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

Abstract

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.

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

“…Prior to data collection a volume centred on the bar spanning 2 m x 5 m x 5 m was wand calibrated using the motion analysis system. Three-dimensional marker coordinates were reconstructed and joint centre locations were determined using measured offsets (Hiley and Yeadon, 2016). The data in each trial for the last 1¾ giant circles and the aerial phase were analysed.…”

“…A simulation model was used since the release window starts before and ends after the gymnast has released the bar. The matching procedure was used to produce a common set of model parameters for the nine trials (Hiley and Yeadon, 2016). All matching simulations for each gymnast used the same set of model parameter values determined from concurrent matching optimisations, but with the initial conditions and joint angle time histories from the individual recorded performances.…”

“…The recommended optimisation algorithm tuning was used except for the selection of single point crossovers (Carroll, 2001). As in Hiley and Yeadon (2016), single point crossovers were chosen so that sections of joint angle time histories could be passed on to the offspring rather than just single parameter values. The optimisation algorithm manipulated 12 time and 12 angle parameters (24 in total) which defined the joint angle time histories at the shoulder, hip and knee.…”

“…This gymnast would have had to change his giant circling technique in order to be successful. In addition to having appropriate release conditions, the size of the release window (Hiley & Yeadon, 2003a) has been shown to have an impact on the success of a release skill (Hiley and Yeadon, 2016). The release window has been defined as the timing window within which the gymnast can release the bar and successfully complete the following skill.…”

“…The coordination precision was subsequently used to represent the level of noise within the motor system that the gymnast must cope with in an upstart (Hiley and Yeadon, 2014). An athlete's technique must be robust to the level of noise within the motor system, so that a successful performance can be achieved even when aspects of the technique are not performed exactly as planned (van Beers et al, 2004;Wilson et al, 2007;Cohen and Sternad, 2009;Hiley and Yeadon, 2016). Thus unsuccessful performance is not always due to mistiming the release.…”