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Minimalist shoe injuries: Three case reports
G Model YFOOT-1273; No. of Pages 4
ARTICLE IN PRESS The Foot xxx (2013) xxx–xxx
Contents lists available at SciVerse ScienceDirect
The Foot journal homepage: www.elsevier.com/locate/foot
Case report
Minimalist shoe injuries: Three case reports David J. Cauthon a , Paul Langer b,∗ , Thomas C. Coniglione c a
Division of Podiatric Medicine and Surgery, Department of Orthopedic Surgery, University of Texas Health Science Center at San Antonio, United States Twin Cities Orthopedics, Adjunct Clinical Professor, University of Minnesota Medical School, 701 25th Avenue South Suite 505, Minneapolis, MN 55454, United States c Oklahoma Sports Science, United States b
a r t i c l e
i n f o
Article history: Received 22 August 2012 Received in revised form 26 February 2013 Accepted 13 March 2013 Keywords: Minimalist shoes Injury Running
a b s t r a c t Running in minimalist shoes continues to increase in popularity and multiple mainstream shoe companies now offer minimalist shoes. While there is no evidence that traditional running shoes prevent injuries, there are concerns that the designs of minimalist shoes may increase injury risk. However, reports of injuries in runners wearing minimalist shoes are rare. We present three injuries occurring in runners that were wearing minimalist shoes at the time of injury. All three of the runners switched immediately to the minimalist shoes with no transition period. We recommend that any transition to minimalist shoe gear be performed gradually. It is our contention that these injuries are quite common and will continue to become more prevalent as more runners change to these shoes. © 2013 Published by Elsevier Ltd.
1. Introduction Running in minimalist shoes continues to increase in popularity. Part of what is driving the current trend toward minimalist footwear is the continued high injury rate among average runners while wearing traditional running shoes. Several authors have questioned the evidence behind the recommendation of cushioned, pronation control shoes [1–3]. The most substantial article was a systematic review written by Richards et al. in 2009. They state that there is no evidence supporting the use of cushioned, pronationcontrol shoes in distance running [4]. A significant proportion of long-distance runners become injured every year. Most of these injuries are chronic, overuse injuries of the lower extremities. In 1982, Koplan et al. found that 35% of 10 km racers (men and women) had sustained an injury in the year prior to the survey [5]. In 1986, Jacobs and Berson found an injury rate of 47% with the most common injuries being knee pain, ankle pain, and shin splints [6]. Recently, Van Middelkoop et al. found the injury rate to be 54.8% amongst male participants of the 2005 Rotterdam marathon with the most common injuries being the knee, the calf and the foot [7]. The injury rate continues to be approximately the same as it was 25 years ago despite advances made in running shoe technology. It is important to point out that in 1980, there were 143,000 American marathon finishers, 90% of which were male with a median finishing time of 3 h 32 min. In 2005, there were 395,000 marathon finishers, of which
∗ Corresponding author. Tel.: +1 612 455 2008x228; fax: +1 612 455 2009. E-mail address: [email protected] (P. Langer).
men made up 59% of the field and the median finishing time was 4 h 20 min [8]. The demographics of the running community have greatly changed in 25 years and, therefore, comparisons of injury rates cannot be completely valid. While inadequate or improper footwear has been implicated as one of the extrinsic risk factors in overuse injuries to runners, approximately 60% of running injuries have been attributed to training errors [9]. It could certainly be argued that injuries sustained in minimalist footwear may be due to a training error in that the runners may not have allowed a proper gradual transition to the different footwear condition. In two of the following cases the runners acknowledged making rather abrupt transition from their previous conventional running footwear. Multiple footwear manufacturers now offer self-described “minimalist shoes” despite the lack of an industry standard or formal definition of what constitutes this type of footwear. These minimalist shoes are generally placed in this category based on a combination of factors and done so at the discretion of the manufactures. They typically contain less midsole cushioning, have a lower heel-to-forefoot height differential, are lighter in weight and may lack stabilizing devices such as shanks or medial posts than do conventional running shoes. Some shoes are placed in this category because of only one or two of the factors, which causes a blurring of the line between minimalist shoes and traditional running shoes. A recent Internet search found shoes that were advertised as minimalist vary in weight from 2.2 oz. to 9.9 oz., had midsole/outsole thicknesses ranging from 4 mm to 20 mm and heel-to forefoot height differentials of zero to 10 mm [10]. Richards proposed the term “pronation control, cushioned elevated heel (PCECH)” to describe traditional running shoes [4] and, despite the lack of defined parameters, we accept this description and use
0958-2592/$ – see front matter © 2013 Published by Elsevier Ltd. http://dx.doi.org/10.1016/j.foot.2013.03.001
Please cite this article in press as: http://dx.doi.org/10.1016/j.foot.2013.03.001
Cauthon
DJ,
et
al.
Minimalist
shoe
injuries:
Three
case
reports.
