Are We Running a Little too Close to the Ground
I’m sure all runners have thought it: what happened to his shoes? Don’t her feet hurt? Yes, people do run without shoes – often long distances and on hard surfaces – and they appear as comfortable as any ‘normal’ shod person. My previous article explored the merits of running shoes, primarily in injury prevention, and how despite innovative technologies the prevalence of running-related injuries has not decreased. This begs the question: are running shoes ineffective? Are we better off running barefoot like our ancestors did or is the answer a little more complex?
Barefoot running kicked off around 2009, largely as a result of the lay publication ‘Born to Run’, but also stemmed from the research of evolutionary biologist Dr Daniel Lieberman[1,2]. Both of these espoused the benefits of barefoot running, especially in terms of injury prevention. Bramble and Lieberman (2004) advanced that humans are designed for endurance running, and cited anatomical and physiological characteristics in support. For example, our capacity to sweat and our structural linearity confer superior thermoregulatory capacity, which enables us to sustain high-intensity exercise for long periods without overheating (or persistence hunting in years gone by). Over time, the theory goes, our ancestors evolved adaptations to run barefoot without injury, including a high foot arch, broad feet, a mid-to-forefoot landing and proprioceptive awareness, rendering barefoot running the most ‘natural’ way to run. Barefoot advocates propose that we are maladapted to the modern phenomenon of cushioned shoes, which significantly reduce proprioceptive feedback, weaken foot muscles, and alter running biomechanics in a manner that promotes injury. Science has since entered the picture to test the theory, assess the implications and scrutinise its purported benefits in the modern era.
The most beneficial facet of barefoot running is purported to be the reduction in the ‘impact transient’ or loading rate at ground contact, which has been positively associated with repetitive stress injuries[1,3]. Any reduction in the magnitude or rate of the force experienced is theorised to be injury-preventative (hence heel-cushioned shoes). Lieberman et al. (2010) compared foot strike patterns and loading rates in habitual shod compared to habitual barefoot runners. All shod runners landed on their heels, whilst 90% of habitual barefoot runners adopted a forefoot landing, which significantly reduced the impact transient. The flatter forefoot landing, with greater ankle plantar flexion and knee flexion at contact, allows the impact to be distributed across a greater surface area than the heel alone, including the toes, ball of the foot and plantar fascia. In addition, the more anterior foot-strike re-concentrates the eccentric loading away from the knee joint towards the ankle joint, calf musculature and Achilles tendon, reducing the knee impact. Given that rearfoot-striking barefoot is typically painful, habitually shod runners generally adjust their running biomechanics and muscle recruitment quickly – reportedly within 30 seconds of acute barefoot exposure. This includes greater stride frequency and reduced ground contact time, increased ankle plantarflexion from enhanced pre-activation of the gastrocnemius and reduced tibialis anterior activity, and shorter time required to reach peak knee flexion. The latter points to less time spent ‘braking’ each stride and more time propelling, which probably partly accounts for the improved running economy and reduced eccentric knee load in the barefoot state[6,7]. Importantly, these biomechanical adjustments, rather than the shod-barefoot transition itself, account for the reduced injury risk. For example, a 2015 prospective cohort study found that over a year there was no difference in overall injury rates between barefoot and shod runners; whereas Daoud et al. (2012) reported that shod runners who habitually rearfoot strike incur higher injury rates than runners who mostly forefoot strike. In the words of Lieberman et al. “how one runs probably is more important than what is on one’s feet, but what is on one’s feet may affect how one runs”.
However, not everyone is able to make these adjustments in the barefoot state, and as reviewed by Tam et al. (2014), barefoot running is not necessarily synonymous with a forefoot landing[4,11,12]. In novice barefoot runners, the consequences of not making adjustments can be dire, including loading rates seven-fold higher than the shod condition. Furthermore, Hashish et al. (2016) recently reported a range of foot-strike responses to acute barefoot exposure: of 22 habitually rearfoot strikers, 8 maintained this pattern, 9 adopted a midfoot strike and 5 a forefoot strike. Only those who adopted a midfoot or forefoot landing reduced their loading rates compared to the shod state. The purported benefits of barefoot running are thus not automatic but are heavily reliant on appropriate ‘skill acquisition’. As with most exercise-related stimuli, barefoot running elicits highly variable responses and is thus not a one-size fit all approach!
