Though all designed for the same essential function, human feet vary significantly in their structure between individuals. The most significant difference in foot structure is the arch, referring to the curve between the ball of your foot and the pad on your heel. The foot arch can range from a very high visible arch all the way to what is considered flat feet, with no visible arch and almost the entire sole of the foot making contact with the ground. This difference in structure changes the biomechanics of the foot, in turn changing the way we walk, run, jump, and complete any athletic feat. So how exactly do our arches play into athletic performance?
The arch of the foot is made up of three main parts, the Medial Longitudinal Arch (MLA), the Lateral Longitudinal Arch (LLA), and the Transverse Arch (TA). The MLA is the most visible, running along the inside of the foot. The role of these arches in the feet are primarily to act as shock absorbers, acting like a spring when the foot is impacted. The arch of the foot also acts as a lever to launch the foot and attached limb upwards while running, walking, jumping, and other athletic functions. Even slight changes in the structure of these arches can lead to alterations in joint kinematics as well as strength and range of motion.
In a first study conducted by researchers, participants with normal arches and participants with flat feet were tracked using a 3D motion analysis system while walking barefoot on a short track. The results showed that the walking speed and step length of both groups were very similar. The differences found were more subtle, boiling down to an overpronation of the foot, where the inner ankle shifted inwards while the rest of the foot stays put as seen below in Image of overpronation.
In a second study done by researchers, the impact of foot arch on collegiate sprinters was analyzed through analysis of vertical jump, 40 yard dash, and a balance test. In all three tests, a higher arch corresponded to better performance in all three tests. As sprinters ran, those with higher arches had faster time of contact on the front of the foot and less on the rear of the foot, a contributor to higher speeds.
In a third study, researchers found that there was another positive correlation between arch height, ankle flexion in both directions, strength, and ankle mobility, though not significant. As the arch of the foot acts as sort of a spring damper system, a flatter foot acts like a flatter spring, dissipating more energy than a foot with a higher arch. Additionally, overpronation of the foot weakens the ankle, shifting some of the burden to the knee and the hip, which reduces instant power coming from the ankle.
Although trends are not entirely clear on whether these links are consistent across all athletes, the biomechanical differences are certain. While it may be slightly preferable to have higher arches, flat feet are not a significant limiter to athletic performance and are remarkably adapted for by the amazing human body.
An interesting YouTube video on flat feet and running if you are interested!