By Erik M. Haniuk, BS; LTC Steven J. Svoboda, MD; Karen Y. Peck, MEd, ATC; Kenneth L. Cameron, PhD, MPH, ATC; and LTC Brett D. Owens, MD
For the majority of evolutionary history, runners were either barefoot or wore minimalist footwear lacking the cushioning of today’s running shoes. Barefoot or minimally shod runners demonstrate differences1 in kinematics and impact forces compared with those wearing modern running shoes, and some research suggests barefoot running may confer biomechanical advantages over more cushioned footwear.2,3
Running barefoot on rough terrain or blacktop is not realistic or safe for a runner without some protection, and De Wit et al,2 for example, noted barefoot running offers little external protection from the elements and minimal external shock reduction. As a result, footwear manufacturers are developing and marketing barefoot-simulating footwear designed to provide minimal protection to the feet to emulate barefoot running without the worry of injuries such as the puncture wounds, cuts, or bruises that can result from running on rough surfaces.4
Barefoot simulating footwear is proving a popular, though controversial, alterative to traditional running shoes. Last month, barefoot-simulating footwear manufacturer Vibram USA was named the defendant in a class action suit, with the plaintiff alleging the company made misleading and scientifically unproven claims about benefits of its FiveFingers running shoes (see “Class action lawsuit alleges deceptive claims about barefoot-simulating shoes”). The complaint also noted the company has been highly successful with its marketing approach, reporting that sales of its minimalist footwear have increased 300% a year since 2006 and were approaching $70 million in 2011.
Barefoot-simulating footwear has been called a fad, but, according to Daniel Lieberman, PhD, a professor of human evolutionary biology at Harvard University and a high-profile researcher in the barefoot running field, “if you think barefoot running is a fad, then it’s a two-million-year-old fad.”5
Researchers have examined the mechanics of running barefoot or using barefoot-simulating footwear versus using a standard running shoe. However, the question of whether these types of footwear and running styles are associated with a reduced risk of running-related injuries is still unsettled.
Understanding the benefits and limitations of this type of running starts with an understanding of the foot strike mechanics associated with running in traditional running shoes in contrast to running barefoot or in barefoot-simulating footwear. Practitioners should also be aware of possible risk factors for injury suggested by existing medical and biomechanical research that are associated with the increased popularity of barefoot-simulating footwear.
The heel/rearfoot strike
Hasegawa et al6 classified rearfoot strike (RFS) as a running gait pattern in which the first contact of the runner’s foot with the ground is limited to the heel or the posterior third of the sole. Runners wearing traditional running shoes (shod runners) commonly adopt a RFS pattern.4 Because the majority of individuals run with a RFS pattern, the cushioned heel in the standard running shoe is designed to decrease plantar pressure in the heel in rearfoot strikers. Nearly 75% of marathon runners exhibited a RFS pattern at the 15-km mark in a recent study,6 which suggests this may be the most common foot strike pattern in this population.
The majority of today’s commercial running shoes are specifically designed and manufactured for the runner with a RFS pattern.6 Therefore, it is possible for the shod runner to comfortably adopt a RFS gait pattern with minimal peak pressure values under the heel.4 However, the increased padding and cushioning associated with traditional running shoes relative to barefoot-simulating footwear can reduce the runner’s ability to monitor the shock and impact forces experienced on foot contact with the ground,7 which may contribute to lower extremity injuries such as tibial stress and exertional compartment syndromes.
