Emerging Evidence On Footstrike Patterns In Running
Given the popularity and perceptions associated with barefoot running and minimalist shoes, this author takes a closer look at the research on foot striking patterns in runners and finds that rearfoot striking is not only far more prevalent but may be more efficient as well.
Much of the relatively recent increase in the popularity of running in America can be traced back to the “running boom” of the early 1970s when United States distance runner Frank Shorter won the marathon in the 1972 Munich Olympic Games.1 With the “running boom” came increased demand for a wider range and number of better running shoes. Now, in the U.S. alone, running shoe sales total over $3 billion and over 50 million Americans currently participate in running as a recreational activity.2
One of the most interesting trends or fads in running since the “running boom” started has been the surge of interest in barefoot running, minimalist running shoes and running footstrike patterns over the past five years. The surge in interest in barefoot and minimalist shoe running and footstrike patterns was at least partially due to the popularity of a 2009 book, Born to Run, by Christopher McDougall.3 Throughout his book, McDougall made claims that because our ancestors ran barefoot, modern humans should also be running barefoot or least be running in thinner-soled shoes that mimic barefoot running and allow a more “natural” running form. In his book, McDougall also claimed that there was no evidence that the modern, thicker-soled, cushioned running shoe, which became popular in the 1970s, actually prevented running injuries.
As a result of believing McDougall’s claims, many runners became captivated by the idea of “natural running.”3 Many of these runners began to try barefoot running or running in thin-soled “minimalist” running shoes with the most popular minimalist shoe for a time being the five-toed Vibram FiveFingers shoe. Even though there were many anecdotal accounts within the popular media that these five-toed shoes helped decrease running injuries, there were also reports within the medical literature that these shoes actually caused injury in some runners.4,5 In fact, in a 2013 study, runners who underwent a 10-week transition period of running in Vibram FiveFingers shoes showed significant increases in foot bone marrow edema versus those runners who trained only in traditional thick-soled running shoes.6 (For a related News and Trends article on the recent Vibram class action settlement, see http://www.podiatrytoday.com/june-2014 .)
Countering The Notion That Forefoot Striking Is More ‘Natural’
Along with the interest in barefoot and minimalist running shoes, there have been suggestions within the popular media that running with a forefoot striking pattern was more “natural” and better than running with a midfoot or rearfoot striking pattern. The most referenced article that seemed to support the idea that forefoot striking running was the “most natural” way to run came from a 2010 study by Lieberman and colleagues, who showed that there were reduced impact forces in habitually barefoot Kenyan runners who ran with a forefoot striking pattern.7 Researchers measured the Kenyan runners’ footstrike patterns at a relatively fast running speed of 5.5 m/sec (4:52 mile pace). In their study conclusion, Lieberman and coworkers maintained that “Forefoot and midfoot-strike gaits were probably more common when humans ran barefoot or in minimal shoes, and may protect the feet and lower limbs from some of the impact related injuries now experienced by a high percentage of runners.”7
However, directly contradicting the findings of the study by Lieberman and colleagues, a more recent study by Hatala and coworkers in 2013 showed that when another group of habitually barefoot Kenyans ran at a much slower and more common recreational running speed of 3.3 m/sec (8:08 mile pace), 72 percent of these barefoot runners were rearfoot strikers, 24 were midfoot strikers and only 4 percent were forefoot strikers during running.7,8Therefore, the idea of Lieberman and coauthors that our ancestors who ran barefoot were predominantly forefoot strikers and were not rearfoot strikers seems unlikely. In addition, the speculation that forefoot striking running is a more “natural” form of running than rearfoot striking or midfoot striking running is not supported by the scientific research literature.
What The Research Reveals: Rearfoot Striking Preferred By Majority Of Runners
In order for the clinician to better understand the footstrike pattern debate and the scientific research on the subject, it is important first to review some of the most significant running research studies involving footstrike patterns.