Foot
(2013),
G Model YFOOT-1273; No. of Pages 4
ARTICLE IN PRESS D.J. Cauthon et al. / The Foot xxx (2013) xxx–xxx
2
Fig. 1. A runner demonstrating common foot strike kinematic differences in gate between conventional shoe (Fig. 1) and minimalist shoe (Fig. 2). Note flatter foot placement in minimalist shoe at contact and heel strike in conventional shoe.
it as a reference point. A search of MEDLINE (1950–June 2012) reveals that there is currently no accepted definition of the term “minimalist shoe” in the medical literature. Each of the three shoe models in this series of cases was marketed by their individual manufacturers as “minimalist”, “barefoot-like” and/or “natural”. All had varying degrees of: lower heel-to-forefoot height differential, lighter weight, less midsole cushioning and thickness as compared to PCECH footwear. In addition, all lacked midsole stability devices such as medial posts or shanks. There are many claims in the popular press about the reduced injury rate in barefoot runners versus shod runners [11–13]. These claims are then extrapolated by shoe manufacturers claiming that using their shoes is like being barefoot. Some of these shoes have indeed been determined to be like the barefoot condition in some ways [14–16]. Most of the claims of reduced injuries are extrapolated from biomechanical studies performed in laboratory situations and there are no published studies in the literature comparing the rates of injuries between barefoot, minimalist shoes and traditional running shoes [4]. Recently, the first article describing injuries occurring while wearing minimalist shoes was published. The article included eight metatarsal stress fractures, one calcaneal stress fracture and one plantar fascia rupture [17]. One claim made by proponents of minimalist shoes is that impact forces are lower when running with a barefoot style. Laboratory studies have demonstrated that barefoot runners have a lower peak impact due to adaptations in gait [14,18–20]. Several authors have suggested that high impact forces in running are part of the reason for injuries [21,9,22]. Nigg has recently called this finding into question because of the paucity of research [23]. Indeed, Hreljac states that as long as rest periods are adequate, structures will adapt to high impact forces and chronic low impact forces will actually weaken bones and supporting structures [24]. Another claim is that barefoot runners have better ankle stability. Subjects do have improved proprioception [25] and increased lateral stability while barefoot [26] which may reduce the incidence of ankle sprains. While ankle sprains are among the most common sport injuries, they typically occur in sports with sideward cutting movements and not in distance running [27] (Fig. 1). It has been speculated that wearers of minimalist shoes will acquire different types of injuries than those wearing traditional running shoes. Given the plantarflexed landing style, minimalist runners may be more at risk for Achilles tendon or gastrocsoleus injuries [28]. With the impact forces occurring at the midfoot there may be an increased risk of injuries to the metatarsals such as stress fractures or plantar plate disruptions [17]. We present three injuries occurring in runners that were wearing minimalist shoes at the time of injury. This article serves as a description of the types of injuries that occur while wearing
Please cite this article in press as: http://dx.doi.org/10.1016/j.foot.2013.03.001
Cauthon
DJ,
et
al.
Fig. 2.
minimalist shoes and does not attempt to quantify these injuries. A cohort study will need to be undertaken to provide epidemiological data of these injuries. Ultimately, a randomized controlled trial is needed to compare the rates of injuries between wearers of minimalist shoes and traditional running shoes. 2. Case report 1: Achilles tendinopathy A 26 year old female presented to clinic with a chief complaint of left posterior lower leg pain. She was a recreational runner who averaged 30 miles per week but was increasing her mileage as she was training for a marathon. She had purchased a minimalist shoe and immediately ran exclusively without any graduated transition from her conventional shoes. She described ankle and lower leg soreness on her left side that developed soon after switching to minimalist shoes. Her minimalist shoe had some midsole cushioning and 4 mm of heel height differential. Her previous shoe was a stability running shoe with a 12 mm heel height differential. Her pain became progressively worse as her mileage increased. Her last run before presenting to clinic was a 20 mile run. During this run her pain worsened to the point that she was limping and visibly swollen to her posterior lower leg and heel afterward. Past medical history was unremarkable. She was taking an oral contraceptive. She had no previous lower extremity injuries or trauma. She had run recreationally for 5+ years, had done four previous marathons, and also swam and biked for fitness. She reported no changes in terms of the mileage and intensity of her training or training surface in relation to her previous marathon training routine. She was in the habit of wearing dress shoes with a 2–4 inch heel for her work. At the time of presentation to clinic, the patient was able to walk without limping and had not run for five days. Physical exam revealed pain and crepitus without fusiform tendon swelling to mid-substance of the left Achilles tendon. She had pain with both active and passive ankle dorsiflexion as well as pain with toe walking. Patient also had pain to palpation without crepitus or edema of her right Achilles that she had been unaware of prior to the exam. Ankle range of motion was normal and symmetric bilaterally as was manual muscle strength testing. She demonstrated a mildly pronated subtalar joint symmetric and bilateral in gait with a resting calcaneal stance position of 2 degrees everted bilateral. Running gait exam was deferred since the patient was injured. Treatment consisted of avoidance of running and initiation of physical therapy which utilized depomedrol iontophoresis, cross frictional massage, stretching modalities and a progression to eccentric triceps surae strengthening exercises. At 4 weeks she was pain free and a graduated running program was restarted with her conventional running shoes. She was able to gradually increase her
Minimalist
shoe
injuries:
Three
case
reports.
