Effects of a long-term triceps surae stretching program on the pennation angle of triceps surae heads in children with hypermobile flat foot and Achilles tendon shortening

BACKGROUND: Triceps surae retraction plays a key role in the pathogenesis of flat feet in children. This is a pennate muscle. The pennation angle is defined as the angle between triceps surae fascicles and aponeurosis. AIM: The aim of the study was to evaluate the effect of a long-term triceps surae stretching program on the pennation angle of the triceps surae head in children with flat feet and Achilles tendon shortening. MATERIALS AND METHODS: The study included a total of 82 children with hypermobile flat feet and Achilles tendon shortening. The pennation angle was measured by ultrasound. Triceps surae stretching was recommended for 6 months as a basic exercise. SPSS v.26.0 was used for statistical analysis of data. RESULTS: The study group included 63 children who performed stretching exercises and the control group included 19 children who did not perform stretching exercises at the required intensity. The study group showed a significant improvement in the Foot Posture Index (FPI)-6, while the control group showed no change. The baseline foot dorsiflexion was 4.84° ± 0.10° in the study group and 4.81° ± 0.17° in the control group. After 6 months of stretching, dorsiflexion was 11.34° ± 0.24° in the study group and 4.85° ± 0.19° in the control group (p 0.01). The pennation angle of the triceps surae heads showed a significant increase in the medial head of the gastrocnemius and soleus muscles. CONCLUSIONS: A long-term stretching program in children with flat feet resulted in a significant increase in foot dorsiflexion. These changes were associated with morphological and functional muscle restructuring, manifested by a significant increase in the pennation angle of the medial head of the gastrocnemius and soleus muscles. Further research will identify the mechanisms underlying anatomical and functional muscle restructuring and their effects on anatomical foot parameters in flat feet.