In the last few years, there’s been a steady growth in the popularity of minimalist running shoes, that claim to offer you the benefits of barefoot running without some of the drawbacks. Science based chiropractor, Dr. Alexander Jimenez investigates.

It had been back in the late 1970s that the running boom really got underway. Since that time, tens of millions of individuals around the world have enjoyed recreational and competitive running, equally as a pastime and as means of getting and keeping healthy. However, as any clinician knows, the biomechanical demands of running are such that the prospect of injury is comparatively high in comparison to other endurance sports like swimming or biking. Not surprisingly, as a result, the growth in the popularity of running was accompanied by a growing number of accidents.

It’s hardly surprising, therefore, that the previous 3 decades has witnessed an explosion in running shoe technologies, together with successive generations of shoes with increasingly complex solutions to guarantee the ideal running gait along with the absorption of their impact forces, that are a particular difficulty when pounding the tarmac or pavements.

Bearing this in mind, you might expect that the rate of injury suffered by runners per mile run has been steadily decreasing. However, studies on the prevalence of running-related accidents conducted from 1989 to the present have found a remarkably consistent rate of injury(1). In other words, despite all the technological advances in shoe development over these past decades, the rate of injury has held pretty steady.

Minimalist Running Shoes

The Barefoot Revolution

In more recent decades, some runners have taken a different approach by embracing quitting running. The proponents of barefoot running claim that this manner of running is much more ‘natural’ and enables the human foot to operate in the manner that Nature meant it to — something that can’t occur when the foot is shod in an artificial shoe. The claimed advantages of barefoot running revolve around the fact that an assessment of seasoned barefoot runners in comparison to shod runners reveals several striking (no pun intended!) differences.

The significance of this fact is that the ground response impact forces generated from the collision of their foot together with the surface are typically much higher when a runner heel-strikes — that the size of the peak impact force during rear-foot attack was shown to function as 1.5 — 3 times your body weight(3). The use of a cushioned running shoe typically decreases this impact force by approximately 10%, which makes it more tolerable. But a far more effective approach to decrease the size of foot-strike impact forces would be to embrace a mid- or forefoot attack (see Figure 1). It follows that with no cushioning underfoot to decrease the effect of rear-foot attack, barefoot runners obviously embrace a mid- or – forefoot strike, which really turns out to be more effective at reducing impact forces, and so (according the proponents) reduces the risk of injury.

Why is it that a mid- or – forefoot strike pattern can reduce the severity of ground impact forces in contrast to some rear-foot strike? Specifically, the researchers looked at the joint kinematics and influence absorption characteristics of the shoulder, hip and knee joints throughout rear-foot strike jogging, forefoot strike running and barefoot running. One of the primary findings was that in rear-foot strike, there was a significantly greater dependence on the knee and hip joints to absorb impact forces compared to barefoot and forefoot strike running.

Specifically, the barefoot and forefoot runners demonstrated increased plantar- flexion at initial ground contact, which increased peak ankle energy absorption and decreased peak knee and hip power absorption. However, in both forefoot strike and barefoot running, the forces at initial contact are transmitted through the comparably smaller middle foot muscles and bones as opposed to throughout the calcaneus, talus and tibia straight, which could be a problem with a few runners. While a structurally sound foot may have the ability to consume these forces efficiently, it’s very likely that different foot types may respond differently to these increased forces to the forefoot (see Box 1).

The data on foot attack differences between shod and barefoot runners are widely accepted across the sports science and running community. What this mean concerning injury danger remains a topic of controversy, yet. Barefoot running proponents assert that (provided a slow transition is created) the introduction of barefoot running to a training program may diminish the risk of injury. But this is contested by a number of investigators. By way of example, Craig Payne, a senior lecturer at the Department of Podiatry at La Trobe University in Melbourne, commented at a recent paper: “The barefoot running community has an appalling track record at how they misinterpret, misuse and misquote research. The simple facts are that not one risk factor study on running injuries has linked high impacts to running injuries, yet the barefoot running community claim that the evidence shows this and consider high impacts as the cause of all injuries.(5)”

Placing this argument to one side for the moment, there are some other, undeniable drawbacks to barefoot running. For instance, running barefoot on extremely hot pavements/tarmac or at extremely cold conditions may hurt the bottoms of the feet. Additionally, there are risks such as nails, glass, pebbles and other objects that could puncture the soles of feet or lead to stubbed toes. Moreover, even if heel strikes are eliminated by running barefoot, using shorter strides typically found in barefoot runners signifies the feet hit the floor more frequently — what’s gained by reducing the power of impact may be offset by the increase in the frequency of impacts.