Foot
(2013),
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ARTICLE IN PRESS D.J. Cauthon et al. / The Foot xxx (2013) xxx–xxx
mileage without any problems and at the time of discharge she was running 15 miles per week. 3. Case report 2: Achilles tendinopathy A 29-year old female presented to clinic with pain and swelling in her lower posterior right leg. Fourteen weeks prior to presentation, shortly after running her fourth marathon, she switched from the neutral plus shoe she had worn for 2 years to a well-advertised “minimalist” shoe with a 6 mm heel height differential. In this new shoe, she continued to maintain a weekly average of 25 miles consisting of 3–4 runs per week including one longer weekend run. During this time, she ran two 5K races and did minimal hill running which was her typical training program. Beginning 10 weeks prior to presentation, she noted morning and post-run aching in the Achilles tendon. By 6 weeks before being seen, she had aching and pain in the Achilles prior to starting her runs, improving during the run only to return 1–2 h following completion of the run. After running the Achilles would tighten whenever she sat for a few minutes. The morning following a run, there was marked tightness and pain in the Achilles when arising. By decreasing her mileage and running less often, the pain seemed to improve. Because of continued pain, three weeks prior to presentation she stopped running. For exercise she used the elliptical trainer and stationery bike. She engaged in no plyometrics, no step aerobics, did minimal stretching and iced the area for a few minutes after each workout. Walking in high heeled shoes provided some relief of the tightness and pain. Whenever she tried to run the pain returned. Because of continued morning pain and tightness combined with the inability to return to running, she presented for evaluation. On exam the most striking finding was fusiform swelling of the Achilles tendon 2–5 cm above its insertion into the calcaneus. This area was tender to compression. No definite nodule was palpable. There was minimal swelling and tenderness with palpation of the retrocalcaneal bursa. Thompson’s Test was negative. The affected gastroachilles complex was tighter than the unaffected side. Subtalar motion was about 5 degrees in each direction. There were minimal forefoot calluses. Walking with a 1/2 heel wedge was more comfortable than walking barefoot. With a diagnosis of Achilles tendonitis, the patient was prescribed a 1/2 heel lift, gentle static gastroachilles stretching exercises, intermittent cryotherapy and formal physical therapy. Because the use of a friend’s plantar fascia night splint helped the morning stiffness, it was recommended she use the splint regularly. After 2 weeks of therapy the pain and morning stiffness were improved. With the aid of a 1/2 heel lift she was able to walk comfortably. Within 6 weeks she resumed light jogging using her former running shoe. The plan was to hold her jogging to minimal levels until the swollen Achilles had totally resolved.
3
was significantly delayed, and the duration of soleus and lateral gastrocnemius activity was increased in those with Achilles tendinopathy. It is possible that this timing imbalance, particularly the increased duration of activity of the ankle plantarflexors may create prolonged loading of the Achilles tendon and contribute to tendinopathy development. Additionally, reduced function of tibialis anterior has been theorized to reduce stiffness of the tendon-muscular system in the lower limb and impede its ability to tolerate and absorb impact forces [31]. This could create increased Achilles tendon loading and lead to tendinopathy. 5. Case report 3: metatarsal stress fracture A 35 year old male marathon runner presented to clinic with chief complaint of pain and swelling to his right forefoot. He had been averaging 25 miles per week for the previous 6 months but had transitioned to a pair of minimalist shoes with the plan of running his next marathon in them. He had been running approximately 3 weeks in the new shoes at the time of presentation. Patient described a gradual onset of pain to his foot pain almost as soon as he started to run in the minimalist shoe. He described an ache to his foot toward the end of runs that would resolve with rest and wearing conventional shoes. He stated that he had expected some “aches and pains” as he made the transition so was not concerned about the persisting pain. On the day that his pain forced him to stop running and seek treatment, he was doing a 12 mile run at a faster pace on sidewalks. His pain worsened to become intense as the run progressed and after completing the run he noticed his foot was swollen. He then sought medical treatment. The patient’s past medical history was unremarkable and he was not taking any medications. His previous running-related injuries include plantar fasciitis and iliotibial band syndrome both of which resolved with rest and physical therapy. The patient had been an avid runner for 8+ years gradually progressing from shorter races to marathons. He had discontinued running in conventional cushioned running shoes as he began his 12 week marathon training program and was following the same marathon program that he had used previously. This marathon training program included a standard gradual increase in mileage that was to peak a few weeks prior to his goal race. On exam, he was limping and had visible and palpable edema to his dorsal right foot with focal pain localized to the shaft of the 3rd metatarsal. No significant biomechanical, strength, or rangeof-motion abnormalities were present. Initial radiographs were negative for fracture but a presumptive diagnosis of 3rd metatarsal stress fracture was made and the patient was placed in a walking cast with instructions to discontinue running and follow up in 2–4 weeks to assess improvement and repeat radiographs. Subsequent follow up radiographs confirmed a stress fracture of the 3rd metatarsal. Patient was able to transition out of the cam boot at week 4 and returned to running in conventional shoes at week 10 without complications.
4. Discussion 6. Discussion The two injuries presented occurred in shoes with heel height differentials of 6 mm or less. This represents the height of the heel compared to the height of the forefoot of the shoe. In the barefoot condition this heel height differential is zero. In the barefoot condition, the gastrosoleus is activated earlier and for a longer duration in order to land with a plantarflexed footstrike [29]. This increased duration of gastrosoleus activation was also found in patients with Achilles tendinopathy. Two studies compared EMG amplitude and onset timing of a number of lower limb muscles in those with and without Achilles tendinopathy [30,31]. Notably, the onset of tibialis anterior activity
Please cite this article in press as: http://dx.doi.org/10.1016/j.foot.2013.03.001
Cauthon
DJ,
et
al.
Running in minimalist shoes with a low heel height differential, like barefoot, results in greater, earlier plantarflexion [14,15] recruiting the flexor digitorum longus to assist [32] thus leading to fatigue of the flexor digitorum longus which causes increased compression strain on the metatarsals [33]. It has been theorized that this increased compression strain leads to metatarsal stress fractures [34]. An alternative explanation is that the impact force in minimalist runners is directed toward the metatarsals instead of the calcaneus, due to the midfoot or forefoot landing style [17].
Minimalist
shoe
injuries:
Three
case
reports.
