As barefoot running gains popularity and the market sees the development of more minimalist shoes, podiatric physicians and athletes have debated barefoot running versus shod running, which is faster and which leads to less chance of injury. Accordingly, this author takes a closer look at the evidence with a focus on biomechanics and physiology.
Running is one of the most important forms of locomotion for the bipedal human. Early humans used the locomotor activity of running to hunt for prey, to escape from dangerous animals and to speed up communication with distant villages.1 Early recorded history also demonstrates that running was an important sporting event over 2,700 years ago. At the first Olympic Games, held in 776 BC in Olympia, Greece, there was only one athletic event, a 190 meter running race.2 In addition, Greek vases from the 5th to 6th century BC are decorated with images of running men.3 As such, running was not only an essential form of locomotion for our early ancestors but has also been a form of sport for thousands of years.
Even though it seems obvious that our earliest human ancestors walked and ran barefoot, early humans were wearing shoes for over a thousand generations. Erik Trinkaus, PhD, has estimated that our human ancestors began wearing shoes at least 40,000 years ago.4 The world’s oldest shoe, made of intricately woven sagebrush, has been radiocarbon dated as being 10,000 years old.5 The oldest surviving leather shoes, lace-up moccasins, have been radiocarbon dated to 3500 BC.6 Therefore, it is likely that our ancestors have used shoes for at least 10,000 to 40,000 years for walking, running and other weightbearing activities.
In modern society, however, running has become less of a means for obtaining food and escaping danger, and more of an activity for sport and exercise. Recreational running has been increasing in popularity ever since the 1970s with an estimated 15 million Americans running on a regular basis.7 In response to the surge in interest in running, running shoe manufacturers have developed a wide range of running shoe models made to allow runners to exercise both comfortably and safely.
Much of the early technological advancement in modern running shoes came during the 1970s when manufacturers began to make the running shoe midsoles with more shock-absorbing materials.8 Furthermore, in the early 1980s, running shoes began to feature “anti-pronation” features such as medial heel bars and dual-density midsoles that were designed to limit rearfoot pronation.9 Since the beginnings of the modern running shoe in the 1970s, the running shoes of today are now comprised of a multitude of advanced technologies including midsoles filled with air, gel and springs. These may or may not reduce the incidence of running injuries.
The concept that having running shoes with thicker, more cushioned midsoles is the best way to run has been under recent challenges with the publication of the book Born to Run. The author, Christopher McDougall, claims that since our early human ancestors all ran barefoot, then runners should be running either in thin-soled shoes or without shoes at all, and that there is no evidence that modern running shoes prevent injuries.10 A number of runners have since been inspired by the back to nature message of Born to Run and have begun to run barefoot or in thinner-soled running shoes. One of the most popular of these “minimalist” running shoes, the Vibram FiveFingers shoe, even has five toe sleeves to mimic the barefoot condition.
For those podiatrists who treat running injuries and give running shoe recommendations, the subjects of barefoot running and minimalist shoes have been growing topics of conversation with runner-patients for the past few years. Certainly, podiatrists should be aware of the research evidence in regard to barefoot running, minimalist shoes and traditional running shoes so their treatment and shoe recommendations for their patients are current.
With this in mind, what are the facts surrounding barefoot versus shod running? What does the scientific research say about the biomechanics and physiology of running in shoes and running without shoes?
How Common Is Barefoot Running Among Elite Runners?
In order to better understand whether running barefoot or running in shoes produces more injuries, it would be helpful to compare large populations of barefoot and shod runners in prospective studies in order to determine their injury risk. Unfortunately, even after all the discussion and media hype over the past few years on the potential benefits of barefoot running, individuals who only run barefoot are still relatively uncommon. In fact, in the last century of track and field, cross country and road racing competitions, there have been only a few notable runners who won races barefoot since the vast majority of elite runners over the past century have chosen to run their races in shoes.
One of the most famous barefoot runners was Abebe Bikila, an Ethiopian who won the 1960 Rome Olympic Marathon while barefoot in a time of 2:15:16. However, four years later, in the 1964 Tokyo Olympics, Bikila ran in shoes and, as a result, broke the world record for the marathon with a time of 2:12:11.11 Therefore, Bikila ran the Olympic marathon 7 seconds per mile faster while in shoes than when he ran barefoot. In fact, in over 50 years since Bikila won the 1960 Olympic marathon barefoot, no other athlete has won an international-level marathon by running the whole race barefoot.
Zola Budd, another famous barefoot runner from South African, broke the women’s 5,000 meter world record in 1984 while running barefoot.12 Now, 28 years later, Budd still runs competitively but prefers running in shoes. “I no longer run barefoot,” noted Budd. “As I got older, I had injuries to my hamstring. I found that wearing shoes gives me more support and protection from injuries.”13
In regard to the elite running athletes of today, even though many of them may use barefoot running as a training aid, very few of them compete while barefoot. No world records have been set while running barefoot for at least the last quarter century. In fact, all current track and field running event records have been set with shoes on. Even though nearly all the elite runners of today have chosen to race in shoes, there is currently no scientific research that explains why the world’s elite running athletes routinely avoid going barefoot while racing.
What The Research Says About Differences In Biomechanics And Physiology
Fortunately, in regard to the biomechanics and physiology of barefoot versus shod running, there is now considerable research evidence that does allow us to draw some conclusions about the differences between the two activities.
