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

Abstract

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.

How do technique and coordination change during learning of a whole-body task: Application to the upstart in gymnastics

“…In the case of the longswing the solution space is somewhat less constrained, since energy can be added to the system with varying contributions from the shoulder and hip joint actions (Williams et al, 2015b). However, as the longswing is a fundamental skill that is used in the development of more advanced skills (Busquets et al, 2011;Hiley & Yeadon, 2016;), coaches do not view success as merely achieving a longswing. If swinging from handstand to handstand is no longer the goal of the longswing and a new set of mechanical constraints is imposed by the coach, it is to be expected that a learner's technique will approach that of an expert (Busquets et al 2013).…”

“…found that elite gymnasts had very consistent joint angle time histories during the mechanically important phases of the longswing, but they were more variable through the upper region of the circle compared to less elite gymnasts. Hiley & Yeadon (2016) subsequently demonstrated the functional nature of this greater variability showing that gymnasts were making feedback corrections through the upper part of the circle based on a strategy for controlling the whole body angular velocity from circle to circle. All of the actions throughout the upstart are mechanically important and therefore, it might be expected that novices will be more variable in technique and coordination compared to experts and may show a reduction in variability of both as they progress.…”

Functional variability in the flight phase of one metre springboard forward dives

“…Traditionally movement variability has been viewed as noise that needs to be minimised or eliminated (Newell & Corcos, 1993). More recently, researchers have been interested in the potentially functional role that variability may play in human movement (Preatoni et al, 2013;Bartlett et al, 2007;Hiley & Yeadon, 2016). For example, an increase in movement variability associated with a diver making feedback corrections in flight would fall under the definition of functional variability, since the adjustments could have the function of controlling the somersault rotation in order to ensure appropriate orientation on entry into the water.…”

“…Feedback control has been demonstrated in a number of acrobatic activities such as handstand balance (Yeadon & Trewartha, 2003), swinging on bars (Hiley & Yeadon, 2016) and twisting somersaults (Yeadon & Mikulcik, 1996;Yeadon & Hiley, 2014). In each case the control strategy was found to use a combination of open loop control or feedforward control together with feedback (closed loop) control to achieve the task goals.…”

“…The feedback control was based on detecting an error in the desired state and providing a correction, after an inherent time delay (Latash, 1998;Jagacinski & Flach, 2003). For example, Hiley and Yeadon (2016) demonstrated that gymnasts made adjustments (feedback control) to their pre-planned movements to regulate the pace of consecutive backward longswings on the horizontal bar. In springboard diving it might be expected that the diver pre-plans the aerial phase (either open loop control or feedforward control) and then makes adjustments during flight (feedback control) to correct for errors generated during the contact phase.…”