Effects of Rhythm Step Training on Radiographic Foot Alignment and Isometric Ankle Muscle Strength in Youth Surfers with Flexible Flatfeet: A Randomized Controlled Trial

Flexible flatfeet may affect foot alignment and ankle muscle function, which may be particularly relevant in children and adolescent surfers who require continuous postural control and weight shifting. This study investigated the effects of a 12-week rhythm step training (RST) program on radiographic foot alignment and isometric ankle muscle strength in children and adolescent surfers with flexible flatfeet. A total of 169 participants were allocated to either the general flat feet training (GFFT) group (n = 86) or the RST group (n = 83). Both groups completed one 50-min exercise session per week for 12 weeks. Radiographic foot alignment was assessed using the calcaneal pitch angle (CPA), calcaneal–first metatarsal angle (CFMA), and navicular–cuboid overlap ratio (OR), while isometric ankle dorsiflexion (DF) and plantarflexion (PF) strength were assessed. Two-way mixed analyses of variance revealed significant time × group interactions for bilateral CPA, CFMA, and navicular–cuboid OR (p < 0.05). The RST demonstrated greater improvements in radiographic foot alignment than the GFFT. Significant time × group interactions were also observed for bilateral PF and DF strength (p < 0.001), with greater improvements in the RST. These findings suggest that RST may be an effective exercise approach for improving radiographic foot alignment and isometric ankle muscle strength in children and adolescent surfers with flexible flatfeet.