Exploring New Horizons In Orthotics Research
These expert panelists expound on maximalist footwear and orthoses for combat boots for soldiers. They also discuss whether orthotics can reduce negative work and under what circumstances runners should be allowed to wear orthoses in competition.
What is the relationship between gait and footwear maximalism?
Steven King, DPM, CPed, notes that maximalist footwear and gait systems “maximally” enhance the protective properties of footwear, enhance the energy efficiency of the user (via lower oxygen and carbohydrate demands), and enhance the stability of the user (via reducing sway and center of motion oscillations).
Dr. King acknowledges that foot care providers have had issues with the minimalist shoe trend such as the overall reduction of the protective qualities of these shoes. He notes minimalist shoes are thinner and made of softer materials and collapsing foams that do not necessarily create ideal platforms for orthotic treatments.
Roy Mathews, DPM, defines maximalist shoes as including rigidity, a high stack height, a large heel to toe drop (12 to 15 mm), rigid structure across the midfoot and maximal cushioning, especially in the forefoot.
While many mechanically sound patterns of gait produce little stress on the body, Richard Blake, DPM, notes many patterns of gait produce abnormal stresses in various body parts that one would consider pathological. He notes that for years the shoe industry has focused on the abnormal pattern of overpronation, developing shoes with maximal anti-pronation capabilities, called maximalist or motion control shoes. In recent years, Dr. Blake says the shoe industry has been developing minimalistic shoes on the opposite side of the spectrum, allowing maximal motion in various forms.
In regard to footwear maximalism, Rob Sobel, CPed, says the “poster child” is the Hoka One One running shoe (Hoka One One Inc.). He recently ran a gait clinic with a group of collegiate and competitive amateur runners, finding there were some who “to their own surprise” really enjoyed running in Hokas and embraced the change.
Dr. King shares his scientific approach to defining maximalism.
Maximalism is the inverse of minimalism. Maximalist shoes may be designed with significant and testable safety features such as increasing puncture protection, according to Dr. King. He notes the American Society of Testing Materials has accepted the safety test standards currently in place and says physicians could use these standards to help better define and judge footwear and orthotic choices.
Energy efficiency optimization of gait. Dr. King calls this a key component of maximalism, noting that if minimalism restricts the use of exterior influences of footwear, maximalism will embrace such exterior influences. The prosthetics industry, he says, has done wonders using advanced composite carbon fiber to enable those with bilateral leg amputations to compete in the Olympics. Dr. King notes future maximalist designs should also include powered gait systems and maximalist footwear must be able to significantly enhance the efficiency of gait.
Stability optimization of gait. Maximalist footwear should provide significant improvements in the stabilization of the user during gait and static stance with the goal of reducing trips and falls, according to Dr. King.
What known research is occurring on orthoses for advanced combat and safety boots? What is the primary focus?
Soldiers in the field are always looking for lighter and temperate footwear that mitigates moisture issues, according to Dr. King. He says one should consider shock reduction and ankle stability for heavy loads over uneven ground due to the fact that soldiers may have to carry more than three-quarters of their body weight in combat gear. Sole treading often is adpated to the field environment requirements and he adds that puncture resistance does not necessarily have high priority since that requirement has not been a part of the combat boot standard since the Vietnam War.
Dr. King notes the Army now requires that all boots be direct molded sole boots, following a 1967 recommendation.1 “This was a step forward and proves that advancing boot technology is of primary concern,” says Dr. King.
In 2011, Dr. King notes the US Department of Defense and Army Medical Research and Materials Command issued Small Business Innovation Research contract proposal SBIR A11-109, “Advanced Composite Insoles for the Reduction of Stress Fractures.”2 Stress fractures reportedly cost the Army over $100 million per year and he notes that soldiers in boot camps and high impact units reportedly have fracture rates ranging from 5 to 15 percent.2
“It is hard to be combat ready if 10 percent of your command cannot carry their weight and the army realizes that,” he notes.
Mr. Sobel calls Dr. King’s combination of levered carbon fiber orthoses with lightweight boots “innovative and revolutionary.” He argues that like so many inventions that start with military applications, the foot orthosis/boot combination could easily find a market in emergency services, forestry service and other areas.
“A recreational model could be a big hit with ultra marathon runners as well since it is also the only orthosis/footwear combination I know of that actually has true energy return, which comes in handy when on a 50 or 100 mile run,” says Mr. Sobel.
Could orthotic systems reduce negative work during gait?
As Dr. Blake explains, negative work occurs when the force of the motion and the displacement of the object are in opposite directions, which occurs when orthotics restrict abnormal pronation or supination. Orthoses permit normal pronation so he says the force and displacement are in the same direction, producing positive work.
One wants orthotic devices to perform positive work on motion that is desirable for function (like normal pronation for shock absorption and push off acceleration), according to Dr. Blake. He adds that one also desires that orthotic devices in pathological conditions produce negative work against the abnormal motions one wants to correct like contact phase overpronation and oversupination.
Dr. Blake adds that many times the force against the motion only slows the motion, but does not change that motion, so the work is still negative in total. However, he says a well-designed orthotic device, even if not producing total correction of abnormal motion, tends to produce negative work. He notes one wants the orthotic device to help in push off, where the motion and displacement are in the same direction, producing positive work. Present orthotic systems do not produce positive work at push off, says Dr. Blake, noting they only place the foot in a position to push off well.
