More than 500 years ago, Leonardo da Vinci asserted, "The foot is a masterpiece of engineering and a work of art." His statement stands in stark contrast with the current prevailing view (widely promoted by footwear, insole, and orthotic marketers, as well as many health care professionals), that the foot is poorly designed and requires artificial support and/or cushioning to function properly.
The "foot is poorly designed" theory first surfaced in the mid-1800's, accompanied by foot function "NORMS" as defined by practitioners of the day. These hypotheses have remained virtually unchanged over the years, sustained by a mountain of white papers and journal articles. In 2000, a study published in the Journal of the American Podiatric Medical Association challenged the reliability of these articles, noting that only 1% of the 322 articles reviewed displayed consistent, reputable and scientific evidence-based information. The authors concluded that the majority of these published articles focused on generating, rather than testing, hypotheses.
The structure of the foot and its biomechanical function have been commonly referred to in medical journals, studies, and consumer publications as being of poor design and function, therefore susceptible to injury. Another common statement is that most foot dysfunctions and resulting pathologies are hereditary. These two myths have been perpetuated within the medical community simply by their repeated exposure in these media,, notwithstanding the fact that there are very few scientific studies to support these hypotheses. In fact, an abundance of research demonstrates otherwise.
There is much debate about what constitutes normal foot function and how "NORMS" are determined. It is important to note that the currently accepted NORMS, as defined in most medical literature, were derived from studies on foot function and gait conducted mainly on sample populations that have worn shoes since childhood. For the most part, these NORMS have been one of the "tools" used to identify the causes of various pathologies and have traditionally formed the foundation of associated treatment options. Furthermore, they have played an integral role in the development of footwear designs and orthotic devices.
Significantly, the NORMS derived from studies on predominantly unshod populations show drastically different trends for foot function. The difference between NORMS derived from shod vs. unshod populations is similar to comparing function and range-of-motion between:
- a limb that has been immobilized by a splint or cast for several years, and
- a limb that has experienced unfettered movement over the same period of time.
It is evident, even to a layperson, that the chronically restricted limb would be weaker and exhibit joint stiffness with an associated limited range-of-motion. Additionally, the restricted limb would be incapable of many of the tasks that would be easily managed by an unfettered limb.
Therefore, NORMS, concerning foot function and upon which the efficacy of standard therapeutic practice is based, are themselves biased. As a result, the accuracy and applicability of a majority of current foot care research is questionable.
For example, most textbooks, journals and studies refer to the terms "pronation" and "supination" when describing foot function NORMS.
The foot's weight bearing or stance phase of motion is most commonly described as consisting of pronation in early stance in association with lowering of the medial longitudinal arch, followed by progressive supination in association with raising of the arch. The foot has been described as behaving much like a twisted plate, in that the arch rises or lowers according to counter motions of the rear-foot and forefoot segments. According to Hunt, et al., “…these commonly defined NORMS are largely speculative, as they are based on the application of static experiments or unquantified observations. Furthermore, they have been applied to the motion of foot segments and bones, although no data yet exists to provide a description of typical inter-bone motion during walking.”
This isn’t new information. There are many studies supporting the above noted conclusions.
“… sensory-induced behavior associated with the physical inter-action of the plantar surface with the ground (in the unshod), or the footwear and underlying surface (in shod), is considered unimportant to the traditional thesis. This omission is astounding because logically, the plantar surface, being a highly sensitive layer, would produce significant sensations in either state, and it is common knowledge that noxious plantar skin sensation can easily induce avoidance behavior…” Robbins SE, Hanna AM, Gouw GJ. Overload Protection: Avoidance Response to Heavy Plantar Surface Loading. Medicine and Science in Sports and Exercise 20(1): p. 85, February 1988.
“The barefoot walker receives a continuous stream of information about the ground and about his relationship to it, while a shod foot sleeps inside an unchanging environment. Sensations that are not listened to become decayed and atrophy.” Platte B. San Francisco Chronicle Interview with Dr. P.W. Brand. Medical Research. www.unshod.org/pfbc/pfmedresearch.html: 1976
“… the arch develops during the first decade of life… … shoes increase the frequency of flat feet (studies from India suggest that shoes actually cause flat feet)…” Dr. James G. Wright, Assistant Professor, Department of Surgery, University of Toronto Faculty. The Hospital for Sick Children. Foot and Ankle Symposium Co-sponsored by the Canadian Orthopaedic Association and the Department of Surgery, Orthopaedic Division University of Toronto, held at Sunnybrook Hospital, April 1996
“The inescapable conclusion is that footwear use is ultimately responsible for ankle injury.” Robbins SE, Waked E, Rappel R. Taping Improves Proprioception Before and After Exercise in Young Men. British Journal of Sports Medicine 29(4): p. 242,1995
“… current treatment of foot disorders is limited…” Dr. Roger A. Mann, Associate Clinical Professor, Department of Surgery, University of California at San Francisco. Foot and Ankle Symposium Co-sponsored by the Canadian Orthopaedic Association and the Department of Surgery, Orthopaedic Division, University of Toronto, held at Sunnybrook Hospital, April 1996
“Shock absorbing materials in the shoe are not required if subtalar joint function is normal.” Tiberio D. The Effect of Excessive Subtalar Joint Pronation on Patello-femoral Mechanics: A Theoretical Model. Journal of Orthopedic & Sports Physical Therapy 9(4): p. 160, 1987.
“… consistent use of (shock absorbing) orthotic inserts did not prevent lower limb pain among healthy soldiers in basic training…” Sherman RA, Karstetter KW, May H, Woerman AL. Prevention of Lower Lim b Pain in Soldiers Using Shock-Absorbing Orthotic Inserts. Journal of the American Podiatric Medical Association, Volume 86, No. 3, March 1996
“We should have a clear body of evidence that orthoses actually work. Unfortunately we don’t.” Hamill J, Derrick TR. Orthoses: Foot/Custom: The Mechanics of Foot Orthoses for Runners. Biomechanics: February 1996
“… the results of a two-year prospective randomized national study on the treatment of heel pain. The study found inexpensive off-the-shelf shoe inserts to be more effective than plastic custom arch supports in the initial treatment of heel pain (plantar fasciitis).” Glenn Pfeffer, M.D., San Francisco, Chairman of the AOFAS Heel Pain Study Group, American Orthopedic Foot and Ankle Society (AOFAS) 1996
“No one method for measuring STJ neutral has been proven accurate and reproducible by different testers.” Miller M, McGuire J. Literature Reveals No Consensus on Subtalar Neutral. Biomechanics: p. 63, August 2000
“… the development of a prophylactic orthotic would be of great benefit in the prevention and treatment of foot disorders.” Dr. Roger A. Mann, Associate Clinical Professor, Department of Surgery, University of California at San Francisco. Foot and Ankle Symposium Co-sponsored by the Canadian Orthopaedic Association and the Department of Surgery, Orthopaedic Division, University of Toronto, held at Sunnybrook Hospital, April 1996
“The experimental changes of shortening of the medial arch and load redistribution to the digits can only be explained by an activation of this normally inactive musculature associated with increased barefoot weight-bearing activity. The data clearly demonstrates that the normally shod foot is capable of rehabilitation of foot musculature.” Robbins SE, Gouw JG, Hanna AM. Running Related Injury Prevention Through Innate Impact-Moderating Behaviour. Medicine and Science in Sports and Exercise 21(2): p. 1390, 1987 (American College of Sports Medicine).