A three-dimensional study on contribution of torso and throwing arm segments to ball velocity in baseball throwing motion

Abstract

We investigated the contribution of the motions in the upper torso and the throwing arm joints to the ba皿velocity during the baseball throw ． The baU velocities caused by the anatomical rotations at the upper 亡 orso ， shoulder ， elbow ， wrist and metacarpophalangea1 joints were calculated as the vector products between the anatomical angular velocity vectors ofjoints and the respective relative displace ' ment vectors from the joint centers to the center of ball ， by usilg a mathematical mOdel reported by Sprigings et a1 ．（ 1994）． Horizontal throws of twenty ・ four male university baseban players were 創 med using a three − dimensional DLT method ． In order to verify the ball velocities obtained from the anatomical joint rotations from the instant of the stride foot contact to the bal1 release ・ the velocity of ball measured directly from video recording was cornpared With that calcUlated by the mathematical modeL A good agreement was acquired between the velocity of ball measured and that calculated ． The velocities obtained from the left − rotation ， flexion at the upper torso joint and the horiZontal fiex − ion at the shoulder joint contributed to the ball velocity in 止 e early phase where the i皿crease of ball velocity was slow ． The ve 且 ocities obtained from the internal − rotation at the shoUlder joint ， extension at the elbow joint ， palmar − flexion at the wrist joint ， and left ・ retation ！ fleXion at the upper torso ｝ o皿 t contrib11ted in the late phase where the increase of ball ve1 ity was rapid ． At the ban reLease ， 廿le con − tribution of each joilt ， which is the ratio of the positive baU ve1 ity obtained from the anatomical joint rotations to the summation of individual positive ball velocities was as follows ；34． 1％ by the in ・ ternal − rotation at the shoulder ， 17 ． 7 ％ by the palmar − flexion at the whst ， 15 ． 2 ％ by the extension at the elbow ， and 9 ． 6％ by the left ・ rotation at the upper torso 亅 oLnt ． Key word 昌： baeeball ， throwimg motion ， anato 皿 ic呂 l joint rotation ， contributiom ， three − dimen8ioml 皿 otion ana 且 y8i8 （ Jap8n J． Phy8 ． Educ ． 41 ： 23 − 37， May ， 1996 ）