2003 Volume 1 Issue 1 Pages 19-23
The effects of the Achilles tendon path change due to muscle contraction on the displacement of the myotendinous junction were determined in the human in vivo. Seven male subjects, whose knees were extended and ankles flexed at a right angle, performed isometric plantar flexion while the Achilles tendon length within the predetermined area (from the point of the myotendinous junction at rest to the calcaneus) was estimated using a high-speed camera and ultrasound apparatus. The Achilles tendon length within the predetermined area decreased by ∼1% at maximal voluntary contraction compared to the relaxed condition, which suggests that the Achilles tendon path change due to isometric contractions moves the myotendinous junction proximally by ∼1%, at the most, of the Achilles tendon length. If we simply calculate the Achilles tendon strain based on the displacement of the myotendinous junction as in previous studies, we would therefore overestimate the strain by ∼1%. This suggests that the tendon path change should be taken into account when tendon strain is calculated from myotendinous junction movements.