The foot’s natural movement during running, known as the gait cycle, involves a subtle inward roll called pronation, which is the body’s method of absorbing impact. Supination, also referred to as underpronation, is the opposite movement, where the foot rolls outward. While a small degree of supination is a normal part of the push-off phase, excessive or prolonged supination during the mid-stance phase can compromise the foot’s ability to absorb shock effectively.
Defining the Biomechanics of Supination
Supination describes the outward rolling motion of the foot as it strikes the ground, causing the runner’s weight to be disproportionately concentrated on the lateral edge of the foot. When the foot rolls outward, it does not achieve the necessary internal rotation, or pronation, that normally allows the arch to flatten slightly and distribute the impact forces. This lack of inward collapse means the foot remains rigid and acts like a poor shock absorber throughout the ground contact phase. The foot’s structure is often a contributing factor, as supinators typically have higher, more rigid arches that resist the natural flattening motion required for efficient shock dampening. This rigidity forces the entire lower leg to bear the brunt of the impact, as the foot’s natural cushioning mechanism is bypassed.
Identifying Supination in Your Stride
Runners can use a couple of simple, practical methods to assess whether they underpronate. One common approach is the “wet test,” which involves wetting the foot and stepping onto a piece of dark paper or concrete to examine the footprint. A supinated foot print will characteristically show a very thin or absent connection between the forefoot and the heel, indicating a high arch that does not collapse to make full contact with the ground. This narrow mid-foot print confirms the arch’s rigidity, which is often associated with underpronation.
Another method involves analyzing the wear pattern on the sole of existing running shoes. A sign of supination is excessive wear concentrated along the outer edge of the shoe, particularly on the lateral side of the heel and the pinky toe area of the forefoot. Normal wear is usually more generalized across the forefoot, but the distinct lateral wear pattern suggests the foot is not properly transitioning through the pronation phase of the gait cycle.
Common Injuries Linked to Underpronation
The rigid foot strike and poor shock absorption inherent in underpronation can lead to a specific range of running-related injuries. Since the foot does not adequately cushion the impact, the forces from landing travel directly up the leg, increasing the likelihood of stress fractures in the metatarsals, tibia, or heel bone.
The constant weight bearing on the outer edge of the foot also puts undue strain on the ankle ligaments, significantly increasing the risk of lateral ankle sprains, especially when running on uneven surfaces.
The altered biomechanics can affect the alignment of the entire leg. This misalignment may lead to the development of iliotibial (IT) band syndrome, a painful condition on the outside of the knee, as the leg muscles and connective tissues attempt to compensate for the foot’s lack of inward roll. Other common issues include Achilles tendinopathy and plantar fasciitis, as the stiff arch and limited movement place increased tension on the plantar fascia and the Achilles tendon.
Selecting the Right Gear and Support
The primary strategy for managing supination focuses on compensating for the foot’s limited ability to absorb shock with appropriate gear. Runners who supinate should specifically look for neutral running shoes that offer maximum cushioning in the midsole. These shoes are designed without the stability features that would further restrict the foot’s already limited inward roll, allowing for more natural movement.
The goal of the footwear is to provide a soft landing platform and improved flexibility, which helps to mitigate the impact forces that a rigid, supinated foot cannot dampen. Shoes with thick, soft midsoles, often featuring high-stack cushioning, are particularly beneficial for absorbing the hard ground contact. Look for shoes described as having a non-prescriptive ride, meaning the sole does not attempt to control the foot’s motion but rather cushions it.
In addition to highly cushioned, neutral shoes, some runners may benefit from the use of custom orthotics or high-quality cushioned insoles. While the running shoe provides the primary shock absorption, an orthotic can offer gentle alignment assistance and extra padding directly under the foot to help distribute pressure more evenly across the sole. This added support can reduce the concentration of force on the outer foot and reduce the risk of supination-related overuse injuries.