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Foot type refers to differences in foot structure and shape, as reflected in pronation (side-to-side tilting of the foot) during heel strike running.
Foot type affects the reduction of impact on the foot while walking, jogging, or running. Specifically, the shape of the individual’s foot as a whole, the shape of their arch, and the extent to which they pronate, determines foot type.
During the gait cycle the foot can pronate in many different ways based on rearfoot and forefoot function.
In anatomy, pronation is a rotational movement of the forearm (at the radioulnar joint) or foot (at the subtalar and talocalcaneonavicular joints). Pronation of the foot refers to how the body distributes weight as it cycles through the gait. Types of pronation include neutral pronation, underpronation (supination), and overpronation.
An individual who neutrally pronates initially strikes the ground on the lateral side of the heel. As the individual transfers weight from the heel to the metatarsus, the foot will roll in a medial direction, such that the weight is distributed evenly across the metatarsus. In this stage of the gait, the knee will generally, but not always, track directly over the hallux.
This rolling inwards motion as the foot progresses from heel to toe is the way that the body naturally absorbs shock. Neutral pronation is the most ideal, efficient type of gait when using a heel strike gait; in a forefoot strike, the body absorbs shock instead via flexation of the foot.
As with a neutral pronator, an individual who overpronates initially strikes the ground on the lateral side of the heel. As the individual transfers weight from the heel to the metatarsus, however, the foot will roll too far in a medial direction, such that the weight is distributed unevenly across the metatarsus, with excessive weight borne on the hallux. In this stage of the gait, the knee will generally, but not always, track inwards.
An overpronator does not absorb shock efficiently. Imagine someone jumping onto a diving board, but the board is so flimsy that when it is struck, it bends and allows the person to plunge straight down into the water instead of back into the air. Similarly, an overpronator's arches will collapse, or the ankles will roll inwards (or a combination of the two) as they cycle through the gait.
An individual whose bone structure involves external rotation at the hip, knee, or ankle will be more likely to overpronate than one whose bone structure has internal rotation or central alignment.
An individual who overpronates tends to wear down their running shoes on the medial (inside) side of the shoe towards the toe area.
When choosing a running or walking shoe, a person with overpronation can choose shoes that have good inside support—usually by strong material at the inside sole and arch of the shoe. It is usually visible. The inside support area is marked by strong greyish material to support the weight when a person lands on the outside foot and then roll onto the inside foot.
An individual who underpronates also initially strikes the ground on the lateral side of the heel. As the individual transfers weight from the heel to the metatarsus, the foot will not roll far enough in a medial direction. The weight is distributed unevenly across the metatarsus, with excessive weight borne on the fifth metatarsal, towards the lateral side of the foot. In this stage of the gait, the knee will generally, but not always, track laterally of the hallux.
Like an overpronator, an underpronator does not absorb shock efficiently - but for the opposite reason. The underpronated foot is like a diving board that, instead of failing to spring someone in the air because it is too flimsy, it fails to do so because it is too rigid. There is virtually no give. An underpronator's arches or ankles don't experience much motion as they cycle through the gait.
An individual whose bone structure involves internal rotation at the hip, knee, or ankle will be more likely to underpronate than one whose bone structure has external rotation or central alignment. Usually - but not always - those who are bow-legged tend to underpronate.
An individual who underpronates tends to wear down their running shoes on the lateral (outside) side of the shoe towards the rear of the shoe in the heel area.
It is a common misconception that those with fallen arches or flat feet overpronate. However, individuals with flat feet can have a neutral, overpronated, or underpronated gait. Likewise, individuals with very high arches can be neutral, overpronated, or underpronated. Pronation depends not on the shape of the foot or on the shape of the static arch, but on the extent to which the arch collapses when the foot goes through its walk cycle.
Some will suggest doing the wet foot test to determine foot type. The wet foot test involves wetting the bottom of the feet and standing on a paper bag to make a footprint. Footprints with a very narrow, curved shape are said to represent high arches and thus underpronated foot types; footprints with a semi-curved shape are said to represent medium arches and thus neutral foot types, and footprints with a very straight shape are said to represent flat feet and thus overpronated foot types.
While it is certainly possible that an individual with a high arch may underpronate, one with a medium arch may be neutral, and so on, this is not always the case. The wet foot test is often inaccurate because it only shows the shape of the foot when the foot is static. The wet foot test fails to determine what happens to the foot while it is in motion - that is, as the foot strikes from heel to toe.
The wet foot test also fails to account for the bone structure of the entire leg; i.e., internal rotation, external rotation, or Genu varum.
A common injury associated with overpronation is plantar fasciitis, which results from the ripping and subsequent inflammation of the plantar fascia underneath the foot as the arch collapses.[1] Orthotics, which are rigid inserts designed to prevent the arch from collapsing, are often prescribed by doctors for various injuries including plantar fasciitis. Over-the-counter inserts function in a similar manner.
A common injury associated with both overpronation and underpronation/supination is iliotibial band syndrome.[2] Pain is generally felt in the hip or the lateral side of the knee.
Stiff shoes tend to support overpronated feet because they prevent the foot from rolling inwards as it progresses from heel to toe. The last of the shoe is generally determinant of the shoe's stiffness: straighter lasts tend to render the shoe stiffer. More curved lasts tend to make the shoe more flexible, and thus more appropriate for neutral pronators or underpronators.
Some running shoes have pieces of denser material built into their medial side. This also helps guide the overpronated foot back into a neutral position.