,” “stability,” and “cushioning,” designed for individuals with low, normal, and high arches, respectively. Despite marketing claims that these shoes would reduce injury rates, coordinated studies in Army, Air Force, and Marine Corps basic training showed that assigning or selecting shoes on this basis had no effect on injury rates. Consistent with this finding, biomechanical studies have shown that the relationships between arch height, foot joint mobility, and rear-foot motion are complex, variable, and frequently not as strong as often assumed. In 1982, the US Army switched from PT in boots to PT in running shoes because of the belief that boots were causing injuries and that running shoes would reduce injury rates. However, a historical comparison of injury rates before and after the switch to running shoes showed virtually no difference in injury risk between the two periods. It is not clear at this point if the type of footwear effects injury incidence’
Due to numerous factors including, I believe, the minimalist movement, there has been an active shift away from the motion control shoe. I think this also has to do with more knowledge of running biomechanics and the ability to film. Previously (and still in certain settings), shop employees would look at customers standing and make a call on what shoe to fit or at best eyeball them running. As mentioned in the study, the biomechanics of the foot are ‘complex, variable’ and of course massively different when in motion. Activation of the dynamic stability mechanism (muscles) during running can transform a dropped looking arch in standing into a beautifully neutral foot. Likewise if somebody is a mid to forefoot striker not only will they typically do well in a neutral shoe, they would naturally nullify any inbuilt stability mechanism in the shoe! Interestingly relative stability shoes used to make up the lions share of the running market. The current statistics in specialist running stores show a roughly 70% neutral to 30% motion control split. This could potentially still be a bit high on the motion control front. Anecdotally, I have had to put very few people in motion control shoes over the years. Very few, but some. I have absolutely no doubt that some people can only successfully run as a result of stability shoes. We can argue nature or nurture being the causative factor in terms of why they need stability but at the end of the day they do as witnessed by a decrease in injuries and the ability to run relatively pain free in these individuals.

Heel to Toe Drop

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This is the real can of worms in terms of shoe dynamics. The barefoot movement attained cult like status a few years ago and although it has decreased in popularity in more recent times it still has an ardent following, largely amongst people to whom it has been quite revolutionary in terms of injury resolution. Despite the claims of fanatics it is not for everybody.

The Reasoning

imageDaniel Lieberman, an anthropologist from Harvard and quoted in Born to Run sums it up very succinctly in his article published in Nature, ‘Humans have engaged in endurance running for millions of years1, but the modern running shoe was not invented until the 1970s. For most of human evolutionary history, runners were either barefoot or wore minimal footwear such as sandals or moccasins with smaller heels and little cushioning relative to modern running shoes. We wondered how runners coped with the impact caused by the foot colliding with the ground before the invention of the modern shoe. Here we show that habitually barefoot endurance runners often land on the fore-foot (fore-foot strike) before bringing down the heel, but they sometimes land with a flat foot (mid-foot strike) or, less often, on the heel (rear-foot strike). In contrast, habitually shod runners mostly rear-foot strike, facilitated by the elevated and cushioned heel of the modern running shoe. Kinematic and kinetic analyses show that even on hard surfaces, barefoot runners who fore-foot strike generate smaller collision forces than shod rear-foot strikers. This difference results primarily from a more plantarflexed foot at landing and more ankle compliance during impact, decreasing the effective mass of the body that collides with the ground. Fore-foot- and mid-foot-strike gaits were probably more common when humans ran barefoot or in minimal shoes, and may protect the feet and lower limbs from some of the impact-related injuries now experienced by a high percentage of runners.’

The Biomechanics
As mentioned above, common biomechanical findings when performed on a force plate show that when running barefoot one is commonly more likely to strike with the front of the foot in comparison to a heel strike in a more traditional shoe. This allows the foot to more naturally shock absorb through unlocking the mid foot and eccentrically decelerating towards the ground. This in tern decreases the ground reaction force and hence the forces higher up the chain through hip and knee. In one study, barefoot running demonstrated less knee flexion during midstance, an 11% decrease in the peak internal knee extension and abduction moments and a 24% decrease in negative work done at the knee compared with shod conditions. The ankle demonstrated less dorsiflexion at initial contact, a 14% increase in peak power generation and a 19% increase in the positive work done during barefoot running compared with shod conditions.