Foot
(2013),
G Model YFOOT-1273; No. of Pages 4
ARTICLE IN PRESS D.J. Cauthon et al. / The Foot xxx (2013) xxx–xxx
4
7. Conclusion We have presented three injuries occurring in runners after switching from traditional cushioned running shoes to minimalist shoes. In two of the three cases, the runners switched to minimalist shoes while at the same time increasing weekly mileage. All three of the runners switched immediately to the minimalist shoes with no transition period. We recommend that any increase in weekly mileage is performed gradually and in shoe gear that has been proven for that particular runner. We also recommend that any transition to minimalist shoe gear be performed gradually. To our knowledge, this is only the second article documented in the literature, although it is our contention that these injuries are quite common and will continue to become more prevalent as more runners change to these shoes. Conflict of interest statement The authors have no conflicts of interest to disclose. Funding No funding was received for this work. References [1] Robbins SE, Gouw GJ. Athletic footwear and chronic overloading. A brief review. Sports Medicine 1990;9(2):76–85. [2] Rossi WA. Why shoes make “normal” gait impossible. Podiatry Management 1999;(March):50. [3] Clinghan R, Arnold GP, Drew TS, et al. Do you get value for money when you buy an expensive pair of running shoes? British Journal of Sports Medicine 2008;42:189–93. [4] Richards CE, Magin PJ, Callister R. Is your prescription of distance running shoes evidenced-based? British Journal of Sports Medicine 2009;43: 159–62. [5] Koplan JP, Powell KE, Sikes RK, et al. An epidemiologic study of the benefits and risks of running. Journal of the American Medical Association 1982;248:3118–21. [6] Jacobs SJ, Berson BL. Injuries to runners: a study of entrants to a 10,000 meter race. American Journal of Sports Medicine 1986;14:151–5. [7] Van Middelkoop M, Kolkman J, Van Ochten J, et al. Risk factors for lower extremity injuries among male marathon runners. Scandinavian Journal of Medicine and Science in Sports 2008;18(6):691–7. [8] Running USA State of the Sport Report. www.runningusa.org/node/76115 [accessed 26.08.11]. [9] James SL, Bates BT, Osternig LR. Injuries to runners. American Journal of Sports Medicine 1978;6:40–50. [10] Internet search via Google August 14, 2012.
Please cite this article in press as: http://dx.doi.org/10.1016/j.foot.2013.03.001
Cauthon
DJ,
et
al.
[11] McDougall C. In: Alfred A, editor. Born to run: a hidden tribe, superathletes, and the greatest race the world has never seen. 1st ed. New York: Knopf/Random House; 2009. p. 16 [Chapter 2]. [12] Parker-pope T. Is barefoot better? Some athletes say running shoeless benefits body and sole. The Wall Street Journal 2006;(June):D1. [13] Burfoot A. Should you be running barefoot? Runner’s World 2004;39(8):61. [14] Squadrone R, Gallozzi C. Biomechanical and physiological comparison of barefoot and two shod conditions in experienced barefoot runners. Journal of Sports Medicine and Physical Fitness 2009;49:6–13. [15] Nigg B. Biomechanical considerations on barefoot movement and barefoot shoe concepts. Footwear Science 2009;1:73. [16] Bruggemann G, Potthast W, Braunstein B, et al. Effect of increased mechanical stimuli on foot muscles functional capacity [online abstract]. American Society of Biomechanics Web site. Available at: http://www.asbweb.org/conferences/ 2005/pdf/0553.pdf [accessed 12.06.12]. [17] Salzler MJ, Bluman EM, Noonan S, et al. Injuries observed in minimalist runners. Foot and Ankle International 2012;33(4):262–6. [18] Divert C, Mornieux G, Baur H, et al. Mechanical comparison of barefoot and shod running. International Journal of Sports Medicine 2005;26:593. [19] Lieberman D, Venkadesan M, Werbel W, et al. Foot strike patterns and collision forces in habitually barefoot versus shod runners. Nature 2010;463:531–5. [20] Divert C, Baur H, Mornieux G, et al. Stiffness adaptations in shod running. Journal of Applied Biomechanics 2005;21:311–21. [21] Cavanagh PR, Lafortune MA. Ground reaction forces in distance running. Journal of Biomechanics 1980;13:397–406. [22] Nigg BM. Biomechanical aspects of running. In: Nigg BM, editor. Biomechanics of running shoes. Champaign, IL: Human Kinetics; 1986. p. 1–25. [23] Nigg B. Biomechanical considerations on barefoot movement and barefoot shoe concepts. Footwear Science 2009;1:73–9. [24] Hreljac A. Impact and overuse injuries in runners. Medicine and Science in Sports and Exercise 2004;36:845–9. [25] Robbins S, Waked E, Mcclaran J. Proprioception and stability: foot position awareness as a function of age and footwear. Age and Ageing 1995;24:67–72. [26] Robbins S, Waked E, Rappel R. Ankle taping improves proprioception before and after exercise in young men. British Journal of Sports Medicine 1995;29:242. [27] Stacoff A, Denoth J, Kalin X, et al. Running injuries and shoe construction: some possible relationships. International Journal of Sport Biomechanics 1988;4:342. [28] Jenkins DW, Cauthon DJ. Barefoot running claims and controversy: a review of the literature. Journal of the American Podiatric Medical Association 2011;101:231. [29] Komi PV, Golhofer A, Schmidtbleicher D, et al. Interaction between man and shoe in running: considerations for a more comprehensive measurement approach. International Journal of Sports Medicine 1987;8:196–202. [30] Baur H, Divert C, Hirschmuller A, Muller S, Belli A, Mayer F. Analysis of gait differences in healthy runners and runners with chronic Achilles tendon complaints. Isokinetics and Exercise Science 2004;12(2):111–6. [31] Azevedo LB, Lambert MI, Vaughan CL, et al. Biomechanical variables associated with Achilles tendinopathy in runners. British Journal of Sports Medicine 2009;43:292–9. [32] Coughlin MJ, Schon LC. Disorders of tendons. In: Coughlin MJ, Mann RA, Saltzman CL, editors. Surgery of the foot and ankle. Philadelphia: Mosby Elsevier; 2007. p. 1262–3. [33] Arndt A, Ekenman I, Westblad P, Lundberg A. Effects of fatigue and load variation on metatarsal deformation measured in vivo during barefoot walking. Journal of Biomechanics 2002;35:621–8. [34] Buckwalter JA, Brandser EA. Stress and insufficiency fractures. American Family Physician 2002;56(1):175–82.
