Flexible flatfoot is one of the most common lower-extremity musculoskeletal deformities and is associated with altered foot alignment, reduced stability, and changes in the activation patterns of lower leg muscles, which may impair functional movement. In addition, foot progression angle and the type of resistance used during exercise are important factors influencing muscle activation and neuromuscular control. Despite the widespread use of compressive and elastic resistance tools in corrective exercise, limited evidence is available regarding their combined effects on lower leg muscle activity in individuals with flexible flatfoot. Therefore, the present study aims to compare the electromyographic activity of the tibialis anterior, peroneus longus, and extensor digitorum muscles in three foot positions (toe-in, toe-out, and neutral) under compressive and elastic resistance in individuals with flexible flatfoot and those with normal foot posture.



This study is a laboratory-based comparative investigation with a repeated-measures design. Twenty-four healthy men aged 18–35 years, including 12 participants with flexible flatfoot and 12 with normal foot posture, will be recruited using purposive sampling. Muscle activity will be recorded using surface electromyography, and muscle activation and co-contraction indices will be calculated after normalization to maximal voluntary isometric contraction (MVIC). Data will be analyzed using repeated-measures analysis of variance with a significance level of 0.05. The findings are expected to improve the understanding of lower leg muscle activation patterns and contribute to the development of more effective corrective exercise and rehabilitation programs for preventing lower-extremity musculoskeletal injuries.