Does barefoot running reduce the risk of lower limb injuries?

Barefoot running has gained a huge amount of popularity among runners, clinicians and scientists due to the alleged benefits for runners of all levels (Tam, et al., 2014). These benefits include an improved understanding of running biomechanics, improved running economics and reduced risk of injury. The popularity behind barefoot running is driven but the notion that learning to run barefoot will make you a better runner and reduce the risk of injury. However, there remains no conclusive evidence supporting these alleged benefits (Tam, et al., 2014).

Barefoot running in its purest form refers to running without shoes. Considering that humans have been wearing shoes for over 50,000 years, barefoot running is now an umbrella term that refers to both choice of footwear and running mechanics. This has been further simplified to say that barefoot running is the use of a minimalistic shoe and a forefoot strike pattern. The debate is that this adaptation back to a more natural running style reduces lower limb injuries in running. However, it may not be that simple.

There are copious amounts are scientific papers exploring the benefits of barefoot running and the impact on injury, because the prevalence of running injuries is currently reported at 50% -79% per annum (van Gent, el al., 2007). Despite the developments of the modern shoe, injury rates have not improved (Lieberman, et al., 2010), which is the premise for the debate that barefoot running may reduce injury risk more that shod running (wearing a structured shoe).

It is currently believed that the lack of conclusive evidence is a result of a combination of four factors; the acquisition of data about running mechanics, the methodology of study design, the large variability in human running mechanics, and the large variability in injury aetiology (Tam, et al., 2014). For the sake of this blog, running mechanics and injury will be the focus.

There are three main topics regarding running mechanics in this debate that barefoot running is more superior to shod running. The first is the evidence supporting the alleged benefits of changing to a barefoot technique. The second is the oversimplification of the concepts behind running biomechanics. The third is the suitability and generalizability of these biomechanical changes to all runners. All of which will be considered here.

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Lieberman and collegues (2010) conducted a study around the natural biomechanics of barefoot and shod running. They showed that shod runners have a greater tendency to strike with a rear foot pattern while barefoot runners strike with a forefoot pattern. This forefoot strike pattern involves a greater degree of ankle plantar flexion, more eccentric loading of the calf and Achilles, and less flexion at the knee. These biomechanical factors result in less load at the knee, more ankle prioprioception and improved strength in the muscles in the foot. This study supports the belief that barefoot running would result in reduced peak impact forces. However, it is not that simple as it implies that everyone runs with the same biomechanics.

One of the earlier beliefs about running was that high impact forces lead to injuries such as tibial stress fractures. From this came the thought that increasing heel height and placing a pronation control system into shoes would reduce the impact forces. There is no evidence showing that these changes in shoe structure have reduced injury risk (Tam, et al., 2014). In fact, it may be related more to the way we run than the shoes that are on our feet. One key point to remember in the debate around structured shoes is that the argument cannot be oversimplified to blame of the shoe. It is the person wearing it that often determines its success or failure. Body weight, training loads, training history and past history of injury are all variables that the shoe cannot control and variables that need to be considered.

While one theory which remains unproven is that shoe cushioning is protective, another is that all barefoot runners adopt a forefoot strike pattern. This too needs to be questioned. Whilst the study by Lienderman et al (2010) suggests that there are tendencies for shod runners to strike more heel strike, there is little evidence saying all barefoot runners adopt a forefoot strike pattern. Some studies have shown in fact that the forefoot patterns are related more to running speed than footwear, with 72% of barefoot runners adopting a heel strike pattern at comfortable running speeds (Tam, et al., 2014).

The debate continues in the topic of foot strike pattern because it has been shown that not all runners will naturally adapt to a forefoot strike pattern when transitioning to barefoot. Up to 40% of runners will continue to heel strike even at faster speeds, which again shows that the belief that barefoot running is more protective is an oversimplification (Tam, et al., 2014). If they continue to heel strike, the ground reactions forces increase seven fold. What we do know is that a forefoot strike pattern has been shown to reduce the risk of tibial stress fractures, knee pain and plantar fasciitis but on the flip side, it increases the risk of developing metatarsal stress fractures and Achilles tendinopathy.

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So where does the minimalistic shoe fit with all this? Heavily structured shoes lack the flexibility to allow for a forefoot strike pattern and therefore a shoe with less heel lift and less pronation control was designed, with the hope that a more natural foot posture would be allowed. The shoes themselves allow for these changes but not everyone has the ability to control the technique. Ryan et al (2013) conducted an analysis of injury rate with transitioning to a minimalistic shoe and found strong evidence that injury rates actually increase. This finding was based on the fact that not all runners naturally transition to a forefoot strike pattern and therefore are at greater risk of higher impacts. Some transition naturally, others take a period of acclimatisation, while some never make the changes.

Minimalistic shoes therefore aren’t the answer to reducing injury risk but definitely can increase it. Other risk factors that have been found are running >64km / week is and previous history of injury (van Gent, et al., 2007). But there remains inconclusive if overtraining or under-conditioning is more of a risk factor in long distance runners (van Gent, et al., 2007) and further research is required to answer these questions. 

The average runner will strike the ground 600 times per a run (Lieberman, et al., 2010) which explains why repetitive strain injuries are so common. One concept that is rarely spoken about is cadence. The suggested cadence for running is 180 steps per minutes, and given that forefoot strike is most commonly seen in faster runners, perhaps this is a direction that would be taken by clinicians trying to reduce injury risk?

As the debate unravels it is clear that there is no evidence to support the alleged benefits of barefoot running, no matter how compelling they may seem. The individual running is a much more important factor to consider in running injuries, than the shoes on their feet. Each strike pattern has it’s on injury risks and further research is required to truly understand what reduces running injury. It definitely is not as simple as originally thought, that barefoot running is the most natural and safe way to run.

Running injuries are related to accumulation of high impact forces. Reduce the load, reduce the risk. Minimalistic footwear does not reduce the risk of all injuries in runners and will only help those who adapt to a forefoot running technique with adequate training and transition. We are still in search of the single predictor variable that determines running injuries and while that search continues, consumers should be aware that many variables are at play. It is not a ‘one size fits all’ theory.

Sian

 

References:

Lieberman, D. E., Venkadesan, M., Werbel, W. A., Daoud, A. I., D’Andrea, S., Davis, I. S., ... & Pitsiladis, Y. (2010). Foot strike patterns and collision forces in habitually barefoot versus shod runners. Nature, 463(7280), 531-535.

Ryan, M., Elashi, M., Newsham-West, R., & Taunton, J. (2013). Examining injury risk and pain perception in runners using minimalist footwear. British journal of sports medicine, bjsports-2012.

Tam, N., Wilson, J. L. A., Noakes, T. D., & Tucker, R. (2014). Barefoot running: an evaluation of current hypothesis, future research and clinical applications. British journal of sports medicine, 48(5), 349-355.

van Gent, B. R., Siem, D. D., van Middelkoop, M., van Os, T. A., Bierma-Zeinstra, S. S., & Koes, B. B. (2007). Incidence and determinants of lower extremity running injuries in long distance runners: a systematic review. British journal of sports medicine.