Minimalist
shoe
injuries:
Three
case
reports.
Foot
(2013),
ARTICLE IN PRESS The Foot xxx (2013) xxx–xxx
Contents lists available at SciVerse ScienceDirect
The Foot journal homepage: www.elsevier.com/locate/foot
Case report
Minimalist shoe injuries: Three case reports David J. Cauthon a , Paul Langer b,∗ , Thomas C. Coniglione c a
Division of Podiatric Medicine and Surgery, Department of Orthopedic Surgery, University of Texas Health Science Center at San Antonio, United States Twin Cities Orthopedics, Adjunct Clinical Professor, University of Minnesota Medical School, 701 25th Avenue South Suite 505, Minneapolis, MN 55454, United States c Oklahoma Sports Science, United States b
a r t i c l e
i n f o
Article history: Received 22 August 2012 Received in revised form 26 February 2013 Accepted 13 March 2013 Keywords: Minimalist shoes Injury Running
a b s t r a c t Running in minimalist shoes continues to increase in popularity and multiple mainstream shoe companies now offer minimalist shoes. While there is no evidence that traditional running shoes prevent injuries, there are concerns that the designs of minimalist shoes may increase injury risk. However, reports of injuries in runners wearing minimalist shoes are rare. We present three injuries occurring in runners that were wearing minimalist shoes at the time of injury. All three of the runners switched immediately to the minimalist shoes with no transition period. We recommend that any transition to minimalist shoe gear be performed gradually. It is our contention that these injuries are quite common and will continue to become more prevalent as more runners change to these shoes. © 2013 Published by Elsevier Ltd.
1. Introduction Running in minimalist shoes continues to increase in popularity. Part of what is driving the current trend toward minimalist footwear is the continued high injury rate among average runners while wearing traditional running shoes. Several authors have questioned the evidence behind the recommendation of cushioned, pronation control shoes [1–3]. The most substantial article was a systematic review written by Richards et al. in 2009. They state that there is no evidence supporting the use of cushioned, pronationcontrol shoes in distance running [4]. A significant proportion of long-distance runners become injured every year. Most of these injuries are chronic, overuse injuries of the lower extremities. In 1982, Koplan et al. found that 35% of 10 km racers (men and women) had sustained an injury in the year prior to the survey [5]. In 1986, Jacobs and Berson found an injury rate of 47% with the most common injuries being knee pain, ankle pain, and shin splints [6]. Recently, Van Middelkoop et al. found the injury rate to be 54.8% amongst male participants of the 2005 Rotterdam marathon with the most common injuries being the knee, the calf and the foot [7]. The injury rate continues to be approximately the same as it was 25 years ago despite advances made in running shoe technology. It is important to point out that in 1980, there were 143,000 American marathon finishers, 90% of which were male with a median finishing time of 3 h 32 min. In 2005, there were 395,000 marathon finishers, of which
∗ Corresponding author. Tel.: +1 612 455 2008x228; fax: +1 612 455 2009. E-mail address: [email protected] (P. Langer).
men made up 59% of the field and the median finishing time was 4 h 20 min [8]. The demographics of the running community have greatly changed in 25 years and, therefore, comparisons of injury rates cannot be completely valid. While inadequate or improper footwear has been implicated as one of the extrinsic risk factors in overuse injuries to runners, approximately 60% of running injuries have been attributed to training errors [9]. It could certainly be argued that injuries sustained in minimalist footwear may be due to a training error in that the runners may not have allowed a proper gradual transition to the different footwear condition. In two of the following cases the runners acknowledged making rather abrupt transition from their previous conventional running footwear. Multiple footwear manufacturers now offer self-described “minimalist shoes” despite the lack of an industry standard or formal definition of what constitutes this type of footwear. These minimalist shoes are generally placed in this category based on a combination of factors and done so at the discretion of the manufactures. They typically contain less midsole cushioning, have a lower heel-to-forefoot height differential, are lighter in weight and may lack stabilizing devices such as shanks or medial posts than do conventional running shoes. Some shoes are placed in this category because of only one or two of the factors, which causes a blurring of the line between minimalist shoes and traditional running shoes. A recent Internet search found shoes that were advertised as minimalist vary in weight from 2.2 oz. to 9.9 oz., had midsole/outsole thicknesses ranging from 4 mm to 20 mm and heel-to forefoot height differentials of zero to 10 mm [10]. Richards proposed the term “pronation control, cushioned elevated heel (PCECH)” to describe traditional running shoes [4] and, despite the lack of defined parameters, we accept this description and use
0958-2592/$ – see front matter © 2013 Published by Elsevier Ltd. http://dx.doi.org/10.1016/j.foot.2013.03.001
Please cite this article in press as: http://dx.doi.org/10.1016/j.foot.2013.03.001
Cauthon
DJ,
et
al.
Minimalist
shoe
injuries:
Three
case
reports.
