Influence of Long-Term Kendo Training on the Geometric and Mechanical Properties of the Achilles Tendon

Abstract

The purpose of this study was to examine the differences in the geometric and elastic properties of the Achilles tendon between right and left ankles in kendo (japanese fencing) athletes, who engaged in kendo training for years, and matched controls. The subjects were twelve kendo athletes and nine controls (21 and 20 yrs, 65 and 60 kg, and 172 and 171 cm, respectively). While the subjects developed maximum voluntary isometric plantarflexion (MVIP) torque (TQ), the tendon displacement and ankle joint rotation was determined using a B-mode ultrasonograph and a goniometer, respectively. The tendon force (F) was calculated from TQ and the moment arm of the Achilles tendon. The elongation of the Achilles tendon (∆X) was obtained from the tendon displacement and ankle joint rotation. The cross-sectional area of the Achilles tendon (CSA) was measured using a B-mode ultrasonography. The Achilles tendon stiffness (k) was defined as F divided by ∆X, stress (σ) as F divided by CSA, strain (e) at MVIP as ΔX divided by the Achilles tendon length at rest (Lr), and Young's modulus (E) as σ divided by e. The results showed that there were no significant differences in TQ, F, σ, Lr, ΔX, e, k, and E between right and left ankles for both control and kendo athlete subjects, and between control and kendo athlete subjects. CSA of kendo athletes' right ankles was significantly greater than that of kendo athletes' left ankles (p=0.03). It was suggested that a long-term kendo training did not affect the elastic properties of the Achilles tendon and resulted in smaller Achilles tendon CSA in left ankles.