title: A method for estimating torque-vector directions of shoulder muscles using surface EMGs.
abstract: In this study, a new method is proposed to estimate the torque-vector directions of each shoulder muscle. The method is based on a multiple regression model that reconstructs shoulder torque, which is calculated from the hand force and posture, from the surface EMG of many muscles recorded simultaneously. The torque-vector directions of eleven shoulder muscles of four subjects were obtained at up to 30 different arm postures with this method. The mean confidence interval (p < 0.05) of the estimated torque-vector direction of each subject was 7.7-10.6 degrees. The correlation coefficient between the measured shoulder torque and reconstructed shoulder torque was between 0.76-0.84. The results for majority of the muscles were in accordance with previous studies, and reasonable from the viewpoint of anatomy. The torque-vector directions of a muscle, which are estimated with this method, have more of a functional meaning than a pure anatomical or mechanical one. These indicate the direction of the shoulder torque accompanying the muscle activation for a normal shoulder action that involves the cooperative contraction of many muscles.
authors.affiliation: College of Medical Technology, Hokkaido University, Sapporo, Japan. yoshida@1994.jukuin.keio.ac.jp
authors.forename: Naoki
authors.initials: N
authors.lastname: Yoshida
authors.forename: Kazuhisa
authors.initials: K
authors.lastname: Domen
authors.forename: Yasuharu
authors.initials: Y
authors.lastname: Koike
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Kawato
mesh_terms: D000328:Adult; D004576:Electromyography / Q000379:methods* / Q000592:standards; D006801:Humans; D008297:Male; D008954:Models, Biological; D009068:Movement / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology*; D011187:Posture / Q000502:physiology; D015203:Reproducibility of Results; D012785:Shoulder Joint / Q000502:physiology*; D019415:Torque