Men's Artistic Gymnastics Research Articles

The margin for error when releasing the high bar for dismounts

In Men's Artistic Gymnastics the current trend in elite high bar dismounts is to perform two somersaults in an extended body shape with a number of twists. Two techniques have been identified in the backward giant circles leading up to release for these dismounts (J. Biomech. 32 (1999) 811). At the Sydney 2000 Olympic Games 95% of gymnasts used the “scooped” backward giant circle technique rather than the “traditional” technique. It was speculated that the advantage gained from the scooped technique was an increased margin for error when releasing the high bar. A four segment planar simulation model of the gymnast and high bar was used to determine the margin for error when releasing the bar in performances at the Sydney 2000 Olympic Games. The eight high bar finalists and the three gymnasts who used the traditional backward giant circle technique were chosen for analysis. Model parameters were optimised to obtain a close match between simulated and actual performances in terms of rotation angle (1.2°), bar displacements (0.014 m) and release velocities (2%). Each matching simulation was used to determine the time window around the actual point of release for which the model had appropriate release parameters to complete the dismount successfully. The scooped backward giant circle technique resulted in a greater margin for error (release window 88–157 ms) when releasing the bar compared to the traditional technique (release window 73–84 ms).

The Margin for Error in Timing the Release for Double Layout Somersault Dismounts from High Bar

Introduction: In the high bar competition in Men's Artistic Gymnastics the backward giant circle is used prior to a dismount in order to generate the required release characteristics. Currently there are two distinct (traditional and scooped) techniques used in the accelerated backward giant circle prior to the double layout somersault dismount. Hiley (1998) showed that each of the techniques was more than capable of producing the rotation required for a double layout somersault dismount. Since the scooped technique is less aesthetically pleasing and may be liable for score deductions by some judges, it is likely that there is some technical advantage associated with this technique. It is speculated that the scooped technique allows a greater margin for error in timing the release for a double layout somersault dismount. This study investigated this by comparing the margin for error in timing the release from traditional and scooped giant circles. Methods: All high bar performances from the Sydney 2000 Olympic games were recorded using two digital camcorders. The last giant circle and the whole of the flight phase of six double layout dismounts (three traditional and three scooped) were analysed. Fifteen body landmarks were digitised in each video field along with the centre of the bar between the gymnast's hands. The two sets of digitised data were used to reconstruct the three-dimensional coordinates of the landmarks using the Direct Linear Transformation technique. Inertia parameters for gymnasts were determined from anthropometric dimensions obtained in the three-dimensional analysis using the mathematical model of Yeadon (1990). Whole body mass centre location and angles describing the orientation and configuration of the gymnast were determined throughout and the angular momentum during the flight phase was calculated (Yeadon, 1990). A simulation model of a gymnast and high bar (Yeadon and Hiley, 2000) was driven using the joint angle time histories obtained from the video analysis. Bar stiffness was determined from static loading. The values for bar stiffness, segmental masses and initial angular velocity in the giant circle were adjusted in order to minimise the difference between recorded and simulated whole body rotation angle, bar displacement and linear and angular momentum at the point of release from the bar. The margin for error was calculated as a release window time interval within which appropriate linear and angular momenta for a double layout somersault dismount were achieved in a simulation. Results and Discussion: On average the simulation model was able to estimate the whole body rotation angle to within 1.8° and the bar displacements to within 0.013 m. The release window was based on the requirement of the horizontal release velocity lying between 0.35 m/s and 2.3 m/s and the angular momentum being sufficient to produce at least 1.4 straight somersaults during flight. The average release windows for the traditional and scooped backward giant circles were 72 ms and 135 ms respectively. The scooped technique results in a bar motion which, coupled with the changes in body shape, produce a less curved path of the mass centre in the last part of the giant circle. As a consequence the flight trajectory is not as sensitive to release timing. This explains why the scooped giant circle has been adopted by the majority of gymnasts in preference to the traditional giant circle. Thus the gymnasts with the best performances may not be those who are able to time the release most accurately. Rather they may be the ones who use a technique that is more forgiving of errors in timing. Acknowledgements: This project was funded by Pfitzer through the IOC Medical Commission.

The mechanics of the backward giant circle on the high bar

In Men's Artistic Gymnastics the backward giant circle on the high bar is used to generate the rotation that the gymnast needs to perform the release–regrasp and dismount skills. Bauer presented a point mass model of high bar circling which indicated that ideally a gymnast should flex around the lowest point and extend around the highest point of a giant circle in order to maximise the increase in energy [cf. Bauer, W. L. (1983). In H. Matsui, K. Kobayashi, Biomechanics VIII-B (pp. 801–806). Champaign, IL: Human Kinetics]. In practice gymnasts follow this technique in only a general sense and flex after the lowest point and extend before the highest point. A four segment planar simulation model of a gymnast was developed to investigate these differences in technique. The model comprised arm, torso, thigh and leg segments with a damped linear spring connecting the arm and torso segments. The high bar was also modelled as a damped linear spring. The model was driven using time histories of hip and shoulder angles. It was found that the simplifications introduced into Bauer's model by neglecting segmental inertias and the elastic characteristics of the gymnast and the bar were not responsible for the differences between the ideal technique and the typical technique of gymnasts. The technique differences could be accounted for by limitations on the torques that are exerted at the shoulder and hip.

Twisting Techniques Used in Dismounts from the Rings

At the 1992 Olympic Games six full twisting double somersault dismounts were recorded with two video cameras during the rings individual apparatus finals in the men's Artistic Gymnastics competition. Angles describing body configuration were determined from video data and were input, together with initial orientation angle values and angular momentum components, into a computer simulation model of aerial movement. Mean absolute deviations between simulation and video after the completion of one half twist were 0.01 rev for somersault, 2.8° for tilt, and 0.08 rev for twist. When the estimate of the initial tilt angle was adjusted by up to 1° these deviations fell to 1.6° for tilt and 0.02 rev for twist. All 6 competitors produced the majority of the tilt using aerial techniques that were predominantly asymmetrical movements of the arms. Contributions to the subsequent removal of tilt were determined using reverse simulations, and again arm movements were the main contributors.