The effect of cost function on optimum technique of the undersomersault on parallel bars

The undersomersault, or felge, to handstand on parallel bars has become an important skill in Men’s Artistic Gymnastics as it forms the basis of many complex variations. To receive no deductions from the judges, the undersomersault must be performed without demonstrating the use of strength to achieve the final handstand position. Two male gymnasts each performed nine undersomersaults from handstand to handstand while data were recorded using an automatic motion capture system. The highest and lowest scoring trials of each gymnast, as determined by four international judges, were chosen for further analysis. Three optimization criteria were used to generate undersomersault technique during the swing phase of the skill using a computer simulation model: minimization of peak joint torques, minimization of horizontal velocity before release, and maximization of angular momentum. The techniques used by both gymnasts could be explained using the second optimization criterion which facilitated further skill development. The first optimization criterion generated a technique advocated for beginners where strength might be expected to be a limiting factor. The third optimization criterion resulted in a different type of undersomersault movement of greater difficulty according to the FIG Code of Points

Investigating optimal technique in the presence of motor system noise: application to the double layout somersault dismount on high bar

Minimising joint torque is often used as an optimisation criterion when investigating human movement. Alternatively, an aspect of performance may be chosen to be maximised when investigating sporting movements. The aim of the study was to optimise the technique in the backward giant circle prior to a double layout somersault dismount from the high bar using various criteria to determine which best characterised the technique adopted by a gymnast. Ten recorded gymnast trials were used to determine bar release parameters and the level of noise in the gymnast’s movements. A computer simulation model of a gymnast and bar was used to optimise giant circle technique under three criteria: minimising joint torques, maximising the release window and maximising success in the presence of motor system noise. Local and global optimisations of technique were performed using the three criteria starting from the average technique of the 10 recorded trials. All global optimum solutions diverged from the gymnast’s technique. The local optimum for maximising success in the presence of noise had a success rate comparable with the global optimum (98% vs. 100%, respectively). It is concluded that the gymnast’s technique is characterised by maximising success despite operating with motor system noise

Optimum technique for generating angular momentum in accelerated backward giant circles prior to a dismount

In Men's Artistic Gymnastics the backward giant circle on high bar is used to produce the angular momentum that the gymnast needs to perform somersaulting dismounts. Dismounts where the gymnast performs two somersaults in the layout (straight body) position require the greatest angular momentum. However, there appear to be two distinct techniques used by elite gymnasts when performing backward giant circles prior to a double layout somersault dismount. The “traditional” technique has been superseded by the “scooped” technique which is now used by the majority of elite gymnasts. To determine whether the scooped technique was better at producing angular momentum a simulation model was used to optimise the angular momentum about the mass centre at release. The model was evaluated using data obtained from a force - video analysis of accelerated giant circles. The model was able to estimate the reaction forces measured by strain gauges on the bar to within 9% of the peak forces and the body rotation angle to within 1% of the total rotation. During the optimisations the joint angle time histories of the model were manipulated in order maximise the angular momentum about the model’s mass centre at release. Two optima were found which were characteristic of the two backward giant circle techniques used by elite gymnasts. The traditional technique produced more angular momentum than the scooped technique although both techniques were capable of producing sufficient angular momentum for a double layout somersault dismount. As a consequence the preference of elite gymnasts for the scooped technique must be based on factors other than the production of angular momentum

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)

Determining the solution space for a coordinated whole body movement in a noisy environment: application to the upstart in gymnastics

The upstart is a fundamental skill in gymnastics, requiring whole body coordination to transfer the gymnast from a swing beneath the bar to a support position above the bar. The aim of this study was to determine the solution space within which a gymnast could successfully perform an upstart. A previous study had shown that the underlying control strategy for the upstart could be accounted for by maximizing the likelihood of success while operating in a noisy environment.1 In the current study, data were collected on a senior gymnast and a computer simulation model of a gymnast and bar was used to determine the solution space for maximizing success while operating in a noisy environment. The effects of timing important actions, gymnast strength, and movement execution noise on the success of the upstart were then systematically determined. The solution space for the senior gymnast was relatively large. Decreasing strength and increasing movement execution noise reduced the size of the solution space. A weaker gymnast would have to use a different technique than that used by the senior gymnast to produce an acceptable success rate

Swinging around the high bar

The motion of a gymnast around the high bar is modelled first as swinging around a rigid rod then more accurately when the rod is considered to be elastic. How the gymnast should best move his hips is also considered

