On the use of spline functions for data smoothing

2012

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.

Section: Discussionmentioning

confidence: 99%

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

2012

“…Upper trunk orientation was determined along with hip angle, knee angle, shoulder angle, wrist angle, knuckle angle, the amount of shoulder retraction/protraction and table position and orientation by minimising the distances between the chain model determined marker coordinates and the recorded marker coordinates. The processed kinematic data were fitted using quintic splines (Wood and Jennings, 1979) in order that derivatives and interpolated values could be obtained.…”

Section: Data Collectionmentioning

confidence: 99%

Optimal technique for maximal forward rotating vaults in men’s gymnastics

Jackson

2015

In vaulting a gymnast must generate sufficient linear and angular momentum during the approach and table contact to complete the rotational requirements in the post-flight phase. This study investigated the optimisation of table touchdown conditions and table contact technique for the maximisation of rotation potential for forwards rotating vaults. A planar seven-segment torque-driven computer simulation model of the contact phase in vaulting was evaluated by varying joint torque activation time histories to match three performances of a handspring double somersault vault by an elite gymnast. The closest matching simulation was used as a starting point to maximise post-flight rotation potential (the product of angular momentum and flight time) for a forwards rotating vault. It was found that the maximised rotation potential was sufficient to produce a handspring double piked somersault vault. The corresponding optimal touchdown configuration exhibited hip flexion in contrast to the hyperextended configuration required for maximal height. Increasing touchdown velocity and angular momentum lead to additional post-flight rotation potential. By increasing the horizontal velocity at table touchdown, within limits obtained from recorded performances, the handspring double somersault tucked with one and a half twists, and the handspring triple somersault tucked became theoretically possible.

“…Synchronised digitised coordinate data from each camera view along with the camera parameters were used to reconstruct the threedimensional locations of the body landmarks using the Direct Linear Transformation. Joint angles for the left and right sides were averaged and quintic splines (Wood and Jennings, 1979) were used to fit the orientation and joint angle time histories so that derivatives could be obtained (Yeadon, 1990a) for input to a planar simulation model.…”

Section: Data Collectionmentioning

confidence: 99%

“…In addition to the shoulder spring, there was a parameter that governed the extent to which the torso segment lengthened (scapular elevation) as the shoulder elevation angle was increased (Begon, Wieber and Yeadon, 2009). Input to the simulation model comprised the segmental inertia parameters, the stiffness and damping coefficients of the bar and shoulder springs, the initial displacement and velocity of the bar, the initial angular velocity of the arm, the initial orientation of the arm and the joint angle time histories of the shoulder, hip and knee in the form of quintic splines (Wood and Jennings, 1979). Output from the model included the time histories of the horizontal and vertical bar displacements and the arm angle  (the angle from the vertical of the line joining the bar to the shoulder centre).…”

Section: Simulation Modelmentioning

confidence: 99%

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

2013

Additional Information:• NOTICE: this is the author's version of a work that was accepted for publication in Human Movement Science.Changes ABSTRACTThe upstart is a fundamental skill in gymnastics which is used to transfer a gymnast from a swing beneath the bar to a position above the bar. The aim of this study was to optimise the technique in the upstart on the uneven bars in order to determine the underlying control strategy used by gymnasts. A previous attempt based on minimising joint torque had failed to find a satisfactory solution without forcing the joint angle histories to pass through a "via-point" (Yamasaki et al., 2010). Using a computer simulation model of a gymnast and bar, the technique (joint angle histories) used in the upstart was optimised under three different criteria: minimising joint torque, minimising joint torque change and maximising success in the presence of movement variability. The third optimisation introduced "noise" into the joint angle time histories based on measurements of kinematic variability. All three optimisations were started from the technique used by a gymnast competing in an Olympic Games uneven bars final. Root mean squared (RMS) differences between the recorded and optimal joint angle time histories were computed. The two optimisations based on minimising joint torque diverged from the gymnast's technique. However, the technique based on maximising the number of successful performances in a noisy environment remained close to the gymnast's technique. It is concluded that the underlying strategy used in the upstart is not based on minimisation of joint torque; rather, it is based on ensuring success in the task despite the inherent variability in technique. Gymnasts develop techniques that are able to cope with the level of kinematic variability present in their movements.