title: Kinetics of throwing arm joints and the trunk motion during an overarm distance throw by skilled Japanese elementary school boys.
abstract: The purpose of this study was to investigate joint kinetics of the throwing arms and role of trunk motion in skilled elementary school boys during an overarm distance throw. Throwing motions of 42 boys from second, fourth, and sixth grade were videotaped with three high-speed cameras operating at 300 fps. Seven skilled boys from each grade were selected on the basis of throwing distance for three-dimensional kinetic analysis. Joint forces, torques, and torque powers of the throwing arm joints were calculated from reconstructed three-dimensional coordinate data smoothed at cut-off frequencies of 10.5-15 Hz and by the inverse dynamics method. Throwing distance and ball velocity significantly increased with school grade. The angular velocity of elbow extension before ball release increased with school grade, although no significant increase between the grades was observed in peak extension torque of elbow joint. The joint torque power of shoulder internal/external rotation tended to increase with school grade. When teaching the overarm throw, elementary school teachers should observe large backward twisting of trunk during the striding phase and should keep in mind that young children, such as second graders (age 8 years), will be unable to effectively utilise shoulder external/internal rotation during the throwing phase.
authors.affiliation: a Faculty of Medical Health, Department of Physical Therapy , Ibaraki Prefectural University of Health Sciences , Ami , Japan.
authors.forename: Yasuto
authors.initials: Y
authors.lastname: Kobayashi
authors.affiliation: b Faculty of Health and Sport Sciences , University of Tsukuba , Tsukuba , Japan.
authors.forename: Michiyoshi
authors.initials: M
authors.lastname: Ae
authors.affiliation: b Faculty of Health and Sport Sciences , University of Tsukuba , Tsukuba , Japan.
authors.forename: Akiyo
authors.initials: A
authors.lastname: Miyazaki
authors.affiliation: b Faculty of Health and Sport Sciences , University of Tsukuba , Tsukuba , Japan.
authors.forename: Norihisa
authors.initials: N
authors.lastname: Fujii
authors.affiliation: c Faculty of Education , Kagoshima University , Kagoshima , Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Iiboshi
authors.affiliation: d Japan Sport Council , Tokyo , Japan.
authors.forename: Hideki
authors.initials: H
authors.lastname: Nakatani
mesh_terms: D001132:Arm / Q000502:physiology*; D001484:Baseball / Q000502:physiology; D001696:Biomechanical Phenomena; D002648:Child; D004551:Elbow Joint / Q000502:physiology*; D006801:Humans; D008297:Male; D009068:Movement; D012399:Rotation; D012785:Shoulder Joint / Q000502:physiology*; D013996:Time and Motion Studies; D060726:Torso / Q000502:physiology*
keywords: Children; joint kinetics; joint torque; power; three-dimensional motion analysis