Biomechanical research and technological developments have guided the journey of the running shoe from the barefoot and minimalist footwear beginnings, to modern day heavily cushioned and supportive shoes. Despite the technological advances, the rate of running related injuries has increased among the running community. Rates of up to 79% per year have been continually reported (Davis, 2014). It has been suggested that these motion controlled, elevated heeled shoes, have changed the way we run, have limited proprioception and sensory feedback, and lead to the development of weak, inflexible feet. Could wearing shoes have actually contributed to the high rate of running injuries? With the recent re-emergence of barefoot running and the development of minimalist footwear, there is a divide in the running community.
I was introduced to the Vibram FiveFinger shoes about three years ago, by a fitness professional with whom I was training. I will admit that when I first saw his footwear, I thought he looked like some kind of gorilla, with his toes all separated and gripping onto things like a gorilla in a tree. Three years down the line, I now practically live in these funky monkey shoes, and I love them! My feet feel free to bend, grip, and function naturally. They aren’t cased into boxes with platforms tied to the bottom (this is my description of normal shoes, in case you haven’t gathered). Best of all, I’m injury free for the first time in ages.
BUT, before you all run out and buy minimalist shoes to run your next half marathon, you need to understand that it’s not as simple as shoving on these shoes and away you go. Vibram have faced litigation in America due to allegations of misleading claims being made about the ability of FiveFinger shoes to strengthen the muscles of the feet, and prevent injuries. However, there is now a body of research which supports the benefits promoted by Vibram. The key point though, which the internet reports about injuries often fail to mention, is that an appropriate transition period is required to change from shod to minimalist running.
A bit of history….
According to fossil evidence, the Homo erectus may have been the first endurance runners, nearly 2 million years ago (Bramble & Lieberman, 2004). The earliest footwear found to date was discovered in 1932, by an archaeologist in Fort Rock Cave, Oregon. The shoes formed from crushed sagebrush bark which was knotted together into a flat surface, were radiocarbon dated to 10,000 years old. It is thought that these were the first running shoes, with the wearers spending the majority of their time hunting for food, and covering long distances on foot (Cavanagh, 1980).
Since then, running shoes have undergone vast changes, particularly in the last 30 years. In the 1970’s, the popularity of running increased, as endurance running was promoted as a means of preventing and managing lifestyle related diseases. This is the point at which the modern running shoe was born. Since then, the incidence rate of running related injuries has been estimated at 30-79% per year, with little change seen in the last 30 years (Daoud et al., 2012). Running shoe companies have subsequently sought to decrease injury and increase performance. In today’s market, there is a divide in the design of running shoes, between the cushioned, protective, supportive and motion controlled shoe, and the minimalist shoe which aims to mimic barefoot running.
The development of cushioned and supportive, modern running shoes….
Biomechanical research denotes that the running gait cycle is composed of two main phases; the stance phase and the swing phase, with a float phase occurring in between. The stance phase is made up of the foot strike, the mid-stance and the take-off. There are different patterns of foot strike, including heel or rear foot strike, mid foot, and forefoot strike. The heel strike is the typical strike pattern seen in runners wearing shoes; otherwise known as shod runners, with 75-95% landing with a rear foot strike (Samaan, Rainbow & Davis, 2014).
When analysing running forces, the vertical ground reaction force (VGRF) is often assessed. The rear foot strike is associated with a peak in the VGRF, known as the impact transient, which reflects the collision with the ground, exerting force on the lower leg of approximately 2 to 3 times the individual’s body weight (Murphy, Curry & Matzkin, 2013). The rate of development of the VGRF is known as the loading rate, and it has been identified that high loading rates and impact transients are associated with running related injuries; including tibial stress fractures, patellofemoral pain, and plantar fasciitis (Samaan, Rainbow & Davis, 2014).
In the 1980s, biomechanical research prompted the development of shoes with shock absorbing midsoles and heel counters. The idea being that these would reduce impact loads and stabilise the position of the foot. However, several studies have found that midsole hardness in modern cushioned running shoes does not alter the risk of running related injuries (Withnall, Eastaugh & Freemantle, 2006; Theisen et al., 2013).
In the late 1980’s through to the 2000’s, running shoe technology was largely based on plantar shapes, which were thought to be reflective of the arch height in the foot. Motion control shoes were developed with the aim of controlling over pronation, cushioned shoes for supination, and stability shoes for those with a neutral gait. However, to examine the effectiveness of wearing running shoes designed to fit plantar shape on injury rates, Knapik et al. (2014) conducted a meta-analysis of three large scale studies conducted on military recruits. It was found in all three studies that injury rates were not reduced by selecting running shoes based on plantar shape and arch height.
Research has suggested that the majority of shod runners land with a heel strike due to the additional cushioning offered in modern cushioned shoes (Larson et al., 2011; Larson, 2014). The cushioned heel dampens the magnitude of the impact transient by approximately 10% and slows the rate of loading by approximately 7 times (Lieberman et al., 2010). This makes rear foot striking comfortable in cushioned running shoes; however, it does not eliminate the impact transient, which has been associated with injuries (Lieberman, 2012). The shock wave is sent up through the leg, and can be measured in the tibia within milliseconds (Lieberman, 2012).
This is an example of a counterproductive way of treating the symptoms of injury, rather than the cause. Wearing cushioned shoes to lessen the pain caused by heel striking on hard surfaces conflicts with the body’s natural adaptation in response to this pain. Proprioception, our body’s sense of its own position, balance and movement, would naturally prevent it from running in a way that generates these high impact forces in the first place, if it were not inhibited by the cushioned heel.
