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* '''Injuries due to over pronation. '''The science around [[Pronation]] and injury rates is quite mixed. Part of the problem is science does not generally look at pronation directly, but uses arch height with the assumption that low arches pronate more. There is some evidence that high or low arches have slightly higher injury rates, or that different arch heights have different patterns of injury.
* '''Running shoes reduce impact. '''There is good evidence that''' '''increased cushioning does not reduce impact forces. Runners who normally run in shoes will have higher impact when initially running barefoot, but after adaptation the impact forces are actually lower without shoes.
* '''Running shoes reduce pronation'''. Motion control shoes (the highest level of anti-pronation) only reduce pronation by about 21.5% when compared with a simple cushioned shoe. It seems unlikely that this is enough to produce any real -world affecteffect.
* '''Running shoes reduce injury'''. There is no evidence that running shoes reduce injury rates. Assigning shoes based on arch height does not change injury rate, nor is there any indication that more cushioned shoes have a lower injury rates. There is some evidence that motion control shoes cause greater leg pain and more training days lost, and this applies to all arch types.
* '''Raised heel. '''Another common feature of running shoes is a raised heel, which is intended to reduce the strain on the Achilles tendon. However there is little evidence that the raised heel actually reduces the strain on the Achilles tendon, and no evidence that the raised heel actually reduces Achilles tendon injuries.
* '''Barefoot running.''' The reduced impact seen with barefoot running late in led many people (myself included) to believe that this would in turn result in lower injury rates. However, there is no evidence that barefoot runners have a lower injury rates. More importantly, and they there is a growing body of evidence to suggest that the transition to barefoot running is associated with a high injury risk.
=The Myth of Running Shoe Types=
There is good evidence to support the widely held belief that injury rates among runners are quite high, with estimates of injury rates varying between 20% and 80% of runners<ref name="van Gent-2007"/>. It is widely assumed that excessive impact forces, and excessive pronation cause running injuries , and that running shoes are therefore designed to mitigate alleviate these problems<ref name="Nigg-2001"/><ref name="HintermannNigg1998"/><ref name="McKenzie-1985"/><ref name="Johnston-2003"/><ref name="Heil1992"/><ref name="Yamashita-2005"/>. This leads to the common recommendation that different types of shoes should be recommended based on a runners arch height. In fact, REI<ref name="www.rei.com"/>, Zappos<ref name="www.zappos.com"/>, Runners' World<ref name="www.runnersworld.com"/>, and Road Runner Sports<ref name="roadrunnersports.com"/> all include this advice.
[[File:The myth of arches and shoe types.jpg|none|thumb|500px|This image probably originated with the "The Running Shoe Book"<ref name="runningshoebook"/>.]]
=Impact & Injury=
The relationship between impact and injury is less clear than one might suppose. It has been suggested that while excessive impact can result in injury, lower levels of impact result in positive adaptation are the stimulus for improved strength and remodelingperformance<ref name="Hreljac-2004"/> and these impacts may be an important part of training<ref name="Nigg-1997"/>(See [[Supercompensation]]. ) There is evidence that the impact seen in running does not result in injury:
* Impact forces are not related to injury rates in epidemiologic studies<ref name="Nigg-1997"/>.
* The impact forces at the heel are not related to the forces at common injury sites such as the ankle, Achilles, or knee.<ref name="Scott-1990"/>.
* A study of 1597 runners found that those with the lowest arches were 2.7x more likely to have knee (patellofemoral) pain than those with the highest arches<ref name="Boling-2009"/>. (Note that this study used navicular drop as an indicator of pronation, but other factors contribute significantly to navicular drop<ref name="Mueller-1993"/>.)
* A retrospective study found that arch height was not different between runners who had previously been injured and those that had never been injured<ref name="Hreljac-2000"/>.
[[File:ImpactAndInjuryBahlsen1988.jpg|rightnone|thumb|300px| A graph of peak vertical impact force and the frequency of running-related injuries<ref name="Bahlsen1988"/>.]]
=Running Shoes & Impact=
There is good evidence that increased cushioning does not reduce impact<ref name="Robbins-1990"/><ref name="WrightNeptune1998"/><ref name="ClarkeFrederick2008"/><ref name="NiggBahlsen1987"/>. However, runners who are normally run in shoes have greater impact forces when running barefoot, but this is reversed with barefoot experience<ref name="Robbins-1990"/><ref name="Divert-2005"/><ref name="Robbins-1987"/>.