The Evidence
Type barefoot running into google scholar and a plethora of articles spring forth. As with all shoe research due to the previously mentioned confounding variables all theories regarding injury causations and prevention are exactly that: theoretical.
The majority of research (very little of it good quality as highlighted by a 2013 systematic review) supports the biomechanical findings highlighted above. Sounds great right. Unfortunately what happens on the force plate and in real life are totally different things.
An interesting study evaluated a large sample of 236 non elite marathon runner’s foot strike at the 10 and 32 km mark. ‘A large percentage of runners switched from mid and forefoot strikes at 10km to rear foot strike at 32km…We found no significant relationship between foot strike and race times.’ 1
Another factor to consider is that even in the most minimalist of shoes, you are not running barefoot. ‘Running in a minimalist and lightweight shoe is not the same as running barefoot: a biomechanical study.’ This solid study published in the British Journal of sports medicine found similar biomechanical findings to the earlier mentioned in terms of the barefoot dynamic. It then compared the biomechanics of 3 shoe types (minimalist, racing flat and traditional neutral shoe) and found they all differed significantly from barefoot running but not from each other in terms of the running gait. 2

To sum it all up. One way or another the dynamics of barefoot running do show some promise in terms of biomechanical findings but wearing a pair of minimalist shoe does not necessarily mean you are running barefoot! As with all shoes, at this stage there is absolutely no evidence it is curative or causative of injuries. In numerous cases, both documented and personally witnessed, minimalist shoes have been revolutionary in changing long standing and often very debilitating running injuries. The cynic in me always wonders whether the enforced change (reduction) in the training load that comes about with the acclimatization into minimalist footwear doesn’t have a significant amount to do with it. One thing to be very cognisent of is the fact that running in minimalist footwear is extremely taxing. The workload of the intrinsic foot and calf musculature is way higher than in a traditional shoe. This may be great as a training modality or when running shorter distances but in extreme distances or on repetitive surfaces such as road a degree of stability and support may be very useful in preventing fatigue and repetitive injuries of other descriptions. The majority of people running 100 milers are doing so in the antithesis of a barefoot shoe with reason. While the majority of neutral, biomechanical sound runners will be able to train themselves with varying speed into more minimalist footwear, I stand by my earlier statement that some runners, likely due to a combination of nature and nurture will not be able to adopt a minimalist approach. Maybe with a laborious, years long approach and numerous setbacks they would but the likelihood of anybody staying the course is slim to none. The fact that more than 150 000 people took the time and effort to claim the 8 USD for their class action against FiveFingers is an obvious indicator they were transformed by the shoes!

What to choose: useful anecdotes.

  • Rule # 1: if it ain’t broke don’t fix it. If you have run 10 comrades in a motion control shoe without a single injury, please don’t listen to the young whippersnapper at your running club that says a racing flat will be revolutionary to your running. Stay with what works.
  • If you have been battling with multiple injuries consult a health professional who knows running. Evidence points towards the fact it will likely be training error based but they will be able to evaluate your biomechanics in conjunction with your current shoes and rule out obvious foot wear issues
  • New to running? Go to a specialist running shop or to the above mentioned. It will save you a host of time, money and future hassles. The benefit of paying the bit extra and seeing a professional is the fact you will likely get training, recovery and strengthening advice thrown into the mix.
  • The vast majority of people fall into the neutral bracket. As with most things in life, everything in moderation generally works best. A neutral shoe, with a degree of inbuilt stability and a moderate heel to toe drop generally works best for most runners, over most distances and in most conditions.
  • People moving into minimalist footwear will generally be more experienced runners or runners who have had a torrid time in more traditional footwear. I probably would not recommend it to new runners.
  • Barring people who have been utilizing them for a sustained time period, Stability shoes should also not be bought without proper guidance at a specialist running store or from a knowledgable health professional.
  • We all believe more expensive is better. Professionally, I’ve kept up to date with all the popular brands and models for years. With one brand, their entry level shoe which they advocate for shorter distance and novice runners is an exact replica of their top of the range shoe (recommended for ultra distance) from 10 years ago!
  • When trying on shoes, they must feel amazing on your feet. Wear socks, lace them up properly and run, jump and lunge in them. If they feel sketchy, try something else.
  • Don’t be guided by trends. At this stage most of the ‘science’ is marketing and smoke and mirrors. From an injury prevention perspective, focus on your training.

by Iain Sykes (physiotherapist)

Iain Sykes Physiotherapy

Cape Town South Africa