Barefoot Running, A matter of preference?

There has been a great interest in barefoot running. Several athletes running in barefoot were epitomized, Abebe Bikila from Ethiopia ran barefoot and won a marathon gold medal in the 1960 Summer Olympics. (In  the 1964 Olympics he won again, but wearing shoes).  British runner Bruce Tulloh won the gold medal in the 1962 European Games running barefoot in a 5000-meter race. In 1985, Zola Budd broke the world record in the 5000 m running barefoot. The Tarahumara people in Mexico are renowned for their long-distance barefoot running.

The book  “Born to Run” by Cris McDougall published in 2009 sparked worldwide interest in barefoot running. It was claimed that based on theory of evolution, long-distance running ability was crucial for human survival. Human has been running for hundreds of thousands of years to chase prey or to outrun predators. This is followed by Daniel Liebermann, professor of human evolutionary biology at Harvard, who published an article “Foot strike patterns and collision forces in habitually barefoot versus shod runners” in the prestigious journal Nature. (see http://www.barefootrunning.fas.harvard.edu/)

Shoes companies also start to make “barefoot” or “minimalist” shoes and many claims have been made about the advantages of barefoot over shod running. Sales of minimalist shoes increased 300 percent in 2012, compared with a 19 percent increase in traditional running shoe sales in that same year. There’s an enormous publicity on barefoot running, and many claims made about its positive effects and superiority over running shoes.

Benno Nigg and Henrik Enders from the Human Performance Laboratory at the University of Calgary investigated and published a critical review in the journal Footwear Science in 2013. They critically examined the claims based on available research evidence into barefoot running’s effects on foot motion, training, running economy and injury. Nigg also presented this work at the Connective Tissues in Sports Medicine Congress in 2013 at the University of Ulm in Germany. This article is based on Benno Nigg’s lecture and paper.

Barefoot running land on forefoot (toe) while people running on shoes (shod) landed on the rear (heel).

Lieberman et al. (2010) wrote: “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.”

An unpublished thesis by Herzog (1978) examined the landing strategy for barefoot running either on asphalt or grass based on 180 trials. Herzog found that running on asphalt, 23% landed on the heel while 77% landed on forefoot. Meanwhile on grass, 54% landed on the heel, while 46% on the forefoot. This implied ground condition heavily influenced landing pattern of the foot. A study by Hatala et al. (2013) observed 23 subjects that are habitually barefoot in Northern Kenya. Subjects ran at self-selected endurance running and sprinting speeds. The data showed that 72% landed on the heel, 24% on midfoot and 4% on the forefoot. These results indicate that not all habitually barefoot people prefer running with a forefoot strike.

Thus, Benno concluded that the statement that barefoot running is associated with forefoot landing is thus not well supported by evidence. The studies suggest that landing strategy depends on many environmental and personal conditions, such as the surface condition, footwear, the subject, speed (e.g. sprinters don’t land on the heel), training, etc.

Forces on barefoot running is smaller than shod

Liebermann et al. (2010) suggested that barefoot forefoot strikers generated lower impact forces compared with shod rearfoot strikers. This is based on studies of ground vertical force, which measures the (vertical) force back against the foot when the foot strikes on the ground during running.   Nigg argued that higher impact forces are not associated with higher risk of injuries. In a review by Zadpoor and Nikooyan (2011), the authors found no significant difference between the ground reaction force impact peaks for people developing a stress fracture compared to controls.

Nigg also suggested that we should look at the internal forces for heel and toe landing. Based on his analysis, in toe-landing, the force is mostly on the achilles tendon, meanwhile, for heel-landing mostly forces is on the tibialis anterior. The change between toe and heel landing created a shift of internal forces, the structure that are loaded are different, where the internal joint forces are similar.

Barefoot running has less injuries

This claim advocated by Robbins and Hanna (1987) based on anecdotal evidence from their work in Haiti that people that come to the clinic are the people who wear shoes. It was believed that toe landing creates smaller impact forces. Likewise, Nigg argued that people that had shoes that can afford to go to the doctor. Robbins and Hanna (1987) proposed that running shoes with supportive structures and absorbent cushioning suppressed sensory feedback and therefore, increased the likelihood of lower extremity injuries. Thus, they recommended barefoot running as a possible solution to running-related injuries. It is also reasoned that toe landing creates smaller impact forces of landing. However, there is no experimental or even theoretical evidence on this claim.

