Hafkamp, M.S.J. (Marijn) (2021) Circular causality in a redundant movement system: joint angles display different dynamics than the end-effector in a rhythmic pointing task. thesis, Human Movement Sciences.
Full text available on request.Abstract
From a Dynamical Systems Approach, movement coordination is regarded to be the result of self-organization. Self-organization in complex systems has been characterized as the emergence of an order parameter on a macroscopic scale, based on complex interactions of many elements on a microscopic, lower scale of the system. The current study was aimed at exploring the relationship between the macroscopic and microscopic level of a redundant movement system during a rhythmic pointing task with varying Indexes of Difficulty (ID) and varying distances between the targets. We examined the dynamical pattern of the end-effector as the macroscopic level and three driving joint angles (Valk et al. 2019) as elements on a microscopic level. We followed the W-method of Beek & Beek (1988) to model the dynamics of the end-effector and the individual joint angles as self-sustaining oscillators. Furthermore, we investigated stability at both levels by calculating the approximate entropy and the largest Lyapunov exponent of all movement patterns. We found that only the end-effector and one of the three joint angles (shoulder plane of elevation) could be modelled as self-sustaining oscillators. However, the characteristics of the dynamics were different between the two levels. Stability of the end-effector movement was significantly higher than that of the joint angles, but changes in stability over varying task conditions were similar at macro- and microscopic level. We concluded that circular causality in a redundant movement system does not imply that individual elements display the same dynamics with the same stability as the macroscopic order parameter.
| Item Type: | Thesis (UNSPECIFIED) |
|---|---|
| Supervisor name: | Bongers, R.M. and Valk, T.A. |
| Faculty: | Medical Sciences |
| Date Deposited: | 13 May 2022 10:02 |
| Last Modified: | 13 May 2022 10:02 |
| URI: | https://umcg.studenttheses.ub.rug.nl/id/eprint/3299 |
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