In 1980, Cavanagh and Lafortune published the first modern scientific study of footstrike patterns of runners.9 In their study, 17 people ran over a force plate to classify their running footstrike patterns. The researchers divided the anterior-posterior length of the shoe sole into equal thirds with those people who first contacted the ground with the proximal third of the shoe being labelled as rearfoot strikers, those contacting in the middle third being midfoot strikers and those contacting in the distal third of the shoe sole being forefoot strikers. At a 4.5 m/sec (5:58 mile pace) running velocity, 12 of the study participants were rearfoot strikers, five were midfoot strikers and none of the runners were forefoot strikers. In 1987, the term “strike index” first arose within the scientific literature to describe the percentage of the running shoe sole length, from anterior to posterior, where the runner first contacted the ground at footstrike.10
In regard to the footstrike patterns of the running population as a whole, there have been seven research studies to date that have measured footstrike patterns in large numbers of runners. Kerr and colleagues measured the footstrike patterns of 753 runners in 10 km and marathon distance races, and found that 81 percent were rearfoot, 19 percent were midfoot and 0 percent were forefoot strikers.11 Hasegawa and coauthors studied the footstrike patterns of 283 elite half-marathoners and found that 74.9 were rearfoot, 23.7 percent were midfoot and only 1.4 percent were forefoot strikers.12 Larson and colleagues measured 936 half-marathon runners and found that 88.9 percent were rearfoot, 3.4 percent were midfoot, 1.8 percent were forefoot and 5.9 percent were asymmetrical foot strikers.13
Out of 903 novice runners, Bertelsen and coworkers found there were 98.1 percent rearfoot, 0.2 percent midfoot, 0.4 percent forefoot strikers and 1.2 percent asymmetrical foot strikers.14 Kasmer and colleagues studied 1,991 runners in a marathon and found that 93.7 percent were rearfoot strikers.15 In a 50 km trail race, Kasmer and coauthors also determined that 85.1 percent of 165 runners were rearfoot strikers.16 Finally, Almeida and coworkers showed that in 514 recreational runners, 95.1 percent were rearfoot strikers, 4.1 percent were midfoot strikers and 0.8 percent were forefoot strikers.17
Of the 5,545 runners who had their footstrike measured in these seven research studies, 90.8 percent (5,034) were rearfoot strikers (see “Seven Studies Show Rearfoot Striking Preferred Form In Runners” below).11-17 This conclusively demonstrates that the preferred footstrike pattern for the vast majority of runners is rearfoot striking.
Is There A Correlation Between Rearfoot Striking And Injury Rates?
There has also been much speculation from the barefoot running and minimalist running shoe advocates that forefoot and midfoot striking running must be the best ways to run since rearfoot striking running results in increased impact forces, which they suggest causes more running injuries. Helping to promote these ideas, Lieberman and coworkers claimed that midfoot and forefoot striking running “may protect the feet and lower limbs from some of the impact related injuries.” However, the available research studies on footstrike patterns and running injury rates do not support the conjecture of the barefoot and minimalist running shoe advocates.
In 2003, Kleindienst prospectively studied 471 runners and found no difference in injury rates between forefoot and rearfoot striking runners.18 In 2005, Walther prospectively studied 1,203 runners and found no differences in injury rates between forefoot and rearfoot striking runners.19 In 1997, Nigg prospectively studied a group of runners and found that there were no significant differences in running injury frequency among those with high-, medium- or low-impact peaks, and those people with higher impact loading rates had fewer running-related injuries than those people with lower impact loading rates.20 Within his latest book on the sports shoe biomechanics, Nigg offered the following opinion: “Currently, there is no conclusive evidence that impact forces during heel-toe running are responsible for development of running-related injuries.”21
Current Insights On Running Form And Efficiency
Much of the media hype over the past few years regarding barefoot and minimalist shoe running has also spawned the development of a number of “alternative running techniques” that have been promoted and marketed to the running communities. These alternative running techniques invite runners to pay for instructional courses on how to learn to run with “better form.” The two most popular alternative running techniques include the Pose Method® of Running and Chi Running®, both of which are based on the notion that rearfoot striking is not only an inefficient “running form” but will lead to an increased incidence of running injuries.22,23
It is interesting to note that the only scientific research that has studied whether these alternative running forms are indeed more metabolically efficient came from a group of researchers, one of whom was Nicholas Romanov, the inventor of the Pose Method of Running.24 In their 2005 study, 16 sub-elite triathletes were divided into one group that was trained to run with the “Pose” method and a control group that maintained their self-selected running technique over a 12-week period. The researchers found that the “Pose” runners became less metabolically efficient in comparison to the runners who maintained their self-selected running form. The oxygen cost for the “Pose” athletes was 7.6 percent greater than the oxygen cost for the control athletes. This indicated that the Pose Method of Running, instead of being a more efficient form of running, was actually a less efficient style of running than what the runners had self-selected as their preferred running form.
