Matching Running Shoes to Foot Type
By Kurt Jepson
Bones of the foot/ankle complex below.
There are 3 basic gait phases. Heel strike where the calcaneus/hindfoot takes load laterally in a slightly tilted position (supinated /varus). Stance is next as the midfoot pronates to adapt to the terrain and dampen load. The ankle is dorsiflexed and the forefoot abducted. Lastly toe off/propulsion occurs when the foot resupinates to become a rigid lever system. The calf muscle plantar flexes the ankle vigorously and the forefoot adducts. All of these motions occur within, or in concert with the shoe.
So you thought you could get just one more summer training season out of your running shoes, but upon inspection, and perhaps “sore dogs” after your first session in them, you decide otherwise.
Athletic running shoes are a major purchase and an important component of your training gear. The athlete should have a basic knowledge of their individual foot structure, dynamic characteristics, gait, specific shoe designs and intended use prior to engaging with retail personnel. This allows for an informed purchase and more comfortable training.
Injuries related to running are prevalent. As many as 37-56% of all runners sustain at least one injury annually that interrupts training (Van Gent, et al ,2006). Running related injuries are likely multifactorial in origin and related to a mix of extrinsic inputs (ie training error, footwear) and intrinsic characteristics (ie bony alignment and strength issues). Wen D, Puffer J, et al. did an exhaustive study of 304 marathon runners in 1997. They gathered data on training practices and injury occurrence over a 12 month period, as well as measurements of arch height, calcaneal position, knee and patellar posture and leg length differences. Interestingly they were unable to correlate alignment data and injury occurrence with acceptable statistical significance (Lower Extremity Alignment and Risk of Overuse Injuries in Runners. Med Sci Sports Exer. May, 1997). Their conclusions correlated with numerous other investigators, but conflicted with prior studies by Cowen, Viitasalo and others. The topic of structural foot and limb characteristics and their relationship to running induced injuries continues to garner much attention in the biomechanical and sports medicine literature. Consensus is still lacking.
Enter shoes. If structure has limited input into one`s development of a running injury per the studies above, how does a device engineered to limit or accentuate extremity movement relate to protection, or running performance? What factors should the athlete base a shoe purchase on? Does shoe design even matter for you?
Let`s start with a look at foot/ankle form and function. There are 26 bones and 33 joints in the human foot. Each has an inherent task of assisting with propulsion and/or adapting to a surface. As with all skeletal components, ligaments connect bone to bone and muscle tendon units insert onto bone to initiate or dampen movement. Muscles may be “intrinsic” (contained within the borders of the foot proper) or “extrinsic” (reside in the calf and shin area).
Biomechanists and kinesiologists often separate the foot into 3 functional regions consisting of the fore-, mid- and hindfoot.
As upright bipedal mammals our feet must be rigid enough to lift and propel our substantial mass against gravity (Forefoot) and at other times act as a loose adapter (Midfoot) to conform to uneven terrain. The foot must also absorb vertical load (Hindfoot) and maintain balance (all sections). These requirements could not be more different in terms of anatomic requisites. Each segment of the foot contributes to all of these mechanical tasks to some degree.
Motions of the foot/ankle complex are “tri-planer” in nature and include; Dorsiflexion (forefoot toward shin), Plantarflexion (toe point), inversion/adduction (twist inward) and eversion/abduction (twist foot outward). Pronation (component of eversion) and supination (component of inversion) are multiaxial movements that occur via hindfoot and midfoot movement at the subtalar joint.
Pronation “unlocks” the foot and joint surfaces become less congruent. Architectural bony support is compromised. Associated ligaments and muscle tendon units must work harder to maintain foot postures. Conversely, Supination places the joints of the foot in a more compact, stable alignment maximizing structural rigidity. It`s important to note that static anatomic alignment is much different than the accentuated positions the foot assumes while running.
Both have important functions during walking or running gait. Running shoe design over the years has arguably focused more effort on affecting transverse plane motion than vertical load attenuation.
Much has been written about normative foot position and what constitutes aberrant pronation or supination during gait. The concept of a “neutral position” which allows the foot to function optimally continues to be debated. When an individual “over pronates” or correspondingly “supinates” too late or too little, soft tissues are stressed as they attempt to compensate for supporting/ propelling one`s mass via a “loose” structure. Medial tissues in the arch or shin are at particular risk (Plantar Fascia, Posterior Tibial Tendon ,etc.).
