title: Association between contraction-induced increases in elbow flexor muscle thickness and distal biceps brachii tendon moment arm depends on the muscle thickness measurement site.
abstract: The purpose of this study was to investigate how the contraction-induced increase in distal biceps brachii tendon moment arm is related to that in elbow flexor muscle thickness, with a specific emphasis on the influence of the site-related differences in muscle thickness. The moment arm and muscle thickness were determined from sagittal and cross-sectional images, respectively, of the right arm obtained by magnetic resonance imaging of nine young men. The muscle thickness was measured at levels from the reference site (60% of the upper arm length from the acromial process of the scapula to the lateral epicondyle of the humerus) to 60 mm distal to it (every 10 mm; 7 measurement sites). At 80° of elbow flexion, the moment arm and muscle thickness were determined at rest and during 60% of maximal voluntary contraction (60%MVC) of isometric elbow flexion. Only the relative change from rest to 60%MVC in muscle thickness at the level 60 mm distal to the reference site correlated significantly with that of the moment arm. This result indicates that the contraction-induced increase in distal biceps brachii tendon moment arm is related to that in elbow flexor muscle thickness near the corresponding muscle-tendon junction.
authors.affiliation: College of Systems Engineering and Science, Shibaura Institute of Technology, Japan.
authors.forename: Ryota
authors.initials: R
authors.lastname: Akagi
authors.forename: Soichiro
authors.initials: S
authors.lastname: Iwanuma
authors.forename: Satoru
authors.initials: S
authors.lastname: Hashizume
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Kanehisa
authors.forename: Toshimasa
authors.initials: T
authors.lastname: Yanai
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Kawakami
mesh_terms: D000328:Adult; D019412:Anatomy, Cross-Sectional; D003198:Computer Simulation; D004551:Elbow Joint / Q000033:anatomy & histology / Q000502:physiology*; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D008297:Male; D008954:Models, Biological; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000033:anatomy & histology / Q000502:physiology*; D009929:Organ Size / Q000502:physiology; D010807:Physical Endurance / Q000502:physiology*; D016059:Range of Motion, Articular / Q000502:physiology*; D013710:Tendons / Q000033:anatomy & histology / Q000502:physiology*; D019415:Torque