Forefoot and midfoot strike
In contrast to RFS, the forefoot strike (FFS) is a gait pattern in which the foot’s first point of contact with the ground is on the front half of the sole, and in which there is no heel contact during the strike phase of ambulation.6 A midfoot strike (MFS) is defined as a foot strike in which the first contact of the foot with the ground while running involves the middle portion of the foot or the entire sole.6
Research has shown foot strike position in runners using barefoot-simulating footwear is similar to foot strike position in individuals tested while running barefoot; changes in lower limb kinematics and kinetics relative to standard shod running were also similar for barefoot-simulating footwear and barefoot running.4 Kinematic data suggest that barefoot runners adopt a flatter foot placement at foot strike, adopting a FFS pattern rather than the traditional RFS pattern common to running in a standard shoe.4 This is most likely the reason for observed decreases in pressure values under the heel or the rearfoot in the well-designed study by Squadrone and Gallozzi.4 Unlike standard running shoes, barefoot-simulating footwear allows for enhanced shock-monitoring; this, however, may force most runners to alter their running gait, which may contribute to injury risk.7
Changing shoes and mechanics
The standard running shoe with which most runners are familiar is designed for the RFS pattern,4 as described above. In contrast, the introduction of barefoot running and barefoot-simulating footwear promotes an entirely different style of running that fosters a FFS pattern. Since the foot is the only body segment to directly transmit force to the ground during ambulation, it is more susceptible to injury during running than any other body part.6 Therefore, it is important to understand how the runner’s foot makes contact with the ground with or without footwear during the different phases of running.6 This is particularly true for runners who are new to running barefoot or in barefoot-simulating footwear. Runners and healthcare professionals must be knowledgeable about possible injury risks associated with switching from one style of running shoe to another without adequately altering gait mechanics; potential injuries related to such a change include stress fractures and other lower extremity overuse syndromes, as well as sprains and strains.8
Research has demonstrated that runners who switch to running shoes equipped with different cushioning material (e.g., a harder material) compensate by changing their running technique to reduce shock and achieve a comfortable level of sensation during impact with the ground, an observable phenomenon that researchers have termed “shock setting.”7 It is reasonable to hypothesize that the same process can occur with a switch from standard to barefoot-simulating footwear.
When a runner switches from regular running shoes to barefoot-simulating footwear, it is possible that the minimal amount of rubber and protective material on the shoe bottom still allows the runner to achieve a plantar sensation (shock setting) and induce an alternate running technique.4,7 For experienced runners who log significant mileage, changes of this nature without alterations to training volume may contribute to injury.8
The FFS pattern, the alternate technique that barefoot runners typically adopt, causes a reduction in peak pressure values under the heel and an increase in pressure under the metatarsal heads4 compared with running with the additional padding available in standard running shoes. It is well-documented that the second to fourth metatarsal bones of the foot are weakest with respect to cross-sectional area.9,10 However, it is the second and third metatarsals that encounter the most pressure during weightbearing activities.9,10 Metatarsal stress fracture is one of the most common overuse injuries in athletics, comprising of 3.7% of all sport-related injuries, with the second and third metatarsal bones accounting for the majority (80%-90%) of such fractures.9-12
Gait and training adaptations are essential to combat the injury risk conferred by the increased stress in alternate locations of the foot that occurs when runners switch to barefoot-simulating footwear.13 Runners with a history of long-term use of traditional running shoes may develop a weak foot structure and reduced sensitivity,4,14 and this may contribute to injury risk if the runner decides to transition to minimalist footwear. Such footwear was implicated recently as the cause of injury in two experienced runners diagnosed with second metatarsal stress fractures; a switch to barefoot-simulating running shoes three to six weeks prior to injury was only change to their running routines.8 This supports the idea that simply changing footwear without adequate changes to gait mechanics or training volume may contribute to injury when transitioning to barefoot-simulating shoes.
Studies indicate the majority of running-related injuries can be associated with training errors.15 The alterations in gait pattern and force attenuation associated with transitioning to barefoot-simulating footwear may affect experienced runners and novice runners differently. Compared with experienced runners, novice runners who have a running routine of minimal duration, frequency, and distance may be better able to adapt to a switch to minimalist footwear over an extended period of time as they progress at a moderate pace in their training.
