Research On The Biomechanical Principles Of Upper Limb Whiplash Movement

Upper Limb Whiplash Movement (ULWM) is one of the most important skills in many sports. To understand this skill, information about the shoulder, elbow, forearm, and wrist of the arm is essential for sports practice. The purpose of this study was to expand existing knowledge of ULWM by quantifying and comparing kinematic and kinetic data of the upper limb for javelin throwing, volleyball smashing, badminton smashing, baseball pitching and shot throwing.Six to eight athletes of each sport participated in the study. Their movements were filmed simultaneously by six MCU (Motion Capture Unit) of QUALISYS ProReflex Motion Measurement System (Photoelectrical testing and analytical system). This system can digitize marks on body in each image automatically. A model of three-segment kinetic chainconsisting of upper arm, forearm and distal segment was build for kinetic calculation. Using Kane method to get resultant muscular moment and using Newton method to get joint reaction force.The following conclusions can be drawn from 3D kinematic and kinetic analysis.(1) In accord with the previous study, velocities of three segment shows that ULWM is performed with a proximal to distal (P-D). The sequence of motion does not show P-D, however, shows upperarm-forearm-upperarm-hand. Magnitude of muscular moment is the reason when a segment begins to move forward.(2) Kinetics reasons are analyzed for each segment. The findings suggest that muscular moment and joint reaction moment work together to make each segment accelerate and decelerate.(3) The results of angular momentum for each segment indicated that "transfer of angular momentum" lead to the velocity of segment increase orderly. Angular momentum of forearm keep rising through the whole ULWM, while the increase of angular momentum of hand was not base on the decrease of angular momentum of forearm.(4) Since the characters of segment movement sequence, segment velocity sequence, angular momentum and kinetics reason are the same basically, upper limb movement of baseball pitching, javelin throwing, volleyball smashing and badminton smashing are called "the ULWM kind". Upper limb movement of shot throwing does not belong to that kind of movement.Correlation analyses show that following are the key element of ULWM: (a) the time when trunk turns to throwing direction, (b) Maximum angle of horizontal abduction of upper arm. (c) Angular velocity of internal rotation of upper arm. (d) The time elbow begins to extend, (e) Elbow velocity when release.