Motion analysis with high speed video

Abstract

Motion analysis is a technique which allows analysts to quantify the movements of a physical structure during activity. It is widely used in different areas including surveillance, medicine, film industries and navigation of vehicles. Sports motion analysis is in fact popularly used by coaches in many sports for both qualitative (subjective) and quantitative evaluation of the performance practiced by their athletes from a 2D point of view. The importance of archery coaching by means of concrete facts rather than through visual-based opinions is presented. The use of inexpensive high-speed cameras and their set-up for capturing athletic motion are also emphasized including the specification of properties such as the best tracking markers (as in shape, size and colour), the frame rate, the resolution and the working distance that should be adopted. Although several motion capture systems are available, the open-source Kinovea software is used for the 2D analysis of the videos captured during this research study. The mandatory techniques for optimal archery performance are illustrated and an auto- mated analysis of the data obtained through the digitisation process is developed through multiple scripts, written in MATLAB. These functions are gathered in ArcherBuddy, a developed user-friendly application that automatically quantifies critical techniques and presents a visual interpretation of weak practices from both top and sagittal views. The use of this application in the coaching industry is also veri ed through an investigative discussion with Mr John Schembri, the President of the Archery Association of Malta. A statistical analysis on the reliability of Kinovea tracking compared to that of the VICON Optical Motion Capture system is also presented. Results conclude that Kinovea tracking is highly accurate if, and only if, all motion is presented on the photographic plane. The use of multiple cameras is therefore imperative for a competent quantitative analysis of the archer biomechanics.