The effect of isokinetic hip muscle strength on normal medial longitudinal arch feet and pes planus.

Pes planus is a common foot and ankle physiologic deformity. The normal medial longitudinal arch is depressed or flattened due to a lack of strength in associated muscles, ligaments, and tendons. This study aimed to investigate how isokinetic hip muscular strength affected normal medial longitudinal arch feet and pea planus. Forty adult subjects participated in this study: 20 with pea planus and 20 with normal medial longitudinal arched feet. Both groups were similar in age (p=.074), weight (p=.324), height (p=.211), and BMI (p=.541). The navicular drop test determined the differences in navicular height. An isokinetic dynamometer was used to determine hip muscular strength (peak torque and total work) during hip flexion, extension, abduction, and adduction at speeds of 90°/s and 180°/s. A Kruskal-Wallis test was computed to determine the comparison between the normal medial longitudinal arch and pea planus. Subjects with normal medial longitudinal arch had more muscle strength than pes planus. Hip muscle strength did not show any significant difference between both groups. The abductor and adductor group muscles' total work were higher in subjects with pes planus. This study showed that normal medial longitudinal arched foot subjects have higher muscle strength than pes planus. However, the hip abductors were significantly lower in pes planus after measuring the total work, suggesting that individuals with pes planus are easily fatigued, possibly due to the overuse of the muscles that compensate for any changes in lower limb alignment.