=Running Shoes & Pronation Control=
The evidence indicates that even Motion Control shoes can only reduce pronation by around 1.5%, which is unlikely to be enough to make any real-world difference. * A meta-analysis of 5 studies showed that motion control shoes can reduce pronation when compared with barefoot or simple cushioned shoes, but only by about 2%<ref name="Cheung-2011"/>. * A study compared a Motion Control shoe (MC) with a Cushioned shoe (CT) with 20 high arched (HA) and 20 low arched (LA) runners<ref name="Butler-2006"/>. The motion control shoe was the New Balance 1122 and the cushioned shoe was the New Balance 1022. The change in pronation (in degrees) is shown below. {| class="wikitable"! ! CT! MC! Change|-| LA| 7.9| 6.3| 1.6|-| HA| 8.0| 7.4| 0.6|}* A study of 10 male runners compared "normal" running shoes with and without a 10 degree orthotic wedge showed the orthotic reduced pronation by 6.7 degrees<ref name="PerryLafortune1995"/>. * A study of 25 inexperienced, over-pronating female runners looked at differences in pronation in motion control and cushioned shoes, before and after a 1.5 Km (~1 mile) run<ref name="CheungNg2008"/>. These runners only averaged 2.1 Km (1.3 miles) per week and had pronation of more than 6 degrees. The Motion Control shoes reduced pronation by 3.3 degrees before the run, but after just this short run the Motion Control shoes made no difference. The motion control shoes were Adidas Supernova Control and the cushioned shoes were Adidas Supernova Cushion. The results are shown below:{| class="wikitable"! ! CT! MC! Change|-| Before 1.5 Km run| 13.9| 10.6| 3.3|-| After 1.5 Km run| 17.7| 17.7| 0|}* A study of 10 experienced rear foot runners were tested with shoes of varying heel flare<ref name="Clarke-1983"/>. This seems unlikely heel flare is how much wider the heel is at the bottom than the top, and the flared heels reduced pronation from 12.6 to 11.1 degrees (1.5 degree decrease) when compared with any heel without any flare. In practice, it's rare for a shoe to be this narrow at its base, and other studies have not shown this effect<ref name="Nigg-1987"/><ref name="Stacoff-2001"/>. [[File:Clarke-1983-Heel-Flare.jpg|none|thumb|200px]]* The heel counter is intended to link the heel of the foot to the shoe, but a study found that a rigid heel counter did not prevent slippage within the shoe any better than a flexible heel counter<ref name="Gheluwe-1995"/>. Also, the pronation of the foot can be significanttwice as large as the pronation when measured on the shoe<ref name="Stacoff-2001"/>.
=Running Shoes and Achilles Strain =
A common feature in running shoes is for the heel to be thicker than the forefoot, something that is commonly called "drop". In the 1980's a drop of 12-15mm was recommended to prevent Achilles tendon and calf injuries<ref name="Clement-1980"/>, but there is little evidence to support this:
* Shoes with the different levels of a drop do not change the range of motion of the ankle during running<ref name="Reinschmidt-1995"/>.
* A study of five runners, each running in five different shoes with heel heights of 2.1-3.3cm (5.0 to 9.5 degrees) did not support the idea that heel height changes stress on the Achilles' tendon<ref name="Reinschmidt-1995"/>.
* A study looked at 30 runners that were either assigned a minimal drop shoe (4mm) or were trained to adopt a midfoot strike (MFS) pattern<ref name="Giandolini-2013"/>. The minimal drop shoe reduced heel impact, but the MFS training had no effect.* A study looked at 12 Rear Foot Strike runners using 16 combinations of midsole thickness and drop<ref name="HorvaisSamozino2013"/>. The lower drop shoes had a more midfoot strike pattern, but the thickness had no impact. (Ground contact time was greater with lower drop shoes.)* A drop of 15mm or 7.5mm did not produce a significant reduction in Achilles tendon stress<ref name="Dixon-1998"/>.
=Injury Rates & Shoes=
Several studies have found there is no evidence to support the idea that running shoes can reduce injury rates<ref name="RichardsMagin2009"/><ref name="van Gent-2007"/><ref name="van Mechelen-1992"/>.
