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Updated: Sep 30, 2026

A Passive Ankle Dorsiflexion Testing System for an In Vivo Model of Overuse-induced Tendinopathy
Published on: March 1, 2024
Length change of human gastrocnemius aponeurosis and tendon during passive joint motion
Tetsuro Muraoka1, Tadashi Muramatsu, Daisuke Takeshita
1Laboratory of Sports Sciences, Department of Life Sciences, Graduate School of Arts and Sciences, University of Tokyo, Japan. cc97726@mail.ecc.u-tokyo.ac.jp
Abstract:
The extent of elongation and slackness of aponeurosis and tendon, and muscle fiber length of human medial gastrocnemius muscle are determined in vivo using ultrasonography. The ankle joint is passively moved at 5 degrees /s within the joint range of -36 to 7 degrees (0 degrees = neutral anatomic position; positive values for dorsiflexion) by a dynamometer while the length change of the aponeurosis and tendon is determined using ultrasonography (n = 8 men). Strain is calculated as the length change relative to the reference length of aponeurosis and tendon when the passive joint moment is 0. Elongation (positive strain values) of aponeurosis and tendon at 7 degrees are 2.1 +/- 1.1 and 2.4 +/- 1.0%, respectively. The extent of slackness (negative strain values) of aponeurosis and tendon at -36 degrees are -1.8 +/- 1.1 and -3.5 +/- 1.6%, respectively, and there is a significant difference between them (p < 0.05). This may be related to the existence of muscle fibers that attach to the aponeurosis over its whole length and do not allow it to fold. The results indicate that the length change of aponeurosis and tendon of medial gastrocnemius muscle occurs over the range of ankle joint positions even during passive joint motions.
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