To avoid injury when transitioning to barefoot running or minimalist footwear experienced runners should alter their gait pattern as well as the frequency, intensity, and duration of the training routine they use with standard running shoes. A training routine of high intensity and volume can result in training loads that are intolerable for the musculoskeletal system,16 and these loads can be further exacerbated with changes in footwear and gait mechanics that are new and unfamiliar to the runner. Therefore, gradual adaption to the new gait pattern and impact forces caused by minimalist footwear is essential to prevent stress injuries.8 Runners making the switch to bare feet or minimalist footwear should progress gradually in training volume to safely adopt a FFS pattern and adapt to the new force attenuation properties of the new shoe style and different surfaces. For experienced runners, some researchers16 have advocated initially limiting running in minimalist footwear or barefoot to approximately 5% to 10% of total training volume and gradually increasing the distance over time. It can take experienced runners three to six months to adapt to running a 5-km to 10-km distance barefoot, according to some reports.16
There are training programs in place to teach runners the proper running technique for adopting a FFS pattern, such as the one designed by Irene Davis, PT, PhD, director of the Spaulding National Running Center in Cambridge, MA. Her training program consists of eight sessions over a two-week period and teaches runners to land more softly on their forefeet rather than harder on their heels.5
Some notable advantages associated with barefoot running and MFS or FFS patterns have been proposed. Research has shown that running barefoot or with minimalist footwear leads to a reduction in stride length and, correspondingly, to a decrease in initial shock at impact.1,4
Hasegawa et al6 in 2004 analyzed 415 half-marathon runners and observed the foot position of each runner as he or she passed a certain point in the race. Although most runners used a RFS pattern, 25% of participants observed during the study did not use this technique. Runners who are already accustomed to running with a FFS pattern will have a safer and easier transition to minimalist footwear, but the majority of individuals should use caution with a gradual transition as described above to avoid potential injury.6,8
In addition, multiple studies have documented the effects of exertion and oxygen consumption of barefoot runners versus those using traditional running shoes.4,6,18,19 Squadron and Gallazzi4 reported that with barefoot-simulating footwear the runner required less oxygen consumption compared with individuals wearing traditional running shoes under identical conditions in which rate and distance remained constant.
In contrast, a 2012 study found that in a running population that predominately adopts the MFS, there is no difference in oxygen uptake (VO2) in those who run barefoot or in lightweight cushioned shoes. The investigators concluded that running in ultra-lightweight running shoes should provide a metabolic savings compared to running barefoot.20 However, they also noted that in runners not using lightweight running shoes, such as those used in this particular study, the added mass to the feet will increase oxygen uptake as stated in previous studies. For every 100 g added to the feet, VO2 increased 0.92% in barefoot runners and 1.92% in shod runners.20
Despite the existing evidence, the role of footwear in injury prevention remains controversial. The variety of running shoes on the market is vast and ever changing. Running shoe technology has continued to advance year after year. Since every runner is different, there are guidelines that recommend finding a style of running shoe that fits an individual’s particular foot structure20 to reduce injury and enhance a comfortable fit.
The idea that such individualized running footwear will prevent injury is widely accepted, but whether existing shoe guidance and fitting programs are effective in reducing injury is questionable. For example, in a recent well-designed study Knapik et al22 used manufacturer guidelines to prescribe running shoes to US Army recruits during basic training based on their static and weight-bearing plantar shape. The study went as far as controlling for unknown risk factors such as physical fitness, age, physical activity before basic training, smoking, and menstrual status. The results of this study suggest that individualizing footwear in this manner did not prevent injury in this high-risk population and should be discontinued
Barefoot-simulating footwear versus the standard running shoe has been an increasing topic of study in recent years; however, the matter of which running condition is better for today’s runners is still controversial. Some literature supports improvements in running technique and oxygen consumption with minimalist footwear and many runners are trending toward this alternative. However, when making a decision to switch from the standard running shoe to barefoot-simulating footwear, novice and experienced runners alike should also consider appropriate changes in their gait mechanics (e.g., adopting a FFS pattern) and training program (e.g., significant reductions in volume and intensity followed by gradual progression back to the individuals baseline levels) to avoid excessive overload and the risk of injury.