* A study of 247 runners over 5 months showed no difference in injury rates between firm and softly cushioned shoes<ref name="TheisenMalisoux2013"/>.
* Three studies compared assigning evaluated the idea that shoe type should be determined by arch height<ref name="KnapikTrone2014"/>. Runners were put into two groups, with one group assigned shoes based on the shape of the arch with , and the other group just assigning assigned a single stability shoe type to runners regardless of their arch<ref name="KnapikTrone2014"/>. These studies found no difference in injury rates. The studies were done by the US Army (2168 men, 951 women), Air Force (1955 men, 718 women), and Marine Corps (840 men, 571 women).
* A study of 81 women training for a half marathon were randomly assigned cushioned, stability and motion control shoes<ref name="RyanValiant2010"/>. The cushioned shoe was a Nike Pegasus, the stability was Nike Structure Triax, and the motion control was Nike Nucleus. The runners were then analyzed based on their arch height.
** The study found that the motion control shoe was associated with the highest levels of pain while running for all foot types, though the difference was only significant for the neutral and pronated foot types.
** All the highly pronated runners wearing the motion control shoe missed a training day due to pain, the highest proportion of any of the subgroups.
** The neutral runners had higher levels of pain in the neutral shoe than the stability shoe, and the pronated . The pronating runners had higher levels of pain in the stability shoe than the neutral shoe. This is the opposite of most recommendations for shoe and foot type. ** (Note that while the overall sample size was reasonable (81), each individual subgroup was quite small (5 to 18 runners) and variation within subgroup of results was large. The subgroups also varied significantly in weight, BMI, age, and years of running experience.)
=Minimalist & Barefoot Running=
Most research looks at factors that might be related to injury risk, rather than injury rates directly. I found no studies that evaluated barefoot or minimalist running and injury rates. So while barefoot and minimalist running tends to have lower impact, it's unclear if this will have any bearing on injury rates. Of greater concern is some compelling evidence that the transition to barefoot or minimalist footwear is correlated with higher injury rates, especially stress fractures in the foot.
** Shoes increase Ground Contact Time compared with barefoot<ref name="Braunstein-2010"/>.
** Compared with barefoot, running shoes reduced the ability to estimate surface angle, with a greater estimation error with thicker shoes<ref name="Sekizawa-2001"/><ref name="Robbins-1995"/>.
* Instances There are some instances of Metatarsal Stress fractures in runners who had changed to minimalist shoes, with no other changes in their training habits<ref name="GiulianiMasini2011"/>.* A study of 99 runners who were randomly assigned a traditional cushioned shoe (Nike Pegasus), partial-minimalist shoes (Nike Free 3.0 V.2) or minimalist shoes (Vibram 5-Finger Bikila)<ref name="RyanElashi2013"/>. The runners had a minimum of 5 years' experience and had no injuries in the previous 6 months. The runners took part in a 12 week training program in which they gradually adopted their assigned footwear . They increased their time in the assigned footware from 10 min (19%) in week 1 to 115 min (58%) in week 12. The Runners in the two minimalist shoes had a greater rate of injury compared with runners in the traditional shoes, . Runners with the partly minimal shoes (Nike Free) having had the highest overall injury rate and . Runners in the minimalist shoes (5 Fingers) having had the greatest shin and calf pain. * A study looked at bone marrow edema in 36 experienced runners transitioning to Vibram FiveFingers (VFF) shoes<ref name="RidgeJohnson2013"/>. 36 experienced The runners were randomly assigned VFF or their normal running shoes, with the VFF runners gradually transitioning based on the recommendations of the Vibram at that time. Only 1 of the 17 runners in the control group showed signs of a bone marrow edema, compared with 9 of the 19 VFF runners. =See Also=* [[Shoes| Running Shoes]]* [[The Journey to Minimalist Running]]* [[Toughening Feet]]* [[Modified Nike Free]]In 2014, Vibram settled a lawsuit that they made false and unsubstantiated claims that their FiveFingers shoes could reduce injury rates.
