title: Shear elastic modulus is a reproducible index reflecting the passive mechanical properties of medial gastrocnemius muscle belly.
abstract: BACKGROUND
  Passive mechanical properties are important in muscle function because they are related to the muscle extensibility. Recently, the assessment of muscle shear elastic modulus using shear-wave elastographic (SWE) imaging was developed. However, reliability and validity of shear elastic modulus measurements during passive stretching remain undefined.
  
  
  OBJECTIVE
  To investigate the reproducibility and validity of the shear elastic modulus measured by SWE imaging during passive stretching.
  
  
  METHODS
  Ten healthy men volunteered for this study. The shear elastic modulus of medial gastrocnemius (MG) muscle belly was measured using ultrasonic SWE imaging during passive dorsiflexion. To assess the intra-session and inter-day reliabilities, the protocol was performed twice by the same investigator with a 5-min rest period between measurement sessions and twice on two different days by the same investigator with a 1-2-week interval between the two sessions. To assess the inter-investigator reliability, the protocol was performed on the same day by two investigators with a 5-min rest between measurement sessions. In addition, B-mode ultrasonography was used to determine the displacement of myotendinous junction (MTJ) of MG during passive ankle dorsiflexion.
  
  
  RESULTS
  The intra-session, inter-day, and inter-investigator reliabilities of the method was confirmed on the basis of acceptably low coefficient of variations and substantially high intraclass correlation coefficients. In addition, a significant correlation was found between MTJ displacement and shear elastic modulus.
  
  
  CONCLUSIONS
  These results suggested that shear elastic modulus measured using SWE imaging is a reproducible index reflecting the passive mechanical properties.
authors.affiliation: Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare, Niigata, Japan; Faculty of Health and Sports Science, Doshisha University, Kyoto, Japan; Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Nakamura
authors.affiliation: Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
authors.forename: Tome
authors.initials: T
authors.lastname: Ikezoe
authors.affiliation: Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Umegaki
authors.affiliation: Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
authors.forename: Takuya
authors.initials: T
authors.lastname: Kobayashi
authors.affiliation: Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
authors.forename: Satoru
authors.initials: S
authors.lastname: Nishisita
authors.affiliation: Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
authors.forename: Noriaki
authors.initials: N
authors.lastname: Ichihashi
keywords: Shear-wave elastographic imaging; myotendinous junction displacement; shear elastic modulus