Erik M. Haniuk, BS, is a research assistant in the Department of Orthopaedic Research at Keller Army Community Hospital in West Point, NY, who will matriculate at The Ohio College of Podiatric Medicine this fall. LTC Steven J. Svoboda, MD, is director of the John A. Feagin Jr. Sports Medicine Fellowship; Karen Y. Peck, MEd, ATC, is a research analyst in the Department of Orthopaedic Research; Kenneth L. Cameron, PhD, MPH, ATC, is director of orthopaedic research for the fellowship; and LTC Brett D. Owens, MD is chief of orthopaedic surgery at Keller.
- Lieberman DE, Venkadesan M, Werbel WA, et al. Foot strike patterns and collision forces in habitually barefoot versus shod runners. Nature 2010;463(7280):531-535.
- De Wit B, De Clercq D, Aerts P. Biomechanical analysis of the stance phase during barefoot and shod running. J Biomech 2000;33(3):269-278.
- Divert C, Morineax G, Baur H, et al. Mechanical comparison of barefoot and shod running. Int J Sports Med 2005;26(7):593-598.
- 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(1):6-13.
- Nearman S. The science of barefoot running. AMAA Journal. Spring/Summer 2011.
- Hasegawa H, Yamauchi T, Kraemer WJ. Foot strike patterns of runners at the 15-km point during an elite-level half marathon. J Strength Cond Res 2007;21(3):888-893.
- Robbins SE, Gouw GJ. Athletic footwear and chronic overloading: A brief review. Sports Med 1990;9(2):76-85.
- Giuliani J, Masini B, Alitz C, Owens BD. Barefoot-simulating footwear associated with metatarsal stress injury in 2 runners. Orthopedics 2011;34(7):e320-323.
- Chuckpaiwong B, Cook C, Pietrobon R, Nunley JA. Second metatarsal stress fracture in sport: comparative risk factors between proximal and non-proximal locations. Br J Sports Med 2007;41(8):510-514.
- Griffen NL, Richmond BG. Cross-sectional geometry of the human forefoot. Bone 2005;37(2):253-260.
- Iwamoto J, Takeda T. Stress fractures in athletes: review of 196 cases. J Orthop Sci 2003;8(3):273-278.
- Weinfield SB, Haddad SL, Myerson MS. Metatarsal stress fractures. Clin Sports Med 1997;16(2):319-338.
- Divert C, Baur H, Mornieux G, et al. Stiffness adaptations in shod running. J Appl Biomech 2005;21(4):311-321.
- Siff MC, Verkhoshansky YV. Supertraining. 4th ed. Denver: Supertraining International;1999.
- Hreljac A. Impact and overuse injuries in runners. Med Sci Sports Exerc 2004;36(5):845-849.
- Henry D. Barefoot running has become trendy, is it safe? The Beaumont Enterprise. March 9, 2012. http://www.beaumontenterprise.com/news/article/Barefoot-running-has-become-trendy-is-it-safe-3393253.php. Accessed April 10, 2012.
- Gabbett TJ. Reductions in pre-season training loads reduce training injury rates in rugby league players. Br J Sports Med 2004;38(6):743-749.
- Burkett LN, Kohrt WM, Buchbinder R. Effects of shoes and foot orthotics on VO2 and selected frontal plane knee kinematics. Med Sci Sports Exerc 1985;17(1):158-163.
- Hanson NJ, Berg K, Deka P, et al. Oxygen cost of running barefoot vs. shod running. Int J Sports Med 2011;32(6):401-406.
- Franz JR, Wierzbinski CM, Kram R. Metabolic cost of running barefoot versus shod: is lighter better? Med Sci Sports Exerc 2012 Mar 2. [Epub ahead of print]
- ePodiatry.com. Running shoes. Available at http://www.epodiatry.com/running-shoes.htm. Accessed December 2011.
- Knapik JJ, Swedler DI, Grier TL, et al. Injury reduction effectiveness of selecting running shoes based on plantar shape. J Strength Cond Res 2009;23(3):685-697.