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The stability of pen-joint and interjoint coordination in loop writing
R G Meulenbroek1, A J Thomassen, P H van Lieshout
1Nijmegen Institute for Cognition and Information (NICI), University of Nijmegen, The Netherlands. meulenbroek@nici.kun.nl
Acta Psychologica
|December 9, 1998
Summary
Handwriting coordination is most stable between the pen tip and wrist, and between the wrist and elbow joints. This stability helps understand control in the arm-pen system during writing tasks.
Area of Science:
- Biomechanics
- Neuroscience
- Robotics
Background:
- Understanding human motor control is crucial for developing advanced robotics and prosthetics.
- Handwriting involves complex coordination between multiple joints and the effector (pen).
- Previous models of handwriting lack detailed analysis of joint-specific coordination stability.
Purpose of the Study:
- To investigate the stability of pen-joint and interjoint coordination during handwriting.
- To identify the locus of coordination control within the arm-pen effector system.
- To analyze how sequence length and position affect coordination stability.
Main Methods:
- Twelve subjects performed loop sequences at varying lengths and positions.
- A 3D-motion tracking system recorded joint excursions and pen-tip displacements.
- Relative phase analyses were used to assess the coordination stability of 15 pairs of 6 degrees of freedom (d.f.s).
Main Results:
- Pen-joint coordination between horizontal pen-tip displacements and wrist excursions showed the highest stability.
- Coordination between vertical pen-tip displacements and finger excursions was less stable.
- Interjoint coordination was generally less stable than pen-joint coordination, with wrist-elbow exhibiting the most stability.
- Sequence length and position on the writing baseline differentially influenced coordination stability.
Conclusions:
- The findings suggest a hierarchical control strategy in handwriting, with more stable synergies at proximal joints.
- Coordination stability varies significantly across different joint pairs and degrees of freedom.
- Results provide empirical data to refine computational models of handwriting and motor control.