The evidence to date is that while barefoot running may provide some theoretical benefits concerning reducing foot strike effect by promoting a more mid/forefoot strike routine, there are incontrovertible disadvantages. In something of a halfway-house evolution, therefore, running shoe manufacturers have recently begun to offer so-called minimalist running shoes. Minimalist shoes (sometimes referred to as ‘barefoot shoes’) have been designed to enable the foot to move through a similar selection and pattern of movement during running as could an unshod foot, while at exactly the exact same time offering some security. Others are slightly more considerable, being designed to help runners slowly transition from rear foot normally shod running to barefoot-style running.

The Minimalist Promise

Implicit in the marketing behind minimalist shoes is your guarantee that (providing they are introduced very slowly) their usage will help runners to come up with a more natural working fashion, resulting in fewer injuries, a much more balanced musculature and much better running posture. However, what does the science say about these claims?

Among the first studies into the use of minimalist sneakers compared the biomechanics of barefoot running with this of running in minimalist footwear and conventional running shoes(6). In the analysis, the mechanical qualities of this foot/shoe-ground port were investigated in eight experienced barefoot runners to be able to appraise the floor pressure supply, sagittal plane kinematics, and running market. The researchers also sought to discover if a minimalist shoe (Vibram Five Fingers) was effective in mimicking the experience of barefoot running and both these conditions were compared to the usage of conventional running shoes.

As mentioned above, it turned out that, when compared with the standard shod condition, when running barefoot the athletes landed at more plantar flexion at the foot, which decreased impact forces and shifted stride kinematics. In particular, significantly shorter stride length, foot contact times, and higher stride frequency were observed. The usage of this Five fingers shoe also led to peak impact forces that were significantly lower than shod running, and much nearer to barefoot running. The lower limb kinematics with Five fingers was comparable to barefoot running, having a foot position which was significantly more plantar flexed than in conventional shoes. The researchers concluded: “The Five fingers shoe seems to be effective in imitating the barefoot conditions while providing a small amount of protection.”

Another purported advantage of minimalist running shoes is that they allow a more precise estimate of dynamic and static foot position in comparison to wearing a conventional cushioned running shoe. The theory is that this increased ‘foot awareness’ may help encourage a more efficient running motion, especially over undulating terrain. In a 2011 analysis, researchers looked at the effect of some five- minute minimal protection shoe on dynamic and static ankle position sense (again, Vibram Five fingers shoe) and compared it equally with a conventional shoe and also barefoot running(7).

Static ankle joint position sense was assessed from the sagittal and frontal plane by asking fourteen experienced amateur runners to estimate the perceived direction and amplitude of a support incline surface plank placed under their right foot while standing. The energetic measures were performed with all the subjects running on a treadmill at 12kmh and requesting them to assess the treadmill surface slope.

The results demonstrated that plantar flexion, dorsiflexion, eversion and inversion moves were underestimated, irrespective of shoe or static/dynamic testing. However, in the static trials there was significantly more angle error underestimation with the running shoe, although no significant differences were found between Five fingers and barefoot condition. While running (dynamic test), the treadmill surface slope was considerably improved estimated with Five hands than with traditional sneakers, or barefoot running.

Question Marks

The above studies suggest that the use of minimalist running shoes could have its location in a training program; however, more recent study is much less positive. To do so, ground reaction force data and kinematics were collected from 22 highly-trained runners throughout overground running while barefoot and in 3 shod conditions (minimalist shoe, racing level along with the athlete’s regular shoe).

The results demonstrated that though there were important differences between barefoot and shod conditions for kinematic and kinetic variables at the knee and ankle, there were no differences between shod states — ie which none of those shod conditions successfully replicated barefoot running.