Foot
(2013),
G Model YFOOT-1273; No. of Pages 4
ARTICLE IN PRESS D.J. Cauthon et al. / The Foot xxx (2013) xxx–xxx
2
Fig. 1. A runner demonstrating common foot strike kinematic differences in gate between conventional shoe (Fig. 1) and minimalist shoe (Fig. 2). Note flatter foot placement in minimalist shoe at contact and heel strike in conventional shoe.
it as a reference point. A search of MEDLINE (1950–June 2012) reveals that there is currently no accepted definition of the term “minimalist shoe” in the medical literature. Each of the three shoe models in this series of cases was marketed by their individual manufacturers as “minimalist”, “barefoot-like” and/or “natural”. All had varying degrees of: lower heel-to-forefoot height differential, lighter weight, less midsole cushioning and thickness as compared to PCECH footwear. In addition, all lacked midsole stability devices such as medial posts or shanks. There are many claims in the popular press about the reduced injury rate in barefoot runners versus shod runners [11–13]. These claims are then extrapolated by shoe manufacturers claiming that using their shoes is like being barefoot. Some of these shoes have indeed been determined to be like the barefoot condition in some ways [14–16]. Most of the claims of reduced injuries are extrapolated from biomechanical studies performed in laboratory situations and there are no published studies in the literature comparing the rates of injuries between barefoot, minimalist shoes and traditional running shoes [4]. Recently, the first article describing injuries occurring while wearing minimalist shoes was published. The article included eight metatarsal stress fractures, one calcaneal stress fracture and one plantar fascia rupture [17]. One claim made by proponents of minimalist shoes is that impact forces are lower when running with a barefoot style. Laboratory studies have demonstrated that barefoot runners have a lower peak impact due to adaptations in gait [14,18–20]. Several authors have suggested that high impact forces in running are part of the reason for injuries [21,9,22]. Nigg has recently called this finding into question because of the paucity of research [23]. Indeed, Hreljac states that as long as rest periods are adequate, structures will adapt to high impact forces and chronic low impact forces will actually weaken bones and supporting structures [24]. Another claim is that barefoot runners have better ankle stability. Subjects do have improved proprioception [25] and increased lateral stability while barefoot [26] which may reduce the incidence of ankle sprains. While ankle sprains are among the most common sport injuries, they typically occur in sports with sideward cutting movements and not in distance running [27] (Fig. 1). It has been speculated that wearers of minimalist shoes will acquire different types of injuries than those wearing traditional running shoes. Given the plantarflexed landing style, minimalist runners may be more at risk for Achilles tendon or gastrocsoleus injuries [28]. With the impact forces occurring at the midfoot there may be an increased risk of injuries to the metatarsals such as stress fractures or plantar plate disruptions [17]. We present three injuries occurring in runners that were wearing minimalist shoes at the time of injury. This article serves as a description of the types of injuries that occur while wearing
Please cite this article in press as: http://dx.doi.org/10.1016/j.foot.2013.03.001
Cauthon
DJ,
et
al.
Fig. 2.
minimalist shoes and does not attempt to quantify these injuries. A cohort study will need to be undertaken to provide epidemiological data of these injuries. Ultimately, a randomized controlled trial is needed to compare the rates of injuries between wearers of minimalist shoes and traditional running shoes. 2. Case report 1: Achilles tendinopathy A 26 year old female presented to clinic with a chief complaint of left posterior lower leg pain. She was a recreational runner who averaged 30 miles per week but was increasing her mileage as she was training for a marathon. She had purchased a minimalist shoe and immediately ran exclusively without any graduated transition from her conventional shoes. She described ankle and lower leg soreness on her left side that developed soon after switching to minimalist shoes. Her minimalist shoe had some midsole cushioning and 4 mm of heel height differential. Her previous shoe was a stability running shoe with a 12 mm heel height differential. Her pain became progressively worse as her mileage increased. Her last run before presenting to clinic was a 20 mile run. During this run her pain worsened to the point that she was limping and visibly swollen to her posterior lower leg and heel afterward. Past medical history was unremarkable. She was taking an oral contraceptive. She had no previous lower extremity injuries or trauma. She had run recreationally for 5+ years, had done four previous marathons, and also swam and biked for fitness. She reported no changes in terms of the mileage and intensity of her training or training surface in relation to her previous marathon training routine. She was in the habit of wearing dress shoes with a 2–4 inch heel for her work. At the time of presentation to clinic, the patient was able to walk without limping and had not run for five days. Physical exam revealed pain and crepitus without fusiform tendon swelling to mid-substance of the left Achilles tendon. She had pain with both active and passive ankle dorsiflexion as well as pain with toe walking. Patient also had pain to palpation without crepitus or edema of her right Achilles that she had been unaware of prior to the exam. Ankle range of motion was normal and symmetric bilaterally as was manual muscle strength testing. She demonstrated a mildly pronated subtalar joint symmetric and bilateral in gait with a resting calcaneal stance position of 2 degrees everted bilateral. Running gait exam was deferred since the patient was injured. Treatment consisted of avoidance of running and initiation of physical therapy which utilized depomedrol iontophoresis, cross frictional massage, stretching modalities and a progression to eccentric triceps surae strengthening exercises. At 4 weeks she was pain free and a graduated running program was restarted with her conventional running shoes. She was able to gradually increase her
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mileage without any problems and at the time of discharge she was running 15 miles per week. 3. Case report 2: Achilles tendinopathy A 29-year old female presented to clinic with pain and swelling in her lower posterior right leg. Fourteen weeks prior to presentation, shortly after running her fourth marathon, she switched from the neutral plus shoe she had worn for 2 years to a well-advertised “minimalist” shoe with a 6 mm heel height differential. In this new shoe, she continued to maintain a weekly average of 25 miles consisting of 3–4 runs per week including one longer weekend run. During this time, she ran two 5K races and did minimal hill running which was her typical training program. Beginning 10 weeks prior to presentation, she noted morning and post-run aching in the Achilles tendon. By 6 weeks before being seen, she had aching and pain in the Achilles prior to starting her runs, improving during the run only to return 1–2 h following completion of the run. After running the Achilles would tighten whenever she sat for a few minutes. The morning following a run, there was marked tightness and pain in the Achilles when arising. By decreasing her mileage and running less often, the pain seemed to improve. Because of continued pain, three weeks prior to presentation she stopped running. For exercise she used the elliptical trainer and stationery bike. She engaged in no plyometrics, no step aerobics, did minimal stretching and iced the area for a few minutes after each workout. Walking in high heeled shoes provided some relief of the tightness and pain. Whenever she tried to run the pain returned. Because of continued morning pain and tightness combined with the inability to return to running, she presented for evaluation. On exam the most striking finding was fusiform swelling of the Achilles tendon 2–5 cm above its insertion into the calcaneus. This area was tender to compression. No definite nodule was palpable. There was minimal swelling and tenderness with palpation of the retrocalcaneal bursa. Thompson’s Test was negative. The affected gastroachilles complex was tighter than the unaffected side. Subtalar motion was about 5 degrees in each direction. There were minimal forefoot calluses. Walking with a 1/2 heel wedge was more comfortable than walking barefoot. With a diagnosis of Achilles tendonitis, the patient was prescribed a 1/2 heel lift, gentle static gastroachilles stretching exercises, intermittent cryotherapy and formal physical therapy. Because the use of a friend’s plantar fascia night splint helped the morning stiffness, it was recommended she use the splint regularly. After 2 weeks of therapy the pain and morning stiffness were improved. With the aid of a 1/2 heel lift she was able to walk comfortably. Within 6 weeks she resumed light jogging using her former running shoe. The plan was to hold her jogging to minimal levels until the swollen Achilles had totally resolved.