With these facts in mind, there is support within the research literature that runners have the ability to self select their most efficient running form as they become more experienced runners. In 1982, Cavanagh and Williams performed a classic running research study that demonstrated that experienced distance runners are able to self select their most metabolically efficient running stride.25 In their experiment, 10 experienced distance running athletes ran at seven different stride lengths on a treadmill at 3.83 m/sec (7:00 mile pace). The stride lengths the athletes were asked to run at included their self-selected stride length, three shorter stride lengths and three longer stride lengths (80 percent, 86.6 percent, 93.3 percent, 100 percent, 106.7 percent, 113.4 percent and 120 percent of their self-selected stride length). The researchers found that when the study participants ran at stride lengths that were either shorter or longer than their self-selected stride length, the runners became less metabolically efficient. These research findings suggest that well-trained runners may be able to find their most metabolically efficient running form without needing to be “coached” in order to run with optimum efficiency.
Since the vast majority of runners choose to rearfoot strike and less than 3 percent of runners choose to forefoot strike, it makes sense that there may be some metabolic advantage to rearfoot striking running.11-14 In fact, there are now a number of recent studies that support the idea that rearfoot striking running may be the predominant footstrike pattern since it is the most metabolically efficient running form at recreational running speeds.
In 2009, Miller and colleagues performed a computer simulation study of rearfoot and midfoot running at 4.0 m/sec (6:42 min/mile).26 They found that rearfoot striking running was 6.3 percent more metabolically efficient than midfoot striking running. In 2013, Gruber and coauthors studied the rates of oxygen uptake during running in 19 habitual rearfoot and 18 habitual forefoot striking runners at three different running speeds, and found that the rearfoot striking pattern was more economical than the forefoot striking pattern at all running speeds.27 From their study, Gruber and coworkers rejected the commonly held idea that habitual rearfoot strikers should have training to be forefoot strikers to make them “more efficient runners.”
Most recently, in 2014, Ogueta-Alday and colleagues studied 20 sub-elite distance runners, 10 who were rearfoot strikers and 10 who were midfoot strikers.28 They found that the rearfoot strikers were 5.4 percent more economical than the midfoot strikers at 3.0 m/sec (8:56 min/mile) and 9.3 percent more economical than the midfoot strikers at 3.6 m/sec (7:26 min/mile).
Overall, there is now overwhelming research evidence that rearfoot striking running is not only the most common footstrike pattern but also the most economical footstrike pattern at recreational running speeds.
Altering Running Form: Can It Have An Impact For Runners With Chronic Exertional Compartment Syndrome?
Even with the scant research evidence supporting the notion that rearfoot strikers may benefit from converting to a midfoot or forefoot striking running form, there is some evidence that altering running form has the potential to benefit select individuals.
In two recent case studies, both by Diebal and colleagues, runners with anterior chronic exertional compartment syndrome who underwent gait retraining from a rearfoot striking pattern to a forefoot striking pattern showed a significant decrease in pain and disability when running.29,30 Therefore, with this gait retraining research in mind, sports podiatrists may consider suggesting that a rearfoot striking runner with anterior chronic exertional compartment syndrome should make a gradual change to a midfoot or forefoot striking running pattern due to the initial positive results reported by Diebal and colleagues in treating this disabling running injury.
In conclusion, the barefoot/minimalist shoe advocates and the “alternative running technique” advocates have made a number of claims about footstrike patterns in running over the past five years. Unfortunately, very few, if any, of these claims have any support within the scientific research literature.
Sports podiatrists who treat recreational and competitive runners need to be aware of the latest running research in order to be able to offer their patients thorough information and advice. Both recreational and competitive running athletes trust that sports podiatrists, as the foot and running shoe experts of their medical communities, are their best source for accurate information on running biomechanics, running injuries and proper footstrike patterns, and that the information they provide is based on scientific fact, not the latest fad.
Dr. Kirby is an Adjunct Associate Professor within 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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30. Diebal AR, Gregory R, Alitz C, Gerber JP. Forefoot running improves pain and disability associated with chronic exertional compartment syndrome. Am J Sports Med. 2012;40(5):1060-1067.