Running barefoot: A natural step for reducing injuries?

Metatarsalgia, fractures, plantar fasciitis, neuromas, blisters, black toenail-easily preventable or inherent, readily manageable or hard to heal, acute or chronic, these are just a few of the maladies that make runners ask, "Why does my foot hurt?" Both runners and researchers seeking answers are taking a close look at barefoot running.

While searching for an answer,marathon runner Christopher McDougall came to believe that "everything we thought we knew about running is wrong," he wrote in his recently released book, Born to Run: A Hidden Tribe, Superathletes, and the Greatest Race the World Has Never Seen (Knopf, May 2009).In advocating barefoot running, McDougall asserted that the technology-based cushioning built into running shoes is more likely to cause than prevent running injuries, because it allows for running styles that result in exertion of excessive ground reaction forces (GRFs) on the foot.

McDougall's anecdotal experience supports his assertion. He ceased experiencing what had been chronic Achilles tendinitis when he started running in a quasi-barefoot style that he learned from Mexico's Tarahumara Indians.

Research has long supported the notion that barefoot running results in a flatter footfall and in decreased peak loading at impact.^1,2 However, the scientific community has not substantiated the assertion that barefoot running is correlated with overall lower contact forces or that the use of minimally cushioned or noncushioned shoes results in lower rates of injury.

Still, several shoe companies are introducing and marketing "minimal running shoes" as a means for distance runners to reduce their risk of sustaining impact-related injuries. Outside Magazine's 2005 Gear of the Year "Running Shoes Category" winner, the Nike Free 5.0, is "designed for the runner who wants the strengthening and natural gait management benefits associated with barefoot running," a recent Nike newsletter explained.³ According to Vibram, an industry leader in performance insoles, wearing its FiveFingers brand of footwear "is so close to going barefoot, you'll enjoy the health and performance benefits of barefooting without some of the risks."⁴ Time named FiveFingers one of the best inventions of 2007.

Determining whether the use of minimal running shoes results in reduced GRFs and alters kinematics in recreational runners is the goal of Richard Willy, a physical therapist and University of Delaware Biomechanics and Movement Science (BIOMS) PhD candidate, and his advisor, Irene Davis, PhD. In his study "Kinematic and Kinetic Comparison of Running in a Neutral Cushioned Shoe and a Minimal Shoe," Willy hypothesized that novel minimal shoe wearers would exhibit a flatter foot position on ground strike and would experience lower average vertical load rates (how quickly they load their lower extremity after foot strike) and lower tibial shock (the shock wave that results from heel strike as it travels up the tibia).

At the onset of testing, the BIOMS subjects, who served as their own controls, were injury-free and capable of comfortably sustaining an 8-minute-mile treadmill running pace. Shoe order was randomized; Nike Free 3.0s were worn for the minimal condition, and Nike Pegasus shoes were donned for the shod condition. Force data collection included the use of a force plate to measure GRFs and tibial mounting of a triaxial accelerometer to measure tibial shock.

Kinematic data collection was realized by 3D motion capture that included rearfoot motion tracking via the direct placement of markers on the calcaneus (windows were cut into the shoe shells). The data were collected over 5 consecutive footfalls at both the onset of running and the 10-minute mark. They were parameterized for comparison across experimental conditions in terms of the average vertical load rate, tibial shock, leg stiffness, and both ankle dorsiflexion and horizontal angle of the foot at heel strike.

Contrary to Willy's hypothesis, all subjects exhibited higher average vertical load rates, higher tibial shock values, and greater dorsiflexion at foot strike while running in the minimal shoes. In fact, during the minimal condition, several subjects exhibited average vertical load rates and tibial shock values that have been associated with an increased risk of tibial stress fractures. Willy concluded that running in minimal shoes does not appear to mimic barefoot running mechanics as identified in the literature, and it appears-at least in the short term-to increase loading of the lower extremity compared with running in standard shoes.

Changes in the foot-ground interface in a group of FiveFingers-adorned, experienced barefoot runners led to changes in running pattern in a study conducted by the Institute of Sport Medicine and Sport Science, Italian Olympic National Committee, in Rome.⁵ The researchers concluded that wearing the Vibram model minimal shoe seemed to be more effective than shod conditions in imitating barefoot running conditions in terms of impact force as well as stride kinematics, such as stride length and frequency (lower, shorter, and higher, respectively).

Further research is needed to determine whether the varying results reported in these studies can be attributed to different products being worn during the minimal conditions, the subjects' amount of barefoot running experience before being tested, or both. Some runners who have been trained to run in highly cushioned shoes may be unable to readily make the switch to a barefoot running style. Those able to alter their gait may not attain the benefits that have been attributed to the barefoot style anecdotally. Ultimately, with the press generated by the release of McDougall's book and the increased availability of minimal running shoes, it may be the running public that determines the fate of these products in the current marketplace.

References:

1. De Wit B, De Clercq D, Aerts P. Biomechanical analysis of the stance phase during barefoot and shod running. J Biomech. 2000;33:269-278.
2. Divert C, Mornieux G, Baur H, et al. Mechanical comparison of barefoot and shod running. Int J Sports Med. 2005;26:593-598.
3. Nike Free 5.0: Bare your feet. Inside Nike Running. http://insidenikerunning.nike.com/2009/04/16/nike-free-50-bare-your-feet. Accessed June 9, 2009.
4. Vibram FiveFingers. Barefooting: Inspired by nature and you. http://www.vibramfivefingers.com/barefooting/index.cfm. Accessed June 9, 2009.
5. Squadrone R, Gallozzi C. Biomechanical and physiological comparison of barefoot and two shod conditions in experienced barefoot runners. J Sports Med Phys Fitness. 2009;49:6-13.