Regardless, transitioning to barefoot running increases injury risk in all runners at least transiently, owing to the sudden exposure of ankle joints and calf muscles to an eccentric load to which they are largely unaccustomed. Indeed runners who make this transition too rapidly and do not modify their training frequency, volume or intensity appropriately appear particularly prone to injury in these areas, as well as the plantar fascia, metatarsals and Achilles tendon[8,13]. It is not surprising that Vibram ‘FiveFinger’ sales, which made up 2% of running shoe sales in 2009-2010, had halved by by early 2012, suggesting many who experimented did not return for a second pair. In 2013 SportsOneSource reported a significant decline in minimalist shoe sales, with runners transitioning from complete minimalism to more conventional but low-cushioned shoes that remain light and close to the ground. This seems more reasonable for most modern runners compared to a sudden abandoning of shoes altogether.
Overall, is it doom and gloom for barefoot running? Perhaps for runners who are simply unable to acquire the necessary skills, and for those who are not patient enough to go back to square one…and then some. For high mileage runners used to 60-100 km/week, starting back at a 1-minute jog in between 4 minutes of walking for a total of 20 minutes is not overly appealing. However, there are runners that have adapted quickly and those who persisted, possibly to combat injury, and found success at the end of the road. In advising clients that may not wish to throw their shoes away but seek some of the ‘barefoot benefits’ (stronger calf muscles, proprioception, ankle stability), one may approach it as any other training modality. This may include wearing minimalist footwear at work or around the house, during warm-ups, and over time incorporating them into shorter training runs. Regardless, it seems wise to tread carefully but be flexible in adjusting progressions to suit the needs and learning capacity of the individual runner.
Lieberman, D. E. et al. Foot strike patterns and collision forces in habitually barefoot versus shod runners. Nature 463, 531–535 (2010).
Bramble, D. & Lieberman, D. Endurance running and the evolution of Homo. Nature 432, (2004).
Salzler, M. et al. Injuries observed in a prospective transition from traditional to minimalist footwear: correlation of high impact transient forces and lower injury severity. Phys. Sportsmed. (2016).
Tam, N., Wilson, J. L. A., Noakes, T. D. & Tucker, R. Barefoot running : an evaluation of current hypothesis , future research and clinical applications. Br. J. Sports Med. 48, 349–355 (2014).
Fleming, N., Walters, J., Grounds, J., Fife, L. & Finch, A. Acute response to barefoot running in habitually shod males. Hum. Mov. Sci. 42, 27–37 (2015).
Perl, D., Daoud, A. & Lieberman, D. Effects of footwear and strike type on running economy. Med. Sci. Sport. Exerc. 44, 1335–1343 (2012).
Hashish, R., Samarawickrame, S., Powers, C. & Salem, G. Lower limb dynamics vary in shod runners who acutely transition to barefoot running. J. Biomech. 49, 284–288 (2016).
Altman, A. R. & Davis, I. S. Prospective comparison of running injuries between shod and barefoot runners. 476–480 (2016).
Daoud, A. et al. Foot strike and injury rates in endurance runners: a retrospective study. Med. Sci. Sport. Exerc. 44, 1325–1334 (2012).
Lieberman, D. E. What we can learn about running from barefoot running. Exerc. Sport Sci. Rev. 40, 63–72 (2012).
Cheung, R. & Rainbow, M. Landing pattern and vertical loading rates during first attempt of barefoot running in habitual shod runners. Hum. Mov. Sci. 34, 120–127 (2014).
Hatala, K., Dingwall, H., Wunderlich, R. & Richmond, B. Variation in Foot Strike Patterns during Running among Habitually Barefoot Populations. PLoS One 8, e52548 (2013).
Salzler, M., Bluman, E., Noonan, S., Chiod, C. & DeAsla, R. Injuries observed in minimalist runners. Foot ankle Int. 33, 262–266 (2012).