THE IDENTIFICATION OF RELEASE ON THE HORIZONTAL BAR

Abstract

A horizontal bar routine in Men's Artistic Gymnastics is characterized by swinging around the bar and by flight elements such as release-regrasp and dismount skills. The release parameters, for these skills, are the primary inputs into any predictive simulations. Cinematography and videography have been the most extensively used data collection methods for analysis of release skills performed on the horizontal bar. Traditionally the release has been defined as the first instant (frame) in which the gymnast is seen to have broken contact with the bar. Harwood et al. (1991) submitted that an error of even one h e can make a large difference to the measured release parameters and any subsequently movement prediction based on those projectile determinants. Harwood defined release as the first instant when the wrist first started moving away from the bar. Given that the image size is often small, considering that a field of view may be as great as 8 meters, identification of release by any definition is subject to error. The purpose of this study was to identifl the point of release from the horizontal bar through direct measurement and to correlate this occurrence to information derived through the traditional method of analysis using cinematography. A local area gymnast performed 6 different release elements from long hang swings. Direct measurement of release was achieved by instrumenting a hand guard with a metal strip that was connected to an A/D board. Using a 3V DC power supply connected directly to the horizontal bar an electrical potential was registered when the circuit was closed (when the grip was in contact with the bar) and no potential was registered when the circuit was open (when the grip was not in contact with the bar). A traditional filming protocol was utilised with a camera placed perpendicular to the movement plane with an 8m field of view. A second high speed cine camera, electronically locked to the other, was zoomed in on the subject's wrist and hand. Standard film data reduction was conducted on the processed film which was shot at 100 framedsecond. Three measures of release were determined, one based on Harwood's definition, one on the traditional definition and the third determined from the close-up view. The results indicated that the first two methods provided similar results yet inferior to the close-up determination of release when compared to the information provided by the hand guard switch. It appears evident that given the opportunity for an additional view that a better estimate of release can be found using a close-up view of the hands and the bar. References Harwood et a1 (1991) Prm. XZIIInt. Congress Biom., Perth, Australia, 73-74.