EuroMov Inaugural Conference

sans-titre.pngAbstract :

Matthieu CASTERAN, Patrick MANCKOUNDIA, Thierry POZZO & Elizabeth THOMAS

A Comparison of the Centre of Mass Trajectories during a Whole Body Pointing Movement between Healthy Young and Elderly Subjects

Many of our actions require the interaction of the postural equilibrium mechanisms and of the focal movement. The whole body pointing (WBP) task is one which involves these two elements [1, 2]. The aim of our study is to compare how the center of mass (CoM) is regulated during such movements for young (Yg) as opposed to elderly (Ed) subjects. In previous research, we have already found that synergies reduced the number of degrees of freedom of the kinematic excursions during these types of movements.  Would such a strategy of using common waveforms be utilized for controlling the anterio-posterior (AP) and vertical (V) displacements of the CoM? Is it altered by ageing? To answer these questions, we examined the CoM trajectories of pointing to a target that was placed in front of the subject. Our first analyses reveal that the relationship of the control between these two variables, measured by dAP (speed of AP displacement) and dV (speed of vertical displacement), was nonlinear. In particular, dV showed a low variability compared to dAP. This raises the possibility that the movement is organized around the vertical rather than the horizontal dimension [Fig.1]. A study of the two trajectories showed stereotyped transition points. Among these were the peak velocity for dV and dAP. We found that the moment at which these transition points occurred were shifted in time in Ed subjects.  Our study will display these shifts and discuss how they may lead to alterations in the equilibrium of the Ed subjects. 

Figure 1

courbes.pngdAp and dV of the CoM normalized by the amplitude Ap and V max of the CoM (Black – Yg ; Blue – Ed)

Every curve represents the mean for 10 trials for one subject



 [1]    B Berret, F Bonnetblanc, C Papaxanthis, and T Pozzo - Modular control of pointing beyond arm's length, The Journal of Neuroscience, 29(1): 191-205, January 2009

 [2]    M Casteran, P Manckoundia, T Pozzo, and E Thomas - Alterations with Movement Duration in the Kinematics of a Whole Body Pointing Movement. PloS one, vol. 8, no 1, p. e52477, January 2013.

France Montpellier

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