Conversely a lack of pronation or “sustained supination” is correlated to poor shock absorbency (limited adaption) and resultant stress fractures, great (big) toe pathology, bursitis, lumbar symptoms, etc. There are very few true “active supinators”, comprising under 5% of all foot types. There are however those that “under pronate” during stance. “Under pronator” is a more accurate classification for this population.
Running shoes have been designed over the years to affect these situations in a biomechanically favorable way by encouraging the foot to operate close to it`s “neutral” position, neither excessively pronated or supinated, at any stage of the gait cycle. The difficulty lies in that there is a wide range of “normal” motion and position, specific to the individual (via their gene pool). As mentioned above there isn`t even agreement on what a “neutral position” is, it`s importance, or how to measure it. Shoe design can therefore be quite varied based upon which biomechanical theory the companies staff subscribe to.
Other influences of foot posturing and function during gait include pace, terrain, tactile input, fitness, and ingrained motor patterns established as a child. Muscle fatigue subsequent to running significantly alters foot function.
Cheung R, et al. were able to demonstrate significantly higher medial plantar (arch region and great toe) peak loading forces at the end of only a 1.5k run using video analysis and indwelling sensor insoles in women runners classified as “excessive” pronators. Study participants were excluded if they had measurable pronation less than 6 degrees or were “professional” athletes. Two shoe designs were used by all subjects (both Adidas), a “neutral” shoe and a “motion control” model. They found a 15% increase in peak medial loading after just 1.5k of running in the neutral shoe. There was no significant change in foot loading while using the motion control shoe. More interestingly, all runners, regardless of shoe use experienced significant reductions in Max Volitional Contraction (MVC) of their invertors. The Posterior Tibialis is a major contributor to load dampening, pronation control and propulsion during gait. It`s peak contraction force decreased 30-40% after just 1.5k of effort. The motion control shoe seemed to be able to compensate for this decline in dynamic muscle input. (Influence of Different Footwear on Force of Landing During Running. Phys Ther 88 (5), 2008).
Intrinsic control of the foot declines as training distance increases. Fatigue accentuates biomechanical inefficiency. Butler and colleagues have shown that hindfoot mechanics change less than the midfoot as a run progress`s. Their studies indicate that a running shoe controls excessive midfoot motion late in a run but has little effect on hindfoot motion at any stage. As with most musculoskeletal issues specific conditioning can positively influence a symptom or provide prophylaxis, especially those exercises targeting the mid foot.
Posterior Tibialis, inverter strengthening with resistance band, below.
Intrinsic muscle conditioning in the NON-symptomatic foot below
For years shoe manufacturers’ have designed and marketed shoes to athletes based on the premise that those runners that are excessive pronators and have excessively mobile feet require a controlling shoe. Conversely, those with more rigid structure, maintaining a supinated position longer in the gait cycle, should use a soft neutral shoe to allow motion to occur.
“Motion Control” shoes are generally designed on a straighter last, have a wider sole geometry, and include denser mid sole foam (EVA) medially in the midfoot (a post). They feature reinforced heel counters, and limited outer sole forefoot flex channels, especially under the great toe. Overall flex and torsional rigidity is “stiff”. Midsole overall thickness is greater and the heel to toe drop/change is typically 12mm or more.
Posted shoe example below
“Neutral” (cushion) shoes tend to be curved, narrow, non-posted and have a soft upper and minimal heel counter. Their outer soles are deeply channeled to enhance mid and forefoot flex during stance and propulsion. Torsional rigidity is very limited. One can easily grasp the front and rear of the shoe, twist and deform it. Midsole drop is usually 4mm or less.
Neutral shoe below
“Stability” shoes are a hybrid design. Platform shape is wider than Neutral shoes especially in the heel. Some are posted but may be abbreviated in length or of a less dense material. Some designs use “cradle” or “rail” midfoot inserts to add stiffness to the chassis. Heel counters vary in stiffness. Heel toe drop of the midsole typically is between 4-12mm. They typically address rearfoot shock via materials or contours.
Stability shoe below.
