BAREFOOT RUNNING
runner strikes the ground 600 times per kilometre, the authors hypothesised that the large, abrupt forces recorded by the RFS group may be transmitted up the body and cause injury when generated repeatedly. Reduced impact forces in barefoot compared to shod runners have been described in other studies (20, 21).
Other reported benefits of barefoot-style running include increased economy of effort (22–24), and increased strength of the intrinsic musculature of the foot (25, 26). Conversely, being shod has been shown to reduce proprioceptive ability (27–30), and increase the risk of foot deformity (31–33). Combined, these factors have led many authors to hypothesise that barefoot runners possess reduced injury risk. However, at present, this hypothesis lacks empirical evidence.
Does running barefoot reduce injury risk? Currently, there is only anecdotal evidence linking a barefoot-style with reduced risk of injury (34). However, there are a number of studies that describe certain biomechanical characteristics seen in chronic overuse running injuries, which other studies have noted to be significantly reduced in a barefoot-style gait. It must be noted that these studies are cross-sectional and therefore cannot determine cause or effect. Pohl et al. collected data from 25 female runners with a history of plantar fasciitis (PF) and compared them to 25 matched controls with no history of PF (35). The authors reported a significantly greater maximum instantaneous load rate in the history of PF group and a trend towards greater vertical impact peak, meaning that the foot experiences greater forces at foot strike, which could predispose the PF to injury with repeated impacts as occurs in running. A similar study compared distance runners with a history of tibial stress fracture (TSF) to uninjured, matched controls and reported greater loading rates in runners with a history of TSF (36). Higher vertical impact forces may therefore predispose runners to developing overuse injuries such as PF and TSF. Considering barefoot running has been reported to reduce these impact forces (19–21), adopting a barefoot running style could potentially reduce the risk of developing these conditions. In addition to reducing impact forces, barefoot running style has also been reported to reduce peak rearfoot eversion (Pohl and Buckley 2008, Stackhouse et al. 2004, Morley et al. 2010), a kinematic variable theoretically linked to many lower limb injuries. Although empirical evidence is lacking to support rearfoot eversion as a risk factor for most conditions, two case-control studies have reported that individuals with tibialis posterior dysfunction (TPD) possess increased rearfoot eversion (Ness et al. 2008, Tome et al. 2006). Therefore, adopting a barefoot running style may also reduce the risk of developing TPD.
Gait retraining The important question raised by the theoretical concepts surrounding the proposed benefits of barefoot running is can runners can be trained to reduce the collision forces experienced during foot strike? After all, a person who has run in barefoot-style all their life will have undergone a long-term process of adaptation to this form of running, which may or may not be possible in later life.
Crowell et al. reported that, after a single 10 minute session of gait retraining in the laboratory using real-time visual feedback, subjects were able to significantly reduce lower extremity loading at impact and maintain this reduction for a further 10 minutes of running without any feedback (37). This finding is important because certain running injuries, such as tibial stress fracture, are partially predicted by loading magnitude (36,38).
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In a further study, subjects with a high tibial acceleration received 8 gait-retraining sessions over a two week period (39). The amount of real-time visual feedback was gradually reduced over the 8 sessions so that only three minutes of feedback were provided for 30 minutes of running during the last session. At one month follow-up, lower extremity loading was significantly reduced for the four measured variables that correspond to lower limb loading, and ranged from a 20% to 50% reduction compared to pre-retraining values. Importantly, no injuries were reported. The authors noted that, on average, the reductions of lower extremity loading achieved were greater than the reductions achieved through the use of cushioning shoes, foot orthoses, or shock reducing insoles, and suggested that gait retraining may be more cost efficient in the long term.
Unfortunately, there is a paucity of large trials evaluating the effectiveness of gait retraining aimed at changing an individual’s strike pattern in preventing or treating lower limb injury. Recently a case series of individuals who were retrained to run with a forefoot strike pattern to treat chronic exertional compartment syndrome (CECS) were described (Diebal et al. 2011). On initial assessment, both patients in the case series were limited to running less than 1km due to severe anterior shin pain. Following a six-week period of retraining, they were able to run 12.87 and 6.44km three times per week, symptom free. A possible explanation for this dramatic improvement is that running with a forefoot strike pattern produces significantly lower anterior compartmental pressures compared to rearfoot striking (Kirby and McDermott, 1983). More larger, controlled clinical trials evaluating the effectiveness of using gait retraining to treat CECS and other lower limb injuries are needed. Additionally, controlled trials are needed to determine whether primary injury risk is decreased by changing from a rearfoot to a forefoot strike pattern.
Potential pitfalls and problems Despite mounting anecdotal evidence and sound theoretical rationale, gait retraining should not be considered a silver bullet, and caution must be exercised when attempting to alter decades of behaviour learned while wearing shoes. Importantly, the biomechanics of barefoot-style runners are quite different to RFS runners. When moving from a RFS to forefoot strike pattern as occurs in barefoot-style running, the knee tends to be more flexed, increasing vertical compliance, and the ankle more plantar flexed to accommodate landing on the forefoot (19). In turn, muscle activation patterns are likely to change given the need for greater eccentric control from the quadriceps and calf musculature. This may theoretically lead to overuse injuries such as patellar and Achilles tendinopathy, particularly in untrained individuals. However, as with the proposed benefits of barefoot running, these theoretical links lack empirical evidence. Furthermore, it has been noted anecdotally that some sports people attempting barefoot-style running force themselves to land on the forefoot by plantar flexing their ankles, rather than gradually letting their bodies adapt to the optimal biomechanical style. This concentrically contracts the calf musculature so that when the sports person lands, they load through an
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