Kazuki Wakamiya

Introduction: Demi-pointe is a characteristic movement in female ballet dancers that requires sufficient foot and ankle joint range of motion (ROM) and muscle strength. This ROM may result from the combined motion of the foot and ankle joints. However, no studies have investigated the characteristics of forefoot varus/valgus ROM and the relationship between ROM and muscle cross-sectional area (CSA) in ballet dancers. Therefore, this study aimed to compare ballet dancers and non-dancers to clarify the characteristics of foot and ankle ROM and CSA of the intrinsic and extrinsic foot muscles and the relationship between ROM and CSA in ballet dancers. Methods: This study included 12 female ballet dancers (24 legs) and 11 non-dancers (22 legs). The ROM of the foot and ankle joints—including plantar flexion and forefoot varus/valgus—and CSA of the intrinsic foot muscle (abductor hallucis, abductor digiti minimi, flexor hallucis brevis, flexor digitorum brevis, and quadratus plantae) and extrinsic foot muscles (peroneus longus, flexor hallucis longus, flexor digitorum longus, and tibialis anterior) were evaluated and compared between the two groups. The relationship between ROM and CSA was also examined. Results: Compared with non-dancers, ballet dancers exhibited greater plantar flexion and forefoot valgus and reduced varus. The CSA of the intrinsic foot muscles and the peroneus longus muscle were significantly greater in ballet dancers. In ballet dancers, a significant negative correlation was observed between the ROM and CSA. Among the ROM variables examined, forefoot valgus showed a significant negative correlation with the CSA of multiple muscles. Conclusions: Ballet dancers demonstrated greater foot and ankle ROM in the sagittal and frontal planes, along with a larger intrinsic foot muscle CSA compared to non-dancers. Among these features, increased forefoot valgus and a negative correlation between forefoot valgus and CSA are particularly noteworthy as it has not been previously reported.