If by definition an orthotic aids the mechanics of the foot during gait, Dr. Mathews says the device should therefore reduce the amount of mechanical work required by the muscles. Specifically, he says functional orthotics aid in reducing body force, most commonly excessive pronation of the foot during heel strike to foot flat, which reduces the mechanical work of the tibialis posterior and anterior muscles.
Mr. Sobel feels orthotics are definitely capable of reducing negative work during gait as long as one customizes the orthotics to the patient’s needs.
“Sometimes the orthotics a patient comes in with either address one part of multiple issues they are having, or partially reduce a single biomechanical abnormality but could go further,” says Mr. Sobel. “Going further may be the difference between reducing pain or injury and eliminating it.”
Dr. King cites research finding that total negative and positive work in level walking was −34 J and 50 J respectively in 34 patients, with the difference in magnitude being statistically significant.3 The authors concluded that walking therefore occurred with 16 J of net positive muscle work per step. He notes an orthotic that has the ability to assist the lower extremity in harvesting and tuning out impact forces and an additive spring element may be able to reduce the negative work required by the body, saying the thigh and leg muscles are required to do non-propulsive work to offset these contact forces. Successful gait orthotic systems could store energy in a material with a high modulus of elasticity, says Dr. King, and be able to return the energy at the right time of gait with enough force to do work.
Furthermore, Dr. King says advanced composite and simple machine orthotic systems may be able to influence positive “propulsive work” required by the user with the use of leverage to assist with the work of lifting the heel and by increasing forefoot toe-off strength with composite reinforcement stiffening of the ball of the foot during the late stance phase of gait.
“An increase in overall gait efficiency will help hold open many doors for those who need it,” says Dr. King.
What medical purposes should exempt runners from being prohibited from wearing orthotics in competition?
As Dr. King notes, US Track and Field rule 143 on athletic attire states that advantageous footwear systems are illegal in competition yet states that “Orthotic inserts required for medical purposes are exempt from this rule.”4
Calling the issue a “slippery slope,” Dr. Mathews notes that orthotics reduce the work required for propulsion and therefore decrease muscular fatigue. Further, he says orthotics stabilize the foot through gait, which increases the efficiency of the foot during gait. If the muscles require less work to stabilize the foot during gait, Dr. Mathews notes there is more energy left for propulsion, which increases performance.
“Most athletes relate they have less muscular fatigue when using functional orthotics, which could create a competitive advantage,” contends Dr. Mathews.
Medical conditions that would not allow the athlete to compete without medical aid such as an orthotic should be the standard of usage, according to Dr. Mathews. However, he notes the question is if the orthotic should aid the athlete in competing at a higher level. As he argues, it is impossible to fabricate a device that only treats the medical condition and does not decrease work for the foot.
In the last 20 to 30 years, Dr. Blake has not known any athletes who are not wearing orthotic devices to produce subtle performance enhancing changes in their gait. Running is a sagittal plane motion, so he says most of the frontal plane motion slows them down. As of now, Dr. Blake says having a doctor’s note stating the medical need of the orthotic is enough to be able to wear an orthotic device in a race. He points out that there are over 20 common injuries related to overpronation, and 17 related to oversupination. With the small space in the track shoes, he says sometimes simple pads can produce biomechanical changes adequate for improving pain syndromes and performance.
Mr. Sobel believes that any device that manages deformities, injuries or biomechanical abnormalities should be acceptable in racing. He advocates having a “fairly broad range” of acceptable devices, saying athletes should be able to participate without being hobbled by injury. As for the “advantages,” Mr. Sobel distinguishes orthoses from the advantages that steroids provide, adding that the differences in orthotic materials and designs should not be an issue as long as they are available to all athletes.
Dr. King notes the question of orthoses in competition has been the hot topic of the International Olympic Committee since Paralympic runners started achieving significant results with their carbon fiber composite based gait systems and prosthetics and will be a hot topic more so in the future as these systems continue to mature and improve.
Dr. Blake is the Past President of the American Academy of Podiatric Sports Medicine. He practices in San Francisco.
Dr. King is a staff physician at the Maui Medical Group and Maui Memorial Medical Center in Hawaii. He is a Co-Principal Investigator of the Advanced Composite Orthotic and Boot Systems tested for SBIR A11-109 for the U.S. Department of Defense and Army Medical Research Command. Dr. King is a Diplomate of the American Board of Multiple Specialties in Podiatry. He is a managing member of Kingetics LLC and patent author of US patent 8,353,968, the Spring Orthotic Device.
Dr. Mathews practices at Vancouver Podiatry in Vancouver, BC. He is affiliated with Vancouver General Hospital and the Royal Columbian Hospital in New Westminster, BC. Mr. Sobel is affiliated with Sobel Orthotics in New Paltz, NY.
1. Available at http://soldiersystems.net/2014/04/28/us-army-issues-rfi-jungle-boot/ .
2. Available at http://www.acq.osd.mil/osbp/sbir/solicitations/sbir20112/army112.htm .
3. DeVita P, Helseth J, Hortobagyi T. Muscles do more positive than negative work in human locomotion. J Exp Biol. 2007; 210(Pt19):3361-73. 4. Available at http://www.usatf.org/usatf/files/f1/f101f17f-1b8b-4f1b-ac9c-d9022155aa94... .