There are some basic assessment tools one can employ to help classify foot type. Years ago retailers and clinicians routinely used the “Wet Test” to classify foot types. This simply involved placing the athlete`s feet in a bucket of water and then having them walk along paper placed on the floor. The focused areas of weight bearing were captured via the “wet” pattern left on the paper. The foot was then classified as “pronated” or “supinated” and the appropriate shoe suggested. This procedure has been replaced in the retail setting with simplistic force plates and pressure sensors producing images via a computer that assist in marketing a “custom” fit.
“Wet Test” foot types; A. “Supinator” B. Pronator C. Neutral (below)
The “Wet Test” does give the athlete a basic sense of their tendency to over, or under pronate during the stance phase. Walking on wet sand will give similar feedback. Running on sand and inspecting your tracks will provide insight as to dynamic foot function. If there is little difference between walking and running footprint shape start exercising!
Inspecting an old pair of shoes for sole wear patterns also provides useful information. If the great toe area on your shoes is worn, you are likely a successful pronator. The extent of wear and /or absence of middle sole wear can add to the picture regarding control needs. The more disperse the wear pattern, the more efficiently your foot is working. Callous pattern on the sole of the foot will typically mimic shoe wear zones and confirm what is noted on footwear. If the heel counter is collapsed inwardly you over compensate. If an abrupt lateral wear pattern and outward tilt of the heel counter is observed, you pronate minimally.
Another assessment tool simply involves observing/photographing the hindfoot from above while the athlete lies prone with their feet off edge and relaxed. Baring significant calf tightness or hip rotational malalignment, the heel will assume a position in line with the lower leg (neutral) or some degree of inward tilt (varus). In rare cases valgus orientation will be noted (true supinators). Subonick and others feel this relaxed foot/ankle position is within 3 degrees of one`s subtalar neutral posture (anecdotally I agree).
Note significant hindfoot varus on the left, subtle on the right.
The athlete then stands, marches in place for a few seconds and then relaxes in equal weight bearing. The hindfoot position is viewed/photographed from behind. The heel will either stay in a relative varus position (rigid supinated), assume a perpendicular position in relation to the floor (if one was to bisect the calcaneus with a vertical line, neutral) or tilt to the outside (valgus, loose, pronated).
Clinicians describe these hind and midfoot responses from non-weight bearing position to weight bearing position as degrees of “compensation” by the subtalar joint. When the hindfoot posture noted in non-weight bearing maintains the same orientation while weight bearing, the foot is said to be “uncompensated”. When the hindfoot moves from a position of varus (or neutral) to valgus while weight bearing it is “compensating” as in the photo above.
Compensating Foot
An uncompensated foot under pronates and requires a neutral shoe that encourages motion not restricts it. A compensated foot readily pronates and may benefit from negating a portion of that with a motion control shoe.
So how important is matching foot type precisely to shoe design in terms of injury prevention? There is a vast amount of literature debating this topic but one study stands out.
Knapik J, et al in 2014 did a meta-analysis of three 2007 investigations involving over 7000 male and female recruits from all branches of the military during basic training (Injury Reduction Effectiveness of Prescribed Running Shoes on the basis of Foot Arch Height: Summary of Military Investigations, JOSPT 44 (10) oct 2014).
Individuals were assigned to either a motion control, stability, or cushioned shoe group based on their plantar foot shape derived via a visual force plate apparatus. A control group received a stability shoe regardless of their plantar shape. Because of the basic training setting, numerous outside factors were well controlled such as shoe manufacturer and model, training load, reporting and injury diagnosis. Basic training duration ranged from 6-12 weeks based on the branch of service. All recruits wore their assigned shoes throughout training. An Injury Incidence Rate (IIR) was calculated to obtain injuries per 1000-person days.
Analysis indicated that there was insignificant difference in injury rates between recruits that wore a running shoe designed for their foot classification and those that received a stability shoe regardless of foot type. The take away is that a stability shoe that fits well, regardless of your foot type, will offer environmental protection, check excessive heel motion yet allow useful mobility, and attenuate shock. Some studies suggest a decreased metabolic cost of running in a stability shoe when compared with minimalist or barefoot running.
Retire those old sneaks to lawn mowing. Classify your foot. Buy new shoes. If you can`t decide, get a stability shoe. Enjoy the summer!