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was significantly delayed, and the duration of soleus and lateral gastrocnemius activity was increased in those with Achilles tendinopathy. It is possible that this timing imbalance, particularly the increased duration of activity of the ankle plantarflexors may create prolonged loading of the Achilles tendon and contribute to tendinopathy development. Additionally, reduced function of tibialis anterior has been theorized to reduce stiffness of the tendon-muscular system in the lower limb and impede its ability to tolerate and absorb impact forces [31]. This could create increased Achilles tendon loading and lead to tendinopathy. 5. Case report 3: metatarsal stress fracture A 35 year old male marathon runner presented to clinic with chief complaint of pain and swelling to his right forefoot. He had been averaging 25 miles per week for the previous 6 months but had transitioned to a pair of minimalist shoes with the plan of running his next marathon in them. He had been running approximately 3 weeks in the new shoes at the time of presentation. Patient described a gradual onset of pain to his foot pain almost as soon as he started to run in the minimalist shoe. He described an ache to his foot toward the end of runs that would resolve with rest and wearing conventional shoes. He stated that he had expected some “aches and pains” as he made the transition so was not concerned about the persisting pain. On the day that his pain forced him to stop running and seek treatment, he was doing a 12 mile run at a faster pace on sidewalks. His pain worsened to become intense as the run progressed and after completing the run he noticed his foot was swollen. He then sought medical treatment. The patient’s past medical history was unremarkable and he was not taking any medications. His previous running-related injuries include plantar fasciitis and iliotibial band syndrome both of which resolved with rest and physical therapy. The patient had been an avid runner for 8+ years gradually progressing from shorter races to marathons. He had discontinued running in conventional cushioned running shoes as he began his 12 week marathon training program and was following the same marathon program that he had used previously. This marathon training program included a standard gradual increase in mileage that was to peak a few weeks prior to his goal race. On exam, he was limping and had visible and palpable edema to his dorsal right foot with focal pain localized to the shaft of the 3rd metatarsal. No significant biomechanical, strength, or rangeof-motion abnormalities were present. Initial radiographs were negative for fracture but a presumptive diagnosis of 3rd metatarsal stress fracture was made and the patient was placed in a walking cast with instructions to discontinue running and follow up in 2–4 weeks to assess improvement and repeat radiographs. Subsequent follow up radiographs confirmed a stress fracture of the 3rd metatarsal. Patient was able to transition out of the cam boot at week 4 and returned to running in conventional shoes at week 10 without complications.
4. Discussion 6. Discussion The two injuries presented occurred in shoes with heel height differentials of 6 mm or less. This represents the height of the heel compared to the height of the forefoot of the shoe. In the barefoot condition this heel height differential is zero. In the barefoot condition, the gastrosoleus is activated earlier and for a longer duration in order to land with a plantarflexed footstrike [29]. This increased duration of gastrosoleus activation was also found in patients with Achilles tendinopathy. Two studies compared EMG amplitude and onset timing of a number of lower limb muscles in those with and without Achilles tendinopathy [30,31]. Notably, the onset of tibialis anterior activity
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Running in minimalist shoes with a low heel height differential, like barefoot, results in greater, earlier plantarflexion [14,15] recruiting the flexor digitorum longus to assist [32] thus leading to fatigue of the flexor digitorum longus which causes increased compression strain on the metatarsals [33]. It has been theorized that this increased compression strain leads to metatarsal stress fractures [34]. An alternative explanation is that the impact force in minimalist runners is directed toward the metatarsals instead of the calcaneus, due to the midfoot or forefoot landing style [17].
