title: Nonuniform strain of human soleus aponeurosis-tendon complex during submaximal voluntary contractions in vivo.
abstract: The distribution of strain along the soleus aponeurosis tendon was examined during voluntary contractions in vivo. Eight subjects performed cyclic isometric contractions (20 and 40% of maximal voluntary contraction). Displacement and strain in the apparent Achilles tendon and in the aponeurosis were calculated from cine phase-contrast magnetic resonance images acquired with a field of view of 32 cm. The apparent Achilles tendon lengthened 2.8 and 4.7% in 20 and 40% maximal voluntary contraction, respectively. The midregion of the aponeurosis, below the gastrocnemius insertion, lengthened 1.2 and 2.2%, but the distal aponeurosis shortened 2.1 and 2.5%, respectively. There was considerable variation in the three-dimensional anatomy of the aponeurosis and muscle-tendon junction. We suggest that the nonuniformity in aponeurosis strain within an individual was due to the presence of active and passive motor units along the length of the muscle, causing variable force along the measurement site. Force transmission along intrasoleus connective tissue may also be a significant source of nonuniform strain in the aponeurosis.
authors.affiliation: Brain Research Institute, University of California, Los Angeles, CA 90095-1527, USA. TFinni@mednet.ucla.edu
authors.forename: Taija
authors.initials: T
authors.lastname: Finni
authors.forename: John A
authors.initials: JA
authors.lastname: Hodgson
authors.forename: Alex M
authors.initials: AM
authors.lastname: Lai
authors.forename: V Reggie
authors.initials: VR
authors.lastname: Edgerton
authors.forename: Shantanu
authors.initials: S
authors.lastname: Sinha
mesh_terms: D000125:Achilles Tendon / Q000293:injuries* / Q000473:pathology; D000328:Adult; D003238:Connective Tissue / Q000293:injuries* / Q000473:pathology; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D007537:Isometric Contraction; D008279:Magnetic Resonance Imaging; D008297:Male; D008858:Microscopy, Phase-Contrast; D018482:Muscle, Skeletal / Q000293:injuries* / Q000473:pathology; D013180:Sprains and Strains / Q000175:diagnosis / Q000209:etiology*