When there are equal magnitudes of pronation and supination during standing and walking, rotational equilibrium results and no significant rotational velocity is imparted to the adjacent structures. A higher-than-normal arch can be a particular problem when there is significant asymmetry, especially if the other foot has little or no arch.
5 This type of foot generally requires improved flexibility ( mobilization, stretching) and stabilizing orthotics to help decrease shock at heel strike. Having a rigid, high-arched foot makes one susceptible to development of stress fractures in the sesamoids, calcaneus, femur and pelvis. This results in poor attenuation of heel-strike shock, much of which is then transmitted up the kinetic chain into the leg and hip. The foot with a higher-than-normal arch remains too rigid and inflexible during walking and running. Problems arise when there is too little or too much mobility in the foot and ankle. Normal amounts of movement are necessary for biomechanical function during activities of stance and gait. 4 While less frequently found, foot stiffness and hypomobility (a lack of pronation, usually with a high arch and fixed supination) can also be the underlying causes of significant lower extremity biomechanical distress. 3Ī 2004 paper dealt with the common problem of excessive foot flexibility and hyperpronation during gait. In fact, a study by Dahle, et al., found that athletes with either excessively pronated or supinated foot types were significantly more susceptible to knee injuries than those who had a normal pronation mechanism to absorb shock. "A high-arched (cavus) foot with limited range of motion attenuates shock poorly and a hypermobile flat foot also does poorly on shock attenuation because of its function near the end of the range of motion." 2 This helps explain how both types of foot dysfunction can contribute to musculoskeletal symptoms and injuries. Whenever there is either too little pronation (as is found in fixed supination), or excessive pronation, the effects of impact loading are amplified.
The study concluded that this was because an elevated arch tends to transmit, rather than absorb, heel-strike shock, as does the foot with a normal arch. In fact, an investigative study by Simkin, et al., conducted during a military basic-training session, found a much higher frequency of femoral stress fractures in recruits who had a cavus (high-arched) foot. However, too much arch can be just as much of a problem as not enough. Many articles have discussed how excessive pronation and the loss of the foot's medial arch ( flat foot) can negatively affect the mechanics of the lower extremities, as well as the pelvis and spine.
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