Determination of subject-specific model parameters for visco-elastic elements

Abstract

The determination of subject-specific model parameter values is necessary in order for a computer simulation model of human motion to be evaluated quantitatively. This study used an optimisation procedure along with a kinematically-driven simulation model of the contact phase in running jumps to determine the elastic parameters of segmental wobbling masses and the foot-ground interface. Kinetic and kinematic data were obtained on a running jump for height and a running jump for distance performed by an elite male high jumper. Stiffness and damping coefficients of the visco-elastic elements in the model were varied until the difference between simulation and performance was minimised. Percentage differences of 6% and 9% between the simulated and recorded performances were obtained in the jumps for height and distance respectively. When the parameters obtained from the jump for height were used in a simulation of the jump for distance (and vice versa) there was poor agreement with the recorded jump. On the other hand a common set of visco-elastic parameters were obtained using the data from both recorded jumps resulting in a mean difference of only 8% (made up of 7% and 10%) between simulation and performance that was almost as good as the individual matches. Simulations were not overly sensitive to perturbations of the common set of visco-elastic parameters. It is concluded that subject-specific elastic parameters should be calculated from more than a single jump in order to provide a robust set of values that can be used in different simulations.

Considerations that affect optimised simulation in a running jump for height

“…In the matching simulation no violations of either angular momentum or anatomical constraints occurred. The horizontal stiffness parameter value at the heel and toe was 63% of the initial estimate taken from Wilson et al (2006) while the vertical stiffness parameter values were 69% and 99% of the initial estimates at the heel and toe respectively. …”

Is a single or double arm technique more advantageous in triple jumping?

“…A common set of viscoelastic parameters representing the attachments of the wobbling masses and the foot-ground interface was determined for the three phases of the triple jump using an adaptation of the method of Wilson et al (2006). The simulation model was angle-driven using performance data and 27 parameters were varied using a simulated annealing algorithm (Corana et al, 1987) in order to minimise the difference between simulation and performance.…”

Stiffness of a wobbling mass models analysed by a smooth orthogonal decomposition of the skin movement relative to the underlying bone

“…According to the recent descriptions of the STA (Andersen et al, 2012;Benoit et al, 2015;Dumas et al, 2015;Grimpampi et al, 2014) and to the wobbling mass models reported in the literature (Alonso et al, 2007;Bélaise et al, 2016;Challis and Pain, 2008;Gittoes et al, 2009;Gruber et al, 1998;Günther et al, 2003;McLean et al, 2003;Wilson et al, 2006), it was useful to retrieve the stiffness matrix corresponding only to the modes defining the marker-cluster geometrical rigid transformations and more specifically to the marker-cluster translations. This stiffness matrix was given by:…”

“…Most of the models of the literature include linear or non-linear springs attached to a wobbling mass that can translate (and eventually rotate) with respect to the bone (Alonso et al, 2007;Gittoes et al, 2006;Gruber et al, 1998;Günther et al, 2003;McLean et al, 2003;Pain and Challis, 2004;Wilson et al, 2006). Identification of the parameters of these wobbling mass models, based on the ground reaction forces, as well as sensitivity analyses have been widely performed (Alonso et al, 2007;Gittoes et al, 2009;Pain and Challis, 2004;Wilson et al, 2006). However, to the best of the author's knowledge, the estimation of the stiffness parameters from the displacements of the skin relative to the underling bone measured in vivo by intra-cortical pins has not been performed yet.…”