title: Longitudinal and transverse deformation of human Achilles tendon induced by isometric plantar flexion at different intensities.
abstract: The present study determined in vivo deformation of the entire Achilles tendon in the longitudinal and transverse directions during isometric plantar flexions. Twelve young women and men performed isometric plantar flexions at 0% (rest), 30%, and 60% of the maximal voluntary contraction (MVC) while a series of oblique longitudinal and cross-sectional magnetic resonance (MR) images of the Achilles tendon were taken. At the distal end of the soleus muscle belly, the Achilles tendon was divided into the aponeurotic (ATapo) and the tendinous (ATten) components. The length of each component was measured in the MR images. The widths of the Achilles tendon were determined at 10 regions along ATapo and at four regions along ATten. Longitudinal and transverse strains were calculated as changes in relative length and width compared with those at rest. The ATapo deformed in both longitudinal and transverse directions at 30%MVC and 60%MVC. There was no difference between the strains of the ATapo at 30%MVC and 60%MVC either in the longitudinal (1.1 and 1.6%) or transverse (5.0∼11.4 and 5.0∼13.9%) direction. The ATten was elongated longitudinally (3.3%) to a greater amount than ATapo, while narrowing transversely in the most distal region (-4.6%). The current results show that the magnitude and the direction of contraction-induced deformation of Achilles tendon are different for the proximal and distal components. This may be related to the different functions of Achilles tendon, i.e., force transmission or elastic energy storage during muscle contractions.
authors.affiliation: Faculty of Sport Sciences, Waseda Univ., 2-579-15 Mikajima, Tokorozawa, Saitama, Japan.
authors.forename: Soichiro
authors.initials: S
authors.lastname: Iwanuma
authors.forename: Ryota
authors.initials: R
authors.lastname: Akagi
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Kurihara
authors.forename: Shigeki
authors.initials: S
authors.lastname: Ikegawa
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Kanehisa
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Fukunaga
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Kawakami
mesh_terms: D000125:Achilles Tendon / Q000033:anatomy & histology / Q000502:physiology*; D000328:Adult; D001696:Biomechanical Phenomena; D004548:Elasticity; D005260:Female; D006801:Humans; D007537:Isometric Contraction; D008279:Magnetic Resonance Imaging; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D013314:Stress, Mechanical; D013997:Time Factors; D019415:Torque; D055815:Young Adult