Science attempts to understand the totality of unknowns through dividing it into manageable units ("disciplines"), and exploring each in depth, with the understanding that integration of information from disciplines will be needed to understand the world around us. However, too many scientists have become rigidly territorial. They defend their territory and respect boundaries of others. This has delayed advancement of knowledge.
Perhaps 50 years ago the new field of study of biomechanics was given the responsibility for investigating human mobility and stability in both healthy and impaired humans. Soon this sleepy field was awakened with massive commercial interest in athletic footwear and immense health cost of injuries with their use. No other discipline has challenged its domain. Thousands of reports in scientific journals later, using their now ancient tools consisting of the EMG, kinematic recordings and force platform, and unwilling to incorporate modern technology or more invasive methods unfamiliar to them, biomechanists are no further advanced in understanding these issues than the day they began their investigations. Perhaps no other scientific field has stagnated so completely. All advancement of our understanding of human gait and stability has come from psychologists through psychophysics and neurophysiologists.
Examples of the biomechanists' malaise is everywhere. Decades ago they had hoped that thick and resilient material in midsoles of shoes might make running safer through moderating impact. It was soon found that impact when subjects run with athletic shoes was unrelated to shoe thickness because of behavioral responses to these footwear. The failure of this solution accounted for excessive injuries by creating a false sense of security with users. Biomechanists have exhibited no interest in what elicits this behavior presumably because this can not be answered with their traditional tools, and they have been unwilling to learn appropriate new methods or collaborate with others who know these methods.(1)
More recently, it was found that humans land with their foot nearly parallel to the support surface when they wear minimalist shoes, which is similar to recordings from barefoot runners.(2-4) From this is was assumed, based of this observation alone, that minimalist shoes would offer the low injury risk seen in barefoot runners.(2) Minimalist shoes became fleetingly popular due to this endorsement of biomechanists only to find, unlike barefoot running, they created an epidemic of previously uncommon forefoot injuries. Runners complained of pain in the front of their feet and MRIs confirmed damage. Biomechanists have not prevented injury with minimalist shoes - they have caused more through, again, causing a false sense of security with users. .(5-7)
Biomechanists created a total fiction regarding relative pronation and supination accounting for injuries, without one datum to support this hypothesis. They went further to create footwear to correct these presumed risk factors. Many users again felt a false sense of security with the use of these shoes which accounted for yet more injuries.
Their detachment from reality seems extraordinary when they talk about subjects "adapting a strategy" as if observed differences are a result of choice rather than a necessity because of protective adaptations. For example, in a recent report it was noted that barefoot runners and wearers of minimalist shoes "adopt a strategy" whereby their feet are near parallel to the support surface when making contact.(4) This is certainly not a choice but a necessary response to discomfort from slamming the unprotected posterior calcaneus against the supporting substrate.
In a parallel universe, the first report which suggested that plantar tactile processes account for protective barefoot adaptations appeared in 1987. while in 1988 it was first reported that SA II mechanoreceptor afferent information probably accounted for these adaptations. A host of other reports commencing in 1992 followed which indicated that discharge from plantar surface SA II mechanoreceptors was also used by humans for maintaining optimal stability - following the parsimony typical of natural selection. A report in 1997 showed that behavior to maintain stable equilibrium at least in part accounts for amplified impact with footwear compared to the barefoot condition.
Inspired by the above reports, some neurophysiologist became interested in the role of the SA II mechanoreceptor in control of mobility and stability in humans. They published reports in 2002 in which they performed recordings of primary afferent fibers of plantar surface SA II mechanoreceptor while mechanically stimulating the plantar surface.(8,9) They found that the distribution and thresholds of these receptors make them likely candidates for providing information that is used by humans in mobility and stability control. The optimal stimulus for these receptors was found to be a combination of localized vertical deformation and shear.(8,9) Sadly they did not examine this further perhaps through respect of biomechanists' territory.
The above reports supported the notion that footwear interfere with human mobility and stability mainly through attenuation of plantar shear via the shoe sole attached to the plantar surface, thereby diminishing SA II mechanoreceptor feedback. This indicated that all shoes would be inadequate compared to the bare foot. Furthermore, the thresholds of these receptors would induce barefoot humans to avoid contact with the metatarsal-phalangeal joints, as had been shown in a earlier report. This explains why barefoot humans preserve their metatarsal-phalangeal joints compared to shod humans, and predicted that minimalist shoes would destroy these structures.(10) It also explains intrinsic foot shock absorption which protects foot structures and perhaps modestly moderates aggregate impact when mobile. An improvement in footwear safety was shown to be possible with the use of extremely low resiliency sole material. Rather than welcoming this potential incremental improvement in safety through improved stability and attenuated impact, biomechanists remained fixated on their refuted notions of "cushioning" probably because the methods used to deal with resiliency were not typical to their discipline.
For nearly 25 years biomechanists have existed in self-imposed solitude. Many of the injuries associated with the use of running shoes could have been prevented if biomechanists hadn't repeatedly given users a false sense of security. Vigilance with the use of running shoes protects. Barefoot weight-bearing and mobility should have been considered as the model for safe and functional mobility considering that so many reports indicated benefits of this approach. The world is paying a heavy cost for biomechanists controlling the territory of human gait and stability. We are waiting impatiently for them to refrain from giving users the impression that footwear are needed to protect runners. Biomechanists need to lose their timidity and embrace the role of plantar tactile sensory processes in mobility and stability.
1 Chambon N., et al. Is midsole thickness a key parameter for the running pattern? Gait Posture. 40:58-63 (2014).
2 Lieberman D., et al. Foot strike patterns and collision forces in habitually barefoot and shod runners. Nature. 463:531-535 (2010).
3 Thompson M., Lee S., Seegmiller J., McGowan C. Kinematic and kinetic comparison of barefoot and shod running in mid/forefoot and rearfoot strike runners. Gait Posture. 41:957–959 (2015).
4 Hollander K., Argubi-Wollensen A., Zech A. Comparison of minimalist footwear strategies for simulating barefoot running: a randomized crossover study. PLoS One. 10:5 (2015).
5 Ridge S., et al. Foot bone marrow edema after a 10-wk transition to minimalist running shoes. Med Sci Sports Exerc. 45:1363-8 (2013).
6 Ryan M., Elashi M., Newsham-West R., Taunton J. Examining injury risk and pain perception in runners using minimalist footwear. Br J Sports Med. 48:1257-62 (2014).
7 Bonacci J., et al. Running in a minimalist and lightweight shoe is not the same as running barefoot: a biomechanical study. Br J Sports Med. 47:387-92 (2013).
8 Inglis J., Kennedy P., Wells C., et al. The role of cutaneous receptors in the foot. Adv Exp Med Biol. 508:111-117 (2002).
9 Kennedy P., Inglis J. Distribution and behaviour of glabrous cutaneous receptors in the human foot sole. J Physiol. 538:995-1002 (2002).
10 Zipfel B., Berger, L. Shod versus unshod: The emergence of forefoot pathology in modern humans. The Foot. 17:205–213 (2007).