RESUMEN
OBJECTIVE: Flexible flatfoot is a common deformity in adults that has been thought to be a causative factor of a lot of lower limb injuries and back pain. Core muscles act as stabilizers for the trunk and weak core places a person at greater risk of low back pain and lower limb injuries. We aimed to compare the core muscles' endurance between individuals with and without flatfeet. METHODS: Thirty subjects with bilateral flexible flatfeet (study group) were compared with thirty healthy subjects (control group). Navicular drop test was used to evaluate the medial longitudinal arch. Modified back extensors, modified flexion and lateral muscles' endurance tests were used to evaluate the endurance of the core muscles. RESULTS: The lateral muscles' endurance time in the flatfeet group was found to be significantly lower than that of the healthy group on both sides (p=0.0001). However, no significant difference was found in the trunk flexors' (p=0.15) and trunk extensors' (p=0.27) endurance time between both groups. CONCLUSIONS: Impairment of the lateral core muscles' endurance was observed in subjects with bilateral flexible flatfeet which may predispose to low back pain and other lower limb injuries in those subjects.