The heel height of modern running shoes has an affect on posture, by changing the alignment of the ankles, knees, hips, back, neck and shoulders. This has a knock on effect on reducing the quality of movement patterns, as the body compensates for the postural modifications. The subsequent development and reinforcement of inefficient and faulty movement patterns, muscle imbalances, and loss of joint mobility can lead to injury.
Furthermore, it has been suggested that shoes with arch support and cushioning restrict the spring motion of the arch, lessening the engagement and eccentric work performed by the intrinsic and extrinsic muscles, causing them to weaken. This can lead to injury caused by a decreased shock absorbing ability of the muscles, increased rear-foot motion, and increased load on the plantar fascia.
Questions have subsequently been raised about the design of these modern running shoes. Above all, the research seems to indicate that these shoes have changed the way we run.
Are shoe manufacturers creating technology and looking for solutions to problems which they have created?
The return of barefoot and minimalist running….
Observations such as that of Tarahumara Indians in Mexico, a group of ultra-runners covering high mileage throughout their lifetime whilst unassisted by running shoe technology, coupled with the barefoot training regimes seen in many running teams, have led researchers to examine the biomechanics of barefoot running.
Barefoot runners are more likely to land with the forefoot or mid foot; this is most likely due to the fact that a large and rapid impact transient associated with a heel strike would be painful. Many studies have shown that there is a significant reduction, and even an absence in some studies, in impact transients identified from the VGRF curve produced by habitually barefoot runners with forefoot strike patterns (Lieberman, 2012; Samaan, Rainbow & Davis, 2014; McCarthy et al., 2015). As well as this, significantly lower average loading rates are seen in comparison to shod runners (Lieberman, 2012; Samaan, Rainbow & Davis, 2014; McCarthy et al., 2015).
Barefoot runners landing with a forefoot strike do so with a more compliant ankle than shod runners landing with a heel strike pattern. The stiffer ankle of the heel striker results in a much greater percentage of mass coming to a stop and exchanging momentum with the ground on impact. Furthermore, the heel strike pattern usually involves landing with a more extended and stiffer knee and ankle than is seen in forefoot strike pattern. During a forefoot strike the ankle dorsi-flexes and the knee flexes, allowing the calf muscles to activate to dampen the forces more effectively (Lieberman, 2012).
The research into the biomechanics of barefoot running has resulted in the re-emergence of the minimalist style of running shoe. Modern minimalist shoes differ from the conventional cushioned shoe with regards to heel to toe drop height, which is 0mm; they have thin soles with no midsole; no arch support or heel counter; and have a more fitted and flexible toe box structure.
A study that compared the biomechanics when running barefoot with that when wearing minimalist running shoes, found that minimalist footwear effectively imitated barefoot conditions. The minimalist shoes conferred the benefits of barefoot running, whilst providing some protection for the plantar surface (Squadrone & Gallozzi, 2009). A key point in this study, is that participants were habitual barefoot or minimalists shoe runners, and results differ from those in studies of novice barefoot or minimalist shoe runners. One such study was carried out by Paquette, Zhang and Baumgartner (2013), who found that vertical impact peaks and rates of loading were higher in the minimalist shoe condition than in cushioned running shoes. This was due to the fact that the habitually shod runners in the study did not automatically change their mechanics during the single test session in minimalist shoes, suggesting that a structured transition period for the change may be necessary.
Running in minimalist shoes has been shown to strengthen the muscles of the feet and promote stiffer arches, due to increased mechanical stimuli and the ability of the muscles to function more naturally as springs (Miller et al. 2014). As well as this, running in minimalist shoes has been found to be more economical than shod running, due to a lower shoe mass, as well as an increased cadence (number of steps per minute) which prevents over striding..
The key point to consider when changing to minimalist footwear….
Research suggests that it is necessary for most shod runners to make a slow transition to minimalist footwear, in order to adequately condition the intrinsic muscles of the feet, and to develop proprioceptive feedback mechanisms. Some researchers have also suggested that calf strengthening and stretching is necessary, as running in minimalist footwear with a forefoot strike pattern loads the calf muscles to a greater extent than shod running (Davis, 2014). Studies of the injuries associated with minimalist shoes have mainly reported stress fractures to the metatarsals, but it has been identified that the occurrence of the injuries is related to short transition times in changing from shod to minimalist running (Salzler et al., 2012; Ridge et al., 2013).
Vibram provide a guide to making the transition from shod to minimalist footwear with every purchase of their FiveFinger shoes. I cannot emphasise enough the importance of implementing a sensible transition period, and the need to condition the feet and body whilst adapting to minimalist running.
- The research available to date suggests that the biomechanics of running in a minimal shoe successfully mimic those of running barefoot, reducing the forces that have been associated with running related injuries (Squadrone & Gallozzi, 2009).
- Minimalist shoes promote stronger feet, increased proprioceptive feedback, and correct postural allignment in comparison to the cushioned and supportive shoes.
- However, injury reports suggest that the musculature of the foot and ankle needs to be developed and strengthened by most shod runners when transitioning to minimalist footwear (Salzler et al., 2012; Ridge et al., 2013; Davis, 2014).
- In terms of performance, minimalist footwear appears to promote a more economical running style (Squadrone & Gallozzi, 2009; Warne & Warrington, 2012).
- With injury prevention and optimal performance being key for runners, recent research suggests that minimalist footwear may have a positive influence on both of these.
- However, great caution must be taken in transitioning from shod running, with a structured transition program required by most.
I would like to thank Paul Thomas for introducing me to Vibram FiveFingers. Paul is a fitness professional with years of experience, and an excellent knowledge of functional anatomy and movement. If you’d like to know more about Paul and the services he offers, please click this link to visit his website.
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