Muscle shear elastic modulus is linearly related to muscle torque over the entire range of isometric contraction intensity

• Published in: Journal of electromyography and kinesiology Vol. 25; no. 4; pp. 703 - 708
• Main Authors: Ateş, Filiz, Hug, François, Bouillard, Killian, Jubeau, Marc, Frappart, Thomas, Couade, Mathieu, Bercoff, Jeremy, Nordez, Antoine
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.08.2015; Elsevier
• Subjects: Abductor Digiti Minimi; Adult; Biomechanics; Elastic Modulus - physiology; Elasticity Imaging Techniques - methods; Engineering Sciences; Ergometry - methods; Fingers - physiology; Force; Humans; Isometric Contraction - physiology; Male; Mechanics; Muscle, Skeletal - physiology; Physical Medicine and Rehabilitation; Shear wave; Supersonic shear imaging; Torque; Ultrasound elastography; Supersonic shear imaging; Abductor Digiti Minimi; Ultrasound elastography; Shear wave; Force
• ISSN: 1050-6411; 1873-5711
• DOI: 10.1016/j.jelekin.2015.02.005

Abstract Muscle shear elastic modulus is linearly related to muscle torque during low-level contractions (<60% of Maximal Voluntary Contraction, MVC). This measurement can therefore be used to estimate changes in individual muscle force. However, it is not known if this relationship remains valid for higher intensities. The aim of this study was to determine: (i) the relationship between muscle shear elastic modulus and muscle torque over the entire range of isometric contraction and (ii) the influence of the size of the region of interest (ROI) used to average the shear modulus value. Ten healthy males performed two incremental isometric little finger abductions. The joint torque produced by Abductor Digiti Minimi was considered as an index of muscle torque and elastic modulus. A high coefficient of determination ( R2 ) (range: 0.86–0.98) indicated that the relationship between elastic modulus and torque can be accurately modeled by a linear regression over the entire range (0% to 100% of MVC). The changes in shear elastic modulus as a function of torque were highly repeatable. Lower R2 values (0.89 ± 0.13 for 1/16 of ROI) and significantly increased absolute errors were observed when the shear elastic modulus was averaged over smaller ROI, half, 1/4 and 1/16 of the full ROI) than the full ROI (mean size: 1.18 ± 0.24 cm2 ). It suggests that the ROI should be as large as possible for accurate measurement of muscle shear modulus.