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7. Conclusion We have presented three injuries occurring in runners after switching from traditional cushioned running shoes to minimalist shoes. In two of the three cases, the runners switched to minimalist shoes while at the same time increasing weekly mileage. All three of the runners switched immediately to the minimalist shoes with no transition period. We recommend that any increase in weekly mileage is performed gradually and in shoe gear that has been proven for that particular runner. We also recommend that any transition to minimalist shoe gear be performed gradually. To our knowledge, this is only the second article documented in the literature, although it is our contention that these injuries are quite common and will continue to become more prevalent as more runners change to these shoes. Conflict of interest statement The authors have no conflicts of interest to disclose. Funding No funding was received for this work. References [1] Robbins SE, Gouw GJ. Athletic footwear and chronic overloading. A brief review. Sports Medicine 1990;9(2):76–85. [2] Rossi WA. Why shoes make “normal” gait impossible. Podiatry Management 1999;(March):50. [3] Clinghan R, Arnold GP, Drew TS, et al. Do you get value for money when you buy an expensive pair of running shoes? British Journal of Sports Medicine 2008;42:189–93. [4] Richards CE, Magin PJ, Callister R. Is your prescription of distance running shoes evidenced-based? British Journal of Sports Medicine 2009;43: 159–62. [5] Koplan JP, Powell KE, Sikes RK, et al. An epidemiologic study of the benefits and risks of running. Journal of the American Medical Association 1982;248:3118–21. [6] Jacobs SJ, Berson BL. Injuries to runners: a study of entrants to a 10,000 meter race. American Journal of Sports Medicine 1986;14:151–5. [7] Van Middelkoop M, Kolkman J, Van Ochten J, et al. Risk factors for lower extremity injuries among male marathon runners. Scandinavian Journal of Medicine and Science in Sports 2008;18(6):691–7. [8] Running USA State of the Sport Report. www.runningusa.org/node/76115 [accessed 26.08.11]. [9] James SL, Bates BT, Osternig LR. Injuries to runners. American Journal of Sports Medicine 1978;6:40–50. [10] Internet search via Google August 14, 2012.
Please cite this article in press as: http://dx.doi.org/10.1016/j.foot.2013.03.001
Cauthon
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[11] McDougall C. In: Alfred A, editor. Born to run: a hidden tribe, superathletes, and the greatest race the world has never seen. 1st ed. New York: Knopf/Random House; 2009. p. 16 [Chapter 2]. [12] Parker-pope T. Is barefoot better? Some athletes say running shoeless benefits body and sole. The Wall Street Journal 2006;(June):D1. [13] Burfoot A. Should you be running barefoot? Runner’s World 2004;39(8):61. [14] Squadrone R, Gallozzi C. Biomechanical and physiological comparison of barefoot and two shod conditions in experienced barefoot runners. Journal of Sports Medicine and Physical Fitness 2009;49:6–13. [15] Nigg B. Biomechanical considerations on barefoot movement and barefoot shoe concepts. Footwear Science 2009;1:73. [16] Bruggemann G, Potthast W, Braunstein B, et al. Effect of increased mechanical stimuli on foot muscles functional capacity [online abstract]. American Society of Biomechanics Web site. Available at: http://www.asbweb.org/conferences/ 2005/pdf/0553.pdf [accessed 12.06.12]. [17] Salzler MJ, Bluman EM, Noonan S, et al. Injuries observed in minimalist runners. Foot and Ankle International 2012;33(4):262–6. [18] Divert C, Mornieux G, Baur H, et al. Mechanical comparison of barefoot and shod running. International Journal of Sports Medicine 2005;26:593. [19] Lieberman D, Venkadesan M, Werbel W, et al. Foot strike patterns and collision forces in habitually barefoot versus shod runners. Nature 2010;463:531–5. [20] Divert C, Baur H, Mornieux G, et al. Stiffness adaptations in shod running. Journal of Applied Biomechanics 2005;21:311–21. [21] Cavanagh PR, Lafortune MA. Ground reaction forces in distance running. Journal of Biomechanics 1980;13:397–406. [22] Nigg BM. Biomechanical aspects of running. In: Nigg BM, editor. Biomechanics of running shoes. Champaign, IL: Human Kinetics; 1986. p. 1–25. [23] Nigg B. Biomechanical considerations on barefoot movement and barefoot shoe concepts. Footwear Science 2009;1:73–9. [24] Hreljac A. Impact and overuse injuries in runners. Medicine and Science in Sports and Exercise 2004;36:845–9. [25] Robbins S, Waked E, Mcclaran J. Proprioception and stability: foot position awareness as a function of age and footwear. Age and Ageing 1995;24:67–72. [26] Robbins S, Waked E, Rappel R. Ankle taping improves proprioception before and after exercise in young men. British Journal of Sports Medicine 1995;29:242. [27] Stacoff A, Denoth J, Kalin X, et al. Running injuries and shoe construction: some possible relationships. International Journal of Sport Biomechanics 1988;4:342. [28] Jenkins DW, Cauthon DJ. Barefoot running claims and controversy: a review of the literature. Journal of the American Podiatric Medical Association 2011;101:231. [29] Komi PV, Golhofer A, Schmidtbleicher D, et al. Interaction between man and shoe in running: considerations for a more comprehensive measurement approach. International Journal of Sports Medicine 1987;8:196–202. [30] Baur H, Divert C, Hirschmuller A, Muller S, Belli A, Mayer F. Analysis of gait differences in healthy runners and runners with chronic Achilles tendon complaints. Isokinetics and Exercise Science 2004;12(2):111–6. [31] Azevedo LB, Lambert MI, Vaughan CL, et al. Biomechanical variables associated with Achilles tendinopathy in runners. British Journal of Sports Medicine 2009;43:292–9. [32] Coughlin MJ, Schon LC. Disorders of tendons. In: Coughlin MJ, Mann RA, Saltzman CL, editors. Surgery of the foot and ankle. Philadelphia: Mosby Elsevier; 2007. p. 1262–3. [33] Arndt A, Ekenman I, Westblad P, Lundberg A. Effects of fatigue and load variation on metatarsal deformation measured in vivo during barefoot walking. Journal of Biomechanics 2002;35:621–8. [34] Buckwalter JA, Brandser EA. Stress and insufficiency fractures. American Family Physician 2002;56(1):175–82.
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