The most consistent research finding regarding the kinematic differences between barefoot and shod running is that individuals will shorten their stride length and increase their stride frequency while running barefoot.14-17 Barefoot runners also decrease their contact times, decrease their stride duration and decrease their flight times.18 Therefore, being barefoot causes a runner to take more steps per mile than while shod.
The most likely explanation for the consistently shortened stride in barefoot running is that, without the protection of a shoe on their feet, most barefoot runners will tend to avoid having their plantar heel impact the ground at foot strike.14 In order to avoid heel strike, barefoot runners will position their ankles in a more plantarflexed position at foot strike by pre-activating their gastrocnemius and soleus muscles before foot strike.14,16,18-21 In support of the idea that barefoot runners tend to avoid heel strike to avoid plantar heel injury, measurement of the heel fat pad deformation during barefoot and shod running demonstrated that the maximal deformation of the heel fat pad was 60.5 percent in barefoot running whereas in shod running, the heel fat pad only deformed 35.5 percent. This study showed that shoes offer significant supportive function to the heel fat pad.22
Even though heel striking runners make up between 75 and 89 percent of runners, recent research may suggest that since most barefoot runners avoid heel strike, they also may be able to reduce their impact load by avoiding the initial loading peak that occurs in the majority of runners who heel strike.23-26
Unfortunately, the literature is undecided as to whether barefoot or shod running is better at decreasing the vertical loading rate (VLR) from ground reaction force (GRF) at foot strike. Even though a few studies have shown that the vertical loading rate is less in barefoot running, other studies have shown that barefoot running actually increases the vertical loading rate.14,22,23,28-31 In addition, some studies have shown that barefoot running reduces the magnitude of the ground reaction force impact peak while other studies show that barefoot running increases the magnitude of the impact peak.14-16,19,23,27
The question of whether barefoot running or shod running is better at reducing the impact loads of running may be an important one since there is some suggestion that certain running injuries, such as tibial stress fractures, may be more prevalent in female runners who exhibit increased vertical loading rate during running.32 However, prospective research has also found that people with a higher vertical loading rate had significantly fewer running-related injuries than those people who had a lower vertical loading rate.33
Other research findings, which weaken the argument that impact shock causes running injuries, are that shock-absorbing insoles have not reduced the incidence of stress fractures and running on hard surfaces did not result in any increase in running-related injuries in comparison to running on softer surfaces.34-36 In his latest book, Benno Nigg, Dr.sc.nat., Dr.h.c, one of the world’s leading researchers in foot and lower extremity biomechanics, offered the following opinion on the importance of impact forces in causing running injuries: “Currently, there is no conclusive evidence that impact forces during heel-toe running are responsible for development of running-related injuries.”37
Does Barefoot Running Offer Metabolic Advantages?
Still, barefoot running does seem to have one clear benefit over running in shoes: running while barefoot is more metabolically efficient than shod running. Research has shown that running in shoes increases the oxygen uptake versus barefoot running and also increases the perceived exertion and heart rate versus barefoot running.16,38 The most likely explanation for the increased metabolic efficiency of barefoot running is that the added mass of the shoe creates extra energy cost for runners in order to accelerate their lower extremity forward with each running stride.39
Previous research has shown that adding 175 g of weight to each running shoe required 3.3 percent more metabolic energy at a 6:22/mile running pace and adding 100 g of weight to each shoe required 1.2 percent more metabolic energy at a 7:00/mile pace.40,41 Another study focused on running in light diving socks with weights added in shod running and barefoot running.15 The study found that the higher metabolic cost of running in shoes was only due to the extra mass induced by the shoe itself and not due to any other mechanical property of the shoe.
With research indicating that barefoot running is more metabolically efficient than shod running, running barefoot should theoretically be faster than running shod since any mass added to the foot increases the oxygen cost of running. However, as mentioned earlier, since nearly all elite runners race in shoes and not barefoot, the increased metabolic efficiency of barefoot running doesn’t seem to equate to faster racing speeds for elite runners. These facts then lead to the following question: why aren’t more elite athletes racing without shoes if barefoot running is more metabolically efficient than shod running?
One possible answer is that faster running speeds, such as those that occur during race situations, will generate significantly higher peak vertical and peak shearing forces on the plantar foot with each foot strike.42-47 The increased ground reaction force that occurs at racing speeds over surfaces of various temperatures, surface contours and textures may deter the elite athlete from risking injury to his or her foot by running barefoot. Another possibility is that the shorter stride lengths forced by barefoot running may limit running velocity sufficiently to limit racing speeds. Another intriguing possibility is that elite runners choose to race in shoes since the running shoe companies that often sponsor elite running athletes offer significant monetary incentive for these elite athletes to race in their shoes rather than racing barefoot.
In regard to whether barefoot or shod running is best, the scientific research evidence to date supports only that barefoot running is more metabolically efficient than shod running. However, the rarity of barefoot runners breaking the finishing tape in all types of running races also points to the fact that there must be other more important factors at work that prevent the vast majority of athletes from running their fastest races while barefoot.
With this in mind, one should advise each runner-patient on the potential risks and benefits of barefoot versus shod running before they attempt to emulate their unshod ancestors by running barefoot. With so many questions remaining unanswered regarding barefoot versus shod running, further research will be necessary to further illuminate this fascinating subject.
Dr. Kirby is an Adjunct Associate Professor in the Department of Applied Biomechanics at the California School of Podiatric Medicine at Samuel Merritt University in Oakland, Calif. He is in private practice in Sacramento, Calif.
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