Achieving consistent performance in a complex whole body movement: The Tkatchev on high bar

Abstract

If the magnitude of timing and angle variability in whole body coordinated movements were known, this would allow more realistic levels of variability to be included within optimisations of technique. The aim of this study was to determine technique for improved consistency of performance of the Tkatchev release and regrasp on high bar, whilst incorporating realistic levels of coordination precision. The effect of gymnast strength and flexibility on consistency of performance was also investigated. Twenty trials (10 successful and 10 unsuccessful) by one national gymnast were recorded using an automatic motion capture system and were analysed to determine variability in coordination of the giant circle technique prior to release. The standard deviation in the hip and shoulder angles and timings at four key instants in the gymnast's performances were 2.3° and 12 ms. A gymnast -high bar simulation model was used to optimise the technique in the giant circle to maximise the success percentage for which the gymnast could release and regrasp the bar with coordination variability introduced into each simulated technique. When the optimal solution was perturbed randomly in 1000 simulations to the level seen in the gymnast performances 69% produced a successful performance compared with only 17% for the gymnast. An increase in strength (by 25%) and a reduction in variability (by 25%) lead to improved consistency (91% success rate). Flexibility did not appear to play a role as none of the optimisations approached the bounds set by the gymnast's performances.

Investigating optimal technique in a noisy environment: Application to the upstart on uneven bars

“…The study used measures of kinematic variability obtained from swinging on bars (Hiley and Yeadon, 2012b). Cohen and Sternad (2009) used a decomposition of movement variability into components of noise, tolerance (how far the movements were from the successful solution space) and covariation (variation that was compensated for by redundancy) in relation to the task outcome.…”

“…Subsequently 999 randomly perturbed simulations were based on the same set of parameters, where perturbations were added to the time and angle parameters of the joint angle histories with a specified standard deviation (i.e. the average standard deviations of 10 ms and 2.3º from Hiley and Yeadon, 2012b) using a random number generator and the method of Hiley and Yeadon (2012b). In the present study the kinematic variability introduced with the perturbations represented the noise component of the movement variability.…”

“…successful completion of the upstart) despite the variability present. Hiley and Yeadon (2012b) calculated the level of kinematic variability in the start and end time of flexions and extensions at the shoulder and hip and in the magnitude of the angle changes during giant circles before a Tkatchev release and regrasp skill in 10 repeated trials. The average standard deviations in the temporal and spatial measures were 10 ms and 2.3º respectively for a senior elite male gymnast.…”

“…The average standard deviations in the temporal and spatial measures were 10 ms and 2.3º respectively for a senior elite male gymnast. The measures of kinematic variability (Hiley and Yeadon, 2012b) would have included components of noise and any feedback corrections made by the gymnast (Cohen and Sternad, 2009;Harris and Wolpert, 1998). When the gymnast's giant circle technique was optimised, realistic solutions were obtained only when the variability present in the actual performances was included.…”

What governs successful performance of a complex whole body movement: The Kovacs release-regrasp on horizontal bar?

“…In the qualifying competition at the London Olympics 84% of Kovacs performed were successfully regrasped, with the remaining 16% resulting in a fall. Since the gymnast is a projectile once the bar has been released, the main reason for missing the regrasp may be due to having inappropriate amounts of linear and angular momenta at release (Holvoet et al, 2002;Hiley et al, 2007;Hiley and Yeadon, 2012a). Holvoet et al (2002) used a simulation model to demonstrate that an unsuccessful Tkatchev (a counter rotation release and regrasp skill, Figure 1) could have been caught if the gymnast had released the bar earlier than in the recorded performance.…”