=References=
<references>
<ref name="GrimstonNigg1994">Susan K. Grimston, Benno M. Nigg, Veronica Fisher, Stanley V. Ajemian, External loads throughout a 45 minute run in stress fracture and non-stress fracture runners, Journal of Biomechanics, volume 27, issue 6, 1994, pages 668, ISSN [http://www.worldcat.org/issn/00219290 00219290], doi [http://dx.doi.org/10.1016/0021-9290(94)90983-0 10.1016/0021-9290(94)90983-0]</ref>
<ref name="Zadpoor-2011">AA. Zadpoor, AA. Nikooyan, The relationship between lower-extremity stress fractures and the ground reaction force: a systematic review., Clin Biomech (Bristol, Avon), volume 26, issue 1, pages 23-8, Jan 2011, doi [http://dx.doi.org/10.1016/j.clinbiomech.2010.08.005 10.1016/j.clinbiomech.2010.08.005], PMID [http://www.ncbi.nlm.nih.gov/pubmed/20846765 20846765]</ref>
<ref name="Giandolini-2013">M. Giandolini, N. Horvais, Y. Farges, P. Samozino, JB. Morin, Impact reduction through long-term intervention in recreational runners: midfoot strike pattern versus low-drop/low-heel height footwear., Eur J Appl Physiol, volume 113, issue 8, pages 2077-90, Aug 2013, doi [http://dx.doi.org/10.1007/s00421-013-2634-7 10.1007/s00421-013-2634-7], PMID [http://www.ncbi.nlm.nih.gov/pubmed/23584279 23584279]</ref>
<ref name="HorvaisSamozino2013">N. Horvais, P. Samozino, Effect of midsole geometry on foot-strike pattern and running kinematics, Footwear Science, volume 5, issue 2, 2013, pages 81–89, ISSN [http://www.worldcat.org/issn/1942-4280 1942-4280], doi [http://dx.doi.org/10.1080/19424280.2013.767863 10.1080/19424280.2013.767863]</ref>
<ref name="Butler-2006">RJ. Butler, IS. Davis, J. Hamill, Interaction of arch type and footwear on running mechanics., Am J Sports Med, volume 34, issue 12, pages 1998-2005, Dec 2006, doi [http://dx.doi.org/10.1177/0363546506290401 10.1177/0363546506290401], PMID [http://www.ncbi.nlm.nih.gov/pubmed/16902231 16902231]</ref>
<ref name="PerryLafortune1995">SD Perry, MA Lafortune, Influences of inversion/eversion of the foot upon impact loading during locomotion, Clinical Biomechanics, volume 10, issue 5, 1995, pages 253–257, ISSN [http://www.worldcat.org/issn/02680033 02680033], doi [http://dx.doi.org/10.1016/0268-0033(95)00006-7 10.1016/0268-0033(95)00006-7]</ref>
<ref name="CheungNg2008">R. T. Cheung, G. Y. Ng, Influence of Different Footwear on Force of Landing During Running, Physical Therapy, volume 88, issue 5, 2008, pages 620–628, ISSN [http://www.worldcat.org/issn/0031-9023 0031-9023], doi [http://dx.doi.org/10.2522/ptj.20060323 10.2522/ptj.20060323]</ref>
<ref name="Clarke-1983">TE. Clarke, EC. Frederick, CL. Hamill, The effects of shoe design parameters on rearfoot control in running., Med Sci Sports Exerc, volume 15, issue 5, pages 376-81, 1983, PMID [http://www.ncbi.nlm.nih.gov/pubmed/6645865 6645865]</ref>
<ref name="Nigg-1987">BM. Nigg, M. Morlock, The influence of lateral heel flare of running shoes on pronation and impact forces., Med Sci Sports Exerc, volume 19, issue 3, pages 294-302, Jun 1987, PMID [http://www.ncbi.nlm.nih.gov/pubmed/3600244 3600244]</ref>
<ref name="Stacoff-2001">A. Stacoff, C. Reinschmidt, BM. Nigg, AJ. Van Den Bogert, A. Lundberg, J. Denoth, E. Stüssi, Effects of shoe sole construction on skeletal motion during running., Med Sci Sports Exerc, volume 33, issue 2, pages 311-9, Feb 2001, PMID [http://www.ncbi.nlm.nih.gov/pubmed/11224823 11224823]</ref>
<ref name="Gheluwe-1995">Van Gheluwe, Bart, Rudi Tielemans, and Philip Roosen. "The influence of heel counter rigidity on rearfoot motion during running." Sort 100 (1995): 250.</ref>
<references/>
[[Category:Science]]
[[Category:Injury]]