Another study published only a couple of months ago examined the claims that minimalist shoes can promote a more efficient running activity, and so improve running economy(9). This analysis compared minimalist and standard running shoes (along with ‘rocker shoes’) for their impacts on energy cost and conducting efficiency. Eighteen endurance female runners who were inexperienced at running barefoot or with minimalist running shoes completed a six-minute sub-maximal treadmill running test for every footwear illness, during which oxygen consumption, carbon dioxide production, heart rate and rate of perceived exertion were measured. The main finding was that compared to the typical shoes, the minimalist shoes did not reduce energy expenditure or improve running economy (despite being lighter). The rocker shoes actually increased energy expenditure, something that the investigators put down to the significant extra mass of the shoe design.

An even more unfavorable evaluation of the minimalist shoe asserts stems from a brand new US study, published in July of 2013(10). In the study, the researchers set out to determine if running in a minimalist shoe ends in a decrease in ground reaction forces and alters kinematics over standard shoe running. They also looked at whether any ‘within- session ‘accommodation to a minimalist shoe occurs.

Fourteen male, rear-foot striking runners that had never run in a minimalist shoe were analyzed while running at 3.35 meters/sec for ten minutes on a treadmill in minimalist and standard shoes while three-dimensional lower extremity kinematics and kinetics were assessed. Data were accumulated after a minute and then again after ten minutes of running in both shoe types.

The first finding was that minimalist shoe running resulted in no changes in step length or step rate. To make matters worse, after ten minutes, the vertical effect peak and moderate vertical loading rate during foot attack improved. To put it differently, the minimalist running shoes hadn’t only increased impact and loading forces initially, as time moved on, there was likewise no accommodation — ie things got steadily worse!

The researchers concluded: “Running in a minimalist shoe appears to (at least in the short term) increase loading of the lower extremity over standard shoe running. Moreover, the accommodation period resulted in less favorable landing mechanics in both shoes. Our findings therefore bring into question whether minimal shoes will provide enough feedback to induce an alteration that is similar to barefoot running.”

Increased Injury Risk

Given that running in minimalist footwear was promoted as a means of eliminating or reducing running accidents by returning to a more natural gait, it may be surprising to learn that the literature includes an increasing number of studies showing an increased chance of harm from minimalist shoe usage. Furthermore, this isn’t the injury risk arising as a consequence of switching unexpectedly to minimalist running shoes without a gradual transition (see box 1above), but instead appears to be an inherent danger in the usage of these shoes themselves.

Patients were interviewed to determine their running history, injury background, transition to minimalist footwear, and also their new injury details. These runners were running an average of 26 miles each week (ie not large mileage) for a mean of 19 decades. After changing into minimalist footwear, an accident occurred in these runners following an average of 2.8 months.

Thirty-six experienced recreational runners underwent magnetic resonance imaging (MRI) before and following a 10-week period. Throughout the ten weeks, 17 subjects conducted only in their conventional (cushioned) sneakers while the other 19 gradually transitioned into the Vibram Fivefinger running shoes. A rating of 4 represented a stress fracture. The pre-training MRI scores weren’t statistically different between the classes. However, the post-training MRI scores showed that from the Vibram group, 10 of the 19 athletes showed gains in bone marrow oedema in a minimum of one bone following 10 months of running. This implies that even using a carefully structured transition period, minimalist running shoes might raise the risk of stress fracture injuries.

Summary & Conclusions

While barefoot running does appear to decrease impact loadings throughout foot strike, there is much controversy and little scientific agreement about any potential benefit concerning injury reduction this could cause. The evidence for using minimalist running shoes, however, is rather more convincing — but sadly in the wrong direction! While they can improve foot proprioception, there’s conflicting evidence about whether minimalist running shoes can successfully mimic barefoot running. Indeed, some studies indicate that they might increase impact loadings throughout foot strike. The evidence for their ability to decrease injury rates is rather more damning as a growing number of studies seem to suggest that far from reducing injury risk, using minimalist shoes may actually raise this risk — even with an extended transition period into minimalist running shoes use.

References
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