Nigg noted that running injuries have not changed over the years despite the massive development of the running-shoe industry.

Bahlsen (1989) evaluated different landing impact forces on relative injury frequency and found no significant differences in injuries for low, medium, and high impact forces. However people with firm landing (high loading rates) significantly have fewer injuries. There is no experimental evidence that barefoot running has less injuries. A review by Murphy et al. (2014) concluded that “barefoot running is not a substantiated preventative running measure to reduce injury rates in runners”.

Reports in 2010 seen a large increase in injuries caused by running barefoot or with minimalist shoes (Fitzgerald, 2010). A study from Griffith University Australia showed that transition to minimalist footwear appears to increase the likelihood of experiencing an injury, specifically increasing pain at the shin and calf (Murphy et al., 2013). The authors speculated that the runners who switched to full-minimalist shoes may have been forced to change their running form. Similarly, a crowd-sourced data showed that the risk to suffer a running-related injury was significantly increased during the period of changing from shod to minimalist running (Daumer et al., 2014). Prof. Lieberman said  that “If you switch to minimal shoes or go barefoot you need to do so gradually so your body can adapt, and you need to learn proper running form.” Recently Vibram, the minimalist shoes company, agreed to pay $3.75 million in refunds to purchasers after a class action lawsuit accused the company of making claims without scientific backup that the Five Fingers shoes could decrease foot injuries and strengthen foot muscles.

Barefoot running requires less energy

This claim is based on the notion that additional weight of a shoe will consume more energy. This aspect can be looked at based on energy consumption on a global (respiration) and local (oxygenation of muscle tissues). Barefoot is believed to consume less oxygen as logically an increase in mass (due to shoes) should increase volume of oxygen (O₂) demand. Frederick et al. (1984) gave a rule of thumb that 100g of additional mass will result in additional 1% of energy demand. However, a recent study by Franz et al. (2012) did not find this relationship to be universal. The increase in shoe mass up to 300 grams, did not result in any change in O₂ consumption. The additional mass added to the foot by the shoe does not seem to have a negative effect on the performance until at a ‘threshold mass’ of about 200 to 250 g. The reason is not fully understood yet, it could be a threshold of mass effects, or different shoe characteristics, etc.

Franz et al. (2012) further studied the effect of mass on 3 types of runners (1) barefoot, (2) with shoes that weigh 150g, (3) barefoot with added 150g weight. The subjects were midfoot landing that run 25 km/week with 8 km/week on barefoot. The results show no difference between barefoot (1) and shoes (2). Furthermore, there is a 3-4% less oxygen use for shoes (2) compared to barefoot (3). Possible factors include stride length or frequency, shoe damping effect from inserts, comfort or preference.

The results of these studies are inconclusive and thus, it is suggested that additional information may be found through the investigation of local energy aspects during running. There is also no significant difference between running barefoot or with running shoes in muscle activity. Nigg and his colleagues studied the soft tissue vibrations, caused by the landing of the foot on the ground which results in waves that travel up the body from the feet to the head. The vibrations of soft tissue compartments due to impact are usually damped. The magnitude of soft tissue vibration damping can serve as an indicator for the amount of work a muscle needs to expend for impact related vibration damping. A study by Enders et al. (2013) looked at participants who ran at 3.5 m/s on a treadmill in shoes and barefoot using a rearfoot and a forefoot strike for each footwear condition. The preferred strike patterns for the subjects were a rearfoot strike and a forefoot strike for shod and barefoot running. The results showed that neither shod and barefoot nor rearfoot and forefoot strike resulted in a consistent change of the damping coefficient. Only preferred movement pattern showed significantly lower damping coefficients compared to the non-preferred strike pattern.  The preferred movement pattern: the combination of chosen footwear and a runner’s preferred strike pattern, is more important.

Energy Storage in Running

Alexander (1987) suggested that runners bounce along their tendons and ligaments. It was suggested that running shoes take away the natural musculature spring of the foot and lower legs.  Running involves a “mass-spring mechanism” an exchange of potential and kinetic energy in the tendons and ligaments. Tendons and ligaments are elastic tissues that can store energy, where they are stretched and then release energy as they recoil. The main springs are the Achilles tendon and the longitudinal arch of the foot. Achilles tendon can store 35 Joule per step for running and, the arch of the foot can store 17 Joule. The mechanical energy per step is 100 Joule, and it was suggested that the arch and Achilles tendon can return 52% of the energy captured in each step when we run.

A study Perl et al. (2012) concluded that minimally shod runners are modestly but significantly more economical than traditionally shod runners regardless of strike type. The likely cause of this difference is more elastic energy storage and release in the lower extremity during minimal-shoe running.

However, there is still a great uncertainty on how much of the energy is returned. Nigg argued that if we were to use the Achilles tendon, we would hop like a kangaroo not run. He also argued that if we were to use 17% of the energy form the arch, then most sprinters will have a high-arch. Similarly, athletes would not use orthothics that do not allow the foot to deform. There is also a high variation of stiffness in the Achilles tendon, from a factor of 100 to 1000. Currently, the theory and data on storage and return of energy in running is not well understood yet.

Conclusions

In conclusion, Nigg said that it’s not the right question to ask or to compare which is better barefoot running or wearing running shoes.  The most important factors in mitigating the risk of foot injuries and raising running performance, are individual preference and comfort. The bottom line is if it doesn’t feel good on your feet, don’t run with it.

References

Alexander R. McN. (1987). The spring in your step. New Scientist 1588, 42-44, 30 April 1987.

Bahlsen, A., (1989). The etiology of running injuries, a longitudinal, prospective study. PhD University of Calgary.

Daumer, Martin, et al. (2014) Overload injuries in barefoot/minimal footwear running: evidence from crowd sourcing. PeerJ PrePrints No. e250v1.

Enders, H., von Tscharner, V., & Nigg, B. M. (2013). The effects of preferred and non-preferred running strike patterns on tissue vibration properties. Journal of Science and Medicine in Sport, 17(2), 218-222.

Fitzgerald, M. (2010). The barefoot running injury epidemic. Competitor

Franz, J. R., Wierzbinski, C. M., & Kram, R. (2012). Metabolic cost of running barefoot versus shod: is lighter better. Med Sci Sports Exerc, 44(8), 1519-25.

Frederick, E.C., Daniels, J.T., Hayes, J.W.(1984) Current Topics in Sports Medicine, pp. 616-625

Gruber AH, Umberger BR, Braun B, Hamill J. “Economy and rate of carbohydrate oxidation during running with rearfoot and forefoot strike patterns.” Journal of Applied Physiology. 2013 Jul;115(2):194-201.

Hatala, K. G., Dingwall, H. L., Wunderlich, R. E., & Richmond, B. G. (2013). Variation in foot strike patterns during running among habitually barefoot populations. PloS one, 8(1), e52548.

Herzog, W. (1978) Thesis Dissertation, ETH, Zurch.

Lieberman, D. E., et al.  (2010). Foot strike patterns and collision forces in habitually barefoot versus shod runners. Nature, 463(7280), 531-535.

Nigg, B., & Enders, H. (2013). Barefoot running–some critical considerations. Footwear Science, 5(1), 1-7.

Lorenz, Daniel S. Pontillo, Marisa. “Is There Evidence to Support a Forefoot Strike Pattern in Barefoot Runners? A Review.” Sports Health. November/December 2012 vol. 4 no. 6 480-484

Murphy, K., Curry, E. J., & Matzkin, E. G. (2013). Barefoot running: does it prevent injuries?. Sports Medicine, 43(11), 1131-1138.

Perl, D. P., Daoud, A. I., & Lieberman, D. E. (2012). Effects of footwear and strike type on running economy. Med Sci Sports Exerc, 44(7), 1335-43. Ryan, Michael, et al. “Examining injury risk and pain perception in runners using minimalist footwear.” British journal of sports medicine (2013): bjsports-2012.

Robbins, S. E., & Hanna, A. M. (1987). Running-related injury prevention through barefoot adaptations. Medicine and Science in Sports and Exercise, 19(2), 148-156.

Zadpoor, A.A. & Nikooyan, A.A. (2011). The relationship between lower-extremity stress fractures and the ground reaction force: A systematic review. Clinical Biomechanics, 26 (1), 23–28.