Introduction:The past,present,and future of research on running barefoot and in m inimal shoes

Editorial

Introduction:The past,present,and future of research on running barefoot and in m inimal shoes

Barefoot running has been around form illions of years,and it is safe to presume that for most of that time,the practice occasioned little interest.Our ancestors ran barefoot because they had no shoes.When footwearwas fi rst invented during the last 40,000 years(no doubt at different times and in different places),shoes were by necessity minimal—essentially sandals and moccasins—designed to protect the sole of the foot but lacking any of the sophisticated features and materials presentin modern running shoes such as elevated cushioned heels,arch supports,and toe springs.Mostof these features were invented in the 1970s,and they quickly became more popular and sophisticated asrunning underwenta worldw ide boom.Today,the vast majority of runners think it is normal to wear cushioned running shoes,and would neverdream of running w ithoutthem.

In the last few years,however,there has been a resurgence of interest in running either barefoot or in m inimal shoes, igniting much passionate discussion and debate among runners,sports scientists,podiatrists,orthopedists,and others. A lthough a handful of studies had been published on barefoot running among habitually shod individuals asked to take off their shoes,interest in the topic was triggered by a 2004 publication in Nature(whose cover title was Born to Run), which argued that humans evolved to run millions of years ago,probably in order to hunt.1The article helped inspire the 2009 bestseller,also entitled Born to Run,which not only claimed that the famed Tarahumara ultrarunners from northern Mexico were phenomenal endurance runners in part because they ran only in minimal sandals,but also blamed many injuries on modern running shoes.2A few months later,a second paper in Nature presented the fi rst biomechanical analysis of habitually barefoot runners,show ing how they are able to run com fortably withoutgenerating an impactpeak when the foot hits the ground by either forefoot or midfoot striking.3As barefootand minimally shod running gained rapid worldw ide popularity,a vociferous public debate began.Is it safe?What are the costs and benefi ts of wearing shoes?How should you run?

There remains much disagreement about barefoot running, but the debate has sparked lots of good research thatultimately should yield many benefi ts.We note that despite a lack of consensus on some key issues,extreme views w ith little grounding in science have tended to get the mostattention in the popular media.Some advocates have argued that modern shoes cause injury,while others claim that barefoot running is a dangerous“fad”.Neither of these views is supported by scientific research,and many journalists and advertisers have further confused the issue by conflating actual barefoot running with running in m inimal shoes,which are often oxymoronically termed“barefoot shoes”.

While dozens of papers have been published in the last few years on barefoot and m inimal shoe running,we believe there is much to learn and resolve,so we are pleased to present the fi rst edited issue devoted specifically to this topic.At the invitation of Walter Herzog,the issue was jointly edited by Irene Davis,Daniel Lieberman,and Benno Nigg.Because our goal was to solicit high quality,original,peer-reviewed research on the topic,we advertised the issue w idely to researchers in the field via listservs and emails.We received 17 submissions,all of which went through rigorous peer-review, resulting in 10 accepted papers that present a w ide variety of views and analyses.To briefl y summarize the results:

Hein and Grau4showed that habitually shod runners who typically rearfoot strike in cushioned shoes still tend to heel strike but w ith a slightly flatter foot placement when asked to run barefoot or in m inimal shoes on a soft surface made of EVA,the same material used in a shoe’s heel.

M iller and colleagues5presented a prospective randomized control study that tested how 12 weeks of running in minimal shoes altered footshape and muscle cross-sectionalarea.They found that m inimally shod runners developed significantly stiffer arches w ith relatively larger cross sections of several intrinsic foot muscles,indicating that the foot adapted to the greater demands required by such shoes.

Lieberman6analyzed running kinematics of Tarahumara Native Americans in Mexico,show ing that Tarahumara who wear only m inimal shoes showed much variation in running form butwere more likely to m idfootstrike and forefootstrike than those who wear conventionalshoes.This study also foundthat m inimally shod Tarahumara had significantly stiffer arches than conventionally shod Tarahumara.

Pontzer and colleagues7analyzed strike type variation among the Hadza hunter-gatherers of Tanzania,who were eitherbarefootorminimally shod.They found thatHadza men tend to midfoot strike,whereas women,children,and inexperienced runners are more likely to rearfoot strike.

Ahn and colleagues8presented a detailed study of kinematics,EMG and kinetics among 40 runners asked to wear conventional shoes versus instrumented socks that on a treadmill.The majority of runners sw itched from a rearfoot strike when shod to a forefootstrike in socks by plantarflexing their ankles and activating the calf muscles earlier and for longer than when rearfoot striking.

Gruber and colleagues9analyzed the frequency distribution of forces measured using accelerometers attached to the head and shank of habitual rearfoot and forefoot strike runners. Shock frequency contentwas significantly different in rearfoot versus forefoot strikers in the tibia but not the head,revealing differences in the pattern and degree of shock attenuation between the two styles of running.

Kasmer and colleagues10compared EMG and kinematics of four experienced m inimalist runners before and after completing two 50-km runs,one in m inimal and one in conventional shoes.In both conditions,runners were more likely to rearfootstrike after the ultramarathon,with a greater degree of increased pressure under the heel in m inimal shoes and increased activity of the anterior tibialis prior to foot contact.

Hryvniak and colleagues’11survey of over 500 runners who sw itched to barefoot or m inimal shoe running found that the vast majority of participants reported that the sw itch resulted in decreased injury or no serious harm.

Larson12analyzed foot strike patterns of a large sample of m inimally shod and barefoot runners ata large outdoor race to test the effects of m inimal shoes on strike type patterns. Among actual barefoot runners,59%were forefoot strikers, 20%were midfoot strikers,and 21%were rearfoot strikers; but among m inimally shod runners,33%were forefoot strikers,19%were midfoot strikers,and 48%were rearfoot strikers.

Samaan and colleagues13tested the effects of gait retraining that incorporated real-time feedback on ground reaction force variables during barefootand shod running.Their results showed that runners could immediately change their gait resulting in significant marked decreases in impact loading.

Good research always generates more questions than answers,and the research presented in this issue w ill be no exception.In our opinion,three broad topics merit the most attention as we go forward.First,to what extent and how do different kinds of forces(e.g.,internalvs.external)affect the developmentof injuries?Second,how do variations in running form interact w ith different kinds of shoes to affect the developmentof injuries among individuals?Finally,how does the body adapt to footwear in ways relevant to developing injuries?We hope that the excellentpapers in this volume w ill help spur even more and better research on these and other important topics regarding barefootand m inimalshoe running.

1.Bramble DM,Lieberman DE.Endurance running and the evolution ofHomo.Nature2004;432:345—52.

2.M cDougall C.Born to run:a hidden tribe,superathletes,and the greatest race the world has never seen.New York:Knopf;2009.p.304.

3.Lieberman DE,Venkadesan M,Werbel WA,Daoud AI,D’Aeandrea S, Davis IS,et al.Foot strike patterns and collision forces in habitually barefoot versus shod runners.Nature2010;463:531—5.

4.Hein T,Grau S.Can m inimal running shoes im itate barefoot heel-toe running patterns?A comparison of lower leg kinematics.J Sport Health Sci2014;3:67—73.

5.M iller EE,Whitcome KK,Lieberman DE,Norton HL,Dyer RE.The effect of m inimal shoes on arch structure and intrinsic foot muscle strength.J Sport Health Sci2014;3:74—85.

6.Lieberman DE.Strike type variation among Tarahumara Indians in m inimal sandals versus conventional running shoes.J Sport Health Sci2014;3:86—94.

7.Pontzer H,Suchman K,Raichlen DA,Wood BM,Mabulla AZP, Marlowe FW.Foot strike patterns and hind limb joint angles during running in Hadza hunter-gatherers.J Sport Health Sci2014;3:95—101.

8.Ahn AN,Brayton C,Bhatia T,Martin P.Muscle activity and kinematics of forefoot and rearfoot strike runners.J Sport Health Sci2014;3:102—12.

9.Gruber AH,Boyer KA,Derrick TR,Ham ill J.Impact shock frequency components and attenuation in rearfoot and forefoot running.J Sport Health Sci2014;3:113—21.

10.Kasmer ME,Ketchum NC,Liu XC.The effect of shoe type on gait in forefoot strike runners during a 50-km run.J Sport Health Sci2014;3:122—30.

11.Hryvniak D,Dicharry J,Wilder R.Barefoot running survey:evidence from the field.J Sport Health Sci2014;3:131—6.

12.Larson P.Comparison of foot strike patterns of barefoot and m inimally shod runners in a recreational road race.JSport HealthSci2014;3:137—42.

13.Samaan CD,Rainbow MJ,Davis IS.Reduction in ground reaction force variables w ith instructed barefoot running.JSport HealthSci2014;3:143—51.

Daniel E.Lieberman,Guest Editor

Department of Human Evolutionary Biology,Harvard University,Cambridge,MA 02138,USA

E-mail address:danlieb@fas.harvard.edu

Irene S.Davis,Guest Editor

Spaulding National Running Center,Department of Physical Medicine and Rehabilitation,Harvard Medical School, Cambridge,MA 02138,USA

E-mail address:isdavis@partners.org

Benno M.Nigg,Guest Editor

Human Performance Laboratory,Faculty of Kinesiology,The University of Calgary,Calgary,Alberta T2N 1N4,Canada

E-mail address:nigg@ucalgary.ca

10 April 2014

Peer review under responsibility of Shanghai University of Sport

2095-2546/$-see front matter CopyrightⒸ2014,Shanghai University of Sport.Production and hosting by Elsevier B.V.A ll rights reserved. http://dx.doi.org/10.1016/j.jshs.2014.04.001