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Excessive pronation has often been associated as a predisposing factor for several lower extremity overuse injuries. Research has investigated the causes of these injuries and their association with various degrees of pronation, finding a positive correlation with excessive pronation and injury in the lower extremity. One field of research that has not been heavily investigated is the improvement of the biomechanical efficiency of the foot and an overall reduction in excessive foot pronation with specific muscular strengthening.
Identifying abnormal foot pronation will only inform the runner of their increased risk for injury, and has no practical application of improving their biomechanical efficiency in the future. It has also been commonly associated that with increased work and fatigue, the degree of pronation will increase as well, indicating muscular fatigue of supporting lower extremity muscle groups. Examining the strength and endurance of those muscles may provide insight into training techniques, decreasing the amount of overuse injuries during training. The purpose of this study is to examine the relationship between lower extremity muscle strengthening and the resulting change in degree of foot pronation in recreational runners. The results will shed light onto possible effective training techniques to reduce excessive pronation in recreational runners. One of the main lower leg muscles that are commonly associated with the anatomical structures relating to foot pronation is the Tibialis Posterior. This muscle “originates on the posterior aspect of the tibia, fibula, and the interosseous membrane. It courses posteriorly and medially around the ankle in a groove adjacent to the medial malleolus and inserts on the midfoot in the area of the navicular tuberosity (Howitt). More specifically the tendon “travels down posteriorly to the medial ankle and inserts on the navicular, two of the cuniforms, the cuboid, and several of the metatarsal bones” (Benjamin). The Tibialis Posterior extends from the posterior aspect of the lower leg and then attaches right beneath the medial aspect of the longitudinal arch. When this muscle fatigues or is weak, poor biomechanics and efficiency of the foot and ankle complex results. The influence of the tibialis posterior was seen in a study that implemented orthotic use and physical therapy to a group of individuals with mild to moderate tibialis posterior dysfunction. The results of the treatment were that 89% of the participants responded to the regime of orthotic use and physical therapy. The results of this study are important to the notion of tibialis posterior muscle strengthening and the positive results that can be obtained through exercise for the foot structures involved during excessive pronation.
Another study examined the anatomical differences between two groups, one with an accessory navicular bone and the other with normal feet. The findings were the group with the accessory navicular bone had a tibialis posterior tendon that inserted directly into the accessory navicular bone, without any continuation to the sole of the foot. These abnormalities were not found in the control group. This means that an insufficient or abnormal tibialis posterior tendon correlates positively with low arches, which is commonly associated with excessive pronation. This indicates the importance of the tibialis posterior muscle in the support of the longitudinal arch and supporting the medial structures of the foot.
The tibialis posterior assists in plantar flexion and plays a key role in supporting the medial arch. This muscle in addition to the peroneous muscle in the lateral leg and foot provide stability to the ankle on uneven surfaces and are often referred to as the “stirrup muscles.” There are three basic movements targeted to strengthen the muscles surrounding the ankle and the supporting structures. The first is called Inner-ankle lift of the foot and is a weighted movement in the medial direction when the leg is fixed on a surface which strengthens the tibialis posterior. The function of this exercise is to increase the strength and endurance of this muscle, providing more support to the medial arch. Using this exercise in conjunction with “outer ankle lifts” and calf raises should increase the overall stability of the foot and ankle complex. There is a strong association with certain anatomical landmarks on the foot that correlates to excessive pronation. Foot posture has been examined in literature using measures of the medial longitudinal arch such as navicular height and arch height ratio. Navicular height has been defined as “the vertical distance from the floor to the navicular bone in standing” and arch height ratio as the “height of the dorsum at 50% of foot length standardized to truncated foot length, the distance from the posterior calcaneus to the first metatarsophalangeal joint. An increase in navicular height or arch height ratio corresponds with an increase in medial longitudinal arch height and is associated with a reduction in pronated foot posture. Based on this research it would suggest that exercises targeting to increase these anatomical measurements would produce a desired reduction in biomechanical foot pronation during running. Strengthening supporting muscles of the lower leg would produce increases in navicular height and arch height ratio resulting in a more normal foot pronation.
Excessive foot pronation has been associated with the risk of overuse injury in running for several years. Limiting the amount of biomechanical abnormalities in running will allow athletes and runners to train with a reduced risk of injury occurrence. This is why previous research has focused heavily on how to “control” excessive pronation through orthotics and motion control footwear. A more proactive approach to correcting overpronation concerns will be to physically alter the anatomical muscles involved in foot pronation to reduce biomechanical inefficiencies and increase overall muscle strength and endurance. Specifically targeting supporting muscles such as the tibialis posterior and lower leg muscles will improve anatomical measures and reduce foot pronation.
write by Ionel Pascan