Optimisation of high bar circling technique for consistent performance of a triple piked somersault dismount

The dismount from the high bar is one of the most spectacular skills performed in Men’s Artistic Gymnastics. Hiley and Yeadon (2005) optimised the technique in the backward giant circle prior to release using a computer simulation model to show that a gymnast could generate sufficient linear and angular momentum to perform a triple piked backward somersault dismount with a sufficiently large release window (the period of time during which the gymnast could release the bar and successfully complete the dismount). In the present study it was found that when the timing of the actions at the hip and shoulder joints from the optimum simulation were perturbed by 30 ms the resulting simulation could no longer meet the criteria for sufficient aerial rotation and release window. Since it is to be expected that a gymnast’s technique can cope with small errors in timing for consistent performance, a requirement of robustness to timing perturbations should be included within the optimisation process. When the technique in the backward giant circle was optimised to be robust to 30 ms perturbations it was found that sufficient linear and angular momentum for a triple piked dismount could be achieved with a realistic release window

The role of functional variability in a whole body co-ordinated movement – application to high bar giant circles

When performing a giant circle on high bar a gymnast flexes at the hips in the lower part of the circle, increasing the kinetic energy, and extends in the upper part of the circle, decreasing the kinetic energy. In order to perform a sequence of giant circles at even tempo, any variation in angular velocity at the end of the flexion phase needs to be reduced by the end of the extension phase. The aim of this study was to determine the nature and contribution of such adjustments. A computer simulation model of a gymnast performing giant circles on high bar was used to investigate strategies of (a) fixed timing of the extension phase (feedforward control) and (b) stretched timing in order to extend at the same point of the giant circle (feedforward with additional feedback control). For three elite gymnasts fixed timing reduced the angular velocity variation on average by 36% whereas stretched timing reduced the variation by 63%. The mean reduction for the actual gymnast techniques was 61%. It was concluded that both feedforward and feedback control strategies are used by gymnasts for controlling such movements

The margin for error when releasing the asymmetric bars for dismounts

It has previously been shown that male gymnasts using the “scooped” giant circling technique were able to flatten the path followed by their mass centre resulting in a larger margin for error when releasing the high bar (Hiley and Yeadon, 2003a). The circling technique prior to performing double layout somersault dismounts from the asymmetric bars in Women’s Artistic Gymnastics appears to be similar to the “traditional” technique used by some male gymnasts on the high bar. It was speculated that as a result the female gymnasts would have margins for error similar to those of male gymnasts who use the traditional technique. However, it is unclear how the technique of the female gymnasts is affected by the need to avoid the lower bar. A four segment planar simulation model of the gymnast and upper bar was used to determine the margins for error when releasing the bar for nine double layout somersault dismounts at the Sydney 2000 Olympic Games. The elastic properties of the gymnast and bar were modelled using damped linear springs. Model parameters, primarily the inertia and spring parameters, were optimised to obtain a close match between simulated and actual performances in terms of rotation angle (1.2°), bar displacement (0.011 m) and release velocities (< 1%). 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 margins for error of the nine female gymnasts (release window 43 - 102 ms) were comparable with those of the three male gymnasts using the traditional technique (release window 79 - 84 ms)

Maximal dismounts from high bar

In Men’s Artistic Gymnastics the triple straight somersault dismount from the high bar has yet to be performed in competition. The present study used a simulation model of a gymnast and the high bar apparatus (Hiley and Yeadon, 2003a) to determine whether a gymnast could produce the required angular momentum and flight to complete a triple straight somersault dismount. Optimisations were carried out to maximise the margin for error in timing the bar release for a given number of straight somersaults in flight. The amount of rotation potential (number of straight somersaults) the model could produce whilst maintaining a realistic margin for error was determined. A simulation model of aerial movement (Yeadon et al., 1990) was used to find dismounts that would be possible with this amount of rotation potential. The model was able to produce sufficient angular momentum and time in the air to complete a triple straight somersault dismount. The margin for error when releasing the bar using the optimum technique was 28 ms, which is small when compared with the mean margin for error determined for high bar finalists at the 2000 Sydney Olympic Games (55 ms). Although the triple straight somersault dismount is theoretically possible, it would require close to maximum effort and precise timing of the release from the bar. However, when the model was required to have a realistic margin for error, it was able to produce sufficient